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Improved limits on short-wavelength gravitational waves from the cosmic
microwave background: The cosmic microwave background (CMB) is affected by the total radiation
density around the time of decoupling. At that epoch, neutrinos comprised a
significant fraction of the radiative energy, but there could also be a
contribution from primordial gravitational waves with frequencies greater than
~ 10^-15 Hz. If this cosmological gravitational wave background (CGWB) were
produced under adiabatic initial conditions, its effects on the CMB and matter
power spectrum would mimic massless non-interacting neutrinos. However, with
homogenous initial conditions, as one might expect from certain models of
inflation, pre big-bang models, phase transitions and other scenarios, the
effect on the CMB would be distinct. We present updated observational bounds
for both initial conditions using the latest CMB data at small scales from the
South Pole Telescope (SPT) in combination with Wilkinson Microwave Anisotropy
Probe (WMAP), current measurements of the baryon acoustic oscillations, and the
Hubble parameter. With the inclusion of the data from SPT the adiabatic bound
on the CGWB density is improved by a factor of 1.7 to 10^6 Omega_gw < 8.7 at
the 95% confidence level (C.L.), with weak evidence in favor of an additional
radiation component consistent with previous analyses. The constraint can be
converted into an upper limit on the tension of horizon-sized cosmic strings
that could generate this gravitational wave component, with Gmu < 2 10^-7 at
95% C.L., for string tension Gmu. The homogeneous bound improves by a factor of
3.5 to 10^6 Omega_gw < 1.0 at 95% C.L., with no evidence for such a component
from current data. | Future dark energy constraints from measurements of quasar parallax:
Gaia, SIM and beyond: (Abridged) A consequence of the Earth's motion with respect to the CMB is
that over a 10 year period it will travel a distance of ~800 AU. As first noted
by Kardashev in 1986, this baseline can be used to carry out astrometric
measurements of quasar parallaxes, so that only microarcsecond precision is
necessary to detect parallax shifts of objects at gigaparsec distances. Such
precision will soon be approached with the launch of the astrometric satellites
Gaia and SIM. We use a Fisher matrix formalism to investigate the constraints
that these and future missions may be able to place on the cosmological
distance scale and dark energy. We find that by observing around a million
quasars as planned, an extended 10 year Gaia mission could detect quasar
parallax shifts at the 2.8 sigma level and so measure the Hubble constant to
within 25 km/s. For the interferometer SIMLite, a Key Project using 2.4 % of
the total mission time to observe 750 quasars could detect the effect at the 2
sigma level. Gaia and a dedicated SIMLite only weakly constrain the presence of
a cosmological constant at the ~1 sigma levels. We also investigate future
mission concepts, such as an interferometer similar in scope and design to
NASA's Terrestrial Planet Finder. This could in principle measure the dark
energy parameters w_0 and w_a with high precision, yielding a Figure of Merit
larger than the stage IV experiments considered by the the Dark Energy Task
Force. Unlike perhaps all other probes of dark energy there appear to be no
obvious astrophysical sources of systematic error. There is however uncertainty
regarding the statistical errors. As well as measurement error, there will be
small additional contributions from image centroiding of variable sources,
quasar peculiar motions and weak microlensing by stars along the line of sight. |
Implementation of two-field inflation for cosmic linear anisotropy
solving system: We outline the modifications in the numerical Boltzmann code Cosmic Linear
Anisotropy Solving System (CLASS) in order to include extra inflationary
fields. The functioning of the code is first described, how and where
modifications are meant to be done are later explained. In the present study,
we focus on the modifications needed for the implementation of a two-field
inflationary model, with canonical kinetic terms and a polynomial potential
with no cross terms, presenting preliminary results for the effect of the
second field on the spectra. The adaptability of the code is exploited, making
use of the classes and structures of C and the generic Runge-Kutta integration
tool provided by the program. | A giant radio halo in the low luminosity X-ray cluster Abell 523: Radio halos are extended and diffuse non-thermal radio sources present at the
cluster center, not obviously associated with any individual galaxy. A strong
correlation has been found between the cluster X-ray luminosity and the halo
radio power. We observe and analyze the diffuse radio emission present in the
complex merging structure Abell 523, classified as a low luminosity X-ray
cluster, to discuss its properties in the context of the halo total radio power
versus X-ray luminosity correlation. We reduced VLA archive observations at 1.4
GHz to derive a deep radio image of the diffuse emission, and compared radio,
optical, and X-ray data. Low-resolution VLA images detect a giant radio halo
associated with a complex merging region. The properties of this new halo agree
with those of radio halos in general discussed in the literature, but its radio
power is about a factor of ten higher than expected on the basis of the cluster
X-ray luminosity. Our study of this giant radio source demonstrates that radio
halos can also be present in clusters with a low X-ray luminosity. Only a few
similar cases have so far been found . This result suggests that this source
represent a new class of objects, that cannot be explained by classical radio
halo models. We suggest that the particle reacceleration related to merging
processes is very efficient and/or the X-ray luminosity is not a good indicator
of the past merging activity of a cluster. |
Nonlinear Behavior of Baryon Acoustic Oscillations in Redshift Space
from the Zel'dovich Approximation: Baryon acoustic oscillations (BAO) are a powerful probe of the expansion
history of the universe, which can tell us about the nature of dark energy. In
order to accurately characterize the dark energy equation of state using BAO,
we must understand the effects of both nonlinearities and redshift space
distortions on the location and shape of the acoustic peak. In a previous paper
we introduced a novel approach to 2nd order perturbation theory in
configuration space using the Zel'dovich approximation, and presented a simple
result for the first nonlinear term of the correlation function. In this paper,
we extend this approach to redshift space. We show how perform the computation,
and present the analytic result for the first nonlinear term in the correlation
function. Finally, we validate our result through comparison to numerical
simulations. | Early-type galaxies at z = 1.3. I. The Lynx supercluster: cluster and
groups at z=1.3. Morphology and color-magnitude relation: We confirm the detection of 3 groups in the Lynx supercluster, at z~1.3, and
give their redshifts and masses. We study the properties of the group galaxies
as compared to the central clusters, RXJ0849+4452 and RXJ0848+4453, selecting
89 galaxies in the clusters and 74 galaxies in the groups. We morphologically
classify galaxies by visual inspection, noting that our early-type galaxy (ETG)
sample would have been contaminated at the 30% -40% level by simple automated
classification methods (e.g. based on Sersic index). In luminosity selected
samples, both clusters and groups show high fractions of Sa galaxies. The ETG
fractions never rise above ~50% in the clusters, which is low compared to the
fractions observed in clusters at z~1. However, ETG plus Sa fractions are
similar to those observed for ETGs in clusters at z~1. Bulge-dominated galaxies
visually classified as Sas might also be ETGs with tidal features or merger
remnants. They are mainly red and passive, and span a large range in
luminosity. Their star formation seems to have been quenched before
experiencing a morphological transformation. Because their fraction is smaller
at lower redshifts, they might be the spiral population that evolves into ETGs.
For mass-selected samples, the ETG fraction show no significant evolution with
respect to local clusters, suggesting that morphological transformations occur
at lower masses and densities. The ETG mass-size relation shows evolution
towards smaller sizes at higher redshift in both clusters and groups, while the
late-type mass-size relation matches that observed locally. The group ETG red
sequence shows lower zero points and larger scatters than in clusters, both
expected to be an indication of a younger galaxy population. The estimated age
difference is small when compared to the difference in age at different galaxy
masses. |
Elementary Theorems Regarding Blue Isocurvature Perturbations: Blue CDM-photon isocurvature perturbations are attractive in terms of
observability and may be typical from the perspective of generic mass relations
in supergravity. We present and apply three theorems useful for blue
isocurvature perturbations arising from linear spectator scalar fields. In the
process, we give a more precise formula for the blue spectrum associated with
the axion model of 0904.3800, which can in a parametric corner give a factor of
O(10) correction. We explain how a conserved current associated with
Peccei-Quinn symmetry plays a crucial role and explicitly plot several example
spectra including the breaks in the spectra. We also resolve a little puzzle
arising from a naive multiplication of isocurvature expression that sheds light
on the gravitational imprint of the adiabatic perturbations on the fields
responsible for blue isocurvature fluctuations. | New measurements of $E_G$: Testing General Relativity with the Weyl
potential and galaxy velocities: We combine measurements of galaxy velocities from galaxy surveys with
measurements of the Weyl potential from the Dark Energy Survey to test the
consistency of General Relativity at cosmological scales. Taking the ratio of
two model-independent observables - the growth rate of structure and the Weyl
potential - we obtain new measurements of the $E_G$ statistic with precision of
$5.8-10.7\%$ at four different redshifts. These measurements provide a
considerable improvement to past measurements of $E_G$. They confirm the
validity of General Relativity at three redshifts, while displaying a tension
of $2.5\sigma$ at $z=0.47$ as a consequence of the tension found in the
measurements of the Weyl potential. Contrary to conventional methods that rely
on a common galaxy sample with spectroscopic resolution to measure two types of
correlations, we directly combine two observables that are independent of the
galaxy bias. This provides a novel approach to testing the relation between the
geometry of our Universe and the motion of galaxies with improved precision. |
Extragalactic large-scale structures in the northern Zone of Avoidance: We used the Nan\c{c}ay Radio Telescope (NRT) to measure the 21 cm line
emission of near-infrared bright galaxies in the northern Zone of Avoidance
(ZoA) without previous redshift determinations. We selected galaxies with
extinction-corrected magnitudes $K_s^o \leq 11\hbox{$.\!\!^{\rm m}$}25$ from
the 2MASS Extended Source Catalog. These data will complement the existing
2MASS Redshift Survey (2MRS; first data release) as well as the ongoing 2MASS
Tully-Fisher survey, both of which exclude the inner ZoA ($|b|< 5^{\circ}$),
where the identification of galaxy candidates is the hardest. Of the $\sim$1000
identified 2MASX galaxy candidates we have so far detected 252 to our 3.0 mJy
rms sensitivity limit and the velocity limit of 10500 km/s. The resulting
redshift distribution reveals various new structures that were hitherto
uncharted. They seem to form part of the larger Perseus-Pisces Supercluster
(PPS). The most conspicuous is a ridge at about $\ell\approx 160^{\circ}$,$v
\approx 6500$ km/s. Within this wall-like structure, two strong radio galaxies
(3C 129 and 3C 129.1) are embedded which lie at the same distance as the ridge.
They seem to form part of an X-ray cluster. Another prominent filament has been
identified crossing the ZoA at $\ell \approx 90^\circ$, hence suggesting the
second Perseus-Pisces arm is more extended than previously thought. | A complete sample of 21-cm absorbers at z~1.3: Giant Metrewave Radio
Telescope Survey Using MgII Systems: We present the results of a systematic Giant Metrewave Radio Telescope (GMRT)
survey of 21-cm absorption in a representative and unbiased sample of 35 strong
MgII systems in the redshift range: zabs~1.10-1.45, 33 of which have W_r>1 \AA.
The survey using ~400hrs of telescope time has resulted in 9 new 21-cm
detections and stringent 21-cm optical depth upper limits (median 3-sigma
optical depth per 10 km/s of 0.017) for the remaining 26 systems. This is by
far the largest number of 21-cm detections from any single survey of
intervening absorbers. Prior to our survey no intervening 21-cm system was
known in the above redshift range and only one system was known in the redshift
range 0.7<z<1.5. We discuss the relation between the detectability of 21-cm
absorption and various properties of UV absorption lines. We show that if MgII
systems are selected with the following criteria, MgII doublet ratio <1.3 and
W_r(MgI)/W_r(MgII)>0.3, then a detection rate of 21-cm absorption up to 90% can
be achieved. We estimate n_{21}, the number per unit redshift of 21-cm
absorbers with W_r(Mg(II)>W_o and integrated optical depth Tau_{21}>Tau_o and
show that n_{21} decreases with increasing redshift. In particular, for W_o=1.0
\AA and Tau_o>0.3 km\s, n_{21} falls by a factor 4 from <z>=0.5 to <z>=1.3. The
evolution seems to be stronger for stronger MgII systems. Using a subsample of
systems for which high frequency VLBA images are available, we show that the
effect is not related to the structure of the background radio sources and is
most probably due to the evolution of the cold neutral medium filling factor in
MgII systems. We find no correlation between the velocity spread of the 21-cm
absorption feature and W_r(MgII) at z~1.3. |
Minkowski Tensors in Three Dimensions - Probing the Anisotropy Generated
by Redshift Space Distortion: We apply the Minkowski tensor statistics to three dimensional Gaussian random
fields. Minkowski tensors contain information regarding the orientation and
shape of excursion sets, that is not present in the scalar Minkowski
functionals. They can be used to quantify globally preferred directions, and
additionally provide information on the mean shape of subsets of a field. This
makes them ideal statistics to measure the anisotropic signal generated by
redshift space distortion in the low redshift matter density field. We review
the definition of the Minkowski tensor statistics in three dimensions, focusing
on two coordinate invariant quantities $W^{0,2}_{1}$ and $W^{0,2}_{2}$. We
calculate the ensemble average of these $3 \times 3$ matrices for an isotropic
Gaussian random field, finding that they are proportional to products of the
identity matrix and a corresponding scalar Minkowski functional. We show how to
numerically reconstruct $W^{0,2}_{1}$ and $W^{0,2}_{2}$ from discretely sampled
fields and apply our algorithm to isotropic Gaussian fields generated from a
linear $\Lambda$CDM matter power spectrum. We then introduce anisotropy by
applying a linear redshift space distortion operator to the matter density
field, and find that both $W^{0,2}_{1}$ and $W^{0,2}_{2}$ exhibit a distinct
signal characterised by inequality between their diagonal components. We
discuss the physical origin of this signal and how it can be used to constrain
the redshift space distortion parameter $\Upsilon \equiv f/b$. | Cosmological tests of modified gravity: constraints on $F(R)$ theories
from the galaxy clustering ratio: The clustering ratio $\eta$, a large-scale structure observable originally
designed to constrain the shape of the power spectrum of matter density
fluctuations, is shown to provide a sensitive probe of the nature of gravity in
the cosmological regime. We apply this analysis to $F(R)$ theories of gravity
using the luminous red galaxy (LRG) sample extracted from the spectroscopic
Sloan Digital Sky Survey (SDSS) data release 7 and 10 catalogues. We find that
General Relativity (GR), complemented with a Friedmann-Robertson-Walker (FRW)
cosmological model with parameters fixed by the Planck satellite, describes
extremely well the clustering of galaxies up to $z\sim 0.6$. On large cosmic
scales, the absolute amplitude of deviations from GR, $|f_{R_0 }|$, is
constrained to be smaller than $4.6 \times 10^{-5}$ at the $95\%$ confidence
level. This bound makes cosmological probes of gravity almost competitive with
the sensitivity of Solar System tests, although still one order of magnitude
less effective than astrophysical tests. We also extrapolate our results to
future large surveys like Euclid and show that the astrophysical bound will
certainly remain out of reach for such a class of modified-gravity models that
only differ from $\Lambda$CDM at low redshifts. |
Rapidly Descending Dark Energy and the End of Cosmic Expansion: If dark energy is a form of quintessence driven by a scalar field $\phi$
evolving down a monotonically decreasing potential $V(\phi)$ that passes
sufficiently below zero, the universe is destined to undergo a series of smooth
transitions. The currently observed accelerated expansion will cease; soon
thereafter, expansion will come to end altogether; and the universe will pass
into a phase of slow contraction. In this paper, we consider how short the
remaining period of expansion can be given current observational constraints on
dark energy. We also discuss how this scenario fits naturally with cyclic
cosmologies and recent conjectures about quantum gravity. | Ultraluminous Star-Forming Galaxies and Extremely Luminous Warm
Molecular Hydrogen Emission at z=2.16 in the PKS 1138-26 Radio Galaxy
Protocluster: A deep Spitzer Infrared Spectrograph map of the PKS 1138-26 galaxy
protocluster reveals ultraluminous PAH emission from obscured star formation in
three protocluster galaxies, including Halpha-emitter (HAE) 229, HAE 131, and
the central Spiderweb Galaxy. Star formation rates of 500-1100 Msun/yr are
estimated from the 7.7 micron PAH feature. At such prodigious formation rates,
the galaxy stellar masses will double in 0.6-1.1 Gyr. We are viewing the peak
epoch of star formation for these protocluster galaxies. However, it appears
that extinction of Halpha is much greater (factor of 40) in the two ULIRG HAEs
compared to the Spiderweb. This may be attributed to different spatial
distributions of star formation--nuclear star formation in the HAEs versus
extended star formation in accreting satellite galaxies in the Spiderweb. We
find extremely luminous mid-IR rotational line emission from warm molecular
hydrogen in the Spiderweb Galaxy, with L(H2 0-0 S(3))= 1.4E44 erg/s (3.7E10
Lsun), 20 times more luminous than any previously known H2 emission galaxy
(MOHEG). Depending on temperature, this corresponds to a very large mass of
>9E6-2E9 Msun of T>300 K molecular gas, heated by the PKS 1138-26 radio jet,
acting to quench nuclear star formation. There is >8 times more warm H2 at
these temperatures in the Spiderweb than what has been seen in low-redshift
(z<0.2) radio galaxies, indicating that the Spiderweb may have a larger
reservoir of molecular gas than more evolved radio galaxies. This is the
highest redshift galaxy yet in which warm molecular hydrogen has been directly
detected. |
Uncovering dark matter density profiles in dwarf galaxies with graph
neural networks: Dwarf galaxies are small, dark matter-dominated galaxies, some of which are
embedded within the Milky Way. Their lack of baryonic matter (e.g., stars and
gas) makes them perfect test beds for probing the properties of dark matter --
understanding the spatial dark matter distribution in these systems can be used
to constrain microphysical dark matter interactions that influence the
formation and evolution of structures in our Universe. We introduce a new
method that leverages simulation-based inference and graph-based machine
learning in order to infer the dark matter density profiles of dwarf galaxies
from observable kinematics of stars gravitationally bound to these systems. Our
approach aims to address some of the limitations of established methods based
on dynamical Jeans modeling. We show that this novel method can place stronger
constraints on dark matter profiles and, consequently, has the potential to
weigh in on some of the ongoing puzzles associated with the small-scale
structure of dark matter halos, such as the core-cusp discrepancy. | Finding the First Cosmic Explosions II: Core-Collapse Supernovae: Understanding the properties of Pop III stars is prerequisite to elucidating
the nature of primeval galaxies, the chemical enrichment and reionization of
the early IGM, and the origin of supermassive black holes. While the primordial
IMF remains unknown, recent evidence from numerical simulations and stellar
archaeology suggests that some Pop III stars may have had lower masses than
previously thought, 15 - 50 \Ms in addition to 50 - 500 \Ms. The detection of
Pop III supernovae by JWST, WFIRST or the TMT could directly probe the
primordial IMF for the first time. We present numerical simulations of 15 - 40
\Ms Pop III core-collapse SNe done with the Los Alamos radiation hydrodynamics
code RAGE. We find that they will be visible in the earliest galaxies out to z
~ 10 - 15, tracing their star formation rates and in some cases revealing their
positions on the sky. Since the central engines of Pop III and
solar-metallicity core-collapse SNe are quite similar, future detection of any
Type II supernovae by next-generation NIR instruments will in general be
limited to this epoch. |
Inflationary dynamics of kinetically-coupled gauge fields: We investigate the inflationary dynamics of two kinetically-coupled massless
$U(1)$ gauge fields with time-varying kinetic-term coefficients. Ensuring that
the system does not have strongly coupled regimes shrinks the parameter space.
Also, we further restrict ourselves to systems that can be quantized using the
standard creation, annihilation operator algebra. This second constraint limits
us to scenarios where the system can be diagonalized into the sum of two
decoupled, massless, vector fields with a varying kinetic-term coefficient.
Such a system might be interesting for magnetogenesis because of how the
strong coupling problem generalizes. We explore this idea by assuming that one
of the gauge fields is the Standard Model $U(1)$ field and that the other dark
gauge field has no particles charged under its gauge group. We consider whether
it would be possible to transfer a magnetic field from the dark sector,
generated perhaps before the coupling was turned on, to the visible sector. We
also investigate whether the simple existence of the mixing provides more
opportunities to generate magnetic fields. We find that neither possibility
works efficiently, consistent with the well-known difficulties in inflationary
magnetogenesis. | The impact of signal-to-noise, redshift, and angular range on the bias
of weak lensing 2-point functions: Weak lensing data follow a naturally skewed distribution, implying the data
vector most likely yielded from a survey will systematically fall below its
mean. Although this effect is qualitatively known from CMB-analyses, correctly
accounting for it in weak lensing is challenging, as a direct transfer of the
CMB results is quantitatively incorrect. While a previous study (Sellentin et
al. 2018) focused on the magnitude of this bias, we here focus on the frequency
of this bias, its scaling with redshift, and its impact on the signal-to-noise
of a survey. Filtering weak lensing data with COSEBIs, we show that weak
lensing likelihoods are skewed up until $\ell \approx 100$, whereas
CMB-likelihoods Gaussianize already at $\ell \approx 20$. While
COSEBI-compressed data on KiDS- and DES-like redshift- and angular ranges
follow Gaussian distributions, we detect skewness at 6$\sigma$ significance for
half of a Euclid- or LSST-like data set, caused by the wider coverage and
deeper reach of these surveys. Computing the signal-to-noise ratio per data
point, we show that precisely the data points of highest signal-to-noise are
the most biased. Over all redshifts, this bias affects at least 10% of a
survey's total signal-to-noise, at high redshifts up to 25%. The bias is
accordingly expected to impact parameter inference. The bias can be handled by
developing non-Gaussian likelihoods. Otherwise, it could be reduced by removing
the data points of highest signal-to-noise. |
A New Method to Measure the Post-Reionization Ionizing Background from
the Joint Distribution of Lyman-$α$ and Lyman-$β$ Forest
Transmission: The amplitude of the ionizing background that pervades the intergalactic
medium (IGM) at the end of the epoch of reionization provides a valuable
constraint on the emissivity of the sources which reionized the Universe. While
measurements of the ionizing background at lower redshifts rely on a
simulation-calibrated mapping between the photoionization rate and the mean
transmission of the Ly$\alpha$ forest, at $z\gtrsim6$ the IGM becomes
increasingly opaque, and transmission arises solely in narrow spikes separated
by saturated Gunn-Peterson troughs. In this regime, the traditional approach of
measuring the average transmission over large $\sim 50$ Mpc$/h$ regions is less
sensitive and sub-optimal. Additionally, the five times smaller oscillator
strength of the Ly$\beta$ transition implies the Ly$\beta$ forest is
considerably more transparent at $z\gtrsim6$, even in the presence of
contamination by foreground $z\sim 5$ Ly$\alpha$ forest absorption. In this
work we present a novel statistical approach to analyze the joint distribution
of transmission spikes in the co-spatial $z\sim 6$ Ly$\alpha$ and Ly$\beta$
forests. Our method relies on Approximate Bayesian Computation (ABC), which
circumvents the necessity of computing the intractable likelihood function
describing the highly correlated Ly$\alpha$ and Ly$\beta$ transmission. We
apply ABC to mock data generated from a large-volume hydrodynamical simulation
combined with a state-of-the-art model of ionizing background fluctuations in
the post-reionization IGM, and show that it is sensitive to higher IGM neutral
hydrogen fractions than previous techniques. As a proof of concept, we apply
this methodology to a real spectrum of a $z=6.54$ quasar and measure the
ionizing background from $5.4\leq z \leq 6.4$ along this sightline with
$\sim0.2$ dex statistical uncertainties. | Subhalo accretion through filaments: We track subhalo orbits of galaxy and group sized halos in cosmological
simulations. We identify filamentary structures around halos and we use these
to define a sample of subhalos accreted from filaments as well as a control
sample of subhalos accreted from other directions. We use these samples to
study differences in satellite orbits produced by filamentary accretion. Our
results depend on host halo mass. We find that for low masses, subhalos
accreted from filaments show $\sim10\%$ shorter lifetimes compared to the
control sample, they show a tendency towards more radial orbits, reach halo
central regions earlier, and are more likely to merge with the host. For higher
mass halos this lifetime difference dissipates and even reverses for cluster
sized halos. This behavior appears to be connected to the fact that more
massive hosts are connected to stronger filaments with higher velocity
coherence and density, with slightly more radial subhalo orbits. Because
subhalos tend to follow the coherent flow of the filament, it is possible that
such thick filaments are enough to shield the subhalo from the effect of
dynamical friction at least during their first infall. We also identify subhalo
pairs/clumps which merge with one another after accretion. They survive as a
clump for only a very short time, which is even shorter for higher subhalo
masses, suggesting that the Magellanic Clouds and other Local group satellite
associations, may have entered the MW virial radius very recently and probably
are in their first infall. Filaments boost the accretion of satellite
associations. |
Recovering Redshift Distributions with Cross-Correlations: Pushing The
Boundaries: Determining accurate redshift distributions for very large samples of objects
has become increasingly important in cosmology. We investigate the impact of
extending cross-correlation based redshift distribution recovery methods to
include small scale clustering information. The major concern in such work is
the ability to disentangle the amplitude of the underlying redshift
distribution from the influence of evolving galaxy bias. Using multiple
simulations covering a variety of galaxy bias evolution scenarios, we
demonstrate reliable redshift recoveries using linear clustering assumptions
well into the non-linear regime for redshift distributions of narrow redshift
width. Including information from intermediate physical scales balances the
increased information available from clustering and the residual bias incurred
from relaxing of linear constraints. We discuss how breaking a broad sample
into tomographic bins can improve estimates of the redshift distribution, and
present a simple bias removal technique using clustering information from the
spectroscopic sample alone. | The velocity function in the local environment from LCDM and LWDM
constrained simulations: Using constrained simulations of the local Universe for generic cold dark
matter and for 1keV warm dark matter, we investigate the difference in the
abundance of dark matter halos in the local environment. We find that the mass
function within 20 Mpc/h of the Local Group is ~2 times larger than the
universal mass function in the 10^9-10^13 M_odot/h mass range. Imposing the
field of view of the on-going HI blind survey ALFALFA in our simulations, we
predict that the velocity function in the Virgo-direction region exceeds the
universal velocity function by a factor of 3. Furthermore, employing a scheme
to translate the halo velocity function into a galaxy velocity function, we
compare the simulation results with a sample of galaxies from the early catalog
release of ALFALFA. We find that our simulations are able to reproduce the
velocity function in the 80-300 km/s velocity range, having a value ~10 times
larger than the universal velocity function in the Virgo-direction region. In
the low velocity regime, 35-80 km/s, the warm dark matter simulation reproduces
the observed flattening of the velocity function. On the contrary, the
simulation with cold dark matter predicts a steep rise in the velocity function
towards lower velocities; for V_max=35 km/s, it forecasts ~10 times more
sources than the ones observed. If confirmed by the complete ALFALFA survey,
our results indicate a potential problem for the cold dark matter paradigm or
for the conventional assumptions about energetic feedback in dwarf galaxies. |
One needs positive signatures for detection of Dark Matter: One believes there is huge amount of Dark Matter particles in our Galaxy
which manifest themselves only gravitationally. There is a big challenge to
prove their existence in a laboratory experiment. To this end it is not
sufficient to fight only for the best exclusion curve, one has to see an annual
recoil spectrum modulation --- the only available positive direct dark matter
detection signature. A necessity to measure the recoil spectra is stressed. | The Integrated Sachs Wolfe effect: unWISE and Planck constraints on
Dynamical Dark Energy: CMB photons redshift and blueshift as they move through gravitational
potentials $\Phi$ while propagating across the Universe. If the potential is
not constant in time, the photons will pick up a net redshift or blueshift,
known as the Integrated Sachs-Wolfe (ISW) effect. In the $z \ll 1000$ universe,
$\dot{\Phi}$ is nonzero on large scales when the Universe transitions from
matter to dark energy domination. This effect is only detectable in
cross-correlation with large-scale structure at $z \sim 1$. In this paper we
present a 3.2$\sigma$ detection of the ISW effect using cross-correlations
between unWISE infrared galaxies and Planck CMB temperature maps. We use 3
tomographic galaxy samples spanning $0 < z < 2$, allowing us to fully probe the
dark energy domination era and the transition into matter domination. This
measurement is consistent with $\Lambda$CDM ($A_{\rm ISW} = 0.96 \pm 0.30$). We
study constraints on a particular class of dynamical dark energy models (where
the dark energy equation of state is different in matter and dark energy
domination), finding that unWISE-ISW improves constraints from type Ia
supernovae due to improved constraints on the time evolution of dark energy.
When combining with BAO measurements, we obtain the tightest constraints on
specific dynamical dark energy models. In the context of a phenomenological
model for freezing quintessence, the Mocker model, we constrain the dark energy
density within 10% at $z < 2$ using ISW, BAO and supernovae. Moreover, the ISW
measurement itself provides an important independent check when relaxing
assumptions about the theory of gravity, as it is sensitive to the
gravitational potential rather than the expansion history. |
AMICO galaxy clusters in KiDS-DR3: cosmological constraints from
large-scale stacked weak lensing profiles: Context. The large-scale mass distribution around dark matter haloes hosting
galaxy clusters provides sensitive cosmological information. Aims. In this
work, we make use of a large photometric galaxy cluster sample, constructed
from the public Third Data Release of the Kilo-Degree Survey, and the
corresponding shear signal, to assess cluster masses and test the concordance
${\Lambda}$-cold dark matter (${\Lambda}$CDM) model. In particular, we study
the weak gravitational lensing effects on scales beyond the cluster virial
radius, where the signal is dominated by correlated and uncorrelated matter
density distributions along the line-of-sight. The analysed catalogue consists
of 6962 galaxy clusters, in the redshift range $0.1 \leq z \leq 0.6$ and with
signal-to-noise ratio larger than 3.5. Methods. We perform a full Bayesian
analysis to model the stacked shear profiles of these clusters. The adopted
likelihood function considers both the small-scale 1-halo term, used primarily
to constrain the cluster structural properties, and the 2-halo term, that can
be used to constrain cosmological parameters. Results. We find that the adopted
modelling is successful to assess both the cluster masses and the total matter
density parameter, ${\Omega}_M$, when fitting shear profiles up to the largest
available scales of 35 Mpc/h. Moreover, our results provide a strong
observational evidence of the 2-halo signal in the stacked gravitational
lensing of galaxy clusters, further demonstrating the reliability of this probe
for cosmological studies. The main result of this work is a robust constraint
on ${\Omega}_M$, assuming a flat ${\Lambda}$CDM cosmology. We get ${\Omega}_M =
0.29 \pm 0.02$, estimated from the full posterior probability distribution,
consistent with the estimates from cosmic microwave background experiments. | Modified gravitational collapse, or the wonders of the MOND: There are many hot discussions in the literature about two competing
paradigms in galactic and extra-galactic astronomy and cosmology, namely the
Dark Matter and the Modified Newtonian Dynamics (MOND). It is very difficult to
challenge MOND from the cosmological side because a full relativistic
realisation is needed in the first place, and any failure can then be
attributed to a particular model, and not to the MOND itself. We propose to
study non-relativistic stages of gravitational collapse in MOND which, we
argue, is a relevant task for this competition. Spherically symmetric dust
cloud collapse and intrinsic unavoidable non-linearities of the deep MOND
regime are discussed. We conclude that complicated, both numerical and
analytic, studies of modified gravitational dynamics are needed in order to
assess the viability of MOND. |
Hyper Suprime-Cam Year 3 Results: Cosmology from Galaxy Clustering and
Weak Lensing with HSC and SDSS using the Minimal Bias Model: We present cosmological parameter constraints from a blind joint analysis of
three two-point correlation functions measured from the Year 3 Hyper
Suprime-Cam (HSC-Y3) imaging data, covering 416 deg$^2$, and the SDSS DR11
spectroscopic galaxies spanning the redshift range $[0.15, 0.70]$. We subdivide
the SDSS galaxies into three volume-limited samples separated in redshift, each
of which acts as a large-scale structure tracer characterized by the
measurement of the projected correlation function, $w_{\rm p}(R)$. We also use
the measurements of the galaxy-galaxy weak lensing signal $\Delta \Sigma(R)$
for each of these SDSS samples which act as lenses for a secure sample of
source galaxies selected from the HSC-Y3 shape catalog based on their
photometric redshifts. We combine these measurements with the cosmic shear
correlation functions, $\xi_{\pm}(\vartheta)$, measured for our HSC source
sample. We model these observables with the minimal bias model of the galaxy
clustering observables in the context of a flat $\Lambda$CDM cosmology. We use
conservative scale cuts, $R>12$ and $8~h^{-1}$Mpc, for $\Delta\Sigma$ and
$w_{\rm p}$, respectively, where the minimal bias model is valid, in addition
to conservative prior on the residual bias in the mean redshift of the HSC
photometric source galaxies. Our baseline analysis yields
$S_8=0.775^{+0.043}_{-0.038}$ (68% C.I.) for the $\Lambda$CDM model, after
marginalizing over uncertainties in other parameters. Our value of $S_8$ is
consistent with that from the Planck 2018 data, but the credible interval of
our result is still relatively large. Our results are statistically consistent
with those of a companion paper, which extends this analysis to smaller scales
with an emulator-based halo model. | Environments of Strong / Ultrastrong, Ultraviolet Fe II Emitting Quasars: We have investigated the strength of ultraviolet Fe II emission from quasars
within the environments of Large Quasar Groups (LQGs) in comparison with
quasars elsewhere, for 1.1 <= <z_LQG> <= 1.7, using the DR7QSO catalogue of the
Sloan Digital Sky Survey. We use the Weymann et al. W2400 equivalent width,
defined between the rest-frame continuum-windows 2240-2255 and 2665-2695 Ang.,
as the measure of the UV Fe II emission. We find a significant shift of the
W2400 distribution to higher values for quasars within LQGs, predominantly for
those LQGs with 1.1 <= <z_LQG> <= 1.5. There is a tentative indication that the
shift to higher values increases with the quasar i magnitude. We find evidence
that within LQGs the ultrastrong emitters with W2400 >= 45 Ang. (more
precisely, ultrastrong-plus with W2400 >= 44 Ang.) have preferred
nearest-neighbour separations of ~ 30-50 Mpc to the adjacent quasar of any
W2400 strength. No such effect is seen for the ultrastrong emitters that are
not in LQGs. The possibilities for increasing the strength of the Fe II
emission appear to be iron abundance, Ly-alpha fluorescence, and
microturbulence, and probably all of these operate. The dense environment of
the LQGs may have led to an increased rate of star formation and an enhanced
abundance of iron in the nuclei of galaxies. Similarly the dense environment
may have led to more active blackholes and increased Ly-alpha fluorescence. The
preferred nearest-neighbour separation for the stronger emitters would appear
to suggest a dynamical component, such as microturbulence. In one particular
LQG, the Huge-LQG (the largest structure known in the early universe), six of
the seven strongest emitters very obviously form three pairings within the
total of 73 members. |
A model-independent fit to Planck and BICEP2 data: Inflation is the leading theory to describe elegantly the initial conditions
that led to structure formation in our universe. In this paper, we present a
novel phenomenological fit to the Planck, WMAP polarisation (WP) and the BICEP2
datasets using an alternative parameterisation. Instead of starting from
inflationary potentials and computing the inflationary observables, we use a
phenomenological parameterisation due to Mukhanov, describing inflation by an
effective equation-of-state, in terms of the number of e-folds and two
phenomenological parameters $\alpha$ and $\beta$. Within such a
parametrisation, which captures the different inflationary models in a
model-independent way, the values of the scalar spectral index $n_s$, its
running and the tensor-to-scalar ratio $r$ are predicted, given a set of
parameters $(\alpha,\beta)$. We perform a Markov Chain Monte Carlo analysis of
these parameters, and we show that the combined analysis of Planck and WP data
favours the Starobinsky and Higgs inflation scenarios. Assuming that the BICEP2
signal is not entirely due to foregrounds, the addition of this last data set
prefers instead the $\phi^2$ chaotic models. The constraint we get from Planck
and WP data alone on the derived tensor-to-scalar ratio is $r<0.18$ at
$95\%$~CL, value which is consistent with the one quoted from the BICEP2
collaboration analysis, $r = 0.16^{+0-06}_{-0.05}$, after foreground
subtraction. This is not necessarily at odds with the $2\sigma$ tension found
between Planck and BICEP2 measurements when analysing data in terms of the
usual $n_s$ and $r$ parameters, given that the parameterisation used here
includes, implicitly, a running spectral index. | Is the Jeffreys' scale a reliable tool for Bayesian model comparison in
cosmology?: We are entering an era where progress in cosmology is driven by data, and
alternative models will have to be compared and ruled out according to some
consistent criterium. The most conservative and widely used approach is
Bayesian model comparison. In this paper we explicitly calculate the Bayes
factors for all models that are linear with respect to their parameters. We do
this in order to test the so called Jeffreys' scale and determine analytically
how accurate its predictions are in a simple case where we fully understand and
can calculate everything analytically. We also discuss the case of nested
models, e.g. one with $M_1$ and another with $M_2\supset M_1$ parameters and we
derive analytic expressions for both the Bayes factor and the Figure of Merit,
defined as the inverse area of the model parameter's confidence contours. With
all this machinery and the use of an explicit example we demonstrate that the
threshold nature of Jeffreys' scale is not a "one size fits all" reliable tool
for model comparison and that it may lead to biased conclusions. Furthermore,
we discuss the importance of choosing the right basis in the context of models
that are linear with respect to their parameters and how that basis affects the
parameter estimation and the derived constraints. |
Massive black hole binaries: dynamical evolution and observational
signatures: The study of the dynamical evolution of massive black hole pairs in mergers
is crucial in the context of a hierarchical galaxy formation scenario. The
timescales for the formation and the coalescence of black hole binaries are
still poorly constrained, resulting in large uncertainties in the expected rate
of massive black hole binaries detectable in the electromagnetic and
gravitational wave spectra. Here we review the current theoretical
understanding of the black hole pairing in galaxy mergers, with a particular
attention to recent developments and open issues. We conclude with a review of
the expected observational signatures of massive binaries, and of the
candidates discussed in literature to date. | Effect of Fourier filters in removing periodic systematic effects from
CMB data: We consider the application of high-pass Fourier filters to remove periodic
systematic fluctuations from full-sky survey CMB datasets. We compare the
filter performance with destriping codes commonly used to remove the effect of
residual 1/f noise from timelines. As a realistic working case, we use
simulations of the typical Planck scanning strategy and Planck Low Frequency
Instrument noise performance, with spurious periodic fluctuations that mimic a
typical thermal disturbance. We show that the application of Fourier high-pass
filters in chunks always requires subsequent normalisation of induced offsets
by means of destriping. For a complex signal containing all the astrophysical
and instrumental components, the result obtained by applying filter and
destriping in series is comparable to the result obtained by destriping only,
which makes the usefulness of Fourier filters questionable for removing this
kind of effects. |
A larger value for $H_0$ by an evolving gravitational constant: We provide further evidence that a massless cosmological scalar field with a
non-minimal coupling to the Ricci curvature of the type $M^2_{\rm pl}(1+\xi
\sigma^n/M_{\rm pl}^n) $ alleviates the existing tension between local
measurements of the Hubble constant and its inference from CMB anisotropies and
baryonic acoustic oscillations data in presence of a cosmological constant. In
these models, the expansion history is modified compared to $\Lambda$CDM at
early time, mimicking a change in the effective number of relativistic species,
and gravity weakens after matter-radiation equality. Compared to $\Lambda$CDM,
a quadratic ($n=2$) coupling increases the Hubble constant when {\em Planck}
2018 (alone or in combination with BAO and SH0ES) measurements data are used in
the analysis. Negative values of the coupling, for which the scalar field
decreases, seem favored and consistency with Solar System can be naturally
achieved for a large portion of the parameter space without the need of any
screening mechanism. We show that our results are robust to the choice of $n$,
also presenting the analysis for $n=4$. | LoCuSS: the connection between brightest cluster galaxy activity, gas
cooling and dynamical disturbance of X-ray cluster cores: We study the distribution of projected offsets between the cluster X-ray
centroid and the brightest cluster galaxy (BCG) for 65 X-ray selected clusters
from the Local Cluster Substructure Survey (LoCuSS), with a median redshift of
z=0.23. We find a clear correlation between X-ray/BCG projected offset and the
logarithmic slope of the cluster gas density profile at 0.04r500 (alpha),
implying that more dynamically disturbed clusters have weaker cool cores.
Furthermore, there is a close correspondence between the activity of the BCG,
in terms of detected H_alpha and radio emission, and the X-ray/BCG offset, with
the line emitting galaxies all residing in clusters with X-ray/BCG offsets of
<~15 kpc. Of the BCGs with alpha < -0.85 and an offset < 0.02r500, 96 per cent
(23/24) have optical emission and 88 per cent (21/24) are radio active, while
none has optical emission outside these criteria. We also study the cluster gas
fraction (fgas) within r500 and find a significant correlation with X-ray/BCG
projected offset. The mean fgas of the `small offset' clusters (< 0.02r500) is
0.106+/-0.005 (sigma=0.03) compared to 0.145+/-0.009 (sigma=0.04) for those
with an offset > 0.02r500, indicating that the total mass may be systematically
underestimated in clusters with larger X-ray/BCG offsets. Our results imply a
link between cool core strength and cluster dynamical state consistent with the
view that cluster mergers can significantly perturb cool cores, and set new
constraints on models of the evolution of the intracluster medium. |
Scale-dependent bias from an inflationary bispectrum: the effect of a
stochastic moving barrier: With the advent of large scale galaxy surveys, constraints on primordial
non-Gaussianity (PNG) are expected to reach ${\cal O}(f_\text{NL}) \sim 1$. In
order to fully exploit the potential of these future surveys, a deep
theoretical understanding of the signatures imprinted by PNG on the large scale
structure of the Universe is necessary. In this paper, we explore the effect of
a stochastic moving barrier on the amplitude of the non-Gaussian bias induced
by local quadratic PNG. We show that, in the peak approach to halo clustering,
the amplitude of the non-Gaussian bias will generally differ from the
peak-background split prediction unless the barrier is flat and deterministic.
For excursion set peaks with a square-root barrier, which reproduce reasonably
well the linear bias $b_1$ and mass function $\bar{n}_\text{h}$ of SO haloes,
the non-Gaussian bias amplitude is $\sim 40$% larger than the peak-background
split expectation $d\ln\bar{n}_\text{h}/d\ln\sigma_8$ for haloes of mass $\sim
10^{13} {\it h}^{-1}M_\odot$ at $z=0$. Furthermore, we argue that the effect of
PNG on squeezed configurations of the halo bispectrum differs significantly
from that predicted by standard local bias approaches. Our predictions can be
easily confirmed, or invalidated, with N-body simulations. | Testing Emergent Gravity on Galaxy Cluster Scales: Verlinde's theory of Emergent Gravity (EG) describes gravity as an emergent
phenomenon rather than a fundamental force. Applying this reasoning in de
Sitter space leads to gravity behaving differently on galaxy and galaxy cluster
scales; this excess gravity might offer an alternative to dark matter. Here we
test these ideas using the data from the Coma cluster and from 58 stacked
galaxy clusters. The X-ray surface brightness measurements of the clusters at
$0.1 < z < 1.2$ along with the weak lensing data are used to test the theory.
We find that the simultaneous EG fits of the X-ray and weak lensing datasets
are significantly worse than those provided by General Relativity (with cold
dark matter). For the Coma cluster, the predictions from Emergent Gravity and
General Relativity agree in the range of 250 - 700 kpc, while at around 1 Mpc
scales, EG total mass predictions are larger by a factor of 2. For the cluster
stack the predictions are only in good agreement at around the 1 - 2 Mpc
scales, while for $r \gtrsim 10$ Mpc EG is in strong tension with the data.
According to the Bayesian information criterion analysis, GR is preferred in
all tested datasets; however, we also discuss possible modifications of EG that
greatly relax the tension with the data. |
Stellar populations of seven early-type dwarf galaxies and their nuclei: Dwarf galaxies are the numerically dominating population in the dense regions
of the universe. Although they seem to be simple systems at first view, the
stellar populations of dwarf elliptical galaxies (dEs) might be fairly complex.
Nucleated dEs are of particular interest, since a number of objects exhibit
different stellar populations in their nuclei and host galaxy. We present
stellar population parameters obtained from integrated optical spectra using a
Lick index analysis of seven nucleated dwarf elliptical galaxies and their
nuclei. After subtracting the scaled galaxy spectra from the nucleus spectra,
we compared them with one another and explore their stellar populations. As a
preliminary result, we find that the luminosity weighted ages of the nuclei
slightly lower than those of galaxies, however, we do not see any significant
difference in metallicity of the host galaxies and their nuclei. | Dependence of peculiar velocity on the host properties of the
gravitational wave sources and its impact on the measurement of Hubble
constant: Accurate measurement of the Hubble constant from standard sirens such as the
gravitational wave (GW) sources with electromagnetic counterparts relies on the
robust peculiar velocity correction of the redshift of the host galaxy. We show
in this work that the peculiar velocity of the host galaxies exhibits a
correlation with the properties of the host galaxy primarily such as its
stellar mass and this correlation also evolves with redshift. As the galaxies
of higher stellar mass tend to form in galaxies with higher halo masses which
are located in spatial regions having a non-linear fluctuation in the density
field of the matter distribution, the root mean square (RMS) peculiar velocity
of more massive galaxies is higher. As a result, depending on the formation
channel of the binary compact objects, the peculiar velocity contamination to
the galaxies will be different. The variation in the peculiar velocity of the
host galaxies can lead to a significant variation in the estimation of the
Hubble constant inferred using sources such as Binary Neutron Stars (BNSs). For
the network of GW detectors such as LIGO-Virgo-KAGRA (LVK), LVK+LIGO-India, and
Cosmic Explorer+Einstein Telescope, the variation in the precision of Hubble
constant inferred from 10 bright siren events can vary from $\sim 5.4 - 6\%$,
$\sim 4.5 - 5.3\%$ and $\sim 1.1 - 2.7\%$ respectively. The impact of such a
correlation between peculiar velocity and stellar mass on the inference of the
Hubble constant is not only limited to GW sources but also applicable to
type-Ia supernovae. |
Reconstruction of the primordial power spectra with Planck and BICEP2: By using the cubic spline interpolation method, we reconstruct the shape of
the primordial scalar and tensor power spectra from the recently released {\it
Planck} temperature and BICEP2 polarization cosmic microwave background data.
We find that the vanishing scalar index running ($\dd n_s/\dd\ln k$) model is
strongly disfavored at more than $3\sigma$ confidence level on the $k=0.0002$
Mpc$^{-1}$ scale. Furthermore, the power-law parameterization gives a blue-tilt
tensor spectrum, no matter using only the first 5 bandpowers $n_t =
1.20^{+0.56}_{-0.64} (95% {\rm CL})$ or the full 9 bandpowers $n_t =
1.24^{+0.51}_{-0.58} (95% {\rm CL})$ of BICEP2 data sets. Unlike the large
tensor-to-scalar ratio value ($r\sim0.20$) under the scale-invariant tensor
spectrum assumption, our interpolation approach gives $r_{0.002} < 0.060 (95%
{\rm CL})$ by using the first 5 bandpowers of BICEP2 data. After comparing the
results with/without BICEP2 data, we find that {\it Planck} temperature with
small tensor amplitude signals and BICEP2 polarization data with large tensor
amplitude signals dominate the tensor spectrum reconstruction on the large and
small scales, respectively. Hence, the resulting blue tensor tilt actually
reflects the tension between {\it Planck} and BICEP2 data. | Effects Of The Ionosphere On Ground-Based Detection Of The Global 21 CM
Signal From The Cosmic Dawn And The Dark Ages: Detection of the global HI 21 cm signal from Cosmic Dawn and Epoch of
Reionization is the key science driver for several ongoing ground-based and
future ground/space-based experiments. The crucial spectral features in the
global 21 cm signal (turning points) occur at low radio frequencies <100 MHz.
In addition to the human-generated RFI, Earth's ionosphere drastically corrupts
low-frequency radio observations from the ground. In this paper, we examine the
effects of time-varying ionospheric refraction, absorption and thermal emission
at these low radio frequencies and their combined effect on any ground-based
global 21 cm experiment. It should be noted that this is the first study of the
effect of a dynamic ionosphere on global 21 cm experiments. The fluctuations in
the ionosphere are influenced by solar activity with flicker noise
characteristics. The same characteristics are reflected in the ionospheric
corruption to any radio signal passing through the ionosphere. As a result, any
ground based observations of the faint global 21 cm signal are corrupted by
flicker noise (or "$1/f$" noise, where "$f$" is the dynamical frequency) which
scales as $\nu^{-2}$ (where $\nu$ is the frequency of observation) in the
presence of a bright galactic foreground ($\propto \nu^{-s}$, where $s$ is
radio spectral index). Hence, the calibration of the ionosphere for any such
experiment is critical. Any attempt to calibrate the ionospheric effects will
be subject to the inaccuracies in the current ionospheric measurements using
GPS ionospheric measurements, riometer measurements, ionospheric soundings,
etc. Even considering an optimistic improvement in the accuracy of GPS-TEC
(Total Electron Content) measurements, we conclude that the detection of the
global 21 cm signal below 100 MHz is best done from above the Earth's
atmosphere in orbit of the Moon. |
Gas expulsion by quasar-driven winds as a solution to the over-cooling
problem in galaxy groups and clusters: Galaxy groups are not scaled down versions of massive galaxy clusters - the
hot gas in groups (known as the intragroup medium, IGrM for short) is, on
average, less dense than the intracluster medium, implying that one or more
non-gravitational processes (e.g., radiative cooling, star formation, and/or
feedback) has had a relatively larger effect on groups. In the present study,
we compare a number of cosmological hydrodynamic simulations that form part of
the OverWhelmingly Large Simulations project to isolate and quantify the
effects of cooling and feedback from supernovae (SNe) and active galactic
nuclei (AGN) on the gas. This is achieved by comparing Lagrangian thermal
histories of the gas in the different runs, which were all started from
identical initial conditions. While radiative cooling, star formation, and SN
feedback are all necessary ingredients, only runs that also include AGN
feedback are able to successfully reproduce the optical and X-ray properties of
groups and low-mass clusters. We isolate how, when, and exactly what gas is
heated by AGN. Interestingly, we find that the gas that constitutes the
present-day IGrM is that which was not strongly heated by AGN. Instead, the low
median density/high median entropy of the gas in present-day groups is achieved
by the ejection of lower entropy gas from low-mass progenitor galaxies at high
redshift (primarily 2 < z < 4). This corresponds to the epoch when supermassive
black holes accreted most of their mass, typically at a rate that is close to
the Eddington limit (i.e., when the black holes are in a `quasar mode'). | BeyondPlanck IV. On end-to-end simulations in CMB analysis -- Bayesian
versus frequentist statistics: End-to-end simulations play a key role in the analysis of any
high-sensitivity CMB experiment, providing high-fidelity systematic error
propagation capabilities unmatched by any other means. In this paper, we
address an important issue regarding such simulations, namely how to define the
inputs in terms of sky model and instrument parameters. These may either be
taken as a constrained realization derived from the data, or as a random
realization independent from the data. We refer to these as Bayesian and
frequentist simulations, respectively. We show that the two options lead to
significantly different correlation structures, as frequentist simulations,
contrary to Bayesian simulations, effectively include cosmic variance, but
exclude realization-specific correlations from non-linear degeneracies.
Consequently, they quantify fundamentally different types of uncertainties, and
we argue that they therefore also have different and complementary scientific
uses, even if this dichotomy is not absolute. Before BeyondPlanck, most
pipelines have used a mix of constrained and random inputs, and used the same
hybrid simulations for all applications, even though the statistical
justification for this is not always evident. BeyondPlanck represents the first
end-to-end CMB simulation framework that is able to generate both types of
simulations, and these new capabilities have brought this topic to the
forefront. The Bayesian BeyondPlanck simulations and their uses are described
extensively in a suite of companion papers. In this paper we consider one
important applications of the corresponding frequentist simulations, namely
code validation. That is, we generate a set of 1-year LFI 30 GHz frequentist
simulations with known inputs, and use these to validate the core low-level
BeyondPlanck algorithms; gain estimation, correlated noise estimation, and
mapmaking. |
Eulerian BAO Reconstructions and N-Point Statistics: As galaxy surveys begin to measure the imprint of baryonic acoustic
oscillations (BAO) on large-scale structure at the sub-percent level,
reconstruction techniques that reduce the contamination from nonlinear
clustering become increasingly important. Inverting the nonlinear continuity
equation, we propose an Eulerian growth-shift reconstruction algorithm that
does not require the displacement of any objects, which is needed for the
standard Lagrangian BAO reconstruction algorithm. In real-space DM-only
simulations the algorithm yields 95% of the BAO signal-to-noise obtained from
standard reconstruction. The reconstructed power spectrum is obtained by adding
specific simple 3- and 4-point statistics to the pre-reconstruction power
spectrum, making it very transparent how additional BAO information from
higher-point statistics is included in the power spectrum through the
reconstruction process. Analytical models of the reconstructed density for the
two algorithms agree at second order. Based on similar modeling efforts, we
introduce four additional reconstruction algorithms and discuss their
performance. | Reconstructing the Cosmic Velocity and Tidal Fields with Galaxy Groups
Selected from the Sloan Digital Sky Survey: [abridge]Cosmic velocity and tidal fields are important for the understanding
of the cosmic web and the environments of galaxies, and can also be used to
constrain cosmology. In this paper, we reconstruct these two fields in SDSS
volume from dark matter halos represented by galaxy groups. Detailed mock
catalogues are used to test the reliability of our method against uncertainties
arising from redshift distortions, survey boundaries, and false identifications
of groups by our group finder. We find that both the velocity and tidal fields,
smoothed on a scale of ~2Mpc/h, can be reliably reconstructed in the inner
region (~66%) of the survey volume. The reconstructed tidal field is used to
split the cosmic web into clusters, filaments, sheets, and voids, depending on
the sign of the eigenvalues of tidal tensor. The reconstructed velocity field
nicely shows how the flows are diverging from the centers of voids, and
converging onto clusters, while sheets and filaments have flows that are
convergent along one and two directions, respectively. We use the reconstructed
velocity field and the Zel'dovich approximation to predict the mass density
field in the SDSS volume as function of redshift, and find that the mass
distribution closely follows the galaxy distribution even on small scales. We
find a large-scale bulk flow of about 117km/s in a very large volume,
equivalent to a sphere with a radius of ~170Mpc/h, which seems to be produced
by the massive structures associated with the SDSS Great Wall. Finally, we
discuss potential applications of our reconstruction to study the environmental
effects of galaxy formation, to generate initial conditions for simulations of
the local Universe, and to constrain cosmological models. The velocity, tidal
and density fields in the SDSS volume, specified on a Cartesian grid with a
spatial resolution of ~700kpc/h, are available from the authors upon request. |
Cosmology with the sub-millimetre galaxies magnification bias:
Tomographic Analysis: As in Gonzalez-Nuevo et al. 2017 and Bonavera et al. 2019, the high-z
sub-millimetre galaxies can be used as background sample for gravitational
lensing studies thanks to their magnification bias. In particular, as in
Bonavera et al. 2020 the magnification bias can be exploited in order to
constrain the free parameters of a Halo Occupation Distribution (HOD) model and
some of the main cosmological parameters. In this work the magnification bias
has been evaluated as cosmological tool in a tomographic set up. The
cross-correlation function (CCF) data have been used to jointly constrain the
astrophysical parameters $M_{min}$, $M_{1}$ and $\alpha$ in each one of the
selected redshift bins and the $\Omega_{M}$, $\sigma_{8}$, and $H_0$
cosmological ones ($\Lambda$CDM). Moreover, we explore the possible time
evolution of the dark energy density introducing also the $\omega_0, \omega_a$
parameters in the joint analysis ($\omega_0$CDM and $\omega_0\omega_a$CDM). The
CCF has been measured between a foreground spectroscopic sample of GAMA
galaxies that has been divided into four redshift bins (0.1-0.2, 0.2-0.3,
0.3-0.5 and 0.5-0.8) and a sample of H-ATLAS galaxies with photometric
redshifts >1.2. The CCF is modelled using a description that depends on HOD and
cosmological parameters that are estimated with MCMC in different cases. For
the $\Lambda$CDM model, the analysis yields a maximum posterior value at 0.26
with $[0.17,0.41]$ 68\% C.I. for $\Omega_M$ and at 0.87 with $[0.75,1]$ 68\%
C.I. for $\sigma_8$. With our current results $H_0$ is not yet constrained.
With the $\omega_0$CDM model, the constraints on $\Omega_M$ and $\sigma_8$ are
similar, but we found a maximum posterior value for $\omega_0$ at -1 with
$[-1.56, -0.47]$ 68\% C.I. In the $\omega_0\omega_a$CDM model, the results are
-1.09 with $[-1.72, -0.66]$ 68\% C.I. for $\omega_0$ and -0.19 with $[-1.88,
1.48]$ 68\% C.I. for $\omega_a$. | Galaxy clustering using photometric redshifts: We investigate the evolution of the galaxy two point correlation function
(CF) over a wide redshift range, 0.2 < z < 3. For the first time the systematic
analysis covers the redshifts above 1 - 1.5. The catalogue of ~250000 galaxies
with i+ < 25 and known photometric redshifts in the Subaru Deep field is used.
The galaxies are divided into three luminosity classes and several
distance/redshift bins. First, the 2D CF is determined for each luminosity
class and distance bin. Calculations are based on the quantitative differences
between the surface distributions of galaxy pairs with comparable and
distinctly different photometric redshifts. The power law approximation for the
CF is used. A limited accuracy of photometric redshifts as compared to the
spectroscopic ones has been examined and taken into account. Then, the 3D
functions for all the selected luminosities and distances are calculated. The
power-law parameters of the CF, the slope and the correlation length, are
determined. Both parameters do not show strong variations over the whole
investigated redshift range. The slope of the luminous galaxies appears to be
consistently steeper than that for the fainter ones. The linear bias factor,
b(z), grows systematically with redshift; assuming the local normalization b(0)
= 1.1-1.2, the bias reaches 3 - 3.5 at the high redshift limit. |
On the suspected timing-offset-induced calibration error in the
Wilkinson microwave anisotropy probe time-ordered data: In the time-ordered data (TOD) files of the WMAP CMB observations, there is
an undocumented timing offset of -25.6 ms between the spacecraft attitude and
radio flux density timestamps. If the offset induced an error during
calibration of the raw TOD, then estimates of the WMAP CMB quadrupole might be
substantially in error. A timing error during calibration would not only induce
an artificial quadrupole-like signal in the mean sky map, it would also add
variance per pixel. This variance would be present in the calibrated TOD.
Low-resolution map-making as a function of timing offset should show a minimum
variance for the correct timing offset. Three years of the calibrated, filtered
WMAP 3-year TOD are compiled into sky maps at HEALPix resolution N_side=8,
individually for each of the K, Ka, Q, V and W band differencing assemblies
(DA's), as a function of timing offset. The median per map of the temperature
fluctuation variance per pixel is calculated and minimised against timing
offset. Minima are clearly present. The timing offsets that minimise the median
variance are -38 \pm 8 ms (K, Ka), -27 \pm 3 ms (Q), -43 \pm 8 ms (V), and -47
\pm 194 ms (W), i.e. an average of -30 \pm 3 ms, where the WMAP collaboration's
preferred offset is 0 \pm 1.7 ms. A non-parametric bootstrap analysis rejects
the latter at a significance of 99.999%. The hypothesis of a -25.6 ms offset,
suggested by Liu, Xiong & Li from the TOD file timing offset, is consistent
with these minima. It is difficult to avoid the conclusion that the WMAP
calibrated TOD and inferred maps are wrongly calibrated. CMB quadrupole
estimates (3/pi)C_2 based on the incorrectly calibrated TOD are overestimated
by roughly 64 \pm 6% (KQ85 mask) to 94 \pm 10% (KQ75 mask). Ideally, the WMAP
map-making pipelines should be redone starting from the uncalibrated TOD and
using the -25.6 ms timing offset correction. | Primordial black holes from metric preheating: mass fraction in the
excursion-set approach: We calculate the mass distribution of Primordial Black Holes (PBHs) produced
during metric preheating. After inflation, the oscillations of the inflaton at
the bottom of its potential source a parametric resonant instability for
small-scale scalar perturbations, that may collapse into black holes. After
reviewing in a pedagogical way different techniques that have been developed in
the literature to compute mass distributions of PBHs, we focus on the
excursion-set approach. We derive a Volterra integral equation that is free of
a singularity sometimes encountered, and apply it to the case of metric
preheating. We find that if the energy density at which the instability stops,
$\rho_\Gamma$, is sufficiently smaller than the one at which inflation ends,
$\rho_\mathrm{end}$, namely if $\rho_\Gamma^{1/4}/\rho_\mathrm{end}^{1/4}<
10^{-5}(\rho_\mathrm{end}^{1/4}/10^{16}\mathrm{GeV})^{3/2}$, then PBHs dominate
the universe content at the end of the oscillatory phase. This confirms the
previous analysis of arXiv:1907.04236 . By properly accounting for the
"cloud-in-cloud" mechanism, we find that the mass distribution is more
suppressed at low masses than previously thought, and peaks several orders of
magnitude above the Hubble mass at the end of inflation. The peak mass ranges
from $10$ g to stellar masses, giving rise to different possible cosmological
effects that we discuss. |
Kiloparsec-scale Spatial Offsets in Double-peaked Narrow-line Active
Galactic Nuclei. I. Markers for Selection of Compelling Dual Active Galactic
Nucleus Candidates: Merger-remnant galaxies with kpc-scale separation dual active galactic nuclei
(AGNs) should be widespread as a consequence of galaxy mergers and triggered
gas accretion onto supermassive black holes, yet very few dual AGNs have been
observed. Galaxies with double-peaked narrow AGN emission lines in the Sloan
Digital Sky Survey are plausible dual AGN candidates, but their double-peaked
profiles could also be the result of gas kinematics or AGN-driven outflows and
jets on small or large scales. To help distinguish between these scenarios, we
have obtained spatial profiles of the AGN emission via follow-up long-slit
spectroscopy of 81 double-peaked narrow-line AGNs in SDSS at 0.03 < z < 0.36
using Lick, Palomar, and MMT Observatories. We find that all 81 systems exhibit
double AGN emission components with ~kpc projected spatial separations on the
sky, which suggests that they are produced by kpc-scale dual AGNs or kpc-scale
outflows, jets, or rotating gaseous disks. In addition, we find that the
subsample (58%) of the objects with spatially compact emission components may
be preferentially produced by dual AGNs, while the subsample (42%) with
spatially extended emission components may be preferentially produced by AGN
outflows. We also find that for 32% of the sample the two AGN emission
components are preferentially aligned with the host galaxy major axis, as
expected for dual AGNs orbiting in the host galaxy potential. Our results both
narrow the list of possible physical mechanisms producing the double AGN
components, and suggest several observational criteria for selecting the most
promising dual AGN candidates from the full sample of double-peaked narrow-line
AGNs. Using these criteria, we determine the 17 most compelling dual AGN
candidates in our sample. | Nuclear Star Clusters - Structure and Stellar Populations: This is an overview of nuclear star cluster observations, covering their
structure, stellar populations, kinematics and possible connection to black
holes at the centers of galaxies. |
Confidence Level Estimator for cosmological model (Research Note): Models of the Universe like the Concordance Model today used to interpret
cosmological observations give expectation values for many cosmological
observable so accurate that frequently peoples speak of Precision Cosmology.
The quoted accuracies however do not include the effects of priors used in
optimizing the Model nor allow to evaluate the confidence one can attach to the
Model. We suggest an estimator of the Confidence Level for Models and the
accuracies of the expectation values of the Model observables | Apparent Superluminality of Lensed Gravitational Waves: We consider gravitational wave (GW) sources with an associated
electromagnetic (EM) counterpart, and analyze the time delay between both
signals in the presence of lensing. If GWs have wavelengths comparable to the
Schwarzschild radius of astrophysical lenses, they must be treated with wave
optics, whereas EM waves are typically well within the approximation of
geometric optics. With concrete examples, we confirm that the GW signal never
arrives before its EM counterpart, if both are emitted at the same time.
However, during the inspiral of a binary, peaks of the GW waveform can arrive
before their EM counterpart. We stress this is only an apparent superluminality
since the GW waveform is both distorted and further delayed with respect to
light. In any case, measuring the multi-messenger time delay and correctly
interpreting it has important implications for unveiling the distribution of
lenses, testing the nature of gravity, and probing the cosmological expansion
history. |
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves: CMB-S4---the next-generation ground-based cosmic microwave background (CMB)
experiment---is set to significantly advance the sensitivity of CMB
measurements and enhance our understanding of the origin and evolution of the
Universe, from the highest energies at the dawn of time through the growth of
structure to the present day. Among the science cases pursued with CMB-S4, the
quest for detecting primordial gravitational waves is a central driver of the
experimental design. This work details the development of a forecasting
framework that includes a power-spectrum-based semi-analytic projection tool,
targeted explicitly towards optimizing constraints on the tensor-to-scalar
ratio, $r$, in the presence of Galactic foregrounds and gravitational lensing
of the CMB. This framework is unique in its direct use of information from the
achieved performance of current Stage 2--3 CMB experiments to robustly forecast
the science reach of upcoming CMB-polarization endeavors. The methodology
allows for rapid iteration over experimental configurations and offers a
flexible way to optimize the design of future experiments given a desired
scientific goal. To form a closed-loop process, we couple this semi-analytic
tool with map-based validation studies, which allow for the injection of
additional complexity and verification of our forecasts with several
independent analysis methods. We document multiple rounds of forecasts for
CMB-S4 using this process and the resulting establishment of the current
reference design of the primordial gravitational-wave component of the Stage-4
experiment, optimized to achieve our science goals of detecting primordial
gravitational waves for $r > 0.003$ at greater than $5\sigma$, or, in the
absence of a detection, of reaching an upper limit of $r < 0.001$ at $95\%$ CL. | Exploring short gamma-ray bursts as gravitational-wave standard sirens: Recent observations support the hypothesis that a large fraction of
"short-hard" gamma-ray bursts (SHBs) are associated with compact binary
inspiral. Since gravitational-wave (GW) measurements of well-localized
inspiraling binaries can measure absolute source distances, simultaneous
observation of a binary's GWs and SHB would allow us to independently determine
both its luminosity distance and redshift. Such a "standard siren" (the GW
analog of a standard candle) would provide an excellent probe of the relatively
nearby universe's expansion, complementing other standard candles. In this
paper, we examine binary measurement using a Markov Chain Monte Carlo technique
to build the probability distributions describing measured parameters. We
assume that each SHB observation gives both sky position and the time of
coalescence, and we take both binary neutron stars and black hole-neutron star
coalescences as plausible SHB progenitors. We examine how well parameters
particularly distance) can be measured from GW observations of SHBs by a range
of ground-based detector networks. We find that earlier estimates overstate how
well distances can be measured, even at fairly large signal-to-noise ratio. The
fundamental limitation to determining distance proves to be a degeneracy
between distance and source inclination. Overcoming this limitation requires
that we either break this degeneracy, or measure enough sources to broadly
sample the inclination distribution. (Abridged) |
Decaying neutrinos: The long way to isotropy: We investigate a scenario in which neutrinos are coupled to a pseudoscalar
degree of freedom $\ph$ and where decays $\nu_1 \to \nu_2+\ph$ and inverse
decays are the responsible mechanism for obtaining equilibrium. In this context
we discuss the implication of the invisible neutrino decay on the
neutrino-pseudoscalar coupling constant and the neutrino lifetime. Assuming the
realistic scenario of a thermal background of neutrinos and pseudoscalar we
update the bound on the (off-diagonal) neutrino-pseudoscalar coupling constant
to $g<2.6\times10^{-13}$ and the bound on the neutrino lifetime to
$\tau<1\times10^{13}\,\rm{s}$. Furthermore we confirm analytically that kinetic
equilibrium is delayed by two Lorentz $\ga$--factors -- one for time dilation
of the (decaying) neutrino lifetime and one from the opening angle. We have
also confirmed this behavior numerically. | The Tilt of Primordial Gravitational Waves Spectra from BICEP2: In this paper we constrain the tilt of the spectra of primordial
gravitational waves from Background Imaging of Cosmic Extragalactic
Polarization (BICEP2) data only. We find $r=0.21_{-0.10}^{+0.04}$ and
$n_t=-0.06_{-0.23}^{+0.25}$ (at $68\%$ C.L.) which implies that a
scale-invariant primordial gravitational waves spectra is consistent with
BICEP2 nicely. Our results provide strong evidence for supporting inflation
model, and the alternative models, for example the ekpyrotic model which
predicts $n_t=2$, are ruled out at more than $5\sigma$ significance. |
A New Insight into the Classification of Type Ia Supernovae: Type Ia Supernovae (SNe Ia) spectra are compared regarding the coefficient of
the largest wavelet scale in their decomposition. Two distinct subgroups were
identified and their occurrence is discussed in light of use of SNe Ia as
cosmological probes. Apart from the group of normal SNe, another trend
characterised by intrinsically redder colours is consisted of many different SN
events that exhibit diverse properties, including the interaction with the
circumstellar material, the existence of specific shell-structure in or
surrounding the SN ejecta or super-Chandrasekhar mass progenitors. Compared
with the normal objects, these SNe may violate the standard width-luminosity
correction, which could influence the cosmological results if they were all
calibrated equally, since their fraction among SNe Ia is not negligible when
performing precision cosmology. Using largest wavelet scale coefficient in
combination with long-baseline B-I colours, we show how to disentangle SN
intrinsic colour from the part that corresponds to the reddening due to dust
extinction in the host galaxy in the SALT2 colour parameter c, discussing how
the intrinsic colour differences may explain the different reddening laws for
two subsamples. There are wavelength intervals for which the measured largest
scale coefficient is invariant to the additional extinction applied to a
spectrum. Combination of wavelet coefficients measured in different wavelength
intervals can be used to develop a technique that allows for estimation of
extinction. | Multiband gravitational wave cosmology with stellar origin black hole
binaries: Massive stellar origin black hole binaries (SBHBs), originating from stars
above the pair-instability mass gap, are primary candidates for multiband
gravitational wave (GW) observations. Here we study the possibility to use them
as effective dark standard sirens to constrain cosmological parameters. The
long lasting inspiral signal emitted by these systems is accessible by the
future $Laser \; Interferometer \; Space \; Antenna$ (LISA), while the late
inspiral and merger are eventually detected by third generation ground-based
telescopes such as the $Einstein \; Telescope$ (ET). The direct measurement of
the luminosity distance and the sky position to the source, together with the
inhomogeneous redshift distribution of possible host galaxies, allow us to
infer cosmological parameters by probabilistic means. The efficiency of this
statistical method relies in high parameter estimation performances. We show
that this multiband approach allows a precise determination of the Hubble
constant H$_0$ with just ${\cal O}(10)$ detected sources. For selected SBHB
population models, assuming $4$ ($10$) years of LISA observations, we find that
H$_0$ is typically determined at $\sim 2\%$ ($\sim 1.5\%$), whereas $\Omega_m$
is only mildly constrained with a typical precision of $30\%$ ($20\%$). We
discuss the origin of some outliers in our final estimates and we comment on
ways to reduce their presence. |
Using Megamaser Disks to Probe Black Hole Accretion: We examine the alignment between H_2O megamaser disks on sub-pc scales with
circumnuclear disks and bars on <500 pc scales observed with HST/WFC3. The HST
imaging reveals young stars, indicating the presence of gas. The megamaser
disks are not well aligned with the circumnuclear bars or disks as traced by
stars in the HST images. We speculate on the implications of the observed
misalignments for fueling supermassive black holes in gas-rich spiral galaxies.
In contrast, we find a strong preference for the rotation axes of the megamaser
disks to align with radio continuum jets observed on >50 pc scales, in those
galaxies for which radio continuum detections are available. Sub-arcsecond
observations of molecular gas with ALMA will enable a more complete
understanding of the interplay between circumnuclear structures. | Electron-positron plasma in GRBs and in cosmology: Electron-positron plasma is believed to play imporant role both in the early
Universe and in sources of Gamma-Ray Bursts (GRBs). We focus on analogy and
difference between physical conditions of electron-positron plasma in the early
Universe and in sources of GRBs. We discuss a) dynamical differences, namely
thermal acceleration of the outflow in GRB sources vs cosmological
deceleration; b) nuclear composition differences as synthesis of light elements
in the early Universe and possible destruction of heavy elements in GRB plasma;
c) different physical conditions during last scattering of photons by
electrons. Only during the acceleration phase of the optically thick
electron-positron plasma comoving observer may find it similar to the early
Universe. This similarity breaks down during the coasting phase. Reprocessing
of nuclear abundances may likely take place in GRB sources. Heavy nuclear
elements are then destroyed, resulting mainly in protons with small admixture
of helium. Unlike the primordial plasma which recombines to form neutral
hydrogen, and emits the Cosmic Microwave Background Radiation, GRB plasma does
not cool down enough to recombine. |
Building a control sample for galaxy pairs: Several observational works have attempted to isolate the effects of galaxy
interactions by comparing galaxies in pairs with isolated galaxies.
However, different authors have proposed different ways to build these
so-called control samples (CS). By using mock galaxy catalogues of the SDSS-DR4
built up from the Millennium Simulation, we explore how the way of building a
CS might introduce biases which could affect the interpretation of results. We
make use of the fact that the physics of interactions is not included in the
semianalytic model, to infer that any difference between the mock control and
pair samples can be ascribed to selection biases. Thus, we find that galaxies
in pairs artificially tend to be older and more bulge-dominated, and to have
less cold gas and different metallicities than their isolated counterparts.
Also because of a biased selection, galaxies in pairs tend to live in higher
density environments, and in haloes of larger masses. We find that imposing
constraints on redshift, stellar masses and local densities diminishes the
selection biases by ~70%. Based on these findings, we suggest observers how to
build an unique and unbiased CS in order to reveal the effect of galaxy
interactions. | Primordial Black Holes With Multi-Modal Mass Spectra: A mechanism for generating primordial black-hole mass spectra with many
spikes is proposed and investigated. This mechanism relies on the choice of
non-Bunch-Davies vacua, these leading to oscillatory features in the
inflationary power spectrum. This in turn generates oscillations in the
primordial black-hole mass function with exponentially enhanced spikes. This
``multimodal'' effect is demonstrated for most of the well-studied models of
primordial black-hole formation. |
An HI Survey of Six Local Group Analogs. II. HI properties of group
galaxies: We have conducted an HI 21 cm emission-line survey of six loose groups of
galaxies chosen to be analogs to the Local Group. The survey was conducted
using the Parkes Multibeam instrument and the Australia Telescope Compact Array
(ATCA) over a ~1 Mpc^2 area and covering the full depth of each group, with a
M(HI) sensitivity of ~7x10^5 M(sun). Our survey detected 110 sources, 61 of
which are associated with the six groups. All of these sources were confirmed
with ATCA observations or were previously cataloged by HIPASS. The sources all
have optical counterparts and properties consistent with dwarf irregular or
late-type spiral galaxies. We present here the HI properties of the groups and
their galaxies. We derive an HI mass function for the groups that is consistent
with being flatter than the equivalent field HIMF. We also derive a circular
velocity distribution function, tracing the luminous dark matter halos in the
groups, that is consistent with those of the Local Group and HIPASS galaxies,
both of which are shallower than that of clusters or predictions from CDM
models of galaxy formation. | The December 2009 gamma-ray flare of 3C 454.3: the multifrequency
campaign: During the month of December, 2009 the blazar 3C 454.3 became the brightest
gamma-ray source in the sky, reaching a peak flux F ~2000E-8 ph/cm2/s for E >
100 MeV. Starting in November, 2009 intensive multifrequency campaigns
monitored the 3C 454 gamma-ray outburst. Here we report the results of a
2-month campaign involving AGILE, INTEGRAL, Swift/XRT, Swift/BAT, RossiXTE for
the high-energy observations, and Swift/UVOT, KANATA, GRT, REM for the
near-IR/optical/UV data. The GASP/WEBT provided radio and additional optical
data. We detected a long-term active emission phase lasting ~1 month at all
wavelengths: in the gamma-ray band, peak emission was reached on December 2-3,
2009. Remarkably, this gamma-ray super-flare was not accompanied by
correspondingly intense emission in the optical/UV band that reached a level
substantially lower than the previous observations in 2007-2008. The lack of
strong simultaneous optical brightening during the super-flare and the
determination of the broad-band spectral evolution severely constrain the
theoretical modelling. We find that the pre- and post-flare broad-band behavior
can be explained by a one-zone model involving SSC plus external Compton
emission from an accretion disk and a broad-line region. However, the spectra
of the Dec. 2-3, 2009 super-flare and of the secondary peak emission on Dec. 9,
2009 cannot be satisfactorily modelled by a simple one-zone model. An
additional particle component is most likely active during these states. |
A High Fidelity Sample of Cold Front Clusters from the Chandra Archive: This paper presents a sample of "cold front" clusters selected from the
Chandra archive. The clusters are selected based purely on the existence of
surface brightness edges in their Chandra images which are modeled as density
jumps. A combination of the derived density and temperature jumps across the
fronts is used to select nine robust examples of cold front clusters:
1ES0657-558, Abell 1201, Abell 1758N, MS1455.0+2232, Abell 2069, Abell 2142,
Abell 2163, RXJ1720.1+2638, and Abell 3667. This sample is the subject of an
ongoing study aimed at relating cold fronts to cluster merger activity, and
understanding how the merging environment affects the cluster constituents.
Here, temperature maps are presented along with the Chandra X-ray images. A
dichotomy is found in the sample in that there exists a subsample of cold front
clusters which are clearly mergers based on their X-ray morphologies, and a
second subsample which harbor cold fronts, but have surprisingly relaxed X-ray
morphologies, and minimal evidence for merger activity at other wavelengths.
For this second subsample, the existence of a cold front provides the sole
evidence for merger activity at X-ray wavelengths. We discuss how cold fronts
can provide additional information which may be used to constrain merger
histories, and also the possibility of using cold fronts to distinguish major
and minor mergers. | A new approach to simulating collisionless dark matter fluids: Recently, we have shown how current cosmological N-body codes already follow
the fine grained phase-space information of the dark matter fluid. Using a
tetrahedral tesselation of the three-dimensional manifold that describes
perfectly cold fluids in six-dimensional phase space, the phase-space
distribution function can be followed throughout the simulation. This allows
one to project the distribution function into configuration space to obtain
highly accurate densities, velocities, and velocity dispersions. Here, we
exploit this technique to show first steps on how to devise an improved
particle-mesh technique. At its heart, the new method thus relies on a
piecewise linear approximation of the phase space distribution function rather
than the usual particle discretisation. We use pseudo-particles that
approximate the masses of the tetrahedral cells up to quadrupolar order as the
locations for cloud-in-cell (CIC) deposit instead of the particle locations
themselves as in standard CIC deposit. We demonstrate that this modification
already gives much improved stability and more accurate dynamics of the
collisionless dark matter fluid at high force and low mass resolution. We
demonstrate the validity and advantages of this method with various test
problems as well as hot/warm-dark matter simulations which have been known to
exhibit artificial fragmentation. This completely unphysical behaviour is much
reduced in the new approach. The current limitations of our approach are
discussed in detail and future improvements are outlined. |
Snowmass 2021 CMB-S4 White Paper: This Snowmass 2021 White Paper describes the Cosmic Microwave Background
Stage 4 project CMB-S4, which is designed to cross critical thresholds in our
understanding of the origin and evolution of the Universe, from the highest
energies at the dawn of time through the growth of structure to the present
day. We provide an overview of the science case, the technical design, and
project plan. | First-year Sloan Digital Sky Survey-II (SDSS-II) supernova results:
consistency and constraints with other intermediate-redshift datasets: We present an analysis of the luminosity distances of Type Ia Supernovae from
the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey in conjunction with
other intermediate redshift (z<0.4) cosmological measurements including
redshift-space distortions from the Two-degree Field Galaxy Redshift Survey
(2dFGRS), the Integrated Sachs-Wolfe (ISW) effect seen by the SDSS, and the
latest Baryon Acoustic Oscillation (BAO) distance scale from both the SDSS and
2dFGRS. We have analysed the SDSS-II SN data alone using a variety of
"model-independent" methods and find evidence for an accelerating universe at
>97% level from this single dataset. We find good agreement between the
supernova and BAO distance measurements, both consistent with a
Lambda-dominated CDM cosmology, as demonstrated through an analysis of the
distance duality relationship between the luminosity (d_L) and angular diameter
(d_A) distance measures. We then use these data to estimate w within this
restricted redshift range (z<0.4). Our most stringent result comes from the
combination of all our intermediate-redshift data (SDSS-II SNe, BAO, ISW and
redshift-space distortions), giving w = -0.81 +0.16 -0.18(stat) +/- 0.15(sys)
and Omega_M=0.22 +0.09 -0.08 assuming a flat universe. This value of w, and
associated errors, only change slightly if curvature is allowed to vary,
consistent with constraints from the Cosmic Microwave Background. We also
consider more limited combinations of the geometrical (SN, BAO) and dynamical
(ISW, redshift-space distortions) probes. |
New- vs. chaotic-inflations: We show that "spiralized" models of new-inflation can be experimentally
identified mostly by their positive spectral running in direct contrast with
most chaotic-inflation models which have negative runnings typically in the
range of $\mathcal{O}(10^{-4}-10^{-3})$. | CO Observations of the Host Galaxy of GRB000418 at z = 1.1: We performed CO(J=2-1) observations of the host galaxy of GRB000418 at
z=1.1181 with the Plateau de Bure Interferometer. Previous studies show that
the host galaxy has properties similar to those of an ultraluminous infrared
galaxy (ULIRG). The star-formation rate (SFR) of the host galaxy as derived
from submillimeter and radio continuum emission is a few 100 M_sun/yr, which is
an order of magnitude greater than the SFR derived from optical line emission.
The large discrepancy between the SFRs derived from different observing
wavelengths indicates the presence of a bulk of dust-obscured star formation
and molecular gas that is enough to sustain the intense star formation. We
failed to detect CO emission and derived 2sigma upper limits on the velocity
integrated CO(2-1) luminosity of L'CO < 6.9 x 10^9 K km/s/pc^2 and the
molecular gas mass of M(H2) < 5.5 x 10^9 M_sun by adopting a velocity width of
300 km/s and a CO-to-H2 conversion factor of alpha_CO = 0.8 M_sun/(K
km/s/pc^2), which are standard values for ULIRGs. The lower limit on the ratio
of far-infrared luminosity to CO luminosity, a measure of the star-formation
efficiency, is higher compared to that of other gamma-ray burst hosts and other
galaxy populations, which is consistent with active star formation taking place
in this galaxy. |
Extreme value statistics of smooth random Gaussian fields: We consider the Gumbel or extreme value statistics describing the
distribution function p_G(x_max) of the maximum values of a random field x
within patches of fixed size. We present, for smooth Gaussian random fields in
two and three dimensions, an analytical estimate of p_G which is expected to
hold in a regime where local maxima of the field are moderately high and weakly
clustered. When the patch size becomes sufficiently large, the negative of the
logarithm of the cumulative extreme value distribution is simply equal to the
average of the Euler Characteristic of the field in the excursion x > x_max
inside the patches. The Gumbel statistics therefore represents an interesting
alternative probe of the genus as a test of non Gaussianity, e.g. in cosmic
microwave background temperature maps or in three-dimensional galaxy catalogs.
It can be approximated, except in the remote positive tail, by a negative
Weibull type form, converging slowly to the expected Gumbel type form for
infinitely large patch size. Convergence is facilitated when large scale
correlations are weaker. We compare the analytic predictions to numerical
experiments for the case of a scale-free Gaussian field in two dimensions,
achieving impressive agreement between approximate theory and measurements. We
also discuss the generalization of our formalism to non-Gaussian fields. | Observational scalings testing modified gravity: We consider different observational effects to test modified gravity approach
involving the cosmological constant in the common description of the dark
matter and the dark energy. We obtain upper limits for the cosmological
constant by studying the scaling relations for 12 nearby galaxy clusters, the
radiated power from gravitational waves and the Tully-Fisher relation for super
spiral galaxies. Our estimations reveal that, for all these cases the upper
limits for $\Lambda$ are consistent with its actual value predicted by the
cosmological observations. |
Constraining Variable High Velocity Winds from Broad Absorption Line
Quasars with Multi-Epoch Spectroscopy: Broad absorption line (BAL) quasars probe the high velocity gas ejected by
luminous accreting black holes. BAL variability timescales place constraints on
the size, location, and dynamics of the emitting and absorbing gas near the
supermassive black hole. We present multi-epoch spectroscopy of seventeen BAL
QSOs from the Sloan Digital Sky Survey (SDSS) using the Fred Lawrence Whipple
Observatory's 1.5m telescope's FAST Spectrograph. These objects were identified
as BALs in SDSS, observed with Chandra, and then monitored with FAST at
observed-frame cadences of 1, 3, 9, 27, and 81 days, as well as 1 and 2 years.
We also monitor a set of non-BAL quasars with matched redshift and luminosity
as controls. We identify significant variability in the BALs, particularly at
the 1 and 2 year cadences, and use its magnitude and frequency to constrain the
outflows impacting the broad absorption line region. | Using SKA Rotation Measures to Reveal the Mysteries of the Magnetised
Universe: We know that magnetic fields are pervasive across all scales in the Universe
and over all of cosmic time and yet our understanding of many of the properties
of magnetic fields is still limited. We do not yet know when, where or how the
first magnetic fields in the Universe were formed, nor do we fully understand
their role in fundamental processes such as galaxy formation or cosmic ray
acceleration or how they influence the evolution of astrophysical objects. The
greatest challenge to addressing these issues has been a lack of deep, broad
bandwidth polarimetric data over large areas of the sky. The Square Kilometre
Array will radically improve this situation via an all-sky polarisation survey
that delivers both high quality polarisation imaging in combination with
observations of 7-14 million extragalactic rotation measures. Here we summarise
how this survey will improve our understanding of a range of astrophysical
phenomena on scales from individual Galactic objects to the cosmic web. |
On constraining Cosmology and the Halo Mass Function with Weak
Gravitational Lensing: The discrepancy between the weak lensing (WL) and the {\it Planck}
measurements of $S_8$ has been a subject of several studies. These studies tend
to show that a suppression of the amplitude of the mass power spectrum $P(k)$
at high $k$ could resolve it. The WL signal at small-scale is sensitive to
various effects, such as baryonic effects and intrinsic alignment. The accuracy
of $P(k)$ depends on the modelling precision of these effects. A common
approach for calculating $P(k)$ relies on a halo model. Amongst the various
components necessary for the construction of $P(k)$, the halo mass function
(HMF) is an important one. Traditionally, the HMF has been assumed to follow a
fixed model. Recent literature shows that baryonic physics, amongst several
other factors, could affect the HMF. In this study, we investigate the impact
of allowing the HMF to vary. This provides a way of testing the validity of the
halo model-HMF calibration using data. We find that the {\it Planck} cosmology
is not compatible with the vanilla HMF for both the DES-y3 and the KiDS-1000
data. When the cosmology and the HMF parameters are allowed to vary, the {\it
Planck} cosmology is no longer in tension. The modified HMF predicts a matter
power spectrum with a $\sim 25\%$ power loss at $k\sim 1~{\rm h/Mpc}$, in
agreement with the recent studies. We show that Stage IV surveys will be able
to measure the HMF parameters with a few percent accuracy. | Scrutinizing Early Dark Energy models through CMB lensing: We investigate early dark energy models in the context of the lensing anomaly
by considering two different Cosmic Microwave Background (CMB) datasets: a
complete Planck, and a second one primarily based on SPTPol and Planck
temperature ($l<1000$). We contrast the effects of allowing the
phenomenological lensing amplitude ($\Al$) to be different from unity. We find
that the fraction of early dark energy, while not immediately affected by the
lensing anomaly, can induce mild deviations, through correlations with the
parameters $H_0$ and $S_8$. {We extend the analysis also by marginalizing the
Newtonian lensing potential, finding a $\gtrsim 1\sigma$ deviation, when
allowing for an amplitude rescaling and scale-dependence. Modeling the
rescaling of the theory lensing potential and the acoustic smoothing of the CMB
spectra, we find that only to a moderate level the anomaly can be addressed by
modifying the lensing signal itself and that an additional $\Al \sim 1.1$ at
$\sim 2\sigma$ significance should be addressed by pre-recombination physics.
Finally, we also comment on the lensing anomaly in a non-flat ($\Omega_{\rm k}
\neq 0$) scenario, finding that the late-time flatness of the universe is
robust and not correlated with the additional smoothing in the CMB spectra. |
Early radio and X-ray observations of the youngest nearby type Ia
supernova PTF11kly (SN 2011fe): On August 24 (UT) the Palomar Transient Factory (PTF) discovered PTF11kly (SN
2011fe), the youngest and most nearby type Ia supernova (SN Ia) in decades. We
followed this event up in the radio (centimeter and millimeter bands) and X-ray
bands, starting about a day after the estimated explosion time. We present our
analysis of the radio and X-ray observations, yielding the tightest constraints
yet placed on the pre-explosion mass-loss rate from the progenitor system of
this supernova. We find a robust limit of dM/dt<10^-8 (w/100 km/s) [M_solar/yr]
from sensitive X-ray non-detections, as well as a similar limit from radio
data, which depends, however, on assumptions about microphysical parameters. We
discuss our results in the context of single-degenerate models for SNe Ia and
find that our observations modestly disfavor symbiotic progenitor models
involving a red giant donor, but cannot constrain systems accreting from
main-sequence or sub-giant stars, including the popular supersoft channel. In
view of the proximity of PTF11kly and the sensitivity of our prompt
observations we would have to wait for a long time (decade or longer) in order
to more meaningfully probe the circumstellar matter of Ia supernovae. | On the lack of stellar bars in Coma dwarf galaxies: We present a study of the bar fraction in the Coma cluster galaxies based on
a sample of ~190 galaxies selected from the SDSS-DR6 and observed with the
Hubble Space Telescope (HST) Advanced Camera for Survey (ACS). The
unprecedented resolution of the HST-ACS images allows us to explore the
presence of bars, detected by visual classification, throughout a luminosity
range of 9 mag (-23 < M_r < -14), permitting us to study the poor known region
of dwarf galaxies. We find that bars are hosted by galaxies in a tight range of
both luminosities (-22 < M_r < -17) and masses (10^9 < M*/Msun < 10^11). In
addition, we find that the bar fraction does not vary significantly when going
from the center to the cluster outskirts, implying that cluster environment
plays a second-order role in bar formation/evolution. The shape of the bar
fraction distribution with respect to both luminosity and mass is well matched
by the luminosity distribution of disk galaxies in Coma, indicating that bars
are good tracers of cold stellar disks. |
Fingerprint of Galactic Loop I on polarized microwave foregrounds: Context: Currently, detection of the primordial gravitational waves by the
B-mode of Cosmic Microwave Background (CMB) is primarily limited by our
knowledge of the polarized microwave foreground emissions. Thus improvements of
the foreground analysis are necessary. As revealed
in~\cite{2018arXiv180410382L}, the E-mode and B-mode of the polarized
foreground have noticeable different properties, both in morphology and
frequency spectrum, suggesting that they arise from different physical
processes, and need to be studied separately.
Aims: I will study the polarized emission from Galactic loops, especially
Loop I, and mainly focus on the following issues: Does it contribute
predominantly to the E-mode or B-mode? In which frequency bands and in which
sky regions can it be identified?
Methods: Based on a well known result about the magnetic field alignment in
supernova explosions, a theoretical expectation is established that the loop
polarizations should be predominantly E-mode. In particular, the expected
polarization angles of Loop I are compared with those from the real microwave
band data of WMAP and Planck.
Results and conclusions: The comparison between model and data shows
remarkable consistency between data and expectation at all bands and for a
large area of the sky. This result suggests that the polarized emission of
Galactic Loop I is a major polarized component in all microwave bands from 23
to 353 GHz, and a considerable part of the polarized foreground is likely
originated from a local bubble associated with Loop I, instead of the far more
distant Galactic emission. The result also provides a possible way to explain
the reported E-to-B excess~\citep{2016A&A...586A.133P} by contribution of the
loops. Finally, this work may also provide the first geometrical evidence that
the Earth was hit by a supernova explosion. | NN bundle method applied to cosmology: an improvement in computational
times: In the last few years, there has been significant progress in the development
of machine learning methods tailored to astrophysics and cosmology. Among the
various methods that have been developed, there is one that allows to obtain a
bundle of solutions of differential systems without the need of using
traditional numerical solvers. We have recently applied this to the
cosmological scenario and showed that in some cases the computational times of
the inference process can be reduced. In this paper, we present an improvement
to the neural network bundle method that results in a significant reduction of
the computational times of the statistical analysis. The novelty of the method
consists in the use of the neural network bundle method to calculate the
luminosity distance of type Ia supernovae, which is usually computed through an
integral with numerical methods. In this work, we have applied this improvement
to the Starobinsky $f(R)$ model, which is more difficult to integrate than the
$f(R)$ models analyzed in our previous work. We performed a statistical
analysis with data from type Ia supernovae of the Pantheon+ compilation and
cosmic chronometers to estimate the values of the free parameters of the
Starobinsky model. We show that the statistical analyses carried out with our
new method require lower computational times than the ones performed with both
the numerical and the neural network method from our previous work. This
reduction in time is more significant in the case of a difficult computational
problem such as the one we address in this work. |
X-ray Groups of Galaxies at 0.5<z<1 in zCOSMOS: Increased AGN Activities
in High Redshift Groups: We present a photometric and spectroscopic study of galaxies at 0.5<z<1 as a
function of environment based on data from the zCOSMOS survey. There is a fair
amount of evidence that galaxy properties depend on mass of groups and
clusters, in the sense that quiescent galaxies prefer more massive systems. We
base our analysis on a mass-selected environment using X-ray groups of galaxies
and define the group membership using a large number of spectroscopic redshifts
from zCOSMOS. We show that the fraction of red galaxies is higher in groups
than in the field at all redshifts probed in our study. Interestingly, the
fraction of [OII] emitters on the red sequence increases at higher redshifts in
groups, while the fraction does not strongly evolve in the field. This is due
to increased dusty star formation activities and/or increased activities of
active galactic nuclei (AGNs) in high redshift groups. We study these
possibilities using the 30-band photometry and X-ray data. We find that the
stellar population of the red [OII] emitters in groups is old and there is no
clear hint of dusty star formation activities in those galaxies. The observed
increase of red [OII] emitters in groups is likely due to increased AGN
activities. However, our overall statistics is poor and any firm conclusions
need to be drawn from a larger statistical sample of z~1 groups. | Model-independent determination of $H_0$ and $Ω_{K0}$ from strong
lensing and type Ia supernovae: We present the first determination of the Hubble constant $H_0$ from strong
lensing time delay data and type Ia supernova luminosity distances that is
independent of the cosmological model. We also determine the spatial curvature
model-independently. We assume that light propagation over long distances is
described by the FLRW metric and geometrical optics holds, but make no
assumption about the contents of the Universe or the theory of gravity on
cosmological scales. We find $H_0=75.7^{+4.5}_{-4.4}$ km/s/Mpc and
$\Omega_{K0}=0.12^{+0.27}_{-0.25}$. This is a 6\% determination of $H_0$. A
weak prior from the cosmic microwave background on the distance to the last
scattering surface improves this to $H_0=76.8^{+4.2}_{-3.8}$ km/s/Mpc and
$\Omega_{K0}=0.18^{+0.25}_{-0.18}$. Assuming zero spatial curvature, we get
$H_0=74.2^{+3.0}_{-2.9}$ km/s/Mpc, a precision of $4\%$. The measurements also
provide a consistency test of the FLRW metric: we find no evidence against it. |
The role of Dark Matter interaction in galaxy clusters: We consider a toy model to analyze the consequences of dark matter
interaction with a dark energy background on the overall rotation of galaxy
clusters and the misalignment between their dark matter and baryon
distributions when compared to {\Lambda}CDM predictions. The interaction
parameters are found via a genetic algorithm search. The results obtained
suggest that interaction is a basic phenomenon whose effects are detectable
even in simple models of galactic dynamics. | Probing galaxy cluster and intra-cluster gas with luminous red galaxies: We use the cross-correlation between the thermal Sunyaev-Zeldovich (tSZ)
signal measured by the Planck satellite and the luminous red galaxy (LRG)
samples provided by the SDSS DR7 to study the properties of galaxy cluster and
intra-cluster gas. We separate the samples into three redshift bins z_1=(0.16,
0.26), z_2=(0.26, 0.36), z_3=(0.36, 0.47), and stack the Planck y-map against
LRGs to derive the averaged y-profile for each redshift bin. We then fit the
stacked profile with the theoretical prediction from the universal pressure
profile (UPP) by using the Markov-Chain Monte-Carlo method. We find that the
best-fit values of the UPP parameters for the three bins are generally
consistent with the previous studies, except for the noticeable evolution of
the parameters in the three redshift bins. We simultaneously fit the data in
the three redshift bins together, and find that the original UPP model cannot
fit the data at small angular scales very well in the first and third redshift
bins. The joint fits can be improved by including an additional parameter eta
to change the redshift-dependence of the model (i.e. E(z)^{8/3} ->
E(z)^{8/3+eta}) with best-fit value as eta=-3.11^{+1.09}_{-1.13}. This suggests
that the original UPP model with less redshift-dependence may provide a better
fit to the stacked thermal Sunyaev-Zeldovich profile. |
The globular clusters-stellar haloes connection in early type galaxies: This paper explores if, and to what an extent, the stellar populations of
early type galaxies can be traced through the colour distribution of their
globular cluster systems. The analysis, based on a galaxy sample from the Virgo
ACS data, is an extension of a previous approach that has been successful in
the cases of the giant ellipticals NGC 1399 and NGC 4486, and assumes that the
two dominant GC populations form along diffuse stellar populations sharing the
cluster chemical abundances and spatial distributions. The results show that a)
Integrated galaxy colours can be matched to within the photometric
uncertainties and are consistent with a narrow range of ages; b) The inferred
mass to luminosity ratios and stellar masses are within the range of values
available in the literature; c) Most globular cluster systems occupy a thick
plane in the volume space defined by the cluster formation efficiency, total
stellar mass and projected surface mass density. The formation efficiency
parameter of the red clusters shows a dependency with projected stellar mass
density that is absent for the blue globulars. In turn, the brightest galaxies
appear clearly detached from that plane as a possible consequence of major past
mergers; d) The stellar mass-metallicity relation is relatively shallow but
shows a slope change at $M_*\approx 10^{10} M_\odot$. Galaxies with smaller
stellar masses show predominantly unimodal globular cluster colour
distributions. This result may indicate that less massive galaxies are not able
to retain chemically enriched intestellar matter. | A Pair of Early- and Late-Forming Galaxy Cluster Samples: a Novel Way of
Studying Halo Assembly Bias Assisted by a Constrained Simulation: The halo assembly bias, a phenomenon referring to dependencies of the
large-scale bias of a dark matter halo other than its mass, is a fundamental
property of the standard cosmological model. First discovered in 2005 from the
Millennium Run simulation, it has been proven very difficult to be detected
observationally, with only a few convincing claims of detection so far. The
main obstacle lies in finding an accurate proxy of the halo formation time. In
this study, by utilizing a constrained simulation that can faithfully reproduce
the observed structures larger than $2\,$Mpc in the local universe, for a
sample of 634 massive clusters at $z\le 0.12$, we find their counterpart halos
in the simulation and use the mass growth history of the matched halos to
estimate the formation time of the observed clusters. This allows us to
construct a pair of early- and late-forming clusters, with similar mass as
measured via weak gravitational lensing, and large-scale bias differing at
$\approx 3\sigma$ level, suggestive of the signature of assembly bias, which is
further corroborated by the properties of cluster galaxies, including the
brightest cluster galaxy, and the spatial distribution and number of member
galaxies. Our study paves a way to further detect assembly bias based on
cluster samples constructed purely on observed quantities. |
Substructure and galaxy formation in the Copernicus Complexio warm dark
matter simulations: We use the Copernicus Complexio (COCO) high resolution $N$-body simulations
to investigate differences in the properties of small-scale structures in the
standard cold dark matter (CDM) model and in a model with a cutoff in the
initial power spectrum of density fluctuations consistent with both a thermally
produced warm dark matter (WDM) particle or a sterile neutrino with mass 7 keV
and leptogenesis parameter $L_6=8.7$. The latter corresponds to the "coldest"
model with this sterile neutrino mass compatible with the identification of the
recently detected 3.5 keV X-ray line as resulting from particle decay. CDM and
WDM predict very different number densities of subhaloes with mass $\leq
10^9\,h^{-1}\,M_\odot$ although they predict similar, nearly universal,
normalised subhalo radial density distributions. Haloes and subhaloes in both
models have cuspy NFW profiles, but WDM subhaloes below the cutoff scale in the
power spectrum (corresponding to maximum circular velocities
$V_{\mathrm{max}}^{z=0} \leq50~\mathrm{kms}^{-1}$) are less concentrated than
their CDM counterparts. We make predictions for observable properties using the
GALFORM semi-analytic model of galaxy formation. Both models predict Milky Way
satellite luminosity functions consistent with observations, although the WDM
model predicts fewer very faint satellites. This model, however, predicts
slightly more UV bright galaxies at redshift $z>7$ than CDM, but both are
consistent with observations. Gravitational lensing offers the best prospect of
distinguishing between the models. | Gravitational Waves from Domain Walls in Pulsar Timing Array Datasets: We present a model-independent search for the gravitational wave background
from cosmic domain walls (DWs) in the NANOGrav 12.5 years dataset and
International PTA Data Release 2. DWs that annihilate at temperatures $\sim
20-50~\text{MeV}$ with tensions $\sim (40-100~\text{TeV})^3$ provide as good a
fit to both datasets as the astrophysical background from supermassive black
hole mergers. DWs may decay into the Standard Model (SM) or a dark sector. In
the latter case we predict an abundance $\Delta N_{\text{eff}}$ of dark
radiation well within the reach of upcoming CMB surveys. Complementary
signatures at colliders and laboratories can arise if couplings to the SM are
present. As an example, we discuss heavy axion scenarios, where DW annihilation
may interestingly be induced by QCD confinement. |
Observational Constraints on Oscillating Dark-Energy Parametrizations: We perform a detailed confrontation of various oscillating dark-energy
parame-trizations with the latest sets of observational data. In particular, we
use data from Joint Light Curve analysis (JLA) sample from Supernoave Type Ia,
Baryon Acoustic Oscillations (BAO) distance measurements, Cosmic Microwave
Background (CMB) observations, redshift space distortion, weak gravitational
lensing, Hubble parameter measurements from cosmic chronometers, and we impose
constraints on four oscillating models. From the analyses we find that the
best-fit characters of almost all models are bent towards the phantom region,
nevertheless in all of them the quintessential regime is also allowed within
1$\sigma$ confidence-level. Furthermore, the deviations from $\Lambda$CDM
cosmology are not significant, however for two of the models they could be
visible at large scales, through the impact on the temperature anisotropy of
the CMB spectra and on the matter power spectra. Finally, we peform the
Bayesian analysis, which shows that the current observational data support the
$\Lambda$CDM paradigm over this set of oscillating dark-energy
parametrizations. | Non-Gaussianities and Curvature Perturbations from Hybrid Inflation: For the original hybrid inflation as well as the supersymmetric F-term and
D-term hybrid models, we calculate the level of non-gaussianities and the power
spectrum of curvature perturbations generated during the waterfall, taking into
account the contribution of entropic modes. We focus on the regime of mild
waterfall, in which inflation continues for more than about 60 e-folds N during
the waterfall. We find that the associated f_nl parameter goes typically from
f_nl \simeq -1 / N_exit in the regime with N >> 60, where N_exit is the number
of e-folds between the time of Hubble exit of a pivot scale and the end of
inflation, down to f_nl ~-0.3 when N \gtrsim 60, i.e. much smaller in magnitude
than the current bound from Planck. Considering only the adiabatic
perturbations, the power spectrum is red, with a spectral index n_s = 1 - 4 /
N_exit, in the case N >> 60, whereas in the case N \gtrsim 60, it increases up
to unity. Including the contribution of entropic modes does not change the
observable predictions in the first case. However, in the second case, they are
a relevant source for the power spectrum of curvature perturbations, of which
the amplitude increases by several orders of magnitudes and can lead to black
hole formation. We conclude that due to the important contribution of entropic
modes, the parameter space leading to a mild waterfall phase is excluded by CMB
observations for all the considered models. |
WMAP 9-year CMB estimation using sparsity: Recovering the Cosmic Microwave Background (CMB) from WMAP data requires
galactic foreground emissions to be accurately separated out. Most component
separation techniques rely on second order statistics such as Internal Linear
Combination (ILC) techniques. In this paper, we present a new WMAP 9-year CMB
map, with 15 arcmin resolution, which is reconstructed using a recently
introduced sparse component separation technique, coined Local Generalized
Morphological Component Analysis (LGMCA). LGMCA emphasizes on the sparsity of
the components to be retrieved in the wavelet domain. We show that although
derived from a radically different separation criterion ({i.e. sparsity), the
LGMCA-WMAP 9 map and its power spectrum are fully consistent with their more
recent estimates from WMAP 9. | The Magellanic Quasars Survey. III. Spectroscopic Confirmation of 758
AGNs Behind the Magellanic Clouds: The Magellanic Quasars Survey (MQS) has now increased the number of quasars
known behind the Magellanic Clouds by almost an order of magnitude. All survey
fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small
Magellanic Cloud (SMC) have been observed. The targets were selected from the
third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on
their optical variability, mid-IR and/or X-ray properties. We spectroscopically
confirmed 758 (565 LMC and 193 SMC) quasars behind the Clouds, of which 94%
(527 LMC and 186 SMC) are newly identified. The MQS quasars have long-term (12
years and growing for OGLE), high-cadence light curves, enabling unprecedented
variability studies of quasars. The MQS quasars also provide a dense reference
grid for measuring both the internal and bulk proper motions of the Clouds, and
50 quasars are bright enough (I<18 mag) for absorption studies of the
interstellar/galactic (ISM/IGM) medium of the Clouds. |
Searching for the shadows of giants: characterising protoclusters with
line of sight Lyman-α absorption: We use state of the art hydrodyamical simulations from the Sherwood, EAGLE
and Illustris projects to examine the signature of $M_{\rm z=0}\simeq
10^{14}M_{\odot}$ protoclusters observed in Ly-$\alpha$ absorption at $z\simeq
2.4$. We find there is a weak correlation between the mass overdensity,
$\delta_{\rm m}$, and the Ly-$\alpha$ effective optical depth relative to the
mean, $\delta_{\tau_\textrm{eff}}$, averaged over $15~h^{-1}\rm\,cMpc$ scales,
although scatter in the $\delta_{\rm m}$--$\delta_{\tau_\textrm{eff}}$ plane
means it is not possible to uniquely identify large scale overdensities with
strong Ly-$\alpha$ absorption. Although all protoclusters are associated with
large scale mass overdensities, most sight lines through protoclusters in a
$\sim 10^{6}$ $\rm cMpc^{3}$ volume probe the low column density Ly-$\alpha$
forest. A small subset of sight lines that pass through protoclusters exhibit
coherent, strong Ly-$\alpha$ absorption on $15h^{-1}\rm\,cMpc$ scales, although
these correspond to a wide range in mass overdensity. Assuming perfect removal
of contamination by Ly-$\alpha$ absorbers with damping wings, more than half of
the remaining sight lines with $\delta_{\tau_{\rm eff}}>3.5$ trace
protoclusters. It is furthermore possible to identify a model dependent
$\delta_{\tau_{\rm eff}}$ threshold that selects only protoclusters. However,
such regions are rare: excluding absorption caused by damped systems, less than
0.1 per cent of sight lines that pass through a protocluster have
$\delta_{\tau_{\rm eff}}>3.5$, meaning that any protocluster sample selected in
this manner will also be highly incomplete. On the other hand, coherent regions
of Ly-$\alpha$ absorption also provide a promising route for identifying and
studying filamentary environments at high redshift. | New measurements of $Ω_m$ from gamma-ray bursts: Context: Data from cosmic microwave background radiation (CMB), baryon
acoustic oscillations (BAO), and supernovae Ia (SNe-Ia) support a constant dark
energy equation of state with $w_0 \sim -1$. Measuring the evolution of $w$
along the redshift is one of the most demanding challenges for observational
cosmology. Aims: We discuss the existence of a close relation for GRBs, named
Combo-relation, based on characteristic parameters of GRB phenomenology such as
the prompt intrinsic peak energy $E_{p,i}$, the X-ray afterglow, the initial
luminosity of the shallow phase $L_0$, the rest-frame duration $\tau$ of the
shallow phase, and the index of the late power-law decay $\alpha_X$. We use it
to measure $\Omega_m$ and the evolution of the dark energy equation of state.
We also propose a new calibration method for the same relation, which reduces
the dependence on SNe Ia systematics. Methods: We have selected a sample of
GRBs with 1) a measured redshift $z$; 2) a determined intrinsic prompt peak
energy $E_{p,i}$, and 3) a good coverage (0.3-10) keV afterglow light curves.
The fitting technique of the rest.frame (0.3-10) keV luminosity light curves
represents the core of the Combo-relation. We separate the early steep decay,
considered a part of the prompt emission, from the X-ray afterglow additional
component. Data with the largest positive residual, identified as flares, are
automatically eliminated until the p-value of the fit becomes greater than 0.3.
Results: We strongly minimize the dependency of the Combo-GRB calibration on
SNe Ia. We also measure a small extra-Poissonian scatter of the Combo-relation,
which allows us to infer from GRBs alone $\Omega_M =0.29^{+0.23}_{-0.15}$
(1$\sigma$) for the $\Lambda$CDM cosmological model, and $\Omega_M
=0.40^{+0.22}_{-0.16}$, $w_0 = -1.43^{+0.78}_{-0.66}$ for the flat-Universe
variable equation of state case. |
The Scale Factor in the Universe with Dark Energy: Friedmans cosmological equations for the scale factor are analyzed for the
Universe containing dark energy. The parameter of the equation of state of the
dark energy is treated as an arbitrary constant whose value lies within the
interval $w \in [-1.5, -0.5]$, the limits of which are set by current
observations. A unified analytic solution is obtained for the scale factor as a
function of physical and conformal time. We obtain approximated solutions for
scale factor to an accuracy of better then 1%. This accuracy is better then
measurement errors of global density parameters and therefore is suitable for
the approximated models of our Universe. An analytic solution is obtained for
the scale factor in $\Lambda$CDM cosmological model both in physical and
conformal time, for the description of the evolution of the Universe from the
epoch of matter domination up to the infinite future. | Unmodified Gravity: By relaxing the conventional assumption of a purely gravitational interaction
between dark energy and dark matter, substantial alterations to the growth of
cosmological structure can occur. In this work we focus on the homogeneous
transfer of energy from a decaying form of dark energy. We present simple
analytic solutions to the modified growth rates of matter fluctuations in these
models, and demonstrate that neglecting physics within the dark sector may
induce a significant bias in the inferred growth rate, potentially offering a
false signature of modified gravity. |
Photometric Estimates of Redshifts and Distance Moduli for Type Ia
Supernovae: Large planned photometric surveys will discover hundreds of thousands of
supernovae (SNe), outstripping the resources available for spectroscopic
follow-up and necessitating the development of purely photometric methods to
exploit these events for cosmological study. We present a light-curve fitting
technique for SN Ia photometric redshift (photo-z) estimation in which the
redshift is determined simultaneously with the other fit parameters. We
implement this "LCFIT+Z" technique within the frameworks of the MLCS2k2 and
SALT-II light-curve fit methods and determine the precision on the redshift and
distance modulus. This method is applied to a spectroscopically confirmed
sample of 296 SNe Ia from the SDSS-II Supernova Survey and 37 publicly
available SNe Ia from the Supernova Legacy Survey (SNLS). We have also applied
the method to a large suite of realistic simulated light curves for existing
and planned surveys, including SDSS, SNLS, and LSST. When intrinsic SN color
fluctuations are included, the photo-z precision for the simulation is
consistent with that in the data. Finally, we compare the LCFIT+Z photo-z
precision with previous results using color-based SN photo-z estimates. | Hemispherical Power Asymmetry from Scale-Dependent Modulated Reheating: We propose a new model for the hemispherical power asymmetry of the CMB based
on modulated reheating. Non-Gaussianity from modulated reheating can be small
enough to satisfy the bound from Planck if the dominant modulation of the
inflaton decay rate is linear in the modulating field $\sigma$. $\sigma$ must
then acquire a spatially-modulated power spectrum with a red scale-dependence.
This can be achieved if the primordial perturbation of $\sigma$ is generated
via tachyonic growth of a complex scalar field. Modulated reheating due to
$\sigma$ then produces a spatially modulated and scale-dependent sub-dominant
contribution to the adiabatic density perturbation. We show that it is possible
to account for the observed asymmetry while remaining consistent with bounds
from quasar number counts, non-Gaussianity and the CMB temperature quadupole.
The model predicts that the adiabatic perturbation spectral index and its
running will be modified by the modulated reheating component. |
Wouthuysen-Field Coupling in the 21 cm Region Around High Redshift
Sources: The 21 cm emission and absorption from gaseous halos around the first
generation of star depend on the Wouthuysen-Field (W-F) coupling, which relates
the spin temperature with the kinetic temperature of hydrogen gas via the
resonant scattering between Lyman alpha photons and neutral hydrogen. Although
the center object generally is a strong source of these photons, the transfer
of these photons in the 21 cm region is inefficient, as the optical depth of
the photons is large. Consequently, these photons from the source may not be
able to transfer to the entire 21 cm region timely to provide the W-F coupling.
This problem is important because the lifetime of first stars generally is
short. The problem is investigated with numerical solution of the
integro-differential equation, which describes the kinetics of these resonant
photons in both physical and frequency spaces. We show that the photon transfer
process in the physical space is actually coupled to that in the frequency
space. Firstly diffusion in the frequency space provides a shortcut for the
diffusion in the physical space. It makes the mean time for the escape of the
resonant photon in optical depth \tau media roughly proportional to the optical
depth \tau, not \tau^2. Secondly the resonant scattering is effective in
bouncing photons with a frequency which is not equal to initial frequency back
to the initial frequency. This process can restore initial frequency photons
and establish the local Boltzmann distribution of the photon spectrum around
the initial frequency. Therefore, the mechanism of 'escape via shortcut' plus
'bounce back' enables W-F coupling to be properly realized in the 21 cm region
around first stars. This mechanism also works for photons injected into the 21
cm region by redshift. | Gravitational lens time-delay as a probe of a possible time variation of
the fine-structure constant: A new method based on large-scale structure observations is proposed to probe
a possible time variation of the fine-structure constant ($\alpha$). Our
analyses are based on time-delay of Strong Gravitational Lensing and Type Ia
Supernovae observations. By considering a class of runaway dilaton models,
where the cosmological evolution of the fine-structure constant is given by
$\frac{\Delta \alpha}{\alpha} \approx -\gamma \ln{(1+z)}$, we obtain limits on
the physical properties parameter of the model ($\gamma$) at the level
$10^{-2}$ ($1\sigma$). Although our limits are less restrictive than those
obtained by quasar spectroscopy, the approach presented here provides new
bounds on the possibility of $\frac{\Delta \alpha}{\alpha} \neq 0$ at a
different range of redshifts. |
The effect of curvature in thawing models: We study the evolution of spatial curvature for thawing class of dark energy
models. We examine the evolution of the equation of state parameter, $w_\phi$,
as a function of the scale factor $a$, for the case in which the scalar field
$\phi$ evolve in nearly flat scalar potential. We show that all such models
provide the corresponding approximate analytical expressions for
$w_\phi(\Omega_\phi,\Omega_k)$ and $w_\phi(a)$. We present observational
constraints on these models. | The X-ray cluster survey with eROSITA: forecasts for cosmology, cluster
physics and primordial non-Gaussianity: Starting in late 2013, the eROSITA telescope will survey the X-ray sky with
unprecedented sensitivity. Assuming a detection limit of 50 photons in the
(0.5-2.0) keV energy band with a typical exposure time of 1.6 ks, we predict
that eROSITA will detect ~ 9.3 X 10^4 clusters of galaxies more massive than 5
X 10^13 Msun/h, with the currently planned all-sky survey. Their median
redshift will be z ~ 0.35. We perform a Fisher-matrix analysis to forecast the
constraining power of eROSITA on the LambdaCDM cosmology and, simultaneously,
on the X-ray scaling relations for galaxy clusters. Special attention is
devoted to the possibility of detecting primordial non-Gaussianity. We consider
two experimental probes: the number counts and the angular clustering of a
photon-count limited sample of clusters. We discuss how the cluster sample
should be split to optimize the analysis and we show that redshift information
of the individual clusters is vital to break the strong degeneracies among the
model parameters. For example, performing a "tomographic" analysis based on
photometric-redshift estimates and combining 1- and 2-point statistics will
give marginal 1-sigma errors of Delta(sigma_8) ~ 0.036 and Delta(Omega_m) ~
0.012 without priors, and improve the current estimates on the slope of the
luminosity-mass relation by a factor of 3. Regarding primordial
non-Gaussianity, eROSITA clusters alone will give Delta(f_NL) = 9, 36, 144 for
the local, orthogonal and equilateral model, respectively. Measuring redshifts
with spectroscopic accuracy would further tighten the constraints by nearly 40
per cent (barring f_NL which displays smaller improvements). Finally, combining
eROSITA data with the analysis of temperature anisotropies in the cosmic
microwave background by the Planck satellite should give sensational
constraints on both the cosmology and the properties of the intracluster
medium. |
Temperature Structure of the Intra-Cluster Medium from SPH and AMR
simulations: Analyses of cosmological hydrodynamic simulations of galaxy clusters suggest
that X-ray masses can be underestimated by 10% to 30%. The largest bias
originates by both violation of hydrostatic equilibrium and an additional
temperature bias caused by inhomogeneities in the X-ray emitting intra-cluster
medium (ICM). To elucidate on this large dispersion among theoretical
predictions, we evaluate the degree of temperature structures in cluster sets
simulated either with smoothed-particle-hydrodynamics (SPH) and
adaptive-mesh-refinement (AMR) codes. We find that the SPH simulations produce
larger temperature variations connected to the persistence of both
substructures and their stripped cold gas. This difference is more evident in
no-radiative simulations, while it is reduced in the presence of radiative
cooling. We also find that the temperature variation in radiative cluster
simulations is generally in agreement with the observed one in the central
regions of clusters. Around R_500 the temperature inhomogeneities of the SPH
simulations can generate twice the typical hydrostatic-equilibrium mass bias of
the AMR sample. We emphasize that a detailed understanding of the physical
processes responsible for the complex thermal structure in ICM requires
improved resolution and high sensitivity observations in order to extend the
analysis to higher temperature systems and larger cluster-centric radii. | Low-power Radio Galaxies in the Distant Universe: A search for FRI at
1<z<2 in the COSMOS field: We present a search for FRI radio galaxies between 1 < z < 2 in the COSMOS
field. In absence of spectroscopic redshift measurements, the selection method
is based on multiple steps which make use of both radio and optical
constraints. The basic assumptions are that 1) the break in radio power between
low-power FRIs and the more powerful FRIIs does not change with redshift, and
2) that the photometric properties of the host galaxies of low power radio
galaxies in the distant universe are similar to those of FRIIs in the same
redshift bin, as is the case for nearby radio galaxies. We describe the results
of our search, which yields 37 low-power radio galaxy candidates that are
possibly FRIs. We show that a large fraction of these low-luminosity radio
galaxies display a compact radio morphology, that does not correspond to the
FRI morphological classification. Furthermore, our objects are apparently
associated with galaxies that show clear signs of interactions, at odds with
the typical behavior observed in low-z FRI hosts. The compact radio morphology
might imply that we are observing intrinsically small and possibly young
objects, that will eventually evolve into the giant FRIs we observe in the
local universe. One of the objects appears as point-like in HST images. This
might belong to a population of FRI-QSOs, which however would represent a tiny
minority of the overall population of high-z FRIs. As for the local FRIs, a
large fraction of our objects are likely to be associated with groups or
clusters, making them "beacons" for high redshift clusters of galaxies. Our
search for candidate high-z FRIs we present in this paper constitutes a pilot
study for objects to be observed with future high-resolution and
high-sensitivity instruments (shortened) |
Testing interacting dark matter and dark energy model with cosmological
data: We investigate the model of dark matter-dark energy (DM-DE) interaction with
coupling strength proportional to the multiplication of dark sector densities
with different power indices $Q = \gamma \rho_{\rm c}^{\alpha} \rho_{\rm
d}^{\beta}$. We first investigate the modification of the cosmic expansion
history, and then further develop the formalism to take into account the
cosmological perturbations and dark matter temperature evolution. We then use
the latest observational cosmology data, including cosmic microwave background
(CMB) data, baryon acoustic oscillations (BAO) data, redshift-space distortion
(RSD) data and Type Ia supernovae (SNe) data to constrain the model parameters.
We find in the phantom region, a positive $\alpha$ is preferred by the data
above $2\, \sigma$ statistic significance. If we choose the power indices to be
integers or half-integers for {\it plausible} physics of particle interaction,
the allowed values within $1\, \sigma$ confidence regions are $\alpha = 0.5$
and $\beta = 0, 0.5, 1$. The inclusion of BAO and RSD data from large-scale
structure and SNe data improves the constraints significantly. Our model
predicts lower values of $f(z) \sigma_8(z)$ at $z<1$ comparing to $\Lambda$CDM
model, which alleviates the tension of $\Lambda$CDM with various RSD data from
optical galaxy surveys. Overall, the DM-DE interaction model is consistent with
the current observational data, especially providing a better fit to the RSD
data. | Particle acceleration and dynamics of double-double radio galaxies:
theory vs. observations: In this paper we show that a small sample of radio galaxies with evidence for
multiple epochs of jet activity (so-called `double-double' radio galaxies) have
the same electron injection spectral index in the two activity episodes, a
result which might be considered surprising given the very different lobe
dynamics expected in the first and second episode. We construct models for the
dynamics of radio galaxies, with an emphasis on their episodic behaviour, and
show that hotspot formation and confinement of lobes for the inner double of
double-double radio galaxies are possible even without any thermal matter in
the outer cocoon. We argue that (i) the observed similar injection spectral
indices are due to similar jet powers in the two episodes, (ii) the `spectral
index--radio power' correlation of a flux limited sample of radio galaxies is
the primary one, and not the `spectral index--redshift correlation', (iii) jets
are made of pair plasma and not electron-proton, (iv) and the Lorentz factor of
the spine of the jet should be $\gapp 10$ to explain the observations.
Furthermore, we argue that the observations show that higher power radio
galaxies do not have a higher jet bulk Lorentz factors, but instead simply have
a higher number density of particles in the jet rest frame. A consequence of
our models is that aligned double-double radio galaxies with very old
($\gapp10^8$ yr) outer doubles, or misaligned double-double radio galaxies, are
statistically more likely to have dissimilar injection indices in two different
episodes, as they will probably have different jet powers. |
DAMA and the self similar infall halo model: The annual modulation in the rate of WIMP recoils observed by the DAMA
collaboration at high significance is often analyzed in the context of an
isothermal Maxwell-Boltzmann velocity distribution. While this is the simplest
model, there is a need to consider other well motivated theories of halo
formation. In this paper, we study a different halo model, that of self similar
infall which is characterized by the presence of a number of cold streams and
caustics, not seen in simulations. It is shown that the self similar infall
model is consistent with the DAMA result both in amplitude and in phase, for
WIMP masses exceeding $\approx$ 250 GeV at the 99.7% confidence level. Adding a
small thermal component makes the parameter space near $m_\chi$ = 12 GeV
consistent with the self similar model. The minimum $\chi^2$ per degree of
freedom is found to be 0.92(1.03) with(without) channeling taken into account,
indicating an acceptable fit. For WIMP masses much greater than the mass of the
target nucleus, the recoil rate depends only on the ratio $\sigma_{\rm
p}/m_\chi$ which is found to be $\approx$ 0.06 femtobarn/TeV. However as in the
case of the isothermal halo, the allowed parameter space is inconsistent with
the null result obtained by the CDMS and Xenon experiments for spin-independent
elastic scattering. Future experiments with directional sensitivity and mass
bounds from accelerator experiments will help to distinguish between different
halo models and/or constrain the contribution from cold flows. | Sidestepping the inversion of the weak-lensing covariance matrix with
Approximate Bayesian Computation: Weak gravitational lensing is one of the few direct methods to map the
dark-matter distribution on large scales in the Universe, and to estimate
cosmological parameters. We study a Bayesian inference problem where the data
covariance $\mathbf{C}$, estimated from a number $n_{\textrm{s}}$ of numerical
simulations, is singular. In a cosmological context of large-scale structure
observations, the creation of a large number of such $N$-body simulations is
often prohibitively expensive. Inference based on a likelihood function often
includes a precision matrix, $\Psi = \mathbf{C}^{-1}$. The covariance matrix
corresponding to a $p$-dimensional data vector is singular for $p \ge
n_{\textrm{s}}$, in which case the precision matrix is unavailable. We propose
the likelihood-free inference method Approximate Bayesian Computation (ABC) as
a solution that circumvents the inversion of the singular covariance matrix. We
present examples of increasing degree of complexity, culminating in a realistic
cosmological scenario of the determination of the weak-gravitational lensing
power spectrum for the upcoming European Space Agency satellite Euclid. While
we found the ABC parameter estimate variances to be mildly larger compared to
likelihood-based approaches, which are restricted to settings with $p <
n_{\textrm{s}}$, we obtain unbiased parameter estimates with ABC even in
extreme cases where $p / n_{\textrm{s}} \gg 1$. The code has been made publicly
available to ensure the reproducibility of the results. |
How to make a clean separation between CMB E and B modes with proper
foreground masking: We investigate the E/B decomposition of CMB polarization on a masked sky. In
real space, operators of E and B mode decomposition involve only differentials
of CMB polarization. We may, therefore in principle, perform a clean E/B
decomposition from incomplete sky data. Since it is impractical to apply second
derivatives to observation data, we usually rely on spherical harmonic
transformation and inverse transformation, instead of using real-space
operators. In spherical harmonic representation, jump discontinuities in a cut
sky produces Gibbs phenomenon, unless a spherical harmonic expansion is made up
to an infinitely high multipole. By smoothing a foreground mask, we may
suppress the Gibbs phenomenon effectively in a similar manner to apodization of
a foreground mask discussed in other works. However, we incur foreground
contamination by smoothing a foreground mask, because zero-value pixels in the
original mask may be rendered non-zero by the smoothing process. In this work,
we investigate an optimal foreground mask, which ensures proper foreground
masking and suppresses Gibbs phenomenon. We apply our method to a simulated map
of the pixel resolution comparable to the Planck satellite. The simulation
shows that the leakage power is lower than unlensed CMB B mode power spectrum
of tensor-to-scalar ratio $r\sim 1\times10^{-7}$. We compare the result with
that of the original mask. We find that the leakage power is reduced by a
factor of $10^{6} \sim 10^{9}$ at the cost of a sky fraction $0.07$, and that
the enhancement is highest at lowest multipoles. We confirm that all the
zero-value pixels in the original mask remain zero in our mask. The application
of this method to the Planck data will improve the detectability of primordial
tensor perturbation. | Simulated differential observations of the Sunyaev-Zel'dovich Effect:
Probing the Dark Ages and Epoch of Reionization: This work presents an analytical approach for studying the cosmological 21cm
background signal from the Dark Ages (DA) and subsequent Epoch of Reionization
(EoR). We simulate differential observations of a galaxy cluster to demonstrate
how these epochs can be studied with a specific form of the Sunyaev-Zel'dovich
Effect called the SZE-21cm. This work produces simulated maps of the SZE-21cm
and shows that the SZE-21cm can be extracted from future observations with
low-frequency radio interferometers such as the Hydrogen Epoch of Reionization
Array (HERA) and the Square Kilometre Array (SKA). In order to simulate near
realistic scenarios, we look into cosmic variance noise, incorporate and take
into account the effects of foregrounds, thermal noise, and angular resolution
for our simulated observations. We further extend this exploration by averaging
over a sample of galaxy clusters to mitigate the effects of cosmic variance and
instrumental noise. The impact of point source contamination is also studied.
Lastly, we apply this technique to the results of the EDGES collaboration,
which in 2018 reported an absorption feature of the global 21cm background
signal centred at 78 MHz. The challenges to be addressed in order to achieve
the objectives of this work include errors that arise due to cosmic variation,
instrumental noise and point source contamination. Our approach demonstrates
the potential of the SZE-21cm as an indirect probe for the DA and EoR, and we
conclude that the spectral features of the SZE-21cm from our simulated
observations yield results that are close to prior theoretical predictions and
that the SZE-21cm can be used to test the validity of the EDGES detection. |
Lessons from cosmic history: The case for a linear star formation -- H2
relation: Observations show that star formation in galaxies is closely correlated with
the abundance of molecular hydrogen. Modeling this empirical relation from
first principles proves challenging, however, and many questions regarding its
properties remain open. For instance, the exact functional form of the relation
is still debated and it is also unknown whether it applies at z>4, where CO
observations are sparse. Here, we analyze how the shape of the star formation
-- gas relation affects the cosmic star formation history and global galaxy
properties using an analytic model that follows the average evolution of
galaxies in dark matter halos across cosmic time. We show that a linear
relation with an H2 depletion time of ~2.5 Gyr, as found in studies of nearby
galaxies, results in good agreement with current observations of galaxies at
both low and high redshift. These observations include the evolution of the
cosmic star formation rate density, the z~4-9 UV luminosity function, the
evolution of the mass -- metallicity relation, the relation between stellar and
halo mass, and the gas-to-stellar mass ratios of galaxies. In contrast, the
short depletion times that result from adopting a highly super-linear star
formation -- gas relation lead to large star formation rates, substantial metal
enrichment (~0.1 solar), and low gas-to-stellar mass ratios already at z~10, in
disagreement with observations. These results can be understood in terms of an
equilibrium picture of galaxy evolution in which gas inflows, outflows, and
star formation drive the metallicities and gas fractions toward equilibrium
values that are determined by the ratio of the accretion time to the gas
depletion time. In this picture, the cosmic modulation of the accretion rate is
the primary process that drives the evolution of stellar masses, gas masses,
and metallicities of galaxies from high redshift until today. | Testing self-interacting dark matter with galaxy warps: Self-interacting dark matter (SIDM) is an able alternative to collisionless
dark matter. If dark matter does have self-interactions, we would expect this
to cause a separation between the collisionless stars and the dark matter halo
of a galaxy as it falls through a dark matter medium. For stars arranged in a
disk, this would generate a U-shaped warp. The magnitude of this warping
depends on the SIDM cross section, type of self-interaction, relative velocity
of galaxy and background, halo structure, and density of the dark matter
medium. In this paper, we set constraints on long-range (light mediator) dark
matter self-interaction by means of this signal. We begin by measuring U-shaped
warps in $3,213$ edge-on disk galaxies within the Sloan Digital Sky Survey. We
then forward-model the expected warp from SIDM on a galaxy-by-galaxy basis by
combining models of halo structure, density and velocity field reconstructions,
and models for the dark matter interactions. We find no evidence for a
contribution to the warps from SIDM. Our constraints are highly dependent on
the uncertain velocities of our galaxies: for a normalized Rutherford-like
cross section we find $\tilde{\sigma}/m_{\rm{DM}} \lesssim 3\times
10^{-13}~\rm{cm}^2/\rm{g}$ at fixed velocity $v = 300~\rm{km/s}$ -- a bound
that scales roughly linearly with increasing $v$. In the appendix we translate
these bounds into limits on the momentum transfer cross section, finding
$\sigma_T(300~\rm{km/s})/m_{\rm{DM}} \lesssim 0.1~\rm{cm}^2/\rm{g}$. [abridged] |
Effect of Template Uncertainties on the WMAP and Planck Measures of the
Optical Depth Due To Reionization: The reionization optical depth is the most poorly determined of the six
$\Lambda$CDM parameters fit to CMB anisotropy data. Instrumental noise and
systematics have prevented uncertainties from reaching their cosmic variance
limit. At present, the datasets providing the most statistical constraining
power are the WMAP, Planck LFI, and Planck HFI full-sky polarization maps. As
the reprocessed HFI data with reduced systematics are not yet publicly
unavailable, we examine determinations of $\tau$ using 9-year WMAP and 2015
Planck LFI data, with an emphasis on characterizing potential systematic bias
resulting from foreground template and masking choices. We find evidence for a
low-level systematic in the LFI polarization data with a roughly common-mode
morphology across the LFI frequencies and a spectrum consistent with leakage of
intensity signal into the polarization channels. We demonstrate significant
bias in the optical depth derived when using the LFI 30 GHz map as a template
to clean synchrotron from WMAP data, and recommend against use of the 2015 LFI
30 GHz polarization data as a foreground template for non-LFI datasets. We find
an inconsistency between versions of the 2015 polarized 353 GHz dust templates
reconstructed from the Planck likelihood and those from delivered maps, which
can affect $\tau$ at the 1$\sigma$ level. The spread in $\tau$ values over the
ensemble of data combinations we study suggests that systematic uncertainties
still contribute significantly to the current uncertainty in $\tau$, but all
values are consistent with the range of $\tau$ = 0.07 +/- 0.02. | Detection of PAH and Far-Infrared Emission from the Cosmic Eye: Probing
the Dust and Star Formation of Lyman Break Galaxies: We report the results of a Spitzer infrared study of the Cosmic Eye, a
strongly lensed, L*_UV Lyman Break Galaxy (LBG) at z=3.074. We obtained Spitzer
IRS spectroscopy as well as MIPS 24 and 70 micron photometry. The Eye is
detected with high significance at both 24 and 70 microns and, when including a
flux limit at 3.5 mm, we estimate an infrared luminosity of L_IR = 8.3
(+4.7-4.4) x10^11 L_sun assuming a magnification of 28+-3. This L_IR is eight
times lower than that predicted from the rest-frame UV properties assuming a
Calzetti reddening law. This has also been observed in other young LBGs, and
indicates that the dust reddening law may be steeper in these galaxies. The
mid-IR spectrum shows strong PAH emission at 6.2 and 7.7 microns, with
equivalent widths near the maximum values observed in star-forming galaxies at
any redshift. The L_PAH-to-L_IR ratio lies close to the relation measured in
local starbursts. Therefore, L_PAH or L_MIR may be used to estimate L_IR and
thus, star formation rate, of LBGs, whose fluxes at longer wavelengths are
typically below current confusion limits. We also report the highest redshift
detection of the 3.3 micron PAH emission feature. The PAH ratio,
L_6.2/L_3.3=5.1+- 2.7, and the PAH-to-L_IR ratio, L_3.3/L_IR = 8.5 +- 4.7
x10^-4, are both in agreement with measurements in local starbursts and ULIRGs,
suggesting that this line may serve as a good proxy for L_PAH or L_IR at z > 3
with the James Webb Space Telescope. |
The evolution of quiescent galaxies at high redshift (z > 1.4): We have studied the evolution of high redshift quiescent galaxies over an
effective area of ~1.7 deg^2 in the COSMOS field. Galaxies have been divided
according to their star-formation activity and the evolution of the different
populations has been investigated in detail. We have studied an IRAC (mag_3.6 <
22.0) selected sample of ~18000 galaxies at z > 1.4 with multi-wavelength
coverage. We have derived accurate photometric redshifts (sigma=0.06) and other
important physical parameters through a SED-fitting procedure. We have divided
our sample into actively star-forming, intermediate and quiescent galaxies
depending on their specific star formation rate. We have computed the galaxy
stellar mass function of the total sample and the different populations at
z=1.4-3.0. We have studied the properties of high redshift quiescent galaxies
finding that they are old (1-4 Gyr), massive (log(M/M_sun)~10.65), weakly star
forming stellar populations with low dust extinction (E(B-V) < 0.15) and small
e-folding time scales (tau ~ 0.1-0.3 Gyr). We observe a significant evolution
of the quiescent stellar mass function from 2.5 < z < 3.0 to 1.4 < z < 1.6,
increasing by ~ 1 dex in this redshift interval. We find that z ~ 1.5 is an
epoch of transition of the GSMF. The fraction of star-forming galaxies
decreases from 60% to 20% from z ~ 2.5-3.0 to z ~ 1.4-1.6 for log(M/M_sun) >
11, while the quiescent population increases from 10% to 50% at the same
redshift and mass intervals. We compare the fraction of quiescent galaxies
derived with that predicted by theoretical models and find that the Kitzbichler
& White (2007) model is the one that better reproduces the data. Finally, we
calculate the stellar mass density of the star-forming and quiescent
populations finding that there is already a significant number of quiescent
galaxies at z > 2.5 (rho~6.0 MsunMpc^-3). | High-Velocity Line Forming Regions in the Type Ia Supernova 2009ig: We report measurements and analysis of high-velocity (> 20,000 km/s) and
photospheric absorption features in a series of spectra of the Type Ia
supernova (SN) 2009ig obtained between -14d and +13d with respect to the time
of maximum B-band luminosity. We identify lines of Si II, Si III, S II, Ca II
and Fe II that produce both high-velocity (HVF) and photospheric-velocity (PVF)
absorption features. SN 2009ig is unusual for the large number of lines with
detectable HVF in the spectra, but the light-curve parameters correspond to a
slightly overluminous but unexceptional SN Ia (M_B = -19.46 mag and Delta_m15
(B) = 0.90 mag). Similarly, the Si II lambda_6355 velocity at the time of B-max
is greater than "normal" for a SN Ia, but it is not extreme (v_Si = 13,400
km/s). The -14d and -13d spectra clearly resolve HVF from Si II lambda_6355 as
separate absorptions from a detached line forming region. At these very early
phases, detached HVF are prevalent in all lines. From -12d to -6d, HVF and PVF
are detected simultaneously, and the two line forming regions maintain a
constant separation of about 8,000 km/s. After -6d all absorption features are
PVF. The observations of SN 2009ig provide a complete picture of the transition
from HVF to PVF. Most SN Ia show evidence for HVF from multiple lines in
spectra obtained before -10d, and we compare the spectra of SN 2009ig to
observations of other SN. We show that each of the unusual line profiles for Si
II lambda_6355 found in early-time spectra of SN Ia correlate to a specific
phase in a common development sequence from HVF to PVF. |
Constraining the average magnetic field in galaxy clusters with current
and upcoming CMB surveys: Galaxy clusters that host radio halos indicate the presence of population(s)
of non-thermal electrons. These electrons can scatter low-energy photons of the
Cosmic Microwave Background, resulting in the non-thermal Sunyaev-Zeldovich
(ntSZ) effect. We measure the average ntSZ signal from 62 radio-halo hosting
clusters using the $Planck$ multi-frequency all-sky maps. We find no direct
evidence of the ntSZ signal in the $Planck$ data. Combining the upper limits on
the non-thermal electron density with the average measured synchrotron power
collected from the literature, we place lower limits on the average magnetic
field strength in our sample. The lower limit on the volume-averaged magnetic
field is $0.1-0.01\,\mu$G, depending on the assumed power-law distribution of
electron energies. We further explore the potential improvement of these
constraints from the upcoming Simons Observatory and Fred Young Submillimeter
Telescope (FYST) of the CCAT-prime collaboration. We find that combining these
two experiments, the constraints will improve by a factor of $3-4$, which can
be sufficient to rule out some power-law models. | CMB Lensing Power Spectrum Biases from Galaxies and Clusters using
High-angular Resolution Temperature Maps: The lensing power spectrum from cosmic microwave background (CMB) temperature
maps will be measured with unprecedented precision with upcoming experiments,
including upgrades to ACT and SPT. Achieving significant improvements in
cosmological parameter constraints, such as percent level errors on sigma_8 and
an uncertainty on the total neutrino mass of approximately 50 meV, requires
percent level measurements of the CMB lensing power. This necessitates tight
control of systematic biases. We study several types of biases to the
temperature-based lensing reconstruction signal from foreground sources such as
radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from
galaxy clusters. These foregrounds bias the CMB lensing signal due to their
non-Gaussian nature. Using simulations as well as some analytical models we
find that these sources can substantially impact the measured signal if left
untreated. However, these biases can be brought to the percent level if one
masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with
masses above M_vir = 10^14 M_sun. To achieve such percent level bias, we find
that only modes up to a maximum multipole of l_max ~ 2500 should be included in
the lensing reconstruction. We also discuss ways to minimize additional bias
induced by such aggressive foreground masking by, for example, exploring a
two-step masking and in-painting algorithm. |
The Websky Extragalactic CMB Simulations: We present a new pipeline for the efficient generation of synthetic
observations of the extragalactic microwave sky, tailored to large ground-based
CMB experiments such as the Simons Observatory, Advanced ACTPol, SPT-3G, and
CMB-S4. Such simulated observations are a key technical challenge in cosmology
because of the dynamic range and accuracy required. The first part of the
pipeline generates a random cosmological realization in the form of a dark
matter halo catalog and matter displacement field, as seen from a given
position. The halo catalog and displacement field are modeled with ellipsoidal
collapse dynamics and Lagrangian perturbation theory, respectively. In the
second part, the cosmological realization is converted into a set of intensity
maps over the range 10 - 10^3 GHz using models based on existing observations
and hydrodynamical simulations. These maps include infrared emission from dusty
star forming galaxies (CIB), Comptonization of CMB photons by hot gas in groups
and clusters through the thermal Sunyaev-Zel'dovich effect (tSZ), Doppler
boosting by Thomson scattering of the CMB by bulk flows through the kinetic
Sunyaev-Zel'dovich effect (kSZ), and weak gravitational lensing of primary CMB
anisotropies by the large-scale distribution of matter in the universe. After
describing the pipeline and its implementation, we present the Websky maps,
created from a realization of the cosmic web on our past light cone in the
redshift interval 0<z<4.6 over the full-sky and a volume of ~(600 Gpc/h)^3
resolved with ~10^12 resolution elements. The Websky maps and halo catalog are
publicly available at mocks.cita.utoronto.ca/websky. | The morphologies and masses of extremely red galaxies in the Groth Strip
survey: We present a new cataloge of EROs from the Groth strip and study the relation
between their morphology and mass. We find 102 EROs (F814W-K=>4, K<=21.0), over
a survey area of 155 arcmin^2. The photometric data include U,B,F606W,F814W,J,K
bands. Morphologies are based on a by eye classification and we distinguish
between 3 basic classes: compact objects, targets with a disc and/or a bulge
component and irregular or merger candidates. The majority of our targets has
either a very compact morphology (33+-6%), or show more or less distinct disc
components (41+-6%). 14+-4% are merger or irregulars and 7 objects could not be
classified. We also study the dependence of structural parameters on
morphological appearance. EROs that are either compact or show a distinct bulge
component have smaller median effective radii (1.22+-0.14 kpc and 3.31+-0.53
kpc) than disc dominated (5.50+-0.51 kpc) or possible irregular galaxies or
merger candidates (4.92+-0.14 kpc). The Sersic index changes from 2.30+-0.34
and 3.24+-0.55, to 1.03+-0.24 and 1.54+-0.40 respectively.
Most the EROs in our sample have redshifts between z=1 and z=2; however,
compact EROs in our sample are found at redshifts as low as z=0.4 and as high
as z=2.8; the latter qualify as well as DRGs. Disc-like EROs are also found up
to z=2.8; however those with a bulge-disc structure are only seen at z<1.5. For
each of these EROs we determined the stellar mass and mean population age by
fitting synthetic Bruzual (2007) spectra to the SED. Mass estimates were
obtained by assuming an exponentially declining star formation rate. Total
stellar masses are in the range 9.1<log(M/M_sun)<11.6. We cannot detect
significant differences between the stellar mass distribution of the
morphological classes. EROs with masses of log(M/M_sun)>11.0 dominantly show
compact morphologies, but also include a significant number of sources with a
disc morphology. |
Molecular Chemistry for Dark Matter II: Recombination, Molecule
Formation, and Halo Mass Function in Atomic Dark Matter: Dissipative dark matter predicts rich observable phenomena that can be tested
with future large-scale structure surveys. As a specific example, we study
atomic dark matter, consisting of a heavy particle and a light particle charged
under a dark electromagnetism. In particular, we calculate the cosmological
evolution of atomic dark matter focusing on dark recombination and
dark-molecule formation. We have obtained the relevant interaction-rate
coefficients by re-scaling the rates for normal hydrogen, and evolved the
abundances for ionized, atomic, and molecular states using a modified version
of Recfast++ (which we have released publicly at
https://github.com/jamesgurian/RecfastJulia). We also provide an analytical
approximation for the final abundances. We then calculate the effects of the
atomic dark matter on the linear power spectrum, which enter through a
dark-photon diffusion and dark acoustic oscillations. At the formation time,
the atomic dark matter model suppresses halo abundances on scales smaller than
the diffusion scale, just like the warm dark matter models suppress the
abundance below the free-streaming scale. The subsequent evolution with
radiative cooling, however, will alter the halo mass function further. | Internal kinematic and physical properties in a BCD galaxy: Haro 15 in
detail: We present a detailed study of the kinematic and physical properties of the
ionized gas in multiple knots of the blue compact dwarf galaxy Haro 15. Using
echelle and long slit spectroscopy data, obtained with different instruments at
Las Campanas Observatory, we study the internal kinematic and physical
conditions (electron density and temperature), ionic and total chemical
abundances of several atoms, reddening and ionization structure. Applying
direct and empirical methods for abundance determination, we perform a
comparative analysis between these regions and in their different components.
On the other hand, our echelle spectra show complex kinematics in several
conspicuous knots within the galaxy. To perform an in-depth 2D spectroscopic
study we complete this work with high spatial and spectral resolution
spectroscopy using the Integral Field Unit mode on the Gemini Multi-Object
Spectrograph instrument at the Gemini South telescope. With these data we are
able to resolve the complex kinematical structure within star forming knots in
Haro 15 galaxy. |
Galaxy disks do not need to survive in the L-CDM paradigm: the galaxy
merger rate out to z~1.5 from morpho-kinematic data: About two-thirds of present-day, large galaxies are spirals such as the Milky
Way or Andromeda, but the way their thin rotating disks formed remains
uncertain. Observations have revealed that half of their progenitors, six
billion years ago, had peculiar morphologies and/or kinematics, which exclude
them from the Hubble sequence. Major mergers, i.e., fusions between galaxies of
similar mass, are found to be the likeliest driver for such strong
peculiarities. However, thin disks are fragile and easily destroyed by such
violent collisions, which creates a critical tension between the observed
fraction of thin disks and their survival within the L-CDM paradigm. Here we
show that the observed high occurrence of mergers amongst their progenitors is
only apparent and is resolved when using morpho-kinematic observations which
are sensitive to all the phases of the merging process. This provides an
original way of narrowing down observational estimates of the galaxy merger
rate and leads to a perfect match with predictions by state-of-the-art L-CDM
semi-empirical models with no particular fine-tuning needed. These results
imply that half of local thin disks do not survive but are actually rebuilt
after a gas-rich major merger occurring in the past nine billion years, i.e.,
two-thirds of the lifetime of the Universe. This emphasizes the need to study
how thin disks can form in halos with a more active merger history than
previously considered, and to investigate what is the origin of the gas
reservoir from which local disks would reform. | Mid-Infrared Properties of Nearby Luminous Infrared Galaxies I: Spitzer
IRS Spectra for the GOALS Sample: The Great Observatories All-Sky LIRG Survey (GOALS) is a multiwavelength
study of luminous infrared galaxies (LIRGs) in the local universe. Here we
present low resolution Spitzer spectra covering 5-38um and provide a basic
analysis of the mid-IR spectral properties for nearby LIRGs. In a companion
paper, we discuss detailed fits to the spectra. The GOALS sample of 244 nuclei
in 180 luminous and 22 ultraluminous IR galaxies represents a complete subset
of the IRAS RBGS and covers a range of merger stages, morphologies and spectral
types. The majority (>60%) of GOALS LIRGs have high 6.2um PAH equivalent widths
(EQW > 0.4um) and low levels of silicate absorption (s_9.7um >-1.0). There is a
general trend among the U/LIRGs for silicate depth and MIR slope to increase
with LIR. U/LIRGs in the late stages of a merger also have on average steeper
MIR slopes and higher levels of dust obscuration. Together these trends suggest
that as gas & dust is funneled towards the center of a coalescing merger, the
nuclei become more compact and obscured. The sources that depart from these
correlations have very low PAH EQW (EQW < 0.1um) consistent with their MIR
emission being dominated by an AGN. The most heavily dust obscured sources are
the most compact in their MIR emission, suggesting that the obscuring (cool)
dust is associated with the outer regions of the starburst. As the merger
progresses a marked decline is seen for the fraction of high EQW (star
formation dominated) sources while the fraction of composite sources increases
but the fraction of AGN-dominated sources remains low. When compared to the MIR
spectra of submillimeter galaxies (SMGs) at z~2, the average GOALS LIRG is more
absorbed at 9.7um and has more PAH emission. However, when the AGN
contributions to both the local LIRGs and the high-z SMGs are removed, the
average local starbursting LIRG closely resembles the starbursting SMGs. |
The Stochastic Gravitational Wave Background Generated by Cosmic String
Networks: the Small-Loop Regime: We consider an alternative approach for the computation of the stochastic
gravitational wave background generated by small loops produced throughout the
cosmological evolution of cosmic string networks and use it to derive an
analytical approximation to the corresponding power spectrum. We show that this
approximation produces an excellent fit to more elaborate results obtained
using the Velocity-dependent One-Scale model to describe cosmic string network
dynamics, over a wide frequency range, in the small-loop regime. | Constraints on compact dark matter from lensing of gravitational waves
for the third-generation gravitational wave detector: Since the first gravitational wave (GW) event from binary black hole (BBH)
was detected by LIGO-Virgo, GWs have become a useful probe on astrophysics and
cosmology. If compact dark matter (DM) objects e.g. primordial black holes,
contribute a significant fraction of dark matter at wide mass range, they will
cause microlensing in the GW signals with long wavelengths that are distinct
from the lensing effects of electromagnetic signals from astrophysical objects.
In this paper, we apply the lensing effect of GW from BBH to derive constraints
on the abundance of compact DM for the Cosmic Explorer, a third-generation
ground-based GW detector. We firstly consider two channels of formation of BBH
that contribute to low and high redshift GW sources, including the
astrophysical origin BBH scenario, and the primordial origin BBH scenario.
Secondly, comparing with the method of optical depth, we use the Bayesian
analysis to derive constraints on the abundance of compact DM with different
mass function of lens taken into consideration. For a null search with $1000$
detected GW events of BBH, we find that the abundance of compact DM could be
constrained to $\lesssim0.1\%$ in the mass range $\geq500~M_{\odot}$ at $68\%$
confidence level. In addition, if a GW event lensed by a compact DM object with
$M_{\rm l}\in[100~M_{\odot},300~M_{\odot}]$ is detected in $100$ detected GW
events of BBH, we can derive that the estimation of the abundance of compact DM
is from $2.3\%$ to $25.2\%$ in this mass range with the Bayesian analysis. |
Gravitational waves and stalled satellites from massive galaxy mergers
at z <= 1: We present a model for merger-driven evolution of the mass function for
massive galaxies and their central supermassive black holes at late times. We
discuss the current observational evidence in favor of merger-driven massive
galaxy evolution during this epoch, and demonstrate that the observed evolution
of the mass function can be reproduced by evolving an initial mass function
under the assumption of negligible star formation. We calculate the stochastic
gravitational wave signal from the resulting black-hole binary mergers in the
low redshift universe (z <= 1) implied by this model, and find that this
population has a signal-to-noise ratio as much as ~5x larger than previous
estimates for pulsar timing arrays, with an expectation value for the
characteristic strain h_c (f=1 yr^{-1}) = 4.1 x 10^{-15} that may already be in
tension with observational constraints, and a {2-sigma, 3-sigma} lower limit
within this model of h_c (f=1 yr^{-1}) = {1.1 x 10^{-15}, 6.8 x 10^{-16}}. The
strength of this signal is sufficient to make it detectable with high
probability under conservative assumptions within the next several years, if
the principle assumption of merger-driven galaxy evolution since z = 1 holds
true. For cases where a galaxy merger fails to lead to a black hole merger, we
estimate the probability for a given number of satellite unmerged black holes
to remain within a massive host galaxy, and interpret the result in light of
ULX observations. In particular, we find that the brightest cluster galaxies
should have 1-2 such sources with luminosities above 10^{39} erg/s, which is
consistent with the statistics of observed ULXs. | Identification of a Complete 160 micron Flux-Limited Sample of Infrared
Galaxies in the ISO Lockman Hole 1-Deg^2 Deep Fields: Source Properties and
Evidence for Strong Evolution in the FIR Luminosity Function for ULIRGs: We have identified a complete, flux-limited, (S_160>120 mJy), sample of 160
micron-selected sources from Spitzer observations of the 1-deg^2 ISO Deep Field
region in the Lockman Hole. Ground-based UV, optical and near-infrared (NIR)
photometry and optical spectroscopy have been used to determine colors,
redshifts and masses for the complete sample of 40 galaxies. Spitzer-IRAC+MIPS
photometry, supplemented by ISOPHOT data at 90 micron and 170 micron, has been
used to calculate accurate total infrared luminosities, LIR(8-1000 micron), and
to determine the IR luminosity function (LF) of luminous infrared galaxies
(LIRGs). The maximum observed redshift is z~0.80 and the maximum total infrared
luminosity is log(L_IR/L_Sun)=12.74. Over the luminosity range
log(L_IR/L_Sun)=10-12, the LF for LIRGs in the Lockman Hole Deep Field is
similar to that found previously for local sources at similar infrared
luminosities. The mean host galaxy mass, log(M/M_Sun)=10.7, and dominance of
HII-region spectral types, is also similar to what has been found for local
LIRGs, suggesting that intense starbursts likely power the bulk of the infrared
luminosity for sources in this range of LIR. However for the most luminous
sources, log(L_IR/L_Sun)>12.0, we find evidence for strong evolution in the LF
\propto (1+z)6\pm1, assuming pure number density evolution. These ultraluminous
infrared galaxies (ULIRGs) have a larger mean host mass, log(M/M_Sun)=11.0, and
exhibit disturbed morphologies consistent with strong-interactions/mergers, and
they are also more likely to be characterized by starburst-AGN composite or AGN
spectral types. |
Non-Gaussianity in the HILC foreground-reduced three-year WMAP CMB map: A detection or nondetection of primordial non-Gaussianity in the CMB data is
essential not only to test alternative models of the physics of the early
universe but also to discriminate among classes of inflationary models. Given
this far reaching consequences of such a non-Gaussianity detection for our
understanding of the physics of the early universe, it is important to employ
alternative indicators in order to have further information about the
Gaussianity features of CMB that may be helpful for identifying their origins.
In this way, a considerable effort has recently gone into the design of
non-Gaussianity indicators, and in their application in the search for
deviation from Gaussianity in the CMB data. Recently we have proposed two new
large-angle non-Gaussianity indicators which provide measures of the departure
from Gaussianity on large angular scales. We have used these indicators to
carry out analyses of Gaussianity of the single frequency bands and of the
available foreground-reduced {\it five-year} maps with and without the KQ75
mask. Here we extend and complement these studies by performing a new analysis
of deviation from Gaussianity of the {\it three-year} harmonic ILC (HILC)
foreground-reduced full-sky and KQ75 masked maps obtained from WMAP data. We
show that this full-sky foreground-reduced maps presents a significant
deviation from Gaussianity, which is brought down to a level of consistency
with Gaussianity when the KQ75 mask is employed. | Enhanced curvature perturbations from spherical domain walls nucleated
during inflation: We investigate spherical domain walls~(DWs) nucleated via quantum tunneling
in multifield inflationary models and curvature perturbations induced by the
inhomogeneous distribution of those DWs. We consider the case that the
Euclidean action $S_{E}$ of DWs changes with time during inflation so that most
of DWs nucleate when $S_{E}$ reaches the minimum value and the radii of DWs are
almost the same. When the Hubble horizon scale exceeds the DW radius after
inflation, DWs begin to annihilate and release their energy into background
radiation. Because of the random nature of the nucleation process, the
statistics of DWs is of the Poisson type and the power spectrum of curvature
perturbations has a characteristic slope ${\cal P}_{\cal R}(k)\propto k^{3}$.
The amplitude of ${\cal P}_{\cal R}(k)$ depends on the tension and abundance of
DWs at the annihilation time while the peak mode depends on the mean separation
of DWs. We also numerically obtain the energy spectra of scalar-induced
gravitational waves from predicted curvature perturbations which are expected
to be observed in multiband gravitational-wave detectors. |
SZ Science with an ALMA Band 1 Receiver System: We present the first full interferometric simulations of galaxy clusters
containing radio plasma bubbles as observed by the proposed band 1 receiver
system for the ALMA telescope. We discuss the observational requirements for
detecting intracluster substructure directly from the SZ signal, including
integration time estimates, and the advantages of these observations over those
made with the current generation of SZ survey instruments. | Gravitational waves and gamma-ray bursts: Gamma-Ray Bursts are likely associated with a catastrophic energy release in
stellar mass objects. Electromagnetic observations provide important, but
indirect information on the progenitor. On the other hand, gravitational waves
emitted from the central source, carry direct information on its nature. In
this context, I give an overview of the multi-messenger study of gamma-ray
bursts that can be carried out by using electromagnetic and gravitational wave
observations. I also underline the importance of joint electromagnetic and
gravitational wave searches, in the absence of a gamma-ray trigger. Finally, I
discuss how multi-messenger observations may probe alternative gamma-ray burst
progenitor models, such as the magnetar scenario. |
Cosmic Evolution of Black Holes and Spheroids. IV. The BH Mass -
Spheroid Luminosity Relation: From high-resolution images of 23 Seyfert-1 galaxies at z=0.36 and z=0.57
obtained with the Near Infrared Camera and Multi-Object Spectrometer on board
the Hubble Space Telescope (HST), we determine host-galaxy morphology, nuclear
luminosity, total host-galaxy luminosity and spheroid luminosity. Keck
spectroscopy is used to estimate black hole mass (M_BH). We study the cosmic
evolution of the M_BH-spheroid luminosity (L_sph) relation. In combination with
our previous work, totaling 40 Seyfert-1 galaxies, the covered range in BH mass
is substantially increased, allowing us to determine for the first time
intrinsic scatter and correct evolutionary trends for selection effects. We
re-analyze archival HST images of 19 local reverberation-mapped active galaxies
to match the procedure adopted at intermediate redshift. Correcting spheroid
luminosity for passive luminosity evolution and taking into account selection
effects, we determine that at fixed present-day V-band spheroid luminosity,
M_BH/L_sph \propto (1+z)^(2.8+/-1.2). When including a sample of 44 quasars out
to z=4.5 taken from the literature, with luminosity and BH mass corrected to a
self-consistent calibration, we extend the BH mass range to over two orders of
magnitude, resulting in M_BH/L_sph \propto (1+z)^(1.4+/-0.2). The intrinsic
scatter of the relation, assumed constant with redshift, is 0.3+/-0.1 dex (<0.6
dex at 95% CL). The evolutionary trend suggests that BH growth precedes
spheroid assembly. Interestingly, the M_BH-total host-galaxy luminosity
relation is apparently non-evolving. It hints at either a more fundamental
relation or that the spheroid grows by a redistribution of stars. However, the
high-z sample does not follow this relation, indicating that major mergers may
play the dominant role in growing spheroids above z~1. | Constraints on primordial black holes and curvature perturbations from
the global 21cm signal: The recent observations of the global 21cm signal by EDGES and gravitational
waves by LIGO/VIGO have revived interest in PBHs. Different from previous
works, we investigate the influence of PBHs on the evolution of the IGM for the
mass range $6\times 10^{13} {\rm g} \lesssim M_{\rm PBH}\lesssim 3\times
10^{14} \rm g$. Since the lifetime of these PBHs is smaller than the present
age of the Universe, they have evaporated by the present day. Due to Hawking
radiation, the heating effects of PBHs on the IGM can suppress the absorption
amplitude of the global 21cm signal. In this work, by requiring that the
differential brightness temperature of the global 21cm signals in the redshift
range of $10\lesssim z \lesssim 30$, e.g., $\delta T_{b} \lesssim -100~\rm mK$,
we obtain upper limits on the initial mass fraction of PBHs. We find that the
strongest upper limit is $\beta_{\rm PBH} \sim 2\times 10^{-30}$. Since the
formation of PBHs is related to primordial curvature perturbations, by using
the constraints on the initial mass fraction of PBHs we obtain the upper limits
on the power spectrum of primordial curvature perturbations for the scale range
$8.0\times 10^{15}\lesssim k \lesssim 1.8\times 10^{16}~\rm Mpc^{-1}$,
corresponding to the mass range considered here. We find that the strongest
upper limit is $\mathcal P_{\mathcal R}(k) \sim 0.0046$. By comparing with
previous works, we find that for the mass range (or the scale range)
investigated in this work the global 21cm signals or the 21cm power spectrum
should give the strongest upper limits on the initial mass fraction of PBHs and
on the power spectrum of primordial curvature perturbations. |
On the road to percent accuracy VI: the nonlinear power spectrum for
interacting dark energy with baryonic feedback and massive neutrinos: Understanding nonlinear structure formation is crucial for fully exploring
the data generated by stage IV surveys, requiring accurate modelling of the
power spectrum. This is challenging for deviations from $\Lambda$CDM, but we
must ensure that alternatives are well tested, to avoid false detections. We
present an extension of the halo model reaction framework for interacting dark
energy. We modify the halo model including the additional force present in the
Dark Scattering model and implement it into ReACT. The reaction is combined
with a pseudo spectrum from EuclidEmulator2 and compared to N-body simulations.
Using standard mass function and concentration-mass relation, we find
predictions to be 1 % accurate at $z=0$ up to $k=0.8~h/{\rm Mpc}$ for the
largest interaction strength tested ($\xi=50$ b/GeV), improving to $2~h/{\rm
Mpc}$ at $z=1$. For smaller interaction strength ($10$ b/GeV), we find 1 %
agreement at $z=1$ up to scales above $3.5~h/{\rm Mpc}$, being close to
$1~h/{\rm Mpc}$ at $z=0$. Finally, we improve our predictions with the
inclusion of baryonic feedback and massive neutrinos and study degeneracies
between the effects of these contributions and those of the interaction.
Limiting the scales to where our modelling is 1 % accurate, we find a
degeneracy between the interaction and feedback, but not with massive
neutrinos. We expect the degeneracy with feedback to be resolvable by including
smaller scales. This work represents the first analytical tool for calculating
the nonlinear spectrum for interacting dark energy models. | A multi-frequency study of the SZE in giant radio galaxies: Radio-galaxy (RG) lobes contain relativistic electrons embedded in a tangled
magnetic field that produce, in addition to low-frequency synchrotron radio
emission, inverse-Compton scattering (ICS) of the cosmic microwave background
(CMB) photons. This produces a relativistic, non-thermal Sunyaev-Zel'dovich
effect (SZE). We study the spectral and spatial properties of the non-thermal
SZE in a sample of radio galaxies and make predictions for their detectability
in both the negative and the positive part of the SZE, with space experiments
like Planck, OLIMPO, and Herschel-SPIRE. These cover a wide range of
frequencies, from radio to sub-mm. We model the SZE in a general formalism that
is equivalent to the relativistic covariant one and describe the electron
population contained in the lobes of the radio galaxies with parameters derived
from their radio observations, namely, flux, spectral index, and spatial
extension. We further constrain the electron spectrum and the magnetic field of
the RG lobes using X-ray, gamma-ray, and microwave archival observations. We
determine the main spectral features of the SZE in RG lobes, namely, the
minimum, the crossover, and the maximum of the SZE. We show that these typical
spectral features fall in the frequency ranges probed by the available space
experiments. We provide the most reliable predictions for the amplitude and
spectral shape of the SZE in a sample of selected RGs with extended lobes. In
three of these objects, we also derive an estimate of the magnetic field in the
lobe at the muG level by combining radio (synchrotron) observations and X-ray
(ICS) observations. These data, together with the WMAP upper limits, set
constraints on the minimum momentum of the electrons residing in the RG lobes
and allow realistic predictions for the visibility of their SZE to be derived
with Planck, OLIMPO, and Herschel-SPIRE. [abridged] |
Perturbed recombination from inhomogeneous photon injection and
application to accreting primordial black holes: Exotic electromagnetic energy injection in the early Universe may alter
cosmological recombination, and ultimately cosmic microwave background (CMB)
anisotropies. Moreover, if energy injection is inhomogeneous, it may induce a
spatially-varying ionization fraction, and non-Gaussianity in the CMB. The
observability of these signals, however, is contingent upon how far the
injected particles propagate and deposit their energy into the primordial
plasma, relative to the characteristic scale of energy injection fluctuations.
In this study we inspect the spatial properties of energy deposition and
perturbed recombination resulting from an inhomogeneous energy injection of
sub-10 MeV photons, relevant to accreting primordial black holes (PBHs). We
develop a novel Monte-Carlo radiation transport code accounting for all
relevant photon interactions in this energy range, and including secondary
electron energy deposition efficiency through a new analytic approximation. For
a specified injected photon spectrum, the code outputs an
injection-to-deposition Green's function depending on time and distance from
the injection point. Combining this output with a linearized solution of the
perturbed recombination problem, we derive time- and scale-dependent
deposition-to-ionization Green's functions. We apply this general framework to
accreting PBHs, whose luminosity is strongly spatially modulated by supersonic
relative velocities between cold dark matter and baryons. We find that the
resulting spatial fluctuations of the free-electron fraction are of the same
magnitude as its mean deviation from standard recombination, from which current
CMB power spectra constraints are derived. This work suggests that the
sensitivity to accreting PBHs might be substantially improved by propagating
these inhomogeneities to CMB anisotropy power spectra and non-Gaussian
statistics, which we study in subsequent papers. | Self-interactions of ULDM to the rescue?: One of the most important questions in cosmology is concerning the
fundamental nature of dark matter (DM). DM could consist of spinless particles
of very small mass i.e. $m \sim 10^{-22}\ \text{eV}$. This kind of ultralight
dark matter (ULDM) would form cored density profiles (called "solitons") at the
centre of galaxies. In this context, recently it has been argued that (a) there
exists a power law relation between the mass of the soliton and mass of the
surrounding halo called the Soliton-Halo (SH) relation, and, (b) the
requirement of satisfying observed galactic rotation curves as well as SH
relations is so stringent that ULDM is disfavoured from comprising $100\%$ of
the total cosmological dark matter. In this work, we revisit these constraints
for ULDM particles with non-negligible quartic self-interactions. Using a
recently obtained soliton-halo relation which takes into account the effect of
self-interactions, we present evidence which suggests that, for $m = 10^{-22}\
\text{eV}$, the requirement of satisfying both galactic rotation curves as well
as SH relations can be fulfilled with repulsive self-coupling $\lambda \sim
\mathcal{O}(10^{-90})$. |
Coupling dark-baryonic matter density profile for vacuum decay scenarios: The cosmological consequences of an interacting model in which vacuum decay
law is deducted from the effect that vacuum decay has on the dark matter
evolution are investigated. Here, the baryonic matter is also considered as a
fluid gravitationally coupled with dark matter. It is made a careful analysis
to constrain this model with the observational data of growth rate of cosmic
structures. The theoretical growth rate is followed since the primordial
recombination and the main physical processes on the baryonic component are
considered. As a complementary constraint, this model is compared with the
observed CMB-BAO ratio as well with the gas mass fraction of cluster of
galaxies. We found the best fit values for dark matter $\Omega_{d0} = 0.269
^{+0.023}_{-0.023}$ and for the decay parameter $\epsilon = 0.02
^{+0.04}_{-0.05}$. | Restoring cosmological concordance with early dark energy and massive
neutrinos?: The early dark energy (EDE) solution to the Hubble tension comes at the cost
of an increased clustering amplitude that has been argued to worsen the fit to
galaxy clustering data. We explore whether freeing the total neutrino mass
$M_{\nu}$, which can suppress small-scale structure growth, improves EDE's fit
to galaxy clustering. Using Planck Cosmic Microwave Background and BOSS galaxy
clustering data, a Bayesian analysis shows that freeing $M_{\nu}$ does not
appreciably increase the inferred EDE fraction $f_{\rm EDE}$: we find the 95%
C.L. upper limits $f_{\rm EDE}<0.092$ and $M_{\nu}<0.15\,{\rm eV}$. Similarly,
in a frequentist profile likelihood setting (where our results support previous
findings that prior volume effects are important), we find that the baseline
EDE model (with $M_{\nu}=0.06\,{\rm eV}$) provides the overall best fit. For
instance, compared to baseline EDE, a model with $M_\nu=0.24\,{\rm eV}$
maintains the same $H_0$(km/s/Mpc)=(70.08, 70.11, respectively) whilst
decreasing $S_8$=(0.837, 0.826) to the $\Lambda$CDM level, but worsening the
fit significantly by $\Delta \chi^2=7.5$. For the datasets used, these results
are driven not by the clustering amplitude, but by background modifications to
the late-time expansion rate due to massive neutrinos, which worsen the fit to
measurements of the BAO scale. |
Relating the inhomogeneous power spectrum to the CMB hemispherical
anisotropy: We relate the observed hemispherical anisotropy in the cosmic microwave
radiation data to an inhomogeneous power spectrum model. The hemispherical
anisotropy can be parameterized in terms of the dipole modulation model. This
model leads to correlations between spherical harmonic coefficients
corresponding to multipoles, l and l+1. We extract the $l$ dependence of the
dipole modulation amplitude, A, by making a fit to the WMAP and PLANCK CMBR
data. We propose an inhomogeneous power spectrum model and show that it also
leads to correlations between multipoles, l and l+1. The model parameters are
determined by making a fit to the data. The spectral index of the inhomogeneous
power spectrum is found to be consistent with zero. | Do the Early Galaxies observed by JWST disagree with Planck's CMB
polarization measurements?: The recent observations from the James Webb Space Telescope have led to a
surprising discovery of a significant density of massive galaxies with masses
of $M \ge 10^{10.5} M_{\odot}$ at redshifts of approximately $z\sim 10$. This
corresponds to a stellar mass density of roughly $\rho_*\sim 10^6 M_{\odot}
Mpc^{-3}$. Despite making conservative assumptions regarding galaxy formation,
this finding may not be compatible with the standard $\Lambda$CDM cosmology
that is favored by observations of CMB Anisotropies from the Planck satellite.
In this paper, we confirm the substantial discrepancy with Planck's results
within the $\Lambda$CDM framework. Assuming a value of $\epsilon=0.2$ for the
efficiency of converting baryons into stars, we indeed find that the
$\Lambda$CDM model is excluded at more than $99.7 \%$ confidence level (C.L.).
An even more significant exclusion is found for $\epsilon \sim 0.1$, while a
better agreement, but still in tension at more than $95 \%$, is obtained for
$\epsilon =0.32$. This tension, as already discussed in the literature, could
arise either from systematics in the JWST measurements or from new physics.
Here, as a last-ditch effort, we point out that disregarding the large angular
scale polarization obtained by Planck, which allows for significantly larger
values of the matter clustering parameter $\sigma_8$, could lead to better
agreement between Planck and JWST within the $\Lambda$CDM framework.
Interestingly, the model compatible with Planck temperature-only data and JWST
observation also favors a higher Hubble constant $H_0=69.0\pm1.1$ km/s/Mpc at
$68\%$ C.L., in better agreement with observations based on SN-Ia luminosity
distances. |
Exploring local fNL estimators based on the binned bispectrum: We explore different estimators of the local non-linear coupling parameter,
fNL, based on the binned bispectrum presented in Bucher et al. Using
simulations of Wilkinson Microwave Anisotropy Probe (WMAP)-7yr data, we compare
the performance of a regression neural network with a \chi^2-minimization and
study the dependence of the results on the presence of the linear term in the
analysis and on the use of inpainting for masked regions. Both methods obtain
similar results and are robust to the use of inpainting, but the neural network
estimator converges considerably faster. We also examine the performance of a
simplified \chi^2 estimator that assumes a diagonal matrix and has the linear
term subtracted, which considerably reduces the computational time; in this
case inpainting is found to be crucial. The estimators are also applied to real
WMAP-7yr data, yielding constraints at 95% confidence level of -3< fNL <83. | The SINS/zC-SINF survey of z~2 galaxy kinematics: evidence for
gravitational quenching: As part of the SINS/zC-SINF surveys of high-z galaxy kinematics, we derive
the radial distributions of H-alpha surface brightness, stellar mass surface
density, and dynamical mass at ~2 kpc resolution in 19 z~2 star-forming disks
with deep SINFONI AO spectroscopy at the ESO VLT. From these data we infer the
radial distribution of the Toomre Q-parameter for these main-sequence star
forming galaxies (SFGs), covering almost two decades of stellar mass (10^9.6 to
10^11.5 solar masses). In more than half of our SFGs, the H-alpha distributions
cannot be fit by a centrally peaked distribution, such as an exponential, but
are better described by a ring, or the combination of a ring and an
exponential. At the same time the kinematic data indicate the presence of a
mass distribution more centrally concentrated than a single exponential
distribution for 5 of the 19 galaxies. The resulting Q-distributions are
centrally peaked for all, and significantly exceed unity there for three
quarters of the SFGs. The occurrence of H-alpha rings and of large nuclear
Q-values is strongly correlated, and is more common for the more massive SFGs.
While our sample is small and there remain substantial uncertainties and
caveats, our observations are consistent with a scenario in which cloud
fragmentation and global star formation are secularly suppressed in gas rich
high-z disks from the inside out, as the central stellar mass density of the
disks grows. |
What do we know about cosmography: In the present paper, we investigate the cosmographic problem using the
bias-variance trade-off. We find that both the z-redshift and the
$y=z/(1+z)$-redshift can present a small bias estimation. It means that the
cosmography can describe the supernova data more accurately. Minimizing risk,
it suggests that cosmography up to the second order is the best approximation.
Forecasting the constraint from future measurements, we find that future
supernova and redshift drift can significantly improve the constraint, thus
having the potential to solve the cosmographic problem. We also exploit the
values of cosmography on the deceleration parameter and equation of state of
dark energy $w(z)$. We find that supernova cosmography cannot give stable
estimations on them. However, much useful information was obtained, such as
that the cosmography favors a complicated dark energy with varying $w(z)$, and
the derivative $dw/dz<0$ for low redshift. The cosmography is helpful to model
the dark energy. | Detection of the Gravitational Lens Magnifying a Type Ia Supernova: Objects of known brightness, like Type Ia supernovae (SNIa), can be used to
measure distances. If a massive object warps spacetime to form multiple images
of a background SNIa, a direct test of cosmic expansion is also possible.
However, these lensing events must first be distinguished from other rare
phenomena. Recently, a supernova was found to shine much brighter than normal
for its distance, which resulted in a debate: was it a new type of
superluminous supernova or a normal SNIa magnified by a hidden gravitational
lens? Here we report that a spectrum obtained after the supernova faded away
shows the presence of a foreground galaxy--the first found to strongly magnify
a SNIa. We discuss how more lensed SNIa may be found than previously predicted. |
Simulations of the Pairwise Kinematic Sunyaev-Zel'dovich Signal: The pairwise kinematic Sunyaev-Zel'dovich (kSZ) signal from galaxy clusters
is a probe of their line-of-sight momenta, and thus a potentially valuable
source of cosmological information. In addition to the momenta, the amplitude
of the measured signal depends on the properties of the intra-cluster gas and
observational limitations such as errors in determining cluster centers and
redshifts. In this work we simulate the pairwise kSZ signal of clusters at z<1,
using the output from a cosmological N-body simulation and including the
properties of the intra-cluster gas via a model that can be varied in
post-processing. We find that modifications to the gas profile due to star
formation and feedback reduce the pairwise kSZ amplitude of clusters by ~50%,
relative to the naive 'gas traces mass' assumption. We demonstrate that
mis-centering can reduce the overall amplitude of the pairwise kSZ signal by up
to 10%, while redshift errors can lead to an almost complete suppression of the
signal at small separations. We confirm that a high-significance detection is
expected from the combination of data from current-generation, high-resolution
CMB experiments, such as the South Pole Telescope, and cluster samples from
optical photometric surveys, such as the Dark Energy Survey. Furthermore, we
forecast that future experiments such as Advanced ACTPol in conjunction with
data from the Dark Energy Spectroscopic Instrument will yield detection
significances of at least 20{\sigma}, and up to 57{\sigma} in an optimistic
scenario. Our simulated maps are publicly available at:
http://www.hep.anl.gov/cosmology/ksz.html | First LIGO search for gravitational wave bursts from cosmic
(super)strings: We report on a matched-filter search for gravitational wave bursts from
cosmic string cusps using LIGO data from the fourth science run (S4) which took
place in February and March 2005. No gravitational waves were detected in 14.9
days of data from times when all three LIGO detectors were operating. We
interpret the result in terms of a frequentist upper limit on the rate of
gravitational wave bursts and use the limits on the rate to constrain the
parameter space (string tension, reconnection probability, and loop sizes) of
cosmic string models. |
Gas cooling in semi-analytic models and SPH simulations: are results
consistent?: We present a detailed comparison between the galaxy populations within a
massive cluster, as predicted by hydrodynamical SPH simulations and by a
semi-analytic model (SAM) of galaxy formation. Both models include gas cooling
and a simple prescription of star formation, which consists in transforming
instantaneously any cold gas available into stars, while neglecting any source
of energy feedback. We find that, in general, galaxy populations from SAMs and
SPH have similar statistical properties, in agreement with previous studies.
However, when comparing galaxies on an object-by-object basis, we find a number
of interesting differences: a) the star formation histories of the brightest
cluster galaxies (BCGs) from SAM and SPH models differ significantly, with the
SPH BCG exhibiting a lower level of star formation activity at low redshift,
and a more intense and shorter initial burst of star formation with respect to
its SAM counterpart; b) while all stars associated with the BCG were formed in
its progenitors in the semi-analytic model used here, this holds true only for
half of the final BCG stellar mass in the SPH simulation, the remaining half
being contributed by tidal stripping of stars from the diffuse stellar
component associated with galaxies accreted on the cluster halo; c) SPH
satellites can loose up to 90 per cent of their stellar mass at the time of
accretion, due to tidal stripping, a process not included in the semi-analytic
model used in this study; d) in the SPH simulation, significant cooling occurs
on the most massive satellite galaxies and this lasts for up to 1 Gyr after
accretion. This physical process is not included in the semi-analytic model
used in our study, as well as in most of the models discussed in the recent
literature. | Turbulence and Radio Mini-halos in the Sloshing Cores of Galaxy Clusters: A number of relaxed, cool-core galaxy clusters exhibit diffuse,
steep-spectrum radio sources in their central regions, known as radio
mini-halos. It has been proposed that the relativistic electrons responsible
for the emission have been reaccelerated by turbulence generated by the
sloshing of the cool core gas. We present a high-resolution MHD simulation of
gas sloshing in a galaxy cluster coupled with subgrid simulations of
relativistic electron acceleration to test this hypothesis. Our simulation
shows that the sloshing motions generate turbulence on the order of $\delta{v}
\sim$ 50-200 km s$^{-1}$ on spatial scales of $\sim$50-100 kpc and below in the
cool core region within the envelope of the sloshing cold fronts, whereas
outside the cold fronts, there is negligible turbulence. This turbulence is
potentially strong enough to reaccelerate relativistic electron seeds (with
initial $\gamma \sim 100-500$) to $\gamma \sim 10^4$ via damping of
magnetosonic waves and non-resonant compression. The seed electrons could
remain in the cluster from, e.g., past AGN activity. In combination with the
magnetic field amplification in the core, these electrons then produce diffuse
radio synchrotron emission that is coincident with the region bounded by the
sloshing cold fronts, as indeed observed in X-rays and the radio. The result
holds for different initial spatial distributions of preexisting relativistic
electrons. The power and the steep spectral index ($\alpha \approx 1-2$) of the
resulting radio emission are consistent with observations of minihalos, though
the theoretical uncertainties of the acceleration mechanisms are high. We also
produce simulated maps of inverse-Compton hard X-ray emission from the same
population of relativistic electrons. |
Primordial perturbations with pre-inflationary bounce: Based on the effective field theory (EFT) of nonsingular cosmologies, we
build a stable model, without the ghost and gradient instabilities, of bounce
inflation (inflation is preceded by a cosmological bounce). We perform a full
simulation for the evolution of scalar perturbation, and find that the
perturbation spectrum has a large-scale suppression (as expected), which is
consistent with the power deficit of the cosmic microwave background (CMB)
TT-spectrum at low multipoles, but unexpectedly, it also shows itself one
marked lower valley, which actually provides a better fit to the dip at
multipole $l\sim 20$. The depth of valley is relevant with the physics around
the bounce scale, which is model-dependent. | The Evolution of Luminous Compact Blue Galaxies: Disks or Spheroids?: Luminous compact blue galaxies (LCBGs) are a diverse class of galaxies
characterized by high luminosity, blue color, and high surface brightness that
sit at the critical juncture of galaxies evolving from the blue to the red
sequence. As part of our multi-wavelength survey of local LCBGs, we have been
studying the HI content of these galaxies using both single-dish telescopes and
interferometers. Our goals are to determine if single-dish HI observations
represent a true measure of the dynamical mass of LCBGs and to look for
signatures of recent interactions that may be triggering star formation in
LCBGs. Our data show that while some LCBGs are undergoing interactions, many
appear isolated. While all LCBGs contain HI and show signatures of rotation,
the population does not lie on the Tully-Fisher relation nor can it evolve onto
it. Furthermore, the HI maps of many LCBGs show signatures of dynamically hot
components, suggesting that we are seeing the formation of a thick disk or
spheroid in at least some LCBGs. There is good agreement between the HI and
H-alpha kinematics for LCBGs, and both are similar in appearance to the H-alpha
kinematics of high redshift star-forming galaxies. Our combined data suggest
that star formation in LCBGs is primarily quenched by virial heating,
consistent with model predictions. |
Galaxy Motions, Turbulence and Conduction in Clusters of Galaxies: Unopposed radiative cooling in clusters of galaxies results in excessive mass
deposition rates. However, the cool cores of galaxy clusters are continuously
heated by thermal conduction and turbulent heat diffusion due to minor mergers
or the galaxies orbiting the cluster center. These processes can either reduce
the energy requirements for AGN heating of cool cores, or they can prevent
overcooling altogether. We perform 3D MHD simulations including field-aligned
thermal conduction and self-gravitating particles to model this in detail.
Turbulence is not confined to the wakes of galaxies but is instead
volume-filling, due to the excitation of large-scale g-modes. We systematically
probe the parameter space of galaxy masses and numbers. For a wide range of
observationally motivated galaxy parameters, the magnetic field is randomized
by stirring motions, restoring the conductive heat flow to the core. The
cooling catastrophe either does not occur or it is sufficiently delayed to
allow the cluster to experience a major merger that could reset conditions in
the intracluster medium. Whilst dissipation of turbulent motions is negligible
as a heat source, turbulent heat diffusion is extremely important; it
predominates in the cluster center. However, thermal conduction becomes
important at larger radii, and simulations without thermal conduction suffer a
cooling catastrophe. Conduction is important both as a heat source and to
reduce stabilizing buoyancy forces, enabling more efficient diffusion.
Turbulence enables conduction, and conduction enables turbulence. In these
simulations, the gas vorticity---which is a good indicator of trapped
g-modes--increases with time. The vorticity growth is approximately mirrored by
the growth of the magnetic field, which is amplified by turbulence. | The Physics and Physical Properties of Quasar Outflows: We describe two studies designed to characterize the total column densities,
kinetic energies, and acceleration physics of broad absorption line (BAL)
outflows in quasars. The first study uses new Chandra X-ray and ground-based
rest-frame UV observations of 7 quasars with mini-BALs at extreme high speeds,
in the range 0.1c to 0.2c, to test the idea that strong radiative shielding is
needed to moderate the mini-BAL ionizations and facilitate their acceleration
to extreme speeds. We find that the X-ray absorption is weak or absent, with
generally N_H < few x 10^22 mc^-2, and that radiative shielding is not
important. We argue that the mini-BAL ionizations are controlled, instead, by
high gas densities of order n_H ~ 4 x 10^8 cm^-3 in small outflow
substructures. If we conservatively assume that the total column density in the
mini-BAL gas is N_H < 10^22 cm^-2, covering >15% of the UV continuum source
along our lines of sight (based on measured line depths), then the radial
thickness of these outflows is only Delta_R < 3 x 10^13 cm and their transverse
size is > 8 x 10^15 cm. Thus the outflow regions have the shape of very thin
"pancakes" viewed face-on, or they occupy larger volumes like a spray of dense
cloudlets with a very small volume filling factor. We speculate that this
situation (with ineffective shielding and small dense outflow substructures)
applies to most quasar outflows, including BALs. Our second study focuses from
BALs of low-abundance ions, mainly PV 1118,1128 A, whose significant strengths
imply large column densities, N_H > 10^22 cm^-2, that can further challenge
models of the outflow acceleration. In spite of the difficulties of finding
this line in the Ly-alpha forest, a search through the SDSS DR9 quasar catalog
reveals >50 BAL sources at redshifts z>2.3 with strong PV BALs, which we are
now using to characterize the general properties of high-column outflows. |
A multi-wavelength strong lensing analysis of baryons and dark matter in
the dynamically active cluster AC 114: Strong lensing studies can provide detailed mass maps of the inner regions
even in dynamically active galaxy clusters. It is shown that proper modelling
of the intracluster medium, i.e. the main baryonic component, can play an
important role. In fact, the addition of a new contribution accounting for the
gas can increase the statistical significance of the lensing model. We propose
a parametric method for strong lensing analyses which exploits multi-wavelength
observations. The mass model accounts for cluster-sized dark matter halos,
galaxies (whose stellar mass can be obtained from optical analyses) and the
intracluster medium. The gas distribution is fitted to lensing data exploiting
prior knowledge from X-ray observations. This gives an unbiased look at each
matter component and allows us to study the dynamical status of a cluster.}The
method has been applied to AC 114, an irregular X-ray cluster. We find positive
evidence for dynamical activity, with the dark matter distribution shifted and
rotated with respect to the gas. On the other hand, the dark matter follows the
galaxy density both for shape and orientation, which hints at its collisionless
nature. The inner region (< 250kpc) is under-luminous in optical bands whereas
the gas fraction (~20+- 5%) slightly exceeds typical values. Evidence from
lensing and X-ray suggests that the cluster develops in the plane of the sky
and is not affected by the lensing over-concentration bias. Despite the
dynamical activity, the matter distribution seems to be in agreement with
predictions from N-body simulations. An universal cusped profile provides a
good description of either the overall or the dark matter distribution whereas
theoretical scaling relations seem to be nicely fitted. | Influence of baryons on the orbital structure of dark matter haloes: We explore the dynamical signatures imprinted by baryons on dark matter
haloes during the formation process using the OverWhelmingly Large Simulations
(OWLS), a set of state-of-the-art high-resolution cosmological hydrodynamical
simulations. We present a detailed study of the effects of the implemented
feedback prescriptions on the orbits of dark matter particles, stellar
particles and subhaloes, analysing runs with no feedback, with stellar feedback
and with feedback from supermassive black holes. We focus on the central
regions (0.25 r_{200}) of haloes with virial masses ~ 6 x 10^{13} (~ 7 x
10^{11}) Msun/h at z = 0(2). We also investigate how the orbital content
(relative fractions of the different orbital types) of these haloes depends on
several key parameters such as their mass, redshift and dynamical state. The
results of spectral analyses of the orbital content of these simulations are
compared, and the change in fraction of box, tube and irregular orbits is
quantified. Box orbits are found to dominate the orbital structure of dark
matter haloes in cosmological simulations. There is a strong anticorrelation
between the fraction of box orbits and the central baryon fraction. While
radiative cooling acts to reduce the fraction of box orbits, strong feedback
implementations result in a similar orbital distribution to that of the dark
matter only case. The orbital content described by the stellar particles is
found to be remarkably similar to that drawn from the orbits of dark matter
particles, suggesting that either they have forgotten their dynamical history,
or that subhaloes bringing in stars are not biased significantly with respect
to the main distribution. The orbital content of the subhaloes is in broad
agreement with that seen in the outer regions of the particle distributions. |
Clustering and Halo Abundances in Early Dark Energy Cosmological Models: LCDM cosmological models with Early Dark Energy (EDE) have been proposed to
resolve tensions between the Hubble constant H0 = 100h km/s/Mpc measured
locally, giving h ~ 0.73, and H0 deduced from Planck cosmic microwave
background (CMB) and other early universe measurements plus LCDM, giving h ~
0.67. EDE models do this by adding a scalar field that temporarily adds dark
energy equal to about 10% of the cosmological energy density at the end of the
radiation-dominated era at redshift z ~ 3500. Here we compare linear and
nonlinear predictions of a Planck-normalized LCDM model including EDE giving h
= 0.728 with those of standard Planck-normalized LCDM with h = 0.678. We find
that nonlinear evolution reduces the differences between power spectra of
fluctuations at low redshifts. As a result, at z = 0 the halo mass functions on
galactic scales are nearly the same, with differences only 1-2%. However, the
differences dramatically increase at high redshifts. The EDE model predicts 50%
more massive clusters at z = 1 and twice more galaxy-mass halos at z = 4. Even
greater increases in abundances of galaxy-mass halos at higher redshifts may
make it easier to reionize the universe with EDE. Predicted galaxy abundances
and clustering will soon be tested by JWST observations. Positions of baryonic
acoustic oscillations (BAOs) and correlation functions differ by about 2%
between the models -- an effect that is not washed out by nonlinearities. Both
standard LCDM and the EDE model studied here agree well with presently
available acoustic-scale observations, but DESI and Euclid measurements will
provide stringent new tests. | LiteBIRD Science Goals and Forecasts: Improving Sensitivity to
Inflationary Gravitational Waves with Multitracer Delensing: We estimate the efficiency of mitigating the lensing $B$-mode polarization,
the so-called delensing, for the $LiteBIRD$ experiment with multiple external
data sets of lensing-mass tracers. The current best bound on the
tensor-to-scalar ratio, $r$, is limited by lensing rather than Galactic
foregrounds. Delensing will be a critical step to improve sensitivity to $r$ as
measurements of $r$ become more and more limited by lensing. In this paper, we
extend the analysis of the recent $LiteBIRD$ forecast paper to include multiple
mass tracers, i.e., the CMB lensing maps from $LiteBIRD$ and CMB-S4-like
experiment, cosmic infrared background, and galaxy number density from
$Euclid$- and LSST-like survey. We find that multi-tracer delensing will
further improve the constraint on $r$ by about $20\%$. In $LiteBIRD$, the
residual Galactic foregrounds also significantly contribute to uncertainties of
the $B$-modes, and delensing becomes more important if the residual foregrounds
are further reduced by an improved component separation method. |
Cool Core Bias in Sunyaev-Zel'dovich Galaxy Cluster Surveys: Sunyaev-Zeldovich (SZ) surveys find massive clusters of galaxies by measuring
the inverse Compton scattering of cosmic microwave background off of
intra-cluster gas. The cluster selection function from such surveys is expected
to be nearly independent of redshift and cluster astrophysics. In this work, we
estimate the effect on the observed SZ signal of centrally-peaked gas density
profiles (cool cores) and radio emission from the brightest cluster galaxy
(BCG) by creating mock observations of a sample of clusters that span the
observed range of classical cooling rates and radio luminosities. For each
cluster, we make simulated SZ observations by the South Pole Telescope and
characterize the cluster selection function, but note that our results are
broadly applicable to other SZ surveys. We find that the inclusion of a cool
core can cause a change in the measured SPT significance of a cluster between
0.01% - 10% at z > 0.3, increasing with cuspiness of the cool core and angular
size on the sky of the cluster (i.e., decreasing redshift, increasing mass). We
provide quantitative estimates of the bias in the SZ signal as a function of a
gas density cuspiness parameter, redshift, mass, and the 1.4 GHz radio
luminosity of the central AGN. Based on this work, we estimate that, for the
Phoenix cluster (one of the strongest cool cores known), the presence of a cool
core is biasing the SZ significance high by ~ 6%. The ubiquity of radio
galaxies at the centers of cool core clusters will offset the cool core bias to
varying degrees. | The Relation Between Line Emission and Brightest Cluster Galaxies in
Three Exceptional Clusters: Evidence for Gas Cooling from the ICM: There is a strong spatial correlation between brightest cluster galaxies
(BCGs) and the peak density and cooling rate of the intra-cluster medium (ICM).
In this paper we combine integral field spectroscopy, CO observations and X-ray
data to study three exceptional clusters (Abell 1991, Abell 3444 and Ophiuchus)
where there is a physical and dynamical offset between the BCG and the cooling
peak to investigate the connection between the cooling of the intracluster
medium, the cold gas being deposited and the central galaxy. We find the
majority of the optical line emission is spatially coincident with the peak in
the soft X-rays. In the case of A1991 we make separate detections of CO(2-1)
emission on the BCG and on the peak of the soft X-ray emission suggesting that
cooling continues to occur in the core despite being offset from the BCG. We
conclude that there is a causal link between the lowest temperature (< 2 keV)
ICM gas and the molecular gas(~ 30K). This link is only apparent in systems
where a transitory event has decoupled the BCG from the soft X-ray peak. We
discuss the prospects for identifying more examples of this rare configuration. |
Nearby Galaxies: Templates for Galaxies Across Cosmic Time: Studies of nearby galaxies including the Milky Way have provided fundamental
information on the evolution of structure in the Universe, the existence and
nature of dark matter, the origin and evolution of galaxies, and the global
features of star formation. Yet despite decades of work, many of the most basic
aspects of galaxies and their environments remain a mystery. In this paper we
describe some outstanding problems in this area and the ways in which large
radio facilities will contribute to further progress. | Features and New Physical Scales in Primordial Observables: Theory and
Observation: All cosmological observations to date are consistent with adiabatic, Gaussian
and nearly scale invariant initial conditions. These findings provide strong
evidence for a particular symmetry breaking pattern in the very early universe
(with a close to vanishing order parameter, $\epsilon$), widely accepted as
conforming to the predictions of the simplest realizations of the inflationary
paradigm. However, given that our observations are only privy to perturbations,
in inferring something about the background that gave rise to them, it should
be clear that many different underlying constructions project onto the same set
of cosmological observables. Features in the primordial correlation functions,
if present, would offer a unique and discriminating window onto the parent
theory in which the mechanism that generated the initial conditions is
embedded. In certain contexts, simple linear response theory allows us to infer
new characteristic scales from the presence of features that can break the
aforementioned degeneracies among different background models, and in some
cases can even offer a limited spectroscopy of the heavier degrees of freedom
that couple to the inflaton. In this review, we offer a pedagogical survey of
the diverse, theoretically well grounded mechanisms which can imprint features
into primordial correlation functions in addition to reviewing the techniques
one can employ to probe observations. These observations include cosmic
microwave background anisotropies and spectral distortions as well as the
matter two and three point functions as inferred from large-scale structure and
potentially, 21 cm surveys. |
A Composite Likelihood Approach for Inference under Photometric Redshift
Uncertainty: Obtaining accurately calibrated redshift distributions of photometric samples
is one of the great challenges in photometric surveys like LSST, Euclid, HSC,
KiDS, and DES. We present an inference methodology that combines the redshift
information from the galaxy photometry with constraints from two-point
functions, utilizing cross-correlations with spatially overlapping
spectroscopic samples, and illustrate the approach on CosmoDC2 simulations. Our
likelihood framework is designed to integrate directly into a typical
large-scale structure and weak lensing analysis based on two-point functions.
We discuss efficient and accurate inference techniques that allow us to scale
the method to the large samples of galaxies to be expected in LSST. We consider
statistical challenges like the parametrization of redshift systematics,
discuss and evaluate techniques to regularize the sample redshift
distributions, and investigate techniques that can help to detect and calibrate
sources of systematic error using posterior predictive checks. We evaluate and
forecast photometric redshift performance using data from the CosmoDC2
simulations, within which we mimic a DESI-like spectroscopic calibration sample
for cross-correlations. Using a combination of spatial cross-correlations and
photometry, we show that we can provide calibration of the mean of the sample
redshift distribution to an accuracy of at least 0.002(1+z), consistent with
the LSST-Y1 science requirements for weak lensing and large-scale structure
probes. | Accurate Analytic Model for the Weak Lensing Convergence One-Point
Probability Distribution Function and its Auto-Covariance: The one-point probability distribution function (PDF) is a powerful summary
statistic for non-Gaussian cosmological fields, such as the weak lensing (WL)
convergence reconstructed from galaxy shapes or cosmic microwave background
(CMB) maps. Thus far, no analytic model has been developed that successfully
describes the high-convergence tail of the WL convergence PDF for small
smoothing scales from first principles. Here, we present a halo-model formalism
to compute the WL convergence PDF, building upon our previous results for the
thermal Sunyaev-Zel'dovich field. Furthermore, we extend our formalism to
analytically compute the covariance matrix of the convergence PDF. Comparisons
to numerical simulations generally confirm the validity of our formalism in the
non-Gaussian, positive tail of the WL convergence PDF, but also reveal the
convergence PDF's strong sensitivity to small-scale systematic effects in the
simulations (e.g., due to finite resolution). Finally, we present a simple
Fisher forecast for a Rubin-Observatory-like survey, based on our new analytic
model. Considering the $\{A_s, \Omega_m, \Sigma m_\nu\}$ parameter space and
assuming a Planck CMB prior on $A_s$ only, we forecast a marginalized
constraint $\sigma(\Sigma m_\nu) \approx 0.08$ eV from the WL convergence PDF
alone, even after marginalizing over parameters describing the halo
concentration-mass relation. This error bar on the neutrino mass sum is
comparable to the minimum value allowed in the normal hierarchy, illustrating
the strong constraining power of the WL convergence PDF. We make our code
publicly available at https://github.com/leanderthiele/hmpdf. |
First Structure Formation under the Influence of Gas-Dark Matter
Streaming Velocity and Density: Impact of the Baryons-trace-dark matter
Approximation: The impact of the streaming between baryons and dark matter on the first
structures has been actively explored by recent studies. We investigate how the
key results are affected by two popular approximations. One is to implement the
streaming by accounting for only the relative motion while assuming ``baryons
trace dark matter" spatially at the initialization of simulation. This neglects
the smoothing on the gas density taking place before the initialization. In our
simulation initialized at $z_i=200$, it overestimates the gas density power
spectrum by up to 40\% at $k\approx10^2~h~\mbox{Mpc}^{-1}$ at $z=20$. Halo mass
($M_h$) and baryonic fraction in halos ($f_{b,h}$) are also overestimated, but
the relation between the two remains unchanged. The other approximation tested
is to artificially amplify the density/velocity fluctuations in the cosmic mean
density to simulate the first minihalos that form in overdense regions. This
gives a head start to the halo growth while the subsequent growth is similar to
that in the mean density. The growth in a true overdense region, on the other
hand, is accelerated gradually in time. For example, raising $\sigma_8$ by 50\%
effectively transforms $z\rightarrow\sqrt{1.5}z$ in the halo mass growth
history while in 2-$\sigma$ overdensity, the growth is accelerated by a
constant in redshift: $z\rightarrow{z+4.8}$. As a result, halos have grown more
in the former than in the latter before $z\approx27$ and vice versa after. The
$f_{b,h}$-$M_h$ relation is unchanged in those cases as well, suggesting that
the Pop III formation rate for a given $M_h$ is insensitive to the tested
approximations. | A test of galaxy cluster fundamental plane for the X-COP sample: We test the galaxy cluster fundamental plane using the X-COP sample of 12
clusters. The fundamental plane is given by the relation $T_X \propto
M_s^{\alpha} r_s^{\beta}$, where $T_X$, $M_s$, and $r_s$ correspond to the gas
temperature, NFW halo mass, and scale radius, respectively. We did this
analysis using two different temperatures: the error-weighted temperature in
$(50-500)h^{-1}$ kpc as well as the mass-weighted temperature in the same
range. With both these temperatures, we find a very tight fundamental plane
with dispersion of about 0.02 dex. The best-fit values for $\alpha$ and $\beta$
are in-between those expected from virial equilibrium and self-similarity
solution for secondary infall and collapse, with $\alpha$ being closer to the
virial expectation. Our best-fit values are also consistent with a recent
re-analyses of the fundamental plane for the CLASH sample, after excluding the
hottest clusters. |
Linear Tidal Vestige found in the WM Sheet: We present a vestige of the linear tidal influence on the spin orientations
of the constituent galaxies of the WM sheet discovered in the vicinity of the
Virgo cluster and the Local Void. The WM sheet is chosen as an optimal target
since it has a rectangular parallelepiped-like shape whose three sides are in
parallel with the supergalactic Cartesian axes. Determining three probability
density functions of the absolute values of the supergalactic Cartesian
components of the spin vectors of the WM sheet galaxies, we investigate their
alignments with the principal directions of the surrounding large-scale tidal
field. When the WM sheet galaxies located in the central region within the
distance of $2\,h^{-1}$Mpc are excluded, the spin vectors of the remaining WM
sheet galaxies are found to be weakly aligned, strongly aligned, and strongly
anti-aligned with the minor, intermediate and major principal directions of the
surrounding large-scale tidal field, respectively. To examine whether or not
the origin of the observed alignment tendency from the WM sheet is the linear
tidal effect, we infer the eigenvalues of the linear tidal tensor from the
axial ratios of the WM sheet with the help of the Zel'dovich approximation and
conduct a full analytic evaluation of the prediction of the linear tidal torque
model for the three probability density functions. A detailed comparison
between the analytical and the observational results reveals a good
quantitative agreement not only in the behaviors but also in the amplitudes of
the three probability density functions. | On the road to percent accuracy III: non-linear reaction of the matter
power spectrum to massive neutrinos: We analytically model the non-linear effects induced by massive neutrinos on
the total matter power spectrum using the halo model reaction framework of
Cataneo et al. 2019. In this approach the halo model is used to determine the
relative change to the matter power spectrum caused by new physics beyond the
concordance cosmology. Using standard fitting functions for the halo abundance
and the halo mass-concentration relation, the total matter power spectrum in
the presence of massive neutrinos is predicted to percent-level accuracy, out
to $k=10 \, h \, {\rm Mpc}^{-1}$. We find that refining the prescriptions for
the halo properties using $N$-body simulations improves the recovered accuracy
to better than 1%. This paper serves as another demonstration for how the halo
model reaction framework, in combination with a single suite of standard
$\Lambda$CDM simulations, can recover percent-level accurate predictions for
beyond-$\Lambda$CDM matter power spectra, well into the non-linear regime. |
Analytical scaling solutions for the evolution of cosmic domain walls in
a parameter-free velocity-dependent one-scale model: We derive an analytical approximation for the linear scaling evolution of the
characteristic length $L$ and the root-mean-squared velocity $\sigma_v$ of
standard frictionless domain wall networks in
Friedmann-Lema\^itre-Robertson-Walker universes with a power law evolution of
the scale factor $a$ with the cosmic time $t$ ($a \propto t^\lambda$). This
approximation, obtained using a recently proposed parameter-free
velocity-dependent one-scale model for domain walls, reproduces well the model
predictions for $\lambda$ close to unity, becoming exact in the $\lambda \to
1^-$ limit. We use this approximation, in combination with the exact results
found for $\lambda=0$, to obtain a fit to the model predictions valid for
$\lambda \in [0, 1[$ with a maximum error of the order of $1 \%$. This fit is
also in good agreement with the results of field theory numerical simulations,
specially for $\lambda \in [0.9, 1[$. Finally, we explicitly show that the
phenomenological energy-loss parameter of the original velocity-dependent
one-scale model for domain walls vanishes in the $\lambda \to 1^-$ limit and
discuss the implications of this result. | Results of the GREAT08 Challenge: An image analysis competition for
cosmological lensing: We present the results of the GREAT08 Challenge, a blind analysis challenge
to infer weak gravitational lensing shear distortions from images. The primary
goal was to stimulate new ideas by presenting the problem to researchers
outside the shear measurement community. Six GREAT08 Team methods were
presented at the launch of the Challenge and five additional groups submitted
results during the 6 month competition. Participants analyzed 30 million
simulated galaxies with a range in signal to noise ratio, point-spread function
ellipticity, galaxy size, and galaxy type. The large quantity of simulations
allowed shear measurement methods to be assessed at a level of accuracy
suitable for currently planned future cosmic shear observations for the first
time. Different methods perform well in different parts of simulation parameter
space and come close to the target level of accuracy in several of these. A
number of fresh ideas have emerged as a result of the Challenge including a
re-examination of the process of combining information from different galaxies,
which reduces the dependence on realistic galaxy modelling. The image
simulations will become increasingly sophisticated in future GREAT challenges,
meanwhile the GREAT08 simulations remain as a benchmark for additional
developments in shear measurement algorithms. |
Modelling the Spoon IRS diagnostic diagram: We explore whether our models for starbursts, quiescent star-forming galaxies
and for AGN dust tori are able to model the full range of IRS spectra measured
with Spitzer. The diagnostic plot of 9.7 mu silicate optical depth versus 6.2
mu PAH equivalent width, introduced by Spoon and coworkers in 2007, gives a
good indication of the age and optical depth of a starburst, and of the
contribution of an AGN dust torus. However there is aliasing between age and
optical depth at later times in the evolution of a starburst, and between age
and the presence of an AGN dust torus.
Modeling the full IRS spectra and using broad-band 25-850 mu fluxes can help
to resolve these aliases. The observed spectral energy distributions require
starbursts of a range of ages with initial dust optical depth ranging from
50-200, optically thin dust emission ('cirrus') illuminated by a range of
surface brightnesses of the interstellar radiation field, and AGN dust tori
with a range of viewing angles. | Evidence for dark matter interactions in cosmological precision data?: We study a two-parameter extension of the cosmological standard model
$\Lambda$CDM in which cold dark matter interacts with a new form of dark
radiation. The two parameters correspond to the energy density in the dark
radiation fluid $\Delta N_\mathrm{fluid}$ and the interaction strength between
dark matter and dark radiation. The interactions give rise to a very weak "dark
matter drag" which damps the growth of matter density perturbations throughout
radiation domination, allowing to reconcile the tension between predictions of
large scale structure from the CMB and direct measurements of $\sigma_8$. We
perform a precision fit to Planck CMB data, BAO, large scale structure, and
direct measurements of the expansion rate of the universe today. Our model
lowers the $\chi$-squared relative to $\Lambda$CDM by about 12, corresponding
to a preference for non-zero dark matter drag by more than $3 \sigma$. Particle
physics models which naturally produce a dark matter drag of the required form
include the recently proposed non-Abelian dark matter model in which the dark
radiation corresponds to massless dark gluons. |
Type II Supernovae as Distance Indicators at Near-IR Wavelengths: Motivated by the advantages of observing at near-IR wavelengths, we
investigate Type II supernovae (SNe II) as distance indicators at those
wavelengths through the Photospheric Magnitude Method (PMM). For the analysis,
we use $BVIJH$ photometry and optical spectroscopy of 24 SNe II during the
photospheric phase. To correct photometry for extinction and redshift effects,
we compute total-to-selective broadband extinction ratios and $K$-corrections
up to $z=0.032$. To estimate host galaxy colour excesses, we use the
colour-colour curve method with the $V\!-\!I$ versus $B\!-\!V$ as colour
combination. We calibrate the PMM using four SNe II in galaxies having Tip of
the Red Giant Branch distances. Among our 24 SNe II, nine are at $cz>2000$ km
s$^{-1}$, which we use to construct Hubble diagrams (HDs). To further explore
the PMM distance precision, we include into HDs the four SNe used for
calibration and other two in galaxies with Cepheid and SN Ia distances. With a
set of 15 SNe II we obtain a HD rms of 0.13 mag for the $J$-band, which
compares to the rms of 0.15-0.26 mag for optical bands. This reflects the
benefits of measuring PMM distances with near-IR instead of optical photometry.
With the evidence we have, we can set the PMM distance precision with $J$-band
below 10 per cent with a confidence level of 99 per cent. | Modified Gravity and Cosmology: In this review we present a thoroughly comprehensive survey of recent work on
modified theories of gravity and their cosmological consequences. Amongst other
things, we cover General Relativity, Scalar-Tensor, Einstein-Aether, and
Bimetric theories, as well as TeVeS, f(R), general higher-order theories,
Horava-Lifschitz gravity, Galileons, Ghost Condensates, and models of extra
dimensions including Kaluza-Klein, Randall-Sundrum, DGP, and higher
co-dimension braneworlds. We also review attempts to construct a Parameterised
Post-Friedmannian formalism, that can be used to constrain deviations from
General Relativity in cosmology, and that is suitable for comparison with data
on the largest scales. These subjects have been intensively studied over the
past decade, largely motivated by rapid progress in the field of observational
cosmology that now allows, for the first time, precision tests of fundamental
physics on the scale of the observable Universe. The purpose of this review is
to provide a reference tool for researchers and students in cosmology and
gravitational physics, as well as a self-contained, comprehensive and
up-to-date introduction to the subject as a whole. |
Cosmological CPT Violation and CMB Polarization Measurements: In this paper we study the possibility of testing Charge-Parity-Time Reversal
(CPT) symmetry with cosmic microwave background (CMB) experiments. We consider
two kinds of Chern-Simons (CS) term, electromagnetic CS term and gravitational
CS term, and study their effects on the CMB polarization power spectra in
detail. By combining current CMB polarization measurements, the seven-year
WMAP, BOOMERanG 2003 and BICEP observations, we obtain a tight constraint on
the rotation angle $\Delta\alpha=-2.28\pm1.02$ deg ($1\,\sigma$), indicating a
$2.2\,\sigma$ detection of the CPT violation. Here, we particularly take the
systematic errors of CMB measurements into account. After adding the QUaD
polarization data, the constraint becomes $-1.34<\Delta\alpha<0.82$ deg at 95%
confidence level. When comparing with the effect of electromagnetic CS term,
the gravitational CS term could only generate TB and EB power spectra with much
smaller amplitude. Therefore, the induced parameter $\epsilon$ can not be
constrained from the current polarization data. Furthermore, we study the
capabilities of future CMB measurements, Planck and CMBPol, on the constraints
of $\Delta\alpha$ and $\epsilon$. We find that the constraint of $\Delta\alpha$
can be significantly improved by a factor of 15. Therefore, if this rotation
angle effect can not be taken into account properly, the constraints of
cosmological parameters will be biased obviously. For the gravitational CS
term, the future Planck data still can not constrain $\epsilon$ very well, if
the primordial tensor perturbations are small, $r <0.1$. We need the more
accurate CMBPol experiment to give better constraint on $\epsilon$. | The Lx-Tvir relation in galaxy clusters: Effects of radiative cooling
and AGN heating: We present a detailed investigation of the X-ray luminosity (Lx)-gas
temperature (Tvir) relation of the complete X-ray flux-limited sample of the 64
brightest galaxy clusters in the sky (HIFLUGCS). We study the influence of two
astrophysical processes, active galactic nuclei (AGN) heating and intracluster
medium (ICM) cooling, on the Lx-Tvir relation, simultaneously for the first
time. We determine best-fit relations for different subsamples using the
cool-core strength and the presence of central radio activity as selection
criteria. We find the strong cool-core clusters (SCCs) with short cooling times
(< 1Gyr)to display the steepest relation (Lx ~ Tvir^{3.33}) and the
non-cool-core clusters (NCCs) with long cooling times (> 7.7Gyr) to display the
shallowest (Lx ~ Tvir^{2.42}). This has the simple implication that on the
high-mass scale (Tvir > 2.5keV) the steepening of the Lx-Tvir relation is
mainly due to the cooling of the intracluster medium gas. We propose that ICM
cooling and AGN heating are both important in shaping the Lx-Tvir relation but
on different length-scales. While our study indicates that ICM cooling
dominates on cluster scales (Tvir > 2.5keV), we speculate that AGN heating
dominates the scaling relation in poor clusters and groups (Tvir < 2.5keV). The
intrinsic scatter about the Lx-Tvir relation in X-ray luminosity for the whole
sample is 45.4% and varies from a minimum of 34.8% for weak cool-core clusters
to a maximum of 59.4% for clusters with no central radio source. We find that
after excising the cooling region, the scatter in the Lx-Tvir relation drops
from 45.4% to 39.1%, implying that the cooling region contributes ~ 27% to the
overall scatter. Lastly, we find the true SCC fraction to be 25% lower than the
observed one and the true normalizations of the Lx-Tvir relations to be lower
by 12%, 7%, and 17% for SCC, WCC, and NCC clusters, respectively. [abridged] |
Nonlocal Gravitational Models and Exact Solutions: A nonlocal gravity model with a function $f(\Box^{-1} R)$, where $\Box$ is
the d'Alembert operator, is considered. The algorithm, allowing to reconstruct
$f(\Box^{-1} R)$, corresponding to the given Hubble parameter and the state
parameter of the matter, is proposed. Using this algorithm, we find the
functions $f(\Box^{-1} R)$, corresponding to de Sitter solutions. | A New Statistic for Analyzing Baryon Acoustic Oscillations: We introduce a new statistic omega_l for measuring and analyzing large-scale
structure and particularly the baryon acoustic oscillations. omega_l is a
band-filtered, configuration space statistic that is easily implemented and has
advantages over the traditional power spectrum and correlation function
estimators. Unlike these estimators, omega_l can localize most of the acoustic
information into a single dip at the acoustic scale while also avoiding
sensitivity to the poorly constrained large scale power (i.e., the integral
constraint) through the use of a localized and compensated filter. It is also
sensitive to anisotropic clustering through pair counting and does not require
any binning. We measure the shift in the acoustic peak due to nonlinear effects
using the monopole omega_0 derived from subsampled dark matter catalogues as
well as from mock galaxy catalogues created via halo occupation distribution
(HOD) modeling. All of these are drawn from 44 realizations of 1024^3 particle
dark matter simulations in a 1h^{-1}Gpc box at z=1. We compare these shifts
with those obtained from the power spectrum and conclude that the results
agree. This indicates that any distance measurements obtained from omega_0 and
P(k) will be consistent with each other. We also show that it is possible to
extract the same amount of acoustic information using either omega_0 or P(k)
from equal volume surveys. |
Testing the Distance-Duality Relation with Galaxy Clusters and Type Ia
Supernovae: In this letter we propose a new and model-independent cosmological test for
the distance-duality (DD) relation, \eta=D_{L}(z)(1+z)^{-2}/D_{A}(z)=1, where
D_{L} and D_{A} are, respectively, the luminosity and angular diameter
distances. For $D_L$ we consider two sub-samples of SNe type Ia taken from
Constitution data (2009) whereas $D_A$ distances are provided by two samples of
galaxy clusters compiled by De Fillipis et al. (2005) and Bonamente et al.
(2006) by combining Sunyaev-Zeldovich effect (SZE) and X-ray surface
brightness. The SNe Ia redshifts of each sub-sample were carefully chosen to
coincide with the ones of the associated galaxy cluster sample (\Delta z<0.005)
thereby allowing a direct test of DD relation. Since for very low redshifts,
D_{A}(z) \approxeq D_{L}(z), we have tested the DD relation by assuming that
$\eta$ is a function of the redshift parametrized by two different expressions:
\eta(z) = 1 + \eta_{0}z and \eta(z) = 1 + \eta_{0}z/(1+z), where \eta_0 is a
constant parameter quantifying a possible departure from the strict validity of
the reciprocity relation (\eta_0=0). In the best scenario (linear
parametrization) we obtain \eta_{0} = -0.28^{+ 0.44}_{- 0.44} (2\sigma$,
statistical + systematic errors) for de Fillipis et al. sample (eliptical
geometry), a result only marginally compatible with the DD relation. However,
for Bonamente et al. sample (spherical geometry) the constraint is \eta_{0} =
-0.42^{+ 0.34}_{- 0.34} (3\sigma$, statistical + systematic errors) which is
clearly incompatible with the duality-distance relation. | Gravitational perturbations from oscillons and transients after
inflation: We study the scalar and tensor perturbations generated by the fragmentation
of the inflaton condensate into oscillons or transients after inflation, using
nonlinear classical lattice simulations. Without including the backreaction of
metric perturbations, we find that the magnitude of scalar metric perturbations
never exceeds a few $\times 10^{-3}$, whereas the maximal strength of the
gravitational wave signal today is $\mathcal{O}(10^{-9})$ for standard
post-inflationary expansion histories. We provide parameter scalings for the
$\alpha$-attractor models of inflation, which can be easily applied to other
models. We also discuss the likelihood of primordial black hole formation, as
well as conditions under which the gravitational wave signal can be at
observationally interesting frequencies and amplitudes.
Finally, we provide an upper bound on the frequency of the peak of the
gravitational wave signal, which applies to all preheating scenarios. |
Dark Matter: I give a review of the development of the concept of dark matter. The dark
matter story passed through several stages from a minor observational puzzle to
a major challenge for theory of elementary particles. Modern data suggest that
dark matter is the dominant matter component in the Universe, and that it
consists of some unknown non-baryonic particles. Dark matter is the dominant
matter component in the Universe, thus properties of dark matter particles
determine the structure of the cosmic web. | Testing one-loop galaxy bias: cosmological constraints from the power
spectrum: We investigate the impact of different assumptions in the modeling of
one-loop galaxy bias on the recovery of cosmological parameters, as a follow up
of the analysis done in the first paper of the series at fixed cosmology. We
use three different synthetic galaxy samples whose clustering properties match
the ones of the CMASS and LOWZ catalogues of BOSS and the SDSS Main Galaxy
Sample. We investigate the relevance of allowing for either short range
non-locality or scale-dependent stochasticity by fitting the real-space galaxy
auto power spectrum or the combination of galaxy-galaxy and galaxy-matter power
spectrum. From a comparison among the goodness-of-fit ($\chi^2$), unbiasedness
of cosmological parameters (FoB), and figure-of-merit (FoM), we find that a
four-parameter model (linear, quadratic, cubic non-local bias, and constant
shot-noise) with fixed quadratic tidal bias provides a robust modelling choice
for the auto power spectrum of the three samples, up to $k_{\rm
max}=0.3\,h\,\mathrm{Mpc}^{-1}$ and for an effective volume of
$6\,h^{-3}\,\mathrm{Gpc}^3$. Instead, a joint analysis of the two observables
fails at larger scales, and a model extension with either higher derivatives or
scale-dependent shot-noise is necessary to reach a similar $k_{\rm max}$, with
the latter providing the most stable results. These findings are obtained with
three, either hybrid or perturbative, prescriptions for the matter power
spectrum, \texttt{RESPRESSO}, gRPT and EFT. In all cases, the inclusion of
scale-dependent shot-noise increases the range of validity of the model in
terms of FoB and $\chi^2$. Interestingly, these model extensions with
additional free parameters do not necessarily lead to an increase in the
maximally achievable FoM for the cosmological parameters
$\left(h,\,\Omega_ch^2,\,A_s\right)$, which are generally consistent to those
of the simpler model at smaller $k_{\rm max}$. |
Clarifying the Hubble constant tension with a Bayesian hierarchical
model of the local distance ladder: Estimates of the Hubble constant, $H_0$, from the distance ladder and the
cosmic microwave background (CMB) differ at the $\sim$3-$\sigma$ level,
indicating a potential issue with the standard $\Lambda$CDM cosmology.
Interpreting this tension correctly requires a model comparison calculation
depending on not only the traditional `$n$-$\sigma$' mismatch but also the
tails of the likelihoods. Determining the form of the tails of the local $H_0$
likelihood is impossible with the standard Gaussian least-squares
approximation, as it requires using non-Gaussian distributions to faithfully
represent anchor likelihoods and model outliers in the Cepheid and supernova
(SN) populations, and simultaneous fitting of the full distance-ladder dataset
to correctly propagate uncertainties. We have developed a Bayesian hierarchical
model that describes the full distance ladder, from nearby geometric anchors
through Cepheids to Hubble-Flow SNe. This model does not rely on any
distributions being Gaussian, allowing outliers to be modeled and obviating the
need for arbitrary data cuts. Sampling from the $\sim$3000-parameter joint
posterior using Hamiltonian Monte Carlo, we find $H_0$ = (72.72 $\pm$ 1.67)
${\rm km\,s^{-1}\,Mpc^{-1}}$ when applied to the outlier-cleaned Riess et al.
(2016) data, and ($73.15 \pm 1.78$) ${\rm km\,s^{-1}\,Mpc^{-1}}$ with SN
outliers reintroduced. Our high-fidelity sampling of the low-$H_0$ tail of the
distance-ladder likelihood allows us to apply Bayesian model comparison to
assess the evidence for deviation from $\Lambda$CDM. We set up this comparison
to yield a lower limit on the odds of the underlying model being $\Lambda$CDM
given the distance-ladder and Planck XIII (2016) CMB data. The odds against
$\Lambda$CDM are at worst 10:1 or 7:1, depending on whether the SNe outliers
are cut or modeled, or 60:1 if an approximation to the Planck Int. XLVI (2016)
likelihood is used. | Implications of the $z>5$ Lyman-$α$ forest for the 21-cm power
spectrum from the epoch of reionization: Our understanding of the intergalactic medium at redshifts $z=5$-$6$ has
improved considerably in the last few years due to the discovery of quasars
with $z>6$ that enable Lyman-$\alpha$ forest studies at these redshifts. A
realisation from this has been that hydrogen reionization could end much later
than previously thought, so that large "islands" of cold, neutral hydrogen
could exist in the IGM at redshifts $z=5$-$6$. By using radiative transfer
simulations of the IGM, we consider the implications of the presence of these
neutral hydrogen islands for the 21-cm power spectrum signal and its potential
detection by experiments such as HERA, SKA, LOFAR, and MWA. In contrast with
previous models of the 21-cm signal, we find that thanks to the late end of
reionization the 21-cm power in our simulation continues to be as high as
$\Delta^2_{21}=10~\mathrm{mK}^2$ at $k\sim 0.1~h/$cMpc at $z=5$-$6$. This value
of the power spectrum is several orders of magnitude higher than that in the
conventional models considered in the literature for these redshifts. Such high
values of the 21-cm power spectrum should be detectable by HERA and SKA1-LOW in
$\sim 1000$ hours, assuming optimistic foreground subtraction. This redshift
range is also attractive due to relatively low sky temperature and potentially
greater abundance of multiwavelength data. |
Resilience of long modes in cosmological observables: By a careful implementation of gauge transformations involving
long-wavelength modes, we show that a variety of effects involving squeezed
bispectrum configurations, for which one Fourier mode is much shorter than the
other two, cannot be gauged away, except for the unphysical exactly
infinite-wavelength ($k=0$) limit. Our result applies, in particular, to the
Maldacena consistency relation for single-field inflation, yielding a local
non-Gaussianity strength $f_{\rm NL}^{\rm local} = - (5/12)(n_S-1)$ (with $n_S$
the primordial spectral index of scalar perturbations), and to the $f_{\rm
NL}^{\rm GR} = -5/3$ term, appearing in the dark matter bispectrum and in the
halo bias, as a consequence of the general relativistic non-linear evolution of
matter perturbations. Such effects are therefore physical and observable in
principle by future high-sensitivity experiments. | The effect of annealing on the RHESSI gamma-ray detectors: The performance of nine RHESSI germanium detectors has been gradually
deteriorating since its launch in 2002 because of radiation damage caused by
passing through the Earth's radiation belts. To restore its former sensitivity,
the spectrometer underwent an annealing procedure in November 2007. It,
however, changed the RHESSI response and affected gamma-ray burst measurements,
e.g., the hardness ratios and the spectral capabilities bellow approximately
100 keV. |
Primordial power spectrum versus extension parameters beyond the
standard model: We reconstruct the shape of the primordial power spectrum of curvature
perturbations in extended cosmological models, including addition of massive
neutrinos, extra relativistic species or varying primordial helium abundance,
from the latest cosmic microwave background data from the Wilkinson Microwave
Anisotropy Probe, the Atacama Cosmology Telescope and the South Pole Telescope.
We find that a scale-invariant primordial spectrum is disfavored by the data at
95% confidence level even in the presence of massive neutrinos, however it can
lie within the 95% confidence region if the effective number of relativistic
species or the primordial helium abundance is allowed to vary freely. The
constraints on the extension parameters from WMAP7+ACT+H0+BAO, are the total
mass of neutrinos sum(m_nu) < 0.48 eV (95% CL), the effective number of
relativistic species N_eff = 4.50 +/- 0.81 and the primordial helium abundance
Y_p = 0.303 +/- 0.075. The constraints from WMAP7+SPT+H0+BAO, are sum(m_nu) <
0.45 eV (95% CL), N_eff = 3.86 +/- 0.63 and Y_p = 0.277 +/- 0.050. | Inverse Depolarization: A Potential Probe of Internal Faraday Rotation
and Helical Magnetic Fields in Extragalactic Radio Jets: Motivated by recent observations that show increasing fractional linear
polarization with increasing wavelength in a small number of optically thin jet
features, i.e. "inverse depolarization", we present a physical model that can
explain this effect and may provide a new and complementary probe of the low
energy particle population and possible helical magnetic fields in
extragalactic radio jets. In our model, structural inhomogeneities in the jet
magnetic field create cancellation of polarization along the line of sight.
Internal Faraday rotation, which increases like wavelength squared, acts to
align the polarization from the far and near sides of the jet, leading to
increased polarization at longer wavelengths. Structural inhomogeneities of the
right type are naturally produced in helical magnetic fields and will also
appear in randomly tangled magnetic fields. We explore both alternatives and
find that, for random fields, the length scale for tangling cannot be too small
a fraction of the jet diameter and still be consistent with the relatively high
levels of fractional polarization observed in these features. We also find that
helical magnetic fields naturally produce transverse structure for inverse
depolarization which may be observable even in partially resolved jets. |
A cosmic-ray dominated ISM in Ultra Luminous Infrared Galaxies: new
initial conditions for star formation: The high-density star formation typical of the merger/starburst events that
power the large IR luminosities of Ultra Luminous
Infrared Galaxies (ULIRGs) (L_{IR}>10^{12}Lsol) throughout the Universe
results to extraordinarily high cosmic ray (CR) energy densities of
U_CR~(few)x(10^3--10^4)U_{CR,Gal} permeating their interstellar medium (ISM), a
direct consequence of the large supernovae remnants (SNRs) number densities in
such systems. Unlike far-UV photons emanating from their numerous star forming
sites, these large CR energy densities in ULIRGs will volumetrically heat and
raise the ionization fraction of dense (n>10^4 cm^{-3}) UV-shielded gas cores
throughout their compact star-forming volumes. Such conditions can turn most of
the large molecular gas masses found in such systems and their high redshift
counterparts (M(H2)~10^9-10^10 M_{sol}) into giant CR-dominated Regions (CRDRs)
rather than ensembles of Photon-dominated Regions (PDRs) which dominate in less
IR-luminous systems where star formation and molecular gas distributions are
much more extended. The molecular gas in CRDRs will have a {\it minimum}
temperature of T_{kin}~(80--160)K, and very high ionization fractions of
x(e)>10^{-6} throughout its UV-shielded dense cores, which in turn will {\it
fundamentally alter the initial conditions for star formation in such
systems.}. Observational tests of CRDRs can be provided by ...... | Relating basic properties of bright early-type dwarf galaxies to their
location in Abell 901/902: We present a study of the population of bright early-type dwarf galaxies in
the multiple-cluster system Abell 901/902. We use data from the STAGES survey
and COMBO-17 to investigate the relation between the color and structural
properties of the dwarfs and their location in the cluster. The definition of
the dwarf sample is based on the central surface brightness and includes
galaxies in the luminosity range -16 >= M_B >~-19 mag. Using a fit to the color
magnitude relation of the dwarfs, our sample is divided into a red and blue
subsample. We find a color-density relation in the projected radial
distribution of the dwarf sample: at the same luminosity dwarfs with redder
colors are located closer to the cluster centers than their bluer counterparts.
Furthermore, the redder dwarfs are on average more compact and rounder than the
bluer dwarfs. These findings are consistent with theoretical expectations
assuming that bright early-type dwarfs are the remnants of transformed
late-type disk galaxies involving processes such as ram pressure stripping and
galaxy harassment. This indicates that a considerable fraction of dwarf
elliptical galaxies in clusters are the results of transformation processes
related to interactions with their host cluster. |
Cross-correlating Astrophysical and Cosmological Gravitational Wave
Backgrounds with the Cosmic Microwave Background: General Relativity provides us with an extremely powerful tool to extract at
the same time astrophysical and cosmological information from the Stochastic
Gravitational Wave Backgrounds (SGWBs): the cross-correlation with other
cosmological tracers, since their anisotropies share a common origin and the
same perturbed geodesics. In this letter we explore the cross-correlation of
the cosmological and astrophysical SGWBs with Cosmic Microwave Background (CMB)
anisotropies, showing that future GW detectors, such as LISA or BBO, have the
ability to measure such cross-correlation signals. We also present, as a new
tool in this context, constrained realization maps of the SGWBs extracted from
the high-resolution CMB {\it Planck} maps. This technique allows, in the
low-noise regime, to faithfully reconstruct the expected SGWB map by starting
from CMB measurements. | Reionization and Cosmic Dawn: theory and simulations: We highlight recent progress in the sophistication and diversification of
cosmic dawn and reionization simulations. The application of these modeling
tools to current observations has allowed us narrow down the timing of
reionization, which we now know to within dz ~ 1 for the bulk of reionization.
The strongest constraints come from the optical depth to the CMB measured with
the {\it Planck} satellite and the first detection of ongoing reionization from
the spectra of the z=7.1 QSOs ULASJ1120+0641. However, we still know virtually
nothing about the astrophysical sources during the first billion years. The
revolution in our understanding will be led by upcoming interferometric
observations of the cosmic 21-cm signal. The properties of the sources and
sinks of UV and X-ray photons are encoded in the 3D patterns of the signal. The
development of Bayesian parameter recovery techniques, which tap into the
wealth of the 21-cm signal, will soon usher in an era of precision
astrophysical cosmology. |
On the IR-Resummation in the EFTofLSS: We propose a simplification for the IR-resummation scheme of Senatore and
Zaldarriaga, and also include its next-to-leading order corrections coming from
the tree-level three-point function of the long displacement field. First we
show that the new simplified formula shares the same properties of the
resummation of Senatore and Zaldarriaga. In Fourier space, the IR-resummed
power spectrum has no residual wiggles and the two-loop calculation matches the
non-linear power spectrum of the Dark Sky simulation at $z=0$ up to
$k\simeq0.34\,h\,\text{Mpc}^{-1}$ within cosmic variance. Then, we find that
the additional subleading terms (although parametrically infrared-enhanced)
modify the leading-order IR-resummed correlation function only in a marginal
way, implying that the IR-resummation scheme can robustly predict the shape of
the BAO peak. | The clustering of galaxies in the SDSS-III Baryon Oscillation
Spectroscopic Survey: Luminosity and Color Dependence and Redshift Evolution: We measure the luminosity and color dependence and the redshift evolution of
galaxy clustering in the Sloan Digital Sky Survey-III Baryon Oscillation
Spectroscopic Survey Ninth Data Release. We focus on the projected two-point
correlation function (2PCF) of subsets of its CMASS sample, which includes
about 260,000 galaxies over ~3,300 sq. deg in the redshift range 0.43<z<0.7. To
minimize the selection effect on galaxy clustering, we construct well-defined
luminosity and color subsamples by carefully accounting for the CMASS galaxy
selection cuts. The 2PCF of the whole CMASS sample, if approximated by a
power-law, has a correlation length of r_0=7.93\pm0.06Mpc/h and an index of
\gamma=1.85\pm0.01. Clear dependences on galaxy luminosity and color are found
for the projected 2PCF in all redshift bins, with more luminous and redder
galaxies generally exhibiting stronger clustering and steeper 2PCF. The color
dependence is also clearly seen for galaxies within the red sequence,
consistent with the behavior of SDSS-II main sample galaxies at lower
redshifts. At a given luminosity (k+e corrected), no significant evolution of
the projected 2PCFs with redshift is detected for red sequence galaxies. We
also construct galaxy samples of fixed number density at different redshifts,
using redshift-dependent magnitude thresholds. The clustering of these galaxies
in the CMASS redshift range is found to be consistent with that predicted by
passive evolution. Our measurements of the luminosity and color dependence and
redshift evolution of galaxy clustering will allow for detailed modeling of the
relation between galaxies and dark matter halos and new constraints on galaxy
formation and evolution. |
Energetic galaxy-wide outflows in high-redshift ultra-luminous infrared
galaxies hosting AGN activity: We present integral field spectroscopy observations, covering the [O
III]4959,5007 emission-line doublet of eight high-redshift (z=1.4-3.4)
ultra-luminous infrared galaxies (ULIRGs) that host Active Galactic Nuclei
(AGN) activity, including known sub-millimetre luminous galaxies (SMGs). The
targets have moderate radio luminosities that are typical of high-redshift
ULIRGs (L(1.4GHz)=10^(24)-10^(25)W/Hz) and therefore are not radio-loud AGN. We
de-couple kinematic components due to the galaxy dynamics and mergers from
those due to outflows. We find evidence in the four most luminous systems (L([O
III])>~10^(43)erg/s) for the signatures of large-scale energetic outflows:
extremely broad [O III] emission (FWHM ~ 700-1400km/s) across ~4-15kpc, with
high velocity offsets from the systemic redshifts (up to ~850km/s). The four
less luminous systems have lower quality data displaying weaker evidence for
spatially extended outflows. We estimate that these outflows are potentially
depositing energy into their host galaxies at considerable rates
(~10^(43)-10^(45)erg/s); however, due to the lack of constraints on the density
of the outflowing material and the structure of the outflow, these estimates
should be taken as illustrative only. Based on the measured maximum velocities
(v(max)~400-1400km/s) the outflows observed are likely to unbind some fraction
of the gas from their host galaxies, but are unlikely to completely remove gas
from the galaxy haloes. By using a combination of energetic arguments and a
comparison to ULIRGs without clear evidence for AGN activity, we show that the
AGN activity could be the dominant power source for driving all of the observed
outflows, although star formation may also play a significant role in some of
the sources. | Molecular Gas in Infrared Ultraluminous QSO Hosts: We report CO detections in 17 out of 19 infrared ultraluminous QSO (IR QSO)
hosts observed with the IRAM 30m telescope. The cold molecular gas reservoir in
these objects is in a range of 0.2--2.1$\times 10^{10}M_\odot$ (adopting a
CO-to-${\rm H_2}$ conversion factor $\alpha_{\rm CO}=0.8 M_\odot {\rm (K km
s^{-1} pc^2)^{-1}}$). We find that the molecular gas properties of IR QSOs,
such as the molecular gas mass, star formation efficiency ($L_{\rm
FIR}/L^\prime_{\rm CO}$) and the CO (1-0) line widths, are indistinguishable
from those of local ultraluminous infrared galaxies (ULIRGs). A comparison of
low- and high-redshift CO detected QSOs reveals a tight correlation between
L$_{\rm FIR}$ and $L^\prime_{\rm CO(1-0)}$ for all QSOs. This suggests that,
similar to ULIRGs, the far-infrared emissions of all QSOs are mainly from dust
heated by star formation rather than by active galactic nuclei (AGNs),
confirming similar findings from mid-infrared spectroscopic observations by
{\it Spitzer}. A correlation between the AGN-associated bolometric luminosities
and the CO line luminosities suggests that star formation and AGNs draw from
the same reservoir of gas and there is a link between star formation on $\sim$
kpc scale and the central black hole accretion process on much smaller scales. |
Dust properties of Lyman break galaxies in cosmological simulations: Recent observations have indicated the existence of dust in high-redshift
galaxies, however, the dust properties in them are still unknown. Here we
present theoretical constraints on dust properties in Lyman break galaxies
(LBGs) at z=3 by post-processing a cosmological smoothed particle hydrodynamics
simulation with radiative transfer calculations. We calculate the dust
extinction in 2800 dark matter halos using the metallicity information of
individual gas particles in our simulation. We use only bright galaxies with
rest-frame UV magnitude M_1700 < -20 mag, and study the dust size,
dust-to-metal mass ratio, and dust composition. From the comparison of
calculated color excess between B and V-band (i.e., E(B-V)) and the
observations, we constrain the typical dust size, and show that the
best-fitting dust grain size is ~ 0.05 micron, which is consistent with the
results of theoretical dust models for Type-II supernova. Our simulation with
the dust extinction effect can naturally reproduce the observed rest-frame UV
luminosity function of LBGs at z=3 without assuming an ad hoc constant
extinction value. In addition, in order to reproduce the observed mean E(B-V),
we find that the dust-to-metal mass ratio needs to be similar to that of the
local galaxies, and that the graphite dust is dominant or at least occupy half
of dust mass. | Discovery of VHE gamma-rays from Centaurus A: We report the discovery of faint very high energy (VHE, E > 100 GeV)
gamma-ray emission from the radio galaxy Centaurus A in deep observations
performed with the H.E.S.S. experiment. A signal with a statistical
significance of 5.0 sigma is detected from the region including the radio core
and the inner kpc jets. The integral flux above an energy threshold of ~250 GeV
is measured to be 0.8% of the flux of the Crab Nebula and the spectrum can be
described by a power law with a photon index of 2.7 +/- 0.5_stat +/- 0.2_sys.
No significant flux variability is detected in the data set. The discovery of
VHE gamma-ray emission from Centaurus A reveals particle acceleration in the
source to >TeV energies and, together with M 87, establishes radio galaxies as
a class of VHE emitters. |
Intermediate redshift calibration of Gamma-ray Bursts and cosmic
constraints in non-flat cosmology: We propose how to calibrate long gamma-ray burst (GRB) correlations employing
intermediate redshift data sets, instead of limiting to $z\simeq0$ catalogs. To
do so, we examine the most updated observational Hubble data (OHD) and baryonic
acoustic oscillations (BAO). We exploit the model-independent technique of
B\'ezier polynomial interpolation, alleviating de facto the well-known
circularity problem affecting GRB correlations. To get constraints on cosmic
parameters, using Markov chain Monte Carlo Metropolis algorithm, we distinguish
the influence on BAO scale, $r_{\rm s}$, Hubble constant $H_0$, luminosity
distance $D_{\rm L}(z)$ and spatial curvature $\Omega_k$. Inspired by the fact
that a few 0.4$\%$ error on $r_{\rm s}$ is got from Planck results, utterly
small compared with current BAO measurement errors, we discern two main cases,
namely $(r_{\rm s}/r_{\rm s}^{\rm fid})=1$ and $(r_{\rm s}/r_{\rm s}^{\rm
fid})\neq1$. For each occurrence, we first fix and then leave free the
Universe's spatial curvature. In all our treatments, we make use of the
well-consolidated \textit{Amati} correlation, furnishing tighter constraints on
the mass density than previous literature. In particular, our findings turn out
to be highly more compatible with those got, adopting the $\Lambda$CDM
paradigm, with standard candle indicators. Finally, we critically re-examine
the recent $H_0$ tension in view of our outcomes. | (Lack of) Cosmological evidence for dark radiation after Planck: We use Bayesian model comparison to determine whether extensions to
Standard-Model neutrino physics -- primarily additional effective numbers of
neutrinos and/or massive neutrinos -- are merited by the latest cosmological
data. Given the significant advances in cosmic microwave background (CMB)
observations represented by the Planck data, we examine whether Planck
temperature and CMB lensing data, in combination with lower redshift data, have
strengthened (or weakened) the previous findings. We conclude that the
state-of-the-art cosmological data do not show evidence for deviations from the
standard cosmological model (which has three massless neutrino families). This
does not mean that the model is necessarily correct -- in fact we know it is
incomplete as neutrinos are not massless -- but it does imply that deviations
from the standard model (e.g., non-zero neutrino mass) are too small compared
to the current experimental uncertainties to be inferred from cosmological data
alone. |
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