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Type 2 Active Galactic Nuclei with Double-Peaked [OIII] Lines. II.
Single AGNs with Complex Narrow-Line Region Kinematics are More Common than
Binary AGNs: (Abridged) Approximately 1% of low redshift (z<0.3) optically-selected type 2
AGNs show a double-peaked [OIII] narrow emission line profile in their
spatially-integrated spectra. Such features are usually interpreted as due
either to kinematics, such as biconical outflows and/or disk rotation of the
narrow line region (NLR) around single black holes, or to the relative motion
of two distinct NLRs in a merging pair of AGNs. Here we report follow-up near
infrared (NIR) imaging and optical slit spectroscopy of 31 double-peaked [OIII]
type 2 AGNs drawn from the SDSS parent sample presented in Liu et al (2010).
These data reveal a mixture of origins for the double-peaked feature. Roughly
10% of our objects are best explained by binary AGNs at (projected) kpc-scale
separations, where two stellar components with spatially coincident NLRs are
seen. ~ 50% of our objects have [OIII] emission offset by a few kpc,
corresponding to the two velocity components seen in the SDSS spectra, but
there are no corresponding double stellar components seen in the NIR imaging.
For those objects with sufficiently high quality slit spectra, we see velocity
and/or velocity dispersion gradients in [OIII] emission, suggestive of the
kinematic signatures of a single NLR. The remaining ~40% of our objects are
ambiguous, and will need higher spatial resolution observations to distinguish
between the two scenarios. Our observations therefore favor the kinematics
scenario with a single AGN for the majority of these double-peaked [OIII] type
2 AGNs. We emphasize the importance of combining imaging and slit spectroscopy
in identifying kpc binary AGNs, i.e., in no cases does one of these alone allow
an unambiguous identification. We estimate that ~ 0.5-2.5% of the z<0.3 type 2
AGNs are kpc-scale binary AGNs of comparable luminosities, with a relative
orbital velocity >~150 km/s. | astro-ph_CO |
Confronting predictions of the galaxy stellar mass function with
observations at high-redshift: We investigate the evolution of the galaxy stellar mass function at
high-redshift ($z\ge 5$) using a pair of large cosmological hydrodynamical
simulations: {\em MassiveBlack} and {\em MassiveBlack-II}. By combining these
simulations we can study the properties of galaxies with stellar masses greater
than $10^{8}\,{\rm M_{\odot}}\,h^{-1}$ and (co-moving) number densities of
$\log_{10}(\phi\, [{\rm Mpc^{-3}\,dex^{-1}}\,h^{3}])>-8$. Observational
determinations of the galaxy stellar mass function at very-high redshift
typically assume a relation between the observed UV luminosity and stellar
mass-to-light ratio which is applied to high-redshift samples in order to
estimate stellar masses. This relation can also be measured from the
simulations. We do this, finding two significant differences with the usual
observational assumption: it evolves strongly with redshift and has a different
shape. Using this relation to make a consistent comparison between galaxy
stellar mass functions we find that at $z=6$ and above the simulation
predictions are in good agreement with observed data over the whole mass range.
Without using the correct UV luminosity and stellar mass-to-light ratio, the
discrepancy would be up to two orders of magnitude for large galaxies
$>10^{10}\,{\rm M_{\odot}}\,h^{-1}$. At $z=5$, however the stellar mass
function for low mass $<10^{9}\,{\rm M_{\odot}}\,h^{-1}$ galaxies is
overpredicted by factors of a few, consistent with the behaviour of the UV
luminosity function, and perhaps a sign that feedback in the simulation is not
efficient enough for these galaxies. | astro-ph_CO |
Testing Parity Symmetry with the Polarized Cosmic Microwave Background: New physics in the early Universe could lead to parity-violation in the late
Universe, sourcing statistics whose sign changes under point reflection. The
best constraints on such phenomena have come from the Planck temperature
fluctuations; however, this is already cosmic-variance-limited down to
relatively small scales, thus only small improvements are expected in the
future. Here, we search for signatures of parity-violation in the polarized
CMB, using the Planck PR4 $T$- and $E$-mode data. We perform both a
simulation-based blind test for any parity-violating signal at $\ell<518$, and
a targeted search for primordial $U(1)$ gauge fields (and the amplitudes of a
generic collapsed model) at $\ell<2000$. In all cases, we find no evidence for
new physics, with the model-independent test finding consistency with the
FFP10/NPIPE simulation suite at $(-)0.4\sigma$, and the gauge field test
constraining the fractional amplitude of gauge fields during inflation to be
below $6\times 10^{-19}$ at $95\%$ confidence level for a fiducial model. The
addition of polarization data can significantly improve the constraints,
depending on the particular model of primordial physics, and the bounds will
tighten significantly with the inclusion of smaller-scale information. | astro-ph_CO |
Pushing the Limits of Detectability: Mixed Dark Matter from Strong
Gravitational Lenses: One of the frontiers for advancing what is known about dark matter lies in
using strong gravitational lenses to characterize the population of the
smallest dark matter halos. There is a large volume of information in strong
gravitational lens images -- the question we seek to answer is to what extent
we can refine this information. To this end, we forecast the detectability of a
mixed warm and cold dark matter scenario using the anomalous flux ratio method
from strong gravitational lensed images. The halo mass function of the mixed
dark matter scenario is suppressed relative to cold dark matter but still
predicts numerous low-mass dark matter halos relative to warm dark matter.
Since the strong lens signal is a convolution over a range of dark matter halo
masses and since the signal is sensitive to the specific configuration of dark
matter halos, not just the halo mass function, degeneracies between different
forms of suppression in the halo mass function, relative to cold dark matter,
can arise. We find that, with a set of lenses with different configurations of
the main deflector and hence different sensitivities to different mass ranges
of the halo mass function, the different forms of suppression of the halo mass
function between the warm dark matter model and the mixed dark matter model can
be distinguished with $40$ lenses with Bayesian odds of 29.4:1. | astro-ph_CO |
Shadows of trans-planckian physics on cosmology and the role of the
zero-point energy density: We consider the role of the zero-point energy of a quantum field in cosmology
and show that the flow of trans-planckian momenta due to redshift acts as a
source for this energy, regularized with a cut-off Lambda in physical momenta.
In order to fulfill Bianchi identity, we generalize Einstein equations, and
discuss the corresponding Friedmann homogeneous and isotropic models. In case
of a de Sitter phase, such as during inflation, the solution shows a
logarithmic behaviour of the Hubble parameter, and a primordial spectrum of
scalar perturbations characterized by the spectral index ns= 1- Lambda2/(3 pi
mP2) with mP the Planck mass. We also discuss possible implications of the
scenario on late accelerating stage of the Universe at small redshifts, and the
emergence of a fluid characterized by an equation of state w=P/rho= -1+
Lambda2/(9 pi mP2). Primordial perturbation spectrum and dark energy parameter
w are thus, predicted to be connected by the simple relation w=-(2+ns)/3. | astro-ph_CO |
Scale-dependent power spectrum from initial excited-de Sitter modes: In this paper, we calculate corrections of scalar perturbations spectra
resulting from excited-de Sitter modes as the nontrivial initial states. To
obtain these modes, we consider the asymptotic expansion of the Hankel
functions up to the higher order of 1/k{\tau} . Actually the Planck and WMAP
data impose some constrains on the Hankel function index. These observational
constraints and back-reaction effects stimulate us to use excited-de Sitter
modes. Finally, we nominate these nontrivial general solutions as the
fundamental mode functions during inflation and we calculate the corrected form
of scale-dependent power spectrum with trans-Planckian corrections, and in de
Sitter space-time limit the results reduce to the scale-invariant power
spectrum. | astro-ph_CO |
T-RaMiSu: The Two-meter Radio Mini Survey I. The Bootes Field: We present wide area, deep, high-resolution 153 MHz GMRT observations of the
NOAO Bootes field, adding to the extensive, multi-wavelength data of this
region. The observations, data reduction, and catalogue construction and
description are described here. The seven pointings produced a final mosaic
covering 30 square degrees with a resolution of 25". The rms noise is 2
mJy/beam in the centre of the image, rising to 4-5 mJy/beam on the edges, with
an average of 3 mJy/beam. Seventy-five per cent of the area has an rms < 4
mJy/beam. The extracted source catalogue contains 1289 sources detected at
5\sigma, of which 453 are resolved. We estimate the catalogue to be 92 per cent
reliable and 95 per cent complete at an integrated flux density limit of 14
mJy. The flux densities and astrometry have been corrected for systematic
errors. We calculate the differential source counts {which are in good
agreement with those in the literature and provide an important step forward in
quantifying the source counts at these low frequencies and low flux densities}.
The GMRT 153 MHz sources have been matched to the 1.4 GHz NVSS and 327 MHz
WENSS catalogues and spectral indices were derived. | astro-ph_CO |
Deep LBT/LUCI Spectroscopy of a Lyman-alpha Emitter Candidate at z ~ 7.7: We present deep spectroscopic observations of a Lyman-alpha emitter (LAE)
candidate at z ~ 7.7 using the infrared spectrograph LUCI on the 2 x 8.4m Large
Binocular Telescope (LBT). The candidate is the brightest among the four z ~
7.7 LAE candidates found in a narrow-band imaging survey by Krug et al. 2012.
Our spectroscopic data include a total of 7.5 hours of integration with
LBT/LUCI and are deep enough to significantly (3.2-4.9 sigma) detect the
Lyman-alpha emission line of this candidate, based on its Lyman-alpha flux 1.2
x 10^{-17} erg s^{-1} cm^{-2} estimated from the narrow-band photometry.
However, we do not find any convincing signal at the expected position of its
Lyman-alpha emission line, suggesting that this source is not an LAE at z ~
7.7. The non-detection in this work, together with the previous studies of z ~
7.7 LAEs, puts a strong constraint on the bright-end Lyman-alpha luminosity
function (LF) at z ~ 7.7. We find a rapid evolution of the Lyman-alpha LF from
z ~ 6.5 to 7.7: the upper limit of the z ~ 7.7 LF is more than 5 times lower
than the z ~ 6.5 LF at the bright end (f > 1.0 x 10^{-17} erg s^{-1} cm^{-2},
or L > 6.9 x 10^{42} erg s^{-1}). This is likely caused by an increasing
neutral fraction in the IGM that substantially attenuates Lyman-alpha emission
at z ~ 7.7. | astro-ph_CO |
Directional detection of Dark Matter: Directional detection of galactic Dark Matter is a promising search strategy
for discriminating genuine WIMP events from background ones. However, to take
full advantage of this powerful detection method, one need to be able to
extract information from an observed recoil map to identify a WIMP signal. We
present a comprehensive formalism, using a map-based likelihood method allowing
to recover the main incoming direction of the signal, thus proving its galactic
origin, and the corresponding significance. Constraints are then deduced in the
(sigma_n, m_chi) plane. | astro-ph_CO |
Evolution of Galaxy Stellar Mass Functions, Mass Densities, and Mass to
Light Ratios from z 7 to z 4: We derive stellar masses from SED fitting to rest-frame optical and UV fluxes
for 401 star-forming galaxies at z 4, 5, and 6 from Hubble-WFC3/IR observations
of the ERS combined with the deep GOODS-S Spitzer/IRAC data (and include a
previously-published z 7 sample). A mass-luminosity relation with strongly
luminosity-dependent M/Luv ratios is found for the largest sample (299
galaxies) at z 4. The relation M \propto L_{UV,1500}^(1.7+/-0.2) has a
well-determined intrinsic sample variance of 0.5 dex. This relation is also
consistent with the more limited samples at z 5-7. This z 4 mass-luminosity
relation, and the well-established faint UV luminosity functions at z 4-7, are
used to derive galaxy mass functions (MF) to masses M~10^8 at z 4-7. A bootstap
approach is used to derive the MFs to account for the large scatter in the
M--Luv relation and the luminosity function uncertainties, along with an
analytical crosscheck. The MFs are also corrected for the effects of
incompleteness. The incompleteness-corrected MFs are steeper than previously
found, with slopes \alpha_M-1.4 to -1.6 at low masses. These slopes are,
however, still substantially flatter than the MFs obtained from recent
hydrodynamical simulations. We use these MFs to estimate the stellar mass
density (SMD) of the universe to a fixed M_{UV,AB}<-18 as a function of
redshift and find a SMD growth \propto(1+z)^{-3.4 +/-0.8} from z 7 to z 4. We
also derive the SMD from the completeness-corrected MFs to a mass limit
M~10^{8} Msun. Such completeness-corrected MFs and the derived SMDs will be
particularly important for model comparisons as future MFs reach to lower
masses. | astro-ph_CO |
Decoding the bispectrum of single-field inflation: Galileon fields arise naturally from the decoupling limit of massive
gravities, and possess special self-interactions which are protected by a
spacetime generalization of Galilean symmetry. We briefly revisit the
inflationary phenomenology of Galileon theories. Working from recent
computations of the fluctuation Lagrangian to cubic order in the most general
model with second-order equations of motion, we show that a distinct shape is
present but with suppressed amplitude. A similar shape has been found in other
higher-derivative models. It may be visible in a theory tuned to suppress the
leading-order shapes, or if the overall bispectrum has large amplitude. Using a
partial-wave expansion of the bispectrum, we suggest a possible origin for the
frequent appearance of this shape. It follows that models with very disparate
microphysics can produce very similar bispectra. We argue that it may be more
profitable to distinguish these models by searching for relations between the
amplitudes of these common shapes. We illustrate this method using the example
of DBI and k-inflation. | astro-ph_CO |
BSG alignment of SDSS galaxy groups: We study the alignment signal between the distribution of brightest satellite
galaxies (BSGs) and the major axis of their host groups using SDSS group
catalog constructed by Yang et al. (2007). After correcting for the effect of
group ellipticity, a statistically significant (~ 5\sigma) major-axis alignment
is detected and the alignment angle is found to be 43.0 \pm 0.4 degrees. More
massive and richer groups show stronger BSG alignment. The BSG alignment around
blue BCGs is slightly stronger than that around red BCGs. And red BSGs have
much stronger major-axis alignment than blue BSGs. Unlike BSGs, other
satellites do not show very significant alignment with group major axis. We
further explore the BSG alignment in semi-analytic model (SAM) constructed by
Guo et al. (2011). We found general good agreement with observations: BSGs in
SAM show strong major-axis alignment which depends on group mass and richness
in the same way as observations; and none of other satellites exhibit prominent
alignment. However, discrepancy also exists in that the SAM shows opposite BSG
color dependence, which is most probably induced by the missing of large scale
environment ingredient in SAM. The combination of two popular scenarios can
explain the detected BSG alignment. The first one: satellites merged into the
group preferentially along the surrounding filaments, which is strongly aligned
with the major axis of the group. The second one: BSGs enter their host group
more recently than other satellites, then will preserve more information about
the assembling history and so the major-axis alignment. In SAM, we found
positive evidence for the second scenario by the fact that BSGs merged into
groups statistically more recently than other satellites. On the other hand,
although is opposite in SAM, the BSG color dependence in observation might
indicate the first scenario as well. | astro-ph_CO |
An indirect measurement of gas evolution in galaxies at $0.5\leq z \leq
2.0$: One key piece of information missing from high redshift galaxy surveys is the
galaxies' cold gas contents. We present a new method to indirectly determine
cold gas surface densities and integrated gas masses from galaxy star formation
rates and to separate the atomic and molecular gas components. Our predicted
molecular and total gas surface densities and integrated masses are in very
good agreement with direct measurements quoted in the literature for low and
high-z galaxies. We apply this method to predict the gas content for a sample
of $\sim 57000$ galaxies in the COSMOS field at $0.5 \leq z \leq 2.0$, selected
to have $I_{AB} < 24$ mag. This approach allows us to investigate in detail the
redshift evolution of galaxy cold and molecular gas content versus stellar mass
and to provide fitting formulae for galaxy gas fractions. We find a clear trend
between galaxy gas fraction, molecular gas fraction and stellar mass with
redshift, suggesting that massive galaxies consume and/or expel their gas at
higher redshift than less massive objects and have lower fractions of their gas
in molecular form. The characteristic stellar mass separating gas- from
stellar-dominated galaxies decreases with time. This indicates that massive
galaxies reach a gas-poor state earlier than less massive objects. These trends
can be considered to be another manifestation of downsizing in star formation
activity. | astro-ph_CO |
Spacetime variation of $α$ and the CMB power spectra after the
recombination: The possible variation of the fine structure constant may be due to the
non-minimal coupling of the electromagnetic field to a light scalar field which
can be the candidate of dark energy. Its dynamical nature renders the fine
structure constant varies with time as well as space. In this paper we point
out the spatial fluctuation of the fine structure will modify the power spectra
of the temperature and the polarization of the cosmic microwave background. We
show explicitly that the fluctuations of the coupled scalar field generate new
temperature anisotropies at the linear order and induce a $B$ mode to the
polarization at higher order in general. | astro-ph_CO |
The first bent double lobe radio source in a known cluster filament:
Constraints on the intra-filament medium: We announce the first discovery of a bent double lobe radio source (DLRS) in
a known cluster filament. The bent DLRS is found at a distance of 3.4 Mpc from
the center of the rich galaxy cluster, Abell~1763. We derive a bend angle
alpha=25deg, and infer that the source is most likely seen at a viewing angle
of Phi=10deg. From measuring the flux in the jet between the core and further
lobe and assuming a spectral index of 1, we calculate the minimum pressure in
the jet, (8.0+-3.2)x10^-13 dyn/cm^2, and derive constraints on the
intra-filament medium (IFM) assuming the bend of the jet is due to ram
pressure. We constrain the IFM to be between (1-20)x10^-29 gm/cm^3. This is
consistent with recent direct probes of the IFM and theoretical models. These
observations justify future searches for bent double lobe radio sources located
several Mpc from cluster cores, as they may be good markers of super cluster
filaments. | astro-ph_CO |
Orbital evolution of the Carina dwarf galaxy and self-consistent star
formation history determination: We present a new study of the evolution of the Carina dwarf galaxy that
includes a simultaneous derivation of its orbit and star formation history. The
structure of the galaxy is constrained through orbital parameters derived from
the observed distance, proper motions, radial velocity and star formation
history. The different orbits admitted by the large proper motion errors are
investigated in relation to the tidal force exerted by an external potential
representing the Milky Way (MW). Our analysis is performed with the aid of
fully consistent N-body simulations that are able to follow the dynamics and
the stellar evolution of the dwarf system in order to determine
self-consistently the star formation history of Carina. We find a star
formation history characterized by several bursts, partially matching the
observational expectation. We find also compatible results between dynamical
projected quantities and the observational constraints. The possibility of a
past interaction between Carina and the Magellanic Clouds is also separately
considered and deemed unlikely. | astro-ph_CO |
Constraints on a mixed model of dark matter particles and primordial
black holes from the Galactic 511 keV line: The galactic 511 keV gamma-ray line has been observed since 1970's, and was
identified as the result of electron-positron annihilation, but the origin of
such positrons is still not clear. Apart from the astrophysical explanations,
the possibilities that such positrons come from dark matter (DM) annihilation
are also widely studied. Primordial black hole (PBH) is also an extensively
studied candidate of DM. If PBHs exist, the DM particles may be gravitationally
bound to the PBHs and form halo around PBHs with density spikes. DM
annihilation in these density spikes can enhance the production rate of
positrons from DM particles, but the signal morphology is similar to the
decaying DM. We consider such a mixed model consisting of DM particles and PBHs
and obtain the upper limit from the data of 511 keV gamma-ray line from
INTEGRAL/SPI on the decaying component of DM particles and the constraint on
the PBH abundance. These constraints are general and independent of particle DM
models. For the mixed model consisting of excited DM and PBHs, the constraints
on the PBH abundance can be down to $O(10^{-17})$ for DM particle with mass
around $1~\mathrm{TeV}$, which is more stringent than that obtained from the
extragalactic gamma-ray background. | astro-ph_CO |
Warm Molecular Hydrogen Emission in Normal Edge-On Galaxies NGC 4565 and
NGC 5907: We have observed warm molecular hydrogen in two nearby edge-on disk galaxies,
NGC 4565 and NGC 5907, using the Spitzer high-resolution infrared spectrograph.
The 0-0 S(0) 28.2 micron and 0-0 S(1) 17.0 micron pure rotational lines were
detected out to 10 kpc from the center of each galaxy on both sides of the
major axis, and in NGC 4565 the S(0) line was detected at r = 15 kpc on one
side. This location lies beyond a steep drop in the radio continuum emission
from cosmic rays in the disk. Despite indications that star formation activity
decreases with radius, the H2 excitation temperature and the ratio of the H2
line and the far-IR luminosity surface densities, Sigma_L(H2}/Sigma_L(TIR},
change very little as a function of radius, even into the diffuse outer region
of the disk of NGC 4565. This suggests that the source of excitation of the H2
operates over a large range of radii, and is broadly independent of the
strength and relative location of UV emission from young stars. Although
excitation in photodissociation regions is the most common explanation for the
widespread H2 emission, cosmic ray heating or shocks cannot be ruled out. The
inferred mass surface densities of warm molecular hydrogen in both edge-on
galaxies differ substantially, being 4(-60) M_solar/pc^2 and 3(-50)
M_solar/pc^2 at r = 10 kpc for NGC 4565 and NGC 5907, respectively. The higher
values represent very unlikely point-source upper limits. The point source case
is not supported by the observed emission distribution in the spectral slits.
These mass surface densities cannot support the observed rotation velocities in
excess of 200 km/s. Therefore, warm molecular hydrogen cannot account for dark
matter in these disk galaxies, contrary to what was implied by a previous ISO
study of the nearby edge-on galaxy NGC 891. | astro-ph_CO |
Cross-correlation of the HI 21-cm Signal and Lyman-alpha Forest: A Probe
Of Cosmology: Separating the cosmological redshifted 21-cm signal from foregrounds is a
major challenge. We present the cross-correlation of the redshifted 21-cm
emission from neutral hydrogen (HI) in the post-reionization era with the
Ly-alpha forest as a new probe of the large scale matter distribution in the
redshift range z=2 to 3 without the problem of foreground contamination. Though
the 21-cm and the Ly-alpha forest signals originate from different
astrophysical systems, they are both expected to trace the underlying dark
matter distribution on large scales. The multi-frequency angular
cross-correlation power spectrum estimator is found to be unaffected by the
discrete quasar sampling, which only affects the noise in the estimate. We
consider a hypothetical redshifted 21-cm observation in a single field of view
1.3 degrees (FWHM) centered at z=2.2 where the binned 21-cm angular power
spectrum can be measured at an SNR of 3 sigma or better across the range 500 <
l < 4000 . Keeping the parameters of the 21-cm observation fixed, we have
estimated the SNR for the cross-correlation signal varying the quasar angular
number density n of the Ly-alpha forest survey. Assuming that the spectra have
SNR ~5 in pixels of length 44 km/s, we find that a 5 sigma detection of the
cross-correlation signal is possible at 600 < l < 2000 with n=4 deg^{-2}. This
value of n is well within the reach of upcoming Ly-alpha forest surveys. The
cross-correlation signal will be a new, independent probe of the astrophysics
of the diffuse IGM, the growth of structure and the expansion history of the
Universe. | astro-ph_CO |
A Massive, Cooling-Flow-Induced Starburst in the Core of a Highly
Luminous Galaxy Cluster: In the cores of some galaxy clusters the hot intracluster plasma is dense
enough that it should cool radiatively in the cluster's lifetime, leading to
continuous "cooling flows" of gas sinking towards the cluster center, yet no
such cooling flow has been observed. The low observed star formation rates and
cool gas masses for these "cool core" clusters suggest that much of the cooling
must be offset by astrophysical feedback to prevent the formation of a runaway
cooling flow. Here we report X-ray, optical, and infrared observations of the
galaxy cluster SPT-CLJ2344-4243 at z = 0.596. These observations reveal an
exceptionally luminous (L_2-10 keV = 8.2 x 10^45 erg/s) galaxy cluster which
hosts an extremely strong cooling flow (dM/dt = 3820 +/- 530 Msun/yr). Further,
the central galaxy in this cluster appears to be experiencing a massive
starburst (740 +/- 160 Msun/yr), which suggests that the feedback source
responsible for preventing runaway cooling in nearby cool core clusters may not
yet be fully established in SPT-CLJ2344-4243. This large star formation rate
implies that a significant fraction of the stars in the central galaxy of this
cluster may form via accretion of the intracluster medium, rather than the
current picture of central galaxies assembling entirely via mergers. | astro-ph_CO |
Integral field spectroscopy of a sample of nearby galaxies: II.
Properties of the H ii regions: In this work we analyze the spectroscopic properties of a large number of H
ii regions, \sim2600, located in 38 galaxies. The sample of galaxies has been
assembled from the face-on spirals in the PINGS survey and a sample described
in M\'armol-Queralt\'o (2011, henceforth Paper I). All the galaxies were
observed using Integral Field Spectroscopy with a similar setup, covering their
optical extension up to \sim2.4 effective radii within a wavelength range from
\sim3700 to \sim6900{\AA}. We develop a new automatic procedure to detect H ii
regions, based on the contrast of the H{\alpha} intensity maps. Once detected,
the procedure provides us with the integrated spectra of each individual
segmented region. A well-tested automatic decoupling procedure has been applied
to remove the underlying stellar population, deriving the main proper- ties of
the strongest emission lines in the considered wavelength range (covering from
[O ii] {\lambda}3727 to [S ii] {\lambda}6731). A final catalogue of the
spectroscopic properties of these regions has been created for each galaxy. In
the current study we focused on the understanding of the average properties of
the H ii regions and their radial distributions. We find that the gas-phase
oxygen abundance and the H{\alpha} equivalent width present negative and
positive gradient, respectively. The distribution of slopes is statistically
compatible with a random Gaussian distribution around the mean value, if the
radial distances are measured in units of the respective effective radius. No
difference in the slope is found for galaxies of different morphologies:
barred/non-barred, grand-design/flocculent. Therefore, the effective radius is
a universal scale length for gradients in the evolution of galaxies. Other
properties have a larger variance across each object. | astro-ph_CO |
Compact molecular disc and ionized gas outflows within 350 pc of the
active nucleus of Mrk 1066: We present stellar and gaseous kinematics of the inner 350 pc radius of the
Seyfert galaxy Mrk1066 derived from J and Kl bands data obtained with the
Gemini NIFS at a spatial resolution of 35 pc. The stellar velocity field is
dominated by rotation in the galaxy plane but shows an S-shape distortion along
the galaxy minor axis which seems to be due to an oval structure seen in an
optical continuum image. Along this oval, between 170 and 280 pc from the
nucleus we find a partial ring of low sigma (~50 km/s) attributed to an
intermediate age stellar population. Fro measurements of the emission-line
fluxes and profiles ([PII]1.19um, [FeII]1.26um, Pa-beta and H2 2.12um), we have
constructed maps for the gas centroid velocity, velocity dispersion, as well as
channel maps. The velocity fields for all emission lines are dominated by a
similar rotation pattern to that observed for the stars, but are distorted by
the presence of two structures: (i) a compact rotating disc with radius r~70
pc; (ii) outflows along the radio jet which is oriented approximately along the
galaxy major axis. The compact rotating disc is more conspicuous in the H2
emitting gas, which presents the smallest sigma values and most clear rotation
pattern, supporting a location in the galaxy plane. We estimate a gas mass for
the disc of ~10^7Msun. The H2 kinematics further suggests that the nuclear disc
is being fed by gas coming from the outer regions. The outflow is more
conspicuous in the [FeII] emitting gas, which presents the highest sigma values
(up to 150 km/s) and the highest blue and redshifts of up to 500 km/s, while
the highest stellar rotation velocity is only 130 km/s. We estimate a
mass-outflow rate in ionized gas of 0.06 Msun/yr. The derived kinematics for
the emitting gas is similar to that observed in previous studies supporting
that the H2 is a tracer of the AGN feeding and the [FeII] of its feedback. | astro-ph_CO |
Galaxy Cluster Science with the Sunyaev-Zel'dovich Effect: Studying galaxy clusters through their Sunyaev-Zel'dovich (SZ) imprint on the
Cosmic Microwave Background has many important advantages. The total SZ signal
is an accurate and precise tracer of the total pressure in the intra-cluster
medium and of cluster mass, the key observable for using clusters as
cosmological probes. Band 5 observations with SKA-MID towards cluster surveys
from the next generation of X-ray telescopes such as e-ROSITA and from Euclid
will provide the robust mass estimates required to exploit these samples. This
will be especially important for high redshift systems, arising from the SZ's
unique independence to redshift. In addition, galaxy clusters are very
interesting astrophysical systems in their own right, and the SKA's excellent
surface brightness sensitivity down to small angular scales will allow us to
explore the detailed gas physics of the intra-cluster medium. | astro-ph_CO |
Scalar-tensor theories of gravity, neutrino physics, and the $H_0$
tension: We use $Planck$ 2018 data to constrain the simplest models of scalar-tensor
theories characterized by a coupling to the Ricci scalar of the type $F(\sigma)
R$ with $F(\sigma) = N_{pl}^2 + \xi \sigma^2$. We update our results with
previous $Planck$ and BAO data releases obtaining the tightest constraints to
date on the coupling parameters, that is $\xi < 5.5 \times 10^{-4}$ for
$N_{pl}=0$ (induced gravity or equivalently extended Jordan-Brans-Dicke) and
$(N_{pl} \sqrt{8 \pi G})-1 < 1.8 \times 10^{-5}$ for $\xi = -1/6$ (conformal
coupling), both at 95% CL. Because of a modified expansion history after
radiation-matter equality compared to the $\Lambda$CDM model, all these
dynamical models accommodate a higher value for $H_0$ and therefore alleviate
the tension between $Planck$/BAO and distance-ladder measurement from SNe Ia
data from $4.4\sigma$ at best to $2.3\sigma$. We show that all these results
are robust to changes in the neutrino physics. In comparison to the
$\Lambda$CDM model, partial degeneracies between neutrino physics and the
coupling to the Ricci scalar allow for smaller values $N_{\rm eff} \sim 2.8$,
$1\sigma$ lower compared to the standard $N_{\rm eff} = 3.046$, and relax the
upper limit on the neutrino mass up to 40%. | astro-ph_CO |
The pre-launch Planck Sky Model: a model of sky emission at
submillimetre to centimetre wavelengths: We present the Planck Sky Model (PSM), a parametric model for the generation
of all-sky, few arcminute resolution maps of sky emission at submillimetre to
centimetre wavelengths, in both intensity and polarisation. Several options are
implemented to model the cosmic microwave background, Galactic diffuse emission
(synchrotron, free-free, thermal and spinning dust, CO lines), Galactic H-II
regions, extragalactic radio sources, dusty galaxies, and thermal and kinetic
Sunyaev-Zeldovich signals from clusters of galaxies. Each component is
simulated by means of educated interpolations/extrapolations of data sets
available at the time of the launch of the Planck mission, complemented by
state-of-the-art models of the emission. Distinctive features of the
simulations are: spatially varying spectral properties of synchrotron and dust;
different spectral parameters for each point source; modeling of the clustering
properties of extragalactic sources and of the power spectrum of fluctuations
in the cosmic infrared background. The PSM enables the production of random
realizations of the sky emission, constrained to match observational data
within their uncertainties, and is implemented in a software package that is
regularly updated with incoming information from observations. The model is
expected to serve as a useful tool for optimizing planned microwave and
sub-millimetre surveys and to test data processing and analysis pipelines. It
is, in particular, used for the development and validation of data analysis
pipelines within the planck collaboration. A version of the software that can
be used for simulating the observations for a variety of experiments is made
available on a dedicated website. | astro-ph_CO |
Constraint on $f(R)$ Gravity through the Redshift Space Distortion: In this paper, a specific family of $f(R)$ models that can produce the
$\Lambda$CDM background expansion history is constrained by using the currently
available geometric and dynamic probes. The scale dependence of the growth rate
$f(z,k)$ in this specific family of $f(R)$ model is shown. Therefore to
eliminate the scale dependence of $f\sigma_8(z)$ in theory, which usually is
defined as the product of $f(z,k)$ and $\sigma_8(z)$, we define
$f\sigma_8(z)=d\sigma_8(z)/d\ln a$ which is obviously scale independent and
reproduces the conventional definition in the standard $\Lambda$CDM cosmology.
In doing so, under the assumption that future probes having the same best fit
values as the current ten data points of $f\sigma_8(z)$, even having $20\%$
error bars enlarged, we find a preliminary constraint
$f_{R0}=-2.58_{-0.58}^{+2.14}\times 10^{-6}$ in $1\sigma$ regions. This
indicates the great potential that redshift space distortions have in
constraining modified gravity theories. We also discuss the nonlinear matter
power spectrum based on different halo fit models. | astro-ph_CO |
Does the Corona Borealis Supercluster form a giant binary-like system?: The distribution of local gravitational potentials generated by a complete
volume-limited sample of galaxy groups and clusters filling the Corona Borealis
region has been derived to search for new gravitational hints in the context of
clus-tering analysis unrevealed by alternative methodologies. Mapping such a
distribution as a function of spatial positions, the deepest potential wells in
the sample trace unambiguously the locations of the densest galaxy cluster
clumps providing the physical keys to bring out gravitational features
connected to the formation, composition and evolution of the major clustered
structures filling that region. As expected, the three deepest potential wells
found at Equatorial coordinates: (~ 230{\deg}, ~ 28{\deg}, z ~ 0.075), (~
240{\deg}, ~ 27{\deg}, z ~ 0.09) and, (227{\deg}, 5.8{\deg}, z ~ 0.0788)
correspond to massive superclusters of galaxy groups and clusters identified as
the Corona Borealis, A2142 and Virgo-Serpent, respectively. However, the
deepest isopotential contours around the Corona Borealis and A2142
superclusters seem to suggest a gravitational feature similar to a giant
binary-like system connected by a filamentary structure. To a first
approximation, it seems unlikely that this hypothesized system could be
gravitationally bound. | astro-ph_CO |
Projected two- and three-point statistics: Forecasts and mitigation of
non-linear RSDs: The combination of two- and three-point clustering statistics of galaxies and
the underlying matter distribution has the potential to break degeneracies
between cosmological parameters and nuisance parameters and can lead to
significantly tighter constraints on parameters describing the composition of
the Universe and the dynamics of inflation. Here we investigate the relation
between biases in the estimated parameters and inaccurate modelling of
non-linear redshift-space distortions for the power spectrum and bispectrum of
projected galaxy density fields and lensing convergence. Non-linear
redshift-space distortions are one of the leading systematic uncertainties in
galaxy clustering. Projections along the line of sight suppress radial modes
and are thus allowing a trade-off between biases due to non-linear
redshift-space distortions and statistical uncertainties. We investigate this
bias-error trade-off for a CMASS-like survey with a varying number of redshift
bins. Improved modelling of the non-linear redshift-space distortions allows
the recovery of more radial information when controlling for biases. Not
modelling non-linear redshift space distortions inflates error bars for almost
all parameters by 20%. The information loss for the amplitude of local
non-Gaussianities is smaller, since it is best constrained from large scales.
In addition, we show empirically that one can recover more than 99% of the 3D
power spectrum information if the depth of the tomographic bins is reduced to
10 $h^{-1}$Mpc. | astro-ph_CO |
Probing the Intermediate-Age Globular Clusters in NGC 5128 from
Ultraviolet Observations: We explore the age distribution of the globular cluster (GC) system of the
nearby elliptical galaxy NGC 5128 using ultraviolet (UV) photometry from Galaxy
Evolution Explorer (GALEX) observations, with UV - optical colors used as the
age indicator. Most GCs in NGC 5128 follow the general trends of GCs in M31 and
Milky Way in UV - optical color-color diagram, which indicates that the
majority of GCs in NGC 5128 are old similar to the age range of old GCs in M31
and Milky Way. A large fraction of spectroscopically identified
intermediate-age GC (IAGC) candidates with ~ 3-8 Gyr are not detected in the
FUV passband. Considering the nature of intermediate-age populations being
faint in the far-UV (FUV) passband, we suggest that many of the
spectroscopically identified IAGCs may be truly intermediate in age. This is in
contrast to the case of M31 where a large fraction of spectroscopically
suggested IAGCs are detected in FUV and therefore may not be genuine IAGCs but
rather older GCs with developed blue horizontal branch stars. Our UV photometry
strengthens the results previously suggesting the presence of GC and stellar
subpopulation with intermediate age in NGC 5128. The existence of IAGCs
strongly indicates the occurrence of at least one more major star formation
episode after a starburst at high redshift. | astro-ph_CO |
The investigations of anisotropy in orientations of galaxies: In 1994 Parnovsky, Karachentsev and Karachentseva suggested a modified method
for investigation of the orientations of galaxies. Using this method they
analyzed galaxies from the UGC and ESO catalogues, as well as from their's own
catalogue inclusive of flat, edge-on galaxies. They found statistically
significant anisotropy in the galaxies orientations'. In 1995 Flin suggested
that this anisotropy has to be specific to LOcal Supercluster (LSC) In the
present paper, using the method proposed by Parnovsky, Karachentsev and
Karachentseva in 1994, we analyzed orientation of galaxies in the sample of
galaxies belonging to LSC founding only a weak anisotropy. The relation of this
method to Hawley and Peebles (1975) method of the investigation of the
orientation of galaxies was discussed as well. | astro-ph_CO |
Revisit of constraints on holographic dark energy: SNLS3 dataset with
the effects of time-varying $β$ and different light-curve fitters: Previous studies have shown that for the Supernova Legacy Survey three-year
(SNLS3) data there is strong evidence for the redshift-evolution of
color-luminosity parameter $\beta$ of type Ia supernovae (SN Ia). In this
paper, we explore the effects of varying $\beta$ on the cosmological
constraints of holographic dark energy (HDE) model. In addition to the SNLS3
data, we also use Planck distance prior data of cosmic microwave background
(CMB), as well as galaxy clustering (GC) data extracted from Sloan Digital Sky
Survey (SDSS) data release 7 and Baryon Oscillation Spectroscopic Survey
(BOSS). We find that, for the both cases of using SN data alone and using
SN+CMB+GC data, involving an additional parameter of $\beta$ can reduce
$\chi^2$ by $\sim$ 36; this shows that $\beta$ deviates from a constant at
6$\sigma$ confidence levels. Adopting SN+CMB+GC data, we find that compared to
the constant $\beta$ case, varying $\beta$ yields a larger fractional matter
density $\Omega_{m0}$ and a smaller reduced Hubble constant $h$; moreover,
varying $\beta$ significantly increases the value of HDE model parameter $c$,
leading to $c\approx 0.8$, consistent with the constraint results obtained
before Planck. These results indicate that the evolution of $\beta$ should be
taken into account seriously in the cosmological fits. In addition, we find
that relative to the differences between the constant $\beta$ and varying
$\beta(z)$ cases, the effects of different light-curve fitters on parameter
estimation are very small. | astro-ph_CO |
The role of multiple images and model priors in measuring $H_0$ from
supernova Refsdal in galaxy cluster MACS J1149.5+2223: Multiple image gravitational lensing systems with measured time delays
provide a promising one-step method for determining $H_0$. MACS J1149, which
lenses SN Refsdal into a quad S1-S4, and two other widely separated images, SX
and SY, is a perfect candidate. If time delays are pinned down, the remaining
uncertainty arises from the mass distribution in the lens. In MACS J1149, the
mass in the relevant lens plane region can be constrained by (i) many multiple
images, (ii) the mass of the galaxy splitting S1-S4 (which, we show, is
correlated with $H_0$), (iii) magnification of SX (also correlated with $H_0$),
and (iv) prior assumptions on the mass distribution. Our goal is not to
estimate $H_0$, but to understand its error budget, i.e., estimate
uncertainties associated with each of these constraints. Using multiple image
positions alone, yields very large uncertainty, despite the fact that the
position of SX is recovered to within $\!\le\!0.036$" (rms $\!\le\!0.36$") by
GRALE lens inversion. Fixing the mass of the galaxy that splits S1-S4 reduces
$1\sigma$ uncertainties to $\sim 23\%$, while fixing the magnification of SX
yields $1\sigma$ uncertainties of $32\%$. We conclude that smaller
uncertainties, of order few percent, are a consequence of imposing prior
assumptions on the shapes of the galaxy and cluster mass distributions, which
may or may not apply in a highly non-equilibrium environment of a merging
cluster. We propose that if a measurement of $H_0$ is to be considered
reliable, it must be supported by a wide range of lens inversion methods. | astro-ph_CO |
Constraint on the minimally extended varying speed of light using time
dilations in type Ia supernovae: The Friedmann-Lema\^{i}tre-Robertson-Walker model establishes the correlation
between redshifts and distances. It has a metric expansion of space. As a
result, the wavelength of photons propagating through the expanding space is
stretched, creating the cosmological redshift, $z$. It also relates the
frequency of light detected by a local observer to that emitted from a distant
source. In standard cosmology (\textit{i.e.}, a constant speed light model),
this relation is given by a factor $1/(1+z)$. However, this ratio is modified
in the minimally extended varying speed of light model (meVSL, $c = c_0
a^{b/4}$) as $1/(1+z)^{1-b/4}$. This time dilation effect is detected as the
observed rate of the time variation in the intensity of emitted radiation. The
spectra of type Ia supernovae (SNe Ia) provide a reliable way to measure the
apparent aging rate of distant objects. We use data on 13 high-redshift ($0.28
\leq z \leq 0.62$) SNe Ia to obtain $b = 0.198 \pm 0.415$ at the $1$-$\sigma$
confidence interval. The current data is too sparse to give meaningful
constrain on the meVSL and cannot distinguish the meVSL model from the standard
model. | astro-ph_CO |
The Absolute Magnitudes of Type Ia Supernovae in the Ultraviolet: We examine the absolute magnitudes and light-curve shapes of 14
nearby(redshift z = 0.004--0.027) Type Ia supernovae (SNe~Ia) observed in the
ultraviolet (UV) with the Swift Ultraviolet/Optical Telescope. Colors and
absolute magnitudes are calculated using both a standard Milky Way (MW)
extinction law and one for the Large Magellanic Cloud that has been modified by
circumstellar scattering. We find very different behavior in the near-UV
filters (uvw1_rc covering ~2600-3300 A after removing optical light, and u
~3000--4000 A) compared to a mid-UV filter (uvm2 ~2000-2400 A). The uvw1_rc-b
colors show a scatter of ~0.3 mag while uvm2-b scatters by nearly 0.9 mag.
Similarly, while the scatter in colors between neighboring filters is small in
the optical and somewhat larger in the near-UV, the large scatter in the
uvm2-uvw1 colors implies significantly larger spectral variability below 2600
A. We find that in the near-UV the absolute magnitudes at peak brightness of
normal SNe Ia in our sample are correlated with the optical decay rate with a
scatter of 0.4 mag, comparable to that found for the optical in our sample.
However, in the mid-UV the scatter is larger, ~1 mag, possibly indicating
differences in metallicity. We find no strong correlation between either the UV
light-curve shapes or the UV colors and the UV absolute magnitudes. With larger
samples, the UV luminosity might be useful as an additional constraint to help
determine distance, extinction, and metallicity in order to improve the utility
of SNe Ia as standardized candles. | astro-ph_CO |
VERITAS Observations of the BL Lac Object PG 1553+113 Between May 2010
and May 2011: VERITAS, an array of imaging atmospheric-Cherenkov telescopes, studies
blazars in the energy range between ~100 GeV and ~30 TeV. With its excellent
sensitivity at these energies, and ever-deepening source exposures, VERITAS is
in a position to probe distant blazars for clear absorption signatures in their
very-high-energy gamma-ray spectra due to interactions with the extragalactic
background light (EBL). We discuss results from recent VERITAS observations of
PG 1553+113 (z > 0.4) which have resulted in the most significant
very-high-energy detection ever obtained for this source. The most recent
VERITAS spectral measurements are used to place an upper limit on the source
redshift of z < 0.5 at the 95% confidence level. Also discussed are the
prospects of using these observations, along with those of other hard- spectrum
blazars, to place constraints on the EBL. | astro-ph_CO |
Quintessence's Last Stand?: Current cosmological data puts increasing pressure on models of dark energy
in the freezing class, e.g. early dark energy or those with equation of state
$w$ substantially different from $-1$. We investigate to what extent data will
distinguish the thawing class of quintessence from a cosmological constant.
Since thawing dark energy deviates from $w=-1$ only at late times, we find that
deviations $1+w\lesssim0.1$ are difficult to see even with next generation
measurements; however, modest redshift drift data can improve the sensitivity
by a factor of two. Furthermore, technical naturalness prefers specific thawing
models. | astro-ph_CO |
SDSS superclusters: morphology and galaxy content: We compare the galaxy populations in superclusters of different morphology in
the nearby Universe (180 < d < 270 Mpc) to see whether the inner structure and
overall morphology of superclusters are important in shaping galaxy properties
in superclusters. Supercluster morphology has been found with Minkowski
functionals. We analyse the probability density distributions of colours,
morphological types, stellar masses, star formation rates (SFR) of galaxies,
and the peculiar velocities of the main galaxies in groups in superclusters of
filament and spider types, and in the field. We show that the fraction of red,
early-type, low SFR galaxies in filament-type superclusters is higher than in
spider-type superclusters; in low-density global environments their fraction is
lower than in superclusters. In all environments the fraction of red, high
stellar mass, and low SFR galaxies in rich groups is higher than in poor
groups. In superclusters of spider morphology red, high SFR galaxies have
higher stellar masses than in filament-type superclusters. Groups of equal
richness host galaxies with larger stellar masses, a larger fraction of
early-type and red galaxies, and a higher fraction of low SFR galaxies, if they
are located in superclusters of filament morphology. The peculiar velocities of
the main galaxies in groups from superclusters of filament morphology are
higher than in those of spider morphology. Groups with higher peculiar
velocities of their main galaxies in filament-type superclusters are located in
higher density environment than those with low peculiar velocities. There are
significant differences between galaxy populations of the individual richest
superclusters. Therefore both local (group) and global (supercluster)
environments and even supercluster morphology play an important role in the
formation and evolution of galaxies. | astro-ph_CO |
A "Light," Centrally-Concentrated Milky Way Halo?: We discuss a novel approach to "weighing" the Milky Way dark matter halo, one
that combines the latest samples of halo stars selected from the Sloan Digital
Sky Survey (SDSS) with state-of-the-art numerical simulations of Milky Way
analogs. The fully cosmological runs employed in the present study include
"Eris", one of the highest-resolution hydrodynamical simulations of the
formation of a M_vir=8e11 M_sun late-type spiral, and the dark-matter only
M_vir=1.7e12 M_sun "Via Lactea II" simulation. Eris provides an excellent
laboratory for creating mock SDSS samples of tracer halo stars, and we
successfully compare their density, velocity anisotropy, and radial velocity
dispersion profiles with the observational data. Most mock SDSS realizations
show the same "cold veil" recently observed in the distant stellar halo of the
Milky Way, with tracers as cold as sigma_los ~ 50 km/s between 100-150 kpc.
Controlled experiments based on the integration of the spherical Jeans equation
as well as a particle tagging technique applied to Via Lactea II show that a
"heavy" M_vir 2e12 M_sun realistic host produces a poor fit to the kinematic
SDSS data. We argue that these results offer added evidence for a "light,"
centrally-concentrated Milky Way halo. | astro-ph_CO |
Separating E and B types of polarization on an incomplete sky: Detection of magnetic-type ($B$-type) polarization in the Cosmic Microwave
Background (CMB) radiation plays a crucial role in probing the relic
gravitational wave (RGW) background. In this paper, we propose a new method to
deconstruct a polarization map on an incomplete sky in real space into purely
electric and magnetic polarization type maps, ${\mathcal{E}}(\hat{\gamma})$ and
${\mathcal{B}}(\hat{\gamma})$, respectively. The main properties of our
approach are as follows: Firstly, the fields ${\mathcal{E}}(\hat{\gamma})$ and
${\mathcal{B}}(\hat{\gamma})$ are constructed in real space with a minimal loss
of information. This loss of information arises due to the removal of a narrow
edge of the constructed map in order to remove various numerical errors,
including those arising from finite pixel size. Secondly, this method is fast
and can be efficiently applied to high resolution maps due to the use of the
fast spherical harmonics transformation. Thirdly, the constructed fields,
${\mathcal{E}}(\hat{\gamma})$ and ${\mathcal{B}}(\hat{\gamma})$, are scalar
fields. For this reason various techniques developed to deal with temperature
anisotropy maps can be directly applied to analyze these fields. As a concrete
example, we construct and analyze an unbiased estimator for the power spectrum
of the $B$-mode of polarization $C_{\ell}^{BB}$. Basing our results on the
performance of this estimator, we discuss the RGW detection ability of two
future ground-based CMB experiments, QUIET and POLARBEAR. | astro-ph_CO |
Exact Results for Propagators in the Geometrical Adhesion Model: The Geometrical Adhesion Model (GAM) we described in previous papers provides
a fully solved model for the nonlinear evolution of fields that mimic the
cosmological evolution of pressureless fluids. In this context we explore the
expected late time properties of the cosmic propagators once halos have formed,
in a regime beyond the domain of application of perturbation theories. Whereas
propagators in Eulerian coordinates are closely related to the velocity field
we show here that propagators defined in Lagrangian coordinates are intimately
related to the halo mass function. Exact results can be obtained in the 1D
case. In higher dimensions, the computations are more intricate because of to
the dependence of the propagators on the detailed shape of the underlying
Lagrangian-space tessellations, that is, on the geometry of the regions that
eventually collapse to form halos. We illustrate these results for both the 1D
and the 2D dynamics. In particular we give here the expected asymptotic
behaviors obtained for power-law initial power spectra. These analytical
results are compared with the results obtained with dedicated numerical
simulations. | astro-ph_CO |
The central dark matter distribution of NGC 2976: We study the mass distribution in the late-type dwarf galaxy NGC 2976 through
stellar kinematics obtained with the VIRUS-P integral-field spectrograph and
anisotropic Jeans models as a test of cosmological simulations and baryonic
processes that putatively alter small-scale structure. Previous measurements of
the H-alpha emission-line kinematics have determined that the dark matter halo
of NGC 2976 is most consistent with a cored density profile. We find that the
stellar kinematics are best fit with a cuspy halo. Cored dark matter halo fits
are only consistent with the stellar kinematics if the stellar mass-to-light
ratio is significantly larger than that derived from stellar population
synthesis, while the best-fitting cuspy model has no such conflict. The
inferred mass distribution from a harmonic decomposition of the gaseous
kinematics is inconsistent with that of the stellar kinematics. This difference
is likely due to the gas disk not meeting the assumptions that underlie the
analysis such as no pressure support, a constant kinematic axis, and planar
orbits. By relaxing some of these assumptions, in particular the form of the
kinematic axis with radius, the gas-derived solution can be made consistent
with the stellar kinematic models. A strong kinematic twist in the gas of NGC
2976's center suggests caution, and we advance the mass model based on the
stellar kinematics as more reliable. The analysis of this first galaxy shows
promising evidence that dark matter halos in late-type dwarfs may in fact be
more consistent with cuspy dark matter distributions than earlier work has
claimed. | astro-ph_CO |
Impact of half-wave plate systematics on the measurement of CMB $B$-mode
polarization: Polarization of the cosmic microwave background (CMB) can help probe the
fundamental physics behind cosmic inflation via the measurement of primordial
$B$ modes. As this requires exquisite control over instrumental systematics,
some next-generation CMB experiments plan to use a rotating half-wave plate
(HWP) as polarization modulator. However, the HWP non-idealities, if not
properly treated in the analysis, can result in additional systematics. In this
paper, we present a simple, semi-analytical end-to-end model to propagate the
HWP non-idealities through the macro-steps that make up any CMB experiment
(observation of multi-frequency maps, foreground cleaning, and power spectra
estimation) and compute the HWP-induced bias on the estimated tensor-to-scalar
ratio, $r$. We find that the effective polarization efficiency of the HWP
suppresses the polarization signal, leading to an underestimation of $r$.
Laboratory measurements of the properties of the HWP can be used to calibrate
this effect, but we show how gain calibration of the CMB temperature can also
be used to partially mitigate it. On the basis of our findings, we present a
set of recommendations for the HWP design that can help maximize the benefits
of gain calibration. | astro-ph_CO |
First star formation in ultra-light particle dark matter cosmology: The formation of the first stars in the high-redshift Universe is a sensitive
probe of the small-scale, particle physics nature of dark matter (DM). We carry
out cosmological simulations of primordial star formation in ultra-light,
axion-like particle DM cosmology, with masses of $10^{-22}$ and $10^{-21}\,{\rm
eV}$, with de Broglie wavelengths approaching galactic scales ($\sim$kpc). The
onset of star formation is delayed, and shifted to more massive host
structures. For the lightest DM particle mass explored here, first stars form
at $z \sim 7$ in structures with $\sim 10^9\,{\rm M}_\odot$, compared to the
standard minihalo environment within the $\Lambda$ cold dark matter
($\Lambda$CDM) cosmology, where $z \sim 20 - 30$ and $\sim 10^5 - 10^6\,{\rm
M}_\odot$. Despite this greatly altered DM host environment, the thermodynamic
behaviour of the metal-free gas as it collapses into the DM potential well
asymptotically approaches a very similar evolutionary track. Thus, the
fragmentation properties are predicted to remain the same as in $\Lambda$CDM
cosmology, implying a similar mass scale for the first stars. These results
predict intense starbursts in the axion cosmologies, which may be amenable to
observations with the {\it James Webb Space Telescope}. | astro-ph_CO |
Star Formation Timescales and the Schmidt Law: We offer a simple parameterization of the rate of star formation in galaxies.
In this new approach, we make explicit and decouple the timescales associated
(a) with disruptive effects the star formation event itself, from (b) the
timescales associated with the cloud assembly and collapse mechanisms leading
up to star formation. The star formation law in near-by galaxies, as measured
on sub-kiloparsec scales, has recently been shown by Bigiel et al. to be
distinctly non-linear in its dependence on total gas density. Our
parameterization of the spatially resolved Schmidt-Sanduleak relation naturally
accommodates that dependence. The parameterized form of the relation is rho_* ~
epsilon x rho_g/(tau_s + rho_g ^{-n}), where rho_g is the gas density, epsilon
is the efficiency of converting gas into stars, and rho_g^{-n} captures the
physics of cloud collapse. Accordingly at high gas densities quiescent star
formation is predicted to progress as rho_* ~ rho_g, while at low gas densities
rho_* ~ rho_g^{1+n}, as is now generally observed. A variable efficiency in
locally converting gas into stars as well as the unknown plane thickness
variations from galaxy to galaxy, and radially within a given galaxy, can
readily account for the empirical scatter in the observed (surface density
rather than volume density) relations, and also plausibly account for the noted
upturn in the relation at very high apparent projected column densities. | astro-ph_CO |
Convergence and shear statistics in galaxy clusters as a result of Monte
Carlo simulations: In this paper the influence of galaxy cluster halo environment on the
deflection properties of its galaxies is investigated. For this purpose
circular and elliptical projected cluster haloes obeying Einasto density
profiles are multiply simulated in the $\Lambda$CDM cosmological model. Using
Monte-Carlo technique external shear and convergence are calculated for random
positions of a test galaxy within its cluster. Throughout the simulations the
total virial mass, profile concentration and slope parameters are varied both
for cluster and its constituent galaxies. The cluster is composed of smooth
matter distribution (intergalactic gas and dark matter) and randomly positioned
galaxies. As a result of multiple runs robust statistical estimations of
external shear and convergence in relation to variable cluster characteristics
and and its redshift are derived. In addition, for the galaxy lens seen through
the cluster IRC-0218 magnification caused by external cluster mass distribution
is modelled. | astro-ph_CO |
Birth of the first stars amidst decaying and annihilating dark matter: The first stars are expected to form through molecular-hydrogen (H$_2$)
cooling, a channel that is especially sensitive to the thermal and ionization
state of gas, and can thus act as a probe of exotic energy injection from
decaying or annihilating dark matter (DM). Here, we use a toy halo model to
study the impact of DM-sourced energy injection on the H$_2$ content of the
first galaxies, and thus estimate the threshold mass required for a halo to
form stars at high redshifts. We find that currently allowed DM models can
significantly change this threshold, producing both positive and negative
feedback. In some scenarios, the extra heating of the gas raises the halo mass
required for collapse, whereas in others, energy injection lowers the threshold
by increasing the free-electron fraction and catalyzing H$_2$ formation. The
direction of the effect can be redshift-dependent. We also bracket the
uncertainties from self-shielding of halos from Lyman-Werner radiation. Hence,
exotic energy injection can both delay and accelerate the onset of star
formation; we show how this can impact the timing of 21cm signals at cosmic
dawn. We encourage detailed simulation follow-ups in the most promising regions
of parameter space identified in this work. | astro-ph_CO |
The density profiles of Dark Matter halos in Spiral Galaxies: In spiral galaxies, we explain their non-Keplerian rotation curves (RCs) by
means of a non-luminous component embedding their stellar-gaseous disks.
Understanding the detailed properties of this component (labelled Dark Matter,
DM) is one of the most pressing issues of Cosmology. We investigate the recent
relationship (claimed by Walker et al. 2010, hereafter W+10) between $r$, the
galaxy radial coordinate, and $V_h(r)$, the dark halo contribution to the
circular velocity at $r$, {\it a}) in the framework of the Universal Rotation
Curve (URC) paradigm and directly {\it b}) by means of the kinematics of a
large sample of DM dominated spirals. We find a general agreement between the
W+10 claim, the distribution of DM emerging from the URC and that inferred in
the (low luminosity) objects of our sample. We show that such a phenomenology,
linking the spiral's luminosity, radii and circular velocities, implies an
evident inconsistency with (naive) predictions in the $\Lambda$ Cold Dark
Matter ($\Lambda$CDM) scenario. | astro-ph_CO |
Formation times, mass growth histories and concentrations of dark matter
haloes: We develop a simple model for estimating the mass growth histories of dark
matter halos. The model is based on a fit to the formation time distribution,
where formation is defined as the earliest time that the main branch of the
merger tree contains a fraction f of the final mass M . Our analysis exploits
the fact that the median formation time as a function of f is the same as the
median of the main progenitor mass distribution as a function of time. When
coupled with previous work showing that the concentration c of the final halo
is related to the formation time tf associated with f \sim 0.04, our approach
provides a simple algorithm for estimating how the distribution of halo
concentrations may be expected to depend on mass, redshift and the expansion
history of the background cosmology. We also show that one can predict log10 c
with a precision of about 0.13 and 0.09 dex if only its mass, or both mass and
tf are known. And, conversely, one can predict log10 tf from mass or c with a
precision of 0.12 and 0.09 dex, approximately independent of f. Adding the mass
to the c-based estimate does not result in further improvement. These latter
results may be useful for studies which seek to compare the age of the stars in
the central galaxy in a halo with the time the core was first assembled. | astro-ph_CO |
Polynomial inflation models after BICEP2: Large field inflation models are favored by the recent BICEP2 that has
detected gravitational wave modes generated during inflation. We study general
large field inflation models for which the potential contains (constant)
quadratic and quartic terms of inflaton field. We show, in this framework,
those inflation models can generate the fluctuation with the tensor-to-scalar
ratio of $0.2$ as well as the scalar spectral index of $0.96$: those are very
close to the center value of the tensor-to-scalar ratio reported by BICEP2 as
well as Planck. Finally, we briefly discuss the particle physics model building
of inflation. | astro-ph_CO |
Anisotropic correlation functions as tracers of central galaxy
alignments in simulations: Motivated by observational results, we use IllustrisTNG hydrodynamical
numerical simulations to study the alignment of the central galaxies in groups
with the surrounding structures. This approach allows us to analyse galaxy and
group properties not available in observations. To perform this analysis, we
use a modified version of the two-point cross-correlation function and a
measure of the angle between the semi-major axes of the central galaxies and
the larger structures. Overall, our results reproduce observational ones, as we
find large-scale anisotropy, which is dominated by the red central galaxies. In
addition, the latter is noticeably more aligned with their group than the blue
ones. In contrast to the observations, we find a strong dependence of the
anisotropy on the central galaxy with mass, probably associated with the
inability of observational methods to determine them. This result allows us to
link the alignment to the process of halo assembly and the well-known
dependence of halo anisotropy on mass. When we include the dark matter
distribution in our analysis, we conclude that the galaxy alignment found in
simulations (and observations) can be explained by a combination of physical
processes at different scales: the central galaxy aligns with the dark matter
halo it inhabits, and this, in turn, aligns with the surrounding structures at
large scales. | astro-ph_CO |
GUT-Scale Primordial Black Holes: Mergers and Gravitational Waves: Tight constraints on the abundance of primordial black holes can be deduced
across a vast range of masses, with the exception of those light enough to
fully evaporate before nucleosynthesis. This hypothetical population is almost
entirely unconstrained, to the point where the early Universe could pass
through a matter-dominated phase with primordial black holes as the primary
component. The only obvious relic of this phase would be Hawking radiated
gravitons which would constitute a stochastic gravitational wave background in
the present-day Universe, albeit at frequencies far beyond the scope of any
planned detector technology. This paper explores the effects of classical
mergers in such a matter dominated phase. For certain ranges of parameters, a
significant fraction of the black holes merge, providing an additional,
classical source of primordial gravitational waves. The resulting stochastic
background typically has a lower amplitude than the Hawking background and lies
at less extreme frequencies, but is unlikely to be easily detectable, with a
maximal present day density of $\Omega_{GW} \sim 10^{-12}$ and frequencies
between $10^{15} - 10^{19}$ Hz. We also asses the impact of radiation accretion
on the lifetimes of such primordial black holes and find that it increases the
black hole mass by $\sim 14 \%$ and the lifetimes by about $50 \%$. However,
this does not qualitatively change any of our conclusions. | astro-ph_CO |
Hubble tensions: a historical statistical analysis: Statistical analyses of the measurements of the Hubble-Lema\^itre constant
$H_0$ (163 measurements between 1976 and 2019) show that the statistical error
bars associated with the observed parameter measurements have been
underestimated -- or the systematic errors were not properly taken into account
-- in at least 15-20\% of the measurements. The fact that the underestimation
of error bars for $H_0$ is so common might explain the apparent discrepancy of
values, which is formally known today as the Hubble tension. Here we have
carried out a recalibration of the probabilities with this sample of
measurements. We find that $x\sigma $ deviation is indeed equivalent in a
normal distribution to $x_{\rm eq.}\sigma $s deviation in the frequency of
values, where $x_{\rm eq.}=0.83x^{0.62}$. Hence, a tension of 4.4$\sigma $,
estimated between the local Cepheid-supernova distance ladder and cosmic
microwave background (CMB) data, is indeed a 2.1$\sigma $ tension in equivalent
terms of a normal distribution of frequencies, with an associated probability
$P(>x_{\rm eq.})=0.036$ (1 in 28). This can be increased up to a equivalent
tension of 2.5$\sigma $ in the worst of the cases of claimed 6$\sigma $
tension, which may anyway happen as a random statistical fluctuation. | astro-ph_CO |
Non-parametric study of the evolution of the cosmological equation of
state with SNeIa, BAO and high redshift GRBs: We study the dark energy equation of state as a function of redshift in a
non-parametric way, without imposing any {\it a priori} $w(z)$ (ratio of
pressure over energy density) functional form. As a check of the method, we
test our scheme through the use of synthetic data sets produced from different
input cosmological models which have the same relative errors and redshift
distribution as the real data. Using the luminosity-time $L_{X}-T_{a}$
correlation for GRB X-ray afterglows (the Dainotti et al. correlation), we are
able to utilize GRB sample from the {\it Swift} satellite as probes of the
expansion history of the Universe out to $z \approx 10$. Within the assumption
of a flat FLRW universe and combining SNeIa data with BAO constraints, the
resulting maximum likelihood solutions are close to a constant $w=-1$. If one
imposes the restriction of a constant $w$, we obtain $w=-0.99 \pm 0.06$
(consistent with a cosmological constant) with the present day Hubble constant
as $H_{0}=70.0 \pm 0.6$ ${\rm km} \, {\rm s}^{-1} {\rm Mpc}^{-1}$ and density
parameter as $\Omega_{\Lambda 0}=0.723 \pm 0.025$, while non-parametric $w(z)$
solutions give us a probability map which is centred at $H_{0}=70.04 \pm 1$
${\rm km} \, {\rm s}^{-1} {\rm Mpc}^{-1}$ and $\Omega_{\Lambda 0}=0.724 \pm
0.03$. Our chosen GRB data sample with full correlation matrix allows us to
estimate the amount, as well as quality (errors) of data, needed to constrain
$w(z)$ in the redshift range extending an order of magnitude in beyond the
farthest SNeIa measured. | astro-ph_CO |
Color Differences between Clockwise and Counterclockwise Spiral Galaxies: While spiral galaxies observed from Earth clearly seem to spin in different
directions, little is yet known about other differences between galaxies that
spin clockwise and galaxies that spin counterclockwise. Here we compared the
color of 64,399 spiral galaxies that spin clockwise to 63,215 spiral galaxies
that spin counterclockwise. The results show that clockwise galaxies tend to be
bluer than galaxies that spin counterclockwise. The probability that the color
differences can be attributed to chance is ~0.019. | astro-ph_CO |
A bias to CMB lensing measurements from the bispectrum of large-scale
structure: The rapidly improving precision of measurements of gravitational lensing of
the Cosmic Microwave Background (CMB) also requires a corresponding increase in
the precision of theoretical modeling. A commonly made approximation is to
model the CMB deflection angle or lensing potential as a Gaussian random field.
In this paper, however, we analytically quantify the influence of the
non-Gaussianity of large-scale structure lenses, arising from nonlinear
structure formation, on CMB lensing measurements. In particular, evaluating the
impact of the non-zero bispectrum of large-scale structure on the relevant CMB
four-point correlation functions, we find that there is a bias to estimates of
the CMB lensing power spectrum. For temperature-based lensing reconstruction
with CMB Stage-III and Stage-IV experiments, we find that this lensing power
spectrum bias is negative and is of order one percent of the signal. This
corresponds to a shift of multiple standard deviations for these upcoming
experiments. We caution, however, that our numerical calculation only evaluates
two of the largest bias terms and thus only provides an approximate estimate of
the full bias. We conclude that further investigation into lensing biases from
nonlinear structure formation is required and that these biases should be
accounted for in future lensing analyses. | astro-ph_CO |
Constraining the Statistics of Population III Binaries: We perform a cosmological simulation in order to model the growth and
evolution of Population III (Pop III) stellar systems in a range of host
minihalo environments. A Pop III multiple system forms in each of the ten
minihaloes, and the overall mass function is top-heavy compared to the
currently observed initial mass function in the Milky Way. Using a sink
particle to represent each growing protostar, we examine the binary
characteristics of the multiple systems, resolving orbits on scales as small as
20 AU. We find a binary fraction of ~36%, with semi-major axes as large as 3000
AU. The distribution of orbital periods is slightly peaked at < 900 yr, while
the distribution of mass ratios is relatively flat. Of all sink particles
formed within the ten minihaloes, ~50% are lost to mergers with larger sinks,
and ~50% of the remaining sinks are ejected from their star-forming disks. The
large binary fraction may have important implications for Pop III evolution and
nucleosynthesis, as well as the final fate of the first stars. | astro-ph_CO |
Evolution of Quiescent and Star-Forming Galaxies Since z~1.5 as a
Function of Their Velocity Dispersions: We measure stellar masses and structural parameters for 5,500 quiescent and
20,000 star-forming galaxies at 0.3<z\leq1.5 in the Newfirm Medium Band Survey
COSMOS and UKIDSS UDS fields. We combine these measurements to infer velocity
dispersions and determine how the number density of galaxies at fixed inferred
dispersion, or the Velocity Dispersion Function (VDF), evolves with time for
each population. We show that the number of galaxies with high velocity
dispersions appears to be surprisingly stable with time, regardless of their
star formation history. Furthermore, the overall VDF for star-forming galaxies
is constant with redshift, extending down to the lowest velocity dispersions
probed by this study. The only galaxy population showing strong evolution are
quiescent galaxies with low inferred dispersions, whose number density
increases by a factor of ~4 since z=1.5. This build-up leads to an evolution in
the quiescent fraction of galaxies such that the threshold dispersion above
which quiescent galaxies dominate the counts moves to lower velocity dispersion
with time. We show that our results are qualitatively consistent with a simple
model in which star-forming galaxies quench and are added to the quiescent
population. In order to compensate for the migration into the quiescent
population, the velocity dispersions of star-forming galaxies must increase,
with a rate that increases with dispersion. | astro-ph_CO |
Inflation and Early Dark Energy with a Stage II Hydrogen Intensity
Mapping Experiment: This white paper envisions a revolutionary post-DESI, post-LSST dark energy
program based on intensity mapping of the redshifted 21cm emission line from
neutral hydrogen at radio frequencies. The proposed intensity mapping survey
has the unique capability to quadruple the volume of the Universe surveyed by
optical programs, provide a percent-level measurement of the expansion history
to $z \sim 6$, open a window to explore physics beyond the concordance
$\Lambda$CDM model, and to significantly improve the precision on standard
cosmological parameters. In addition, characterization of dark energy and new
physics will be powerfully enhanced by cross-correlations with optical surveys
and cosmic microwave background measurements. The rich dataset obtained by the
proposed intensity mapping instrument will be simultaneously useful in
exploring the time-domain physics of fast radio transients and pulsars,
potentially in live "multi-messenger" coincidence with other observatories. The
core dark energy/inflation science advances enabled by this program are the
following: (i) Measure the expansion history of the universe over $z=0.3-6$
with a single instrument, extending the range deep into the pre-acceleration
era, providing an unexplored window for new physics; (ii) Measure the growth
rate of structure in the universe over the same redshift range; (iii) Observe,
or constrain, the presence of inflationary relics in the primordial power
spectrum, improving existing constraints by an order of magnitude; (iv)
Observe, or constrain, primordial non-Gaussianity with unprecedented precision,
improving constraints on several key numbers by an order of magnitude. Detailed
mapping of the enormous, and still largely unexplored, volume of cosmic space
will thus provide unprecedented information on fundamental questions of the
vacuum energy and early-universe physics. | astro-ph_CO |
Real or Interloper? The Redshift Likelihoods of z>8 Galaxies in the
HUDF12: In the absence of spectra, fitting template model spectra to observed
photometric fluxes, known as Spectral Energy Distribution (SED) fitting, has
become the workhorse for identifying high-z galaxies. In this paper, we present
an analysis of the most recent and possibly most distant galaxies discovered in
the Hubble Ultra Deep Field using a more robust method of redshift estimation
based on Markov Chain Monte Carlo fitting (MCMC), rather than relying on the
redshift of "best fit" models obtained using common chi^2 minimization
techniques. The advantage of MCMC fitting is the ability to accurately estimate
the probability density function of the redshift, as well as any other input
model parameters, allowing us to derive accurate credible intervals by properly
marginalizing over all other input model parameters. We apply our method to 13
recently identified sources and show that, despite claims based on chi^2
minimization, none of these sources can be securely ruled out as low redshift
interlopers given the low signal-to-noise of currently available observations.
We estimate that there is an average probability of 21% that these sources are
low redshift interlopers. | astro-ph_CO |
Probing High-Column Outflows in BALQSOs Using Metastable Helium: Outflows are believed to be ubiquitous and fundamentally important in active
galaxies. Despite their importance, key physical properties of outflows remain
poorly unconstrained; this severely limits study of the acceleration process.
It is especially difficult to constrain the column density since most of the
lines are saturated. However, column densities can be measured using ions that
are expected to be relatively rare in the gas, since they are least likely to
be saturated. Phosphorus, specifically the PV doublet at 1118 and 1128A, is
generally regarded as a useful probe of high column densities because of its
low abundance. We have found that the metastable neutral helium triplet is an
equally valuable probe of high column densities in BALQSOs. The significant
advantage is that it can be observed in the infrared (HeI*10830) and the
optical (HeI*3889) bands from the ground in low-redshift (z<1.2) objects.
We report the discovery of the first HeI*10830 BALQSO FBQS J1151+3822, and
discuss constraints on the column density obtained from the optical and IR HeI*
lines. In addition, a new observation revealing MgII and FeII absorption
provides further constraints, and Cloudy modeling of HeI*, MgII, and FeII
suggests that the difference between LoBALs and FeLoBALs is column density
along the line of sight. | astro-ph_CO |
Clustering properties of galaxies selected in stellar mass: Breaking
down the link between luminous and dark matter in massive galaxies from z=0
to z=2: We present a study on the clustering of a stellar mass selected sample of
18,482 galaxies with stellar masses M*>10^10M(sun) at redshifts 0.4<z<2.0,
taken from the Palomar Observatory Wide-field Infrared Survey. We examine the
clustering properties of these stellar mass selected samples as a function of
redshift and stellar mass, and discuss the implications of measured clustering
strengths in terms of their likely halo masses. We find that galaxies with high
stellar masses have a progressively higher clustering strength, and amplitude,
than galaxies with lower stellar masses. We also find that galaxies within a
fixed stellar mass range have a higher clustering strength at higher redshifts.
We furthermore use our measured clustering strengths, combined with models from
Mo & White (2002), to determine the average total masses of the dark matter
haloes hosting these galaxies. We conclude that for all galaxies in our sample
the stellar-mass-to-total-mass ratio is always lower than the universal
baryonic mass fraction. Using our results, and a compilation from the
literature, we furthermore show that there is a strong correlation between
stellar-mass-to-total-mass ratio and derived halo masses for central galaxies,
such that more massive haloes contain a lower fraction of their mass in the
form of stars over our entire redshift range. For central galaxies in haloes
with masses M(halo)>10^13M(sun) we find that this ratio is <0.02, much lower
than the universal baryonic mass fraction. We show that the remaining baryonic
mass is included partially in stars within satellite galaxies in these haloes,
and as diffuse hot and warm gas. We also find that, at a fixed stellar mass,
the stellar-to-total-mass ratio increases at lower redshifts. This suggests
that galaxies at a fixed stellar mass form later in lower mass dark matter
haloes, and earlier in massive haloes. We interpret this as a "halo downsizing"
effect, however some of this evolution could be attributed to halo assembly
bias. | astro-ph_CO |
The evolution of the rest-frame J- and H-band luminosity function of
galaxies to z=3.5: We present the rest-frame J- and H-band luminosity function (LF) of field
galaxies, based on a deep multi-wavelength composite sample from the MUSYC,
FIRES and FIREWORKS survey public catalogues, covering a total area of 450
arcmin^2. The availability of flux measurements in the Spitzer IRAC 3.6, 4.5,
5.8, and 8 um channels allows us to compute absolute magnitudes in the
rest-frame J and H bands up to z=3.5 minimizing the dependence on the stellar
evolution models. We compute the LF in the four redshift bins 1.5<z<2.0,
2.0<z<2.5, 2.5<z<3.0 and 3.0<z<3.5. Combining our results with those already
available at lower redshifts, we find that (1) the faint end slope is
consistent with being constant up to z=3.5, with alpha=-1.05+/-0.03 for the
rest-frame J band and alpha=-1.15+/-0.02 for the rest-frame H band; (2) the
normalization phi* decreases by a factor of 6 between z=0 and z~1.75 and by a
factor 3 between z~1.75 and z=3.25; (3) the characteristic magnitude M* shows a
brightening from z=0 to z~2 followed by a slow dimming to z=3.25. We finally
compute the luminosity density (LD) in both rest-frame J and H bands. The
analysis of our results together with those available in the literature shows
that the LD is approximately constant up to z~1, and it then decreases by a
factor of 6 up to z=3.5. | astro-ph_CO |
Thawing models in the presence of a generalized Chaplygin gas: In this paper we consider a cosmological model whose main components are a
scalar field and a generalized Chaplygin gas. We obtain an exact solution for a
flat arbitrary potential. This solution have the right dust limit when the
Chaplygin parameter $A\rightarrow 0$. We use the dynamical systems approach in
order to describe the cosmological evolution of the mixture for an exponential
self-interacting scalar field potential. We study the scalar field with an
arbitrary self-interacting potential using the "Method of $f$-devisers." Our
results are illustrated for the special case of a coshlike potential. We find
that usual scalar-field-dominated and scaling solutions cannot be late-time
attractors in the presence of the Chaplygin gas (with $\alpha>0$). We recover
the standard results at the dust limit ($A\rightarrow 0$). In particular, for
the exponential potential, the late-time attractor is a pure generalized
Chaplygin solution mimicking an effective cosmological constant. In the case of
arbitrary potentials, the late-time attractors are de Sitter solutions in the
form of a cosmological constant, a pure generalized Chaplygin solution or a
continuum of solutions, when the scalar field and the Chaplygin gas densities
are of the same orders of magnitude. The different situations depend on the
parameter choices. | astro-ph_CO |
Scaling Laws in High-Energy Inverse Compton Scattering: Based upon the rate equations for the photon distribution function obtained
in the previous paper, we study the inverse Compton scattering process for
high-energy nonthermal electrons. Assuming the power-law electron distribution,
we find a scaling law in the probability distribution function P_1(s), where
the peak height and peak position depend only on the power index parameter. We
solved the rate equation analytically. It is found that the spectral intensity
function also has the scaling law, where the peak height and peak position
depend only on the power index parameter. The present study will be
particularly important to the analysis of the X-ray and gamma-ray emission
models from various astrophysical objects such as radio galaxies and supernova
remnants. | astro-ph_CO |
Lyman Alpha Emitters at z=7 in the Subaru/XMM-Newton Deep Survey Field:
Photometric Candidates and Luminosity Function: We conducted a deep narrowband NB973 (FWHM = 200 A centered at 9755 A) survey
of z=7 Lyman alpha emitters (LAEs) in the Subaru/XMM-Newton Deep Survey Field,
using the fully depleted CCDs newly installed on the Subaru Telescope
Suprime-Cam, which is twice more sensitive to z=7 Lyman alpha at ~ 1 micron
than the previous CCDs. Reaching the depth 0.5 magnitude deeper than our
previous survey in the Subaru Deep Field that led to the discovery of a z=6.96
LAE, we detected three probable z=7 LAE candidates. Even if all the candidates
are real, the Lyman alpha luminosity function (LF) at z=7 shows a significant
deficit from the LF at z=5.7 determined by previous surveys. The LAE number and
Lyman alpha luminosity densities at z=7 is ~ 7.7-54% and ~5.5-39% of those at
z=5.7 to the Lyman alpha line luminosity limit of L(Ly-alpha) >~ 9.2 x 10^{42}
erg s^{-1}. This could be due to evolution of the LAE population at these
epochs as a recent galaxy evolution model predicts that the LAE modestly
evolves from z=5.7 to 7. However, even after correcting for this effect of
galaxy evolution on the decrease in LAE number density, the z=7 Lyman alpha LF
still shows a deficit from z=5.7 LF. This might reflect the attenuation of
Lyman alpha emission by neutral hydrogen remaining at the epoch of reionization
and suggests that reionization of the universe might not be complete yet at
z=7. If we attribute the density deficit to reionization, the intergalactic
medium (IGM) transmission for Lyman alpha photons at z=7 would be 0.4 <=
T_{Ly-alpha}^{IGM} <= 1, supporting the possible higher neutral fraction at the
earlier epochs at z > 6 suggested by the previous surveys of z=5.7-7 LAEs, z ~
6 quasars and z > 6 gamma-ray bursts. | astro-ph_CO |
Constraining warm dark matter with 21 cm line fluctuations due to
minihalos: Warm dark matter (WDM) with mass m_WDM = O(1) keV has long been discussed as
a promising solution for discrepancies between cosmic structures observed at
small scales and predications of the concordance CDM model. Though several
cosmological observations such as the Lyman-alpha forest have already begun to
constrain the range of m_WDM, WDM is yet to be fully excluded as a solution for
these so-called small-scale problems. In this paper, we study 21 cm line
fluctuations from minihalos in a WDM model and evaluate constraints on m_WDM
for future cosmological 21 cm surveys, such as SKA and FFTT. We show that,
since WDM with mass m_WDM>10 keV decreases the abundance of minihalos by
suppressing the matter power spectrum on small scales via free-streaming, such
WDM can significantly affect the resultant 21 cm line fluctuations from
minihalos. We find that if the 21 cm signal from minihalos can be observed
above z>5, SKA and FFTT can give lower bounds m_WDM>24 keV and 31 keV,
respectively, which are tighter than the current constraint. These future 21 cm
surveys might be able to rule out a WDM model as a solution of small-scale
problems. | astro-ph_CO |
Baryon acoustic oscillations with the cross-correlation of spectroscopic
and photometric samples: The baryon acoustic oscillation (BAO) experiment requires a sufficiently
dense sampling of large-scale structure tracers with spectroscopic redshift,
which is observationally expensive especially at high redshifts $z\simgt 1$.
Here we present an alternative route of the BAO analysis that uses the
cross-correlation of sparse spectroscopic tracers with a much denser
photometric sample, where the spectroscopic tracers can be quasars or bright,
rare galaxies that are easier to access spectroscopically. We show that
measurements of the cross-correlation as a function of the transverse comoving
separation rather than the angular separation avoid a smearing of the BAO
feature without mixing the different scales at different redshifts in the
projection, even for a wide redshift slice $\Delta z\simeq 1$. The bias,
scatter, and catastrophic redshift errors of the photometric sample affect only
the overall normalization of the cross-correlation which can be marginalized
over when constraining the angular diameter distance. As a specific example, we
forecast an expected accuracy of the BAO geometrical test via the
cross-correlation of the SDSS and BOSS spectroscopic quasar sample with a dense
photometric galaxy sample that is assumed to have a full overlap with the
SDSS/BOSS survey region. We show that this cross-correlation BAO analysis
allows us to measure the angular diameter distances to a fractional accuracy of
about 10% at each redshift bin over $1\simlt z\simlt 3$, if the photometric
redshift errors of the galaxies, $\sigma_z/(1+z)$, are better than 10-20%
level. | astro-ph_CO |
The Mass-Metallicity relation explored with CALIFA: I. Is there a
dependence on the star formation rate?: We present the results on the study of the global and local M-Z relation
based on the first data available from the CALIFA survey (150 galaxies). This
survey provides integral field spectroscopy of the complete optical extent of
each galaxy (up to 2-3 effective radii), with enough resolution to separate
individual HII regions and/or aggregations. Nearly $\sim$3000 individual HII
regions have been detected. The spectra cover the wavelength range between
[OII]3727 and [SII]6731, with a sufficient signal-to-noise to derive the oxygen
abundance and star-formation rate associated with each region. In addition, we
have computed the integrated and spatially resolved stellar masses (and surface
densities), based on SDSS photometric data. We explore the relations between
the stellar mass, oxygen abundance and star-formation rate using this dataset.
We derive a tight relation between the integrated stellar mass and the
gas-phase abundance, with a dispersion smaller than the one already reported in
the literature ($\sigma_{\Delta{\rm log(O/H)}}=$0.07 dex). Indeed, this
dispersion is only slightly larger than the typical error derived for our
oxygen abundances. However, we do not find any secondary relation with the
star-formation rate, other than the one induced due to the primary relation of
this quantity with the stellar mass. We confirm the result using the $\sim$3000
individual HII regions, for the corresponding local relations.
Our results agree with the scenario in which gas recycling in galaxies, both
locally and globally, is much faster than other typical timescales, like that
of gas accretion by inflow and/or metal loss due to outflows. In essence,
late-type/disk dominated galaxies seem to be in a quasi-steady situation, with
a behavior similar to the one expected from an instantaneous
recycling/closed-box model. | astro-ph_CO |
A Geometric Probe of Cosmology: I. Gravitational Lensing Time Delays and
Quasar Reverberation Mapping: We present a novel, purely geometric probe of cosmology based on measurements
of differential time delays between images of strongly lensed quasars due to
finite source effects. Our approach is solely dependent on cosmology via a
ratio of angular diameter distances, the image separation, and the source size.
It thereby entirely avoids the challenges of lens modelling that conventionally
limit time delay cosmography, and instead entails the lensed reverberation
mapping of the quasar Broad Line Region. We demonstrate that differential time
delays are measurable with short cadence spectroscopic monitoring of lensed
quasars, through the timing of kinematically identified features within the
broad emission lines. This provides a geometric determination of an angular
diameter distance ratio complementary to standard probes, and as a result is a
potentially powerful new method of constraining cosmology. | astro-ph_CO |
Dust in the Early (z>1) Universe: Although dust emission at cosmological distances has only been detected a
little more than a decade ago, remarkable progress has been achieved since then
in characterizing the far-infrared emission of high-redshift systems. The mere
fact that dust can be detected in galaxies at high redshift is remarkable for
two reasons: (a) even at very early cosmic epochs (all the way to the first Gyr
of the universe), dust production was apparently very effective, (b) due to the
inverse K-correction (`the magic of (sub-)millimeter') is it actually possible
to detect this dust emission using current facilities. Deep blind surveys using
bolometer cameras on single dish telescopes have uncovered a population of
massively starforming systems at z~2, the so-called submillimeter galaxies
(SMGs). Follow-up radio and millimeter interferometric observations helped to
characterize their main physical properties (such as far-infrared luminosities
and implied star formation rates). Average FIR properties of fainter
optically/NIR-selected classes of galaxies have been constrained using stacking
techniques. Targeted observations of the rare quasars have provided evidence
for major star formation activity in quasar host galaxies throughout cosmic
times. Molecular gas and PAH features have been detected in both SMGs and
quasars, providing additional evidence for major star formation episodes (SFR
500-3000 M_sun/yr) in the brightest systems. Even though remarkable progress
has been achieved in recent years, current facilities fail to uncover the
counterparts of even major local starbursts (such as Arp220) at any significant
redshift (z>0.5). Only ALMA will be able to go beyond the tip of the iceberg to
study the dust and FIR properties of typical star forming systems, all the way
out to the epoch of cosmic reionization (z>>6). | astro-ph_CO |
How closely do baryons follow dark matter on large scales?: We investigate the large-scale clustering and gravitational interaction of
baryons and dark matter (DM) over cosmic time using a set of collisionless
N-body simulations. Both components, baryons and DM, are evolved from distinct
primordial density and velocity power spectra as predicted by early-universe
physics. We first demonstrate that such two-component simulations require an
unconventional match between force and mass resolution (i.e. force softening on
at least the mean particle separation scale). Otherwise, the growth on any
scale is not correctly recovered because of a spurious coupling between the two
species at the smallest scales. With these simulations, we then demonstrate how
the primordial differences in the clustering of baryons and DM are
progressively diminished over time. In particular, we explicitly show how the
BAO signature is damped in the spatial distribution of baryons and imprinted in
that of DM. This is a rapid process, yet it is still not fully completed at low
redshifts. On large scales, the overall shape of the correlation function of
baryons and DM differs by 2% at z = 9 and by 0.2% at z = 0. The differences in
the amplitude of the BAO peak are approximately a factor of 5 larger: 10% at z
= 9 and 1% at z = 0. These discrepancies are, however, smaller than effects
expected to be introduced by galaxy formation physics in both the shape of the
power spectrum and in the BAO peak, and are thus unlikely to be detected given
the precision of the next generation of galaxy surveys. Hence, our results
validate the standard practice of modelling the observed galaxy distribution
using predictions for the total mass clustering in the Universe. | astro-ph_CO |
The connection between radio halos and cluster mergers and the
statistical properties of the radio halo population: We discuss the statistical properties of the radio halo population in galaxy
clusters. Radio bi-modality is observed in galaxy clusters: a fraction of
clusters host giant radio halos while the majority of clusters do not show
evidence of diffuse cluster-scale radio emission. The radio bi-modality has a
correspondence in terms of dynamical state of the hosting clusters showing that
merging clusters host radio halos and follow the well known radio--X-ray
correlation, while more relaxed clusters do not host radio halos and populate a
region well separated from that correlation. These evidences can be understood
in the framework of a scenario where merger-driven turbulence re-accelerate the
radio emitting electrons. We discuss the main statistical expectations of this
scenario underlining the important role of upcoming LOFAR surveys to test
present models. | astro-ph_CO |
Pushing the Limits of Detectability: Mixed Dark Matter from Strong
Gravitational Lenses: One of the frontiers for advancing what is known about dark matter lies in
using strong gravitational lenses to characterize the population of the
smallest dark matter halos. There is a large volume of information in strong
gravitational lens images -- the question we seek to answer is to what extent
we can refine this information. To this end, we forecast the detectability of a
mixed warm and cold dark matter scenario using the anomalous flux ratio method
from strong gravitational lensed images. The halo mass function of the mixed
dark matter scenario is suppressed relative to cold dark matter but still
predicts numerous low-mass dark matter halos relative to warm dark matter.
Since the strong lens signal is a convolution over a range of dark matter halo
masses and since the signal is sensitive to the specific configuration of dark
matter halos, not just the halo mass function, degeneracies between different
forms of suppression in the halo mass function, relative to cold dark matter,
can arise. We find that, with a set of lenses with different configurations of
the main deflector and hence different sensitivities to different mass ranges
of the halo mass function, the different forms of suppression of the halo mass
function between the warm dark matter model and the mixed dark matter model can
be distinguished with $40$ lenses with Bayesian odds of 29.4:1. | astro-ph_CO |
Heating Galaxy Clusters with Interacting Dark Matter: The overcooling of cool core clusters is a persistent puzzle in the
astrophysics of galaxy clusters. We propose that it may naturally be resolved
via interactions between the baryons of the intracluster medium (ICM) and its
dark matter (DM). DM-baryon interactions can inject heat into the ICM to offset
bremmstrahlung cooling, but these interactions are also strongly constrained by
existing experiments and astrophysical observations. We survey existing
constraints and combine these with the energetic needs of an observed sample of
cool core clusters. We find that a robust parameter space exists for baryon-DM
scattering solutions to the cooling flow problem, provided that only a
sub-component of DM interacts strongly with the baryons. Interestingly,
baryon-DM scattering is a thermally stable heating source so long as the baryon
temperature is greater than $1/3-1/2$ the DM temperature, a condition that
seems to be satisfied observationally. | astro-ph_CO |
Precision cosmology from large-scale structure of the Universe: Large scale structure of the Universe becomes a leading source of precision
cosmological information. We present two particular tools that can be used in
cosmological analyses of the redshift space galaxy clustering data: a new
open-source code CLASS-PT and the theoretical error approach. CLASS-PT computes
one-loop power auto- and cross-power spectra for matter fields and biased
tracers in real and redshift spaces. We show that the code meets the precision
standards set by the upcoming high-precision large-scale structure surveys. The
theoretical error likelihood approach allows one to analyze galaxy clustering
data without having to measure the scale cut $k_{\rm max}$. This approach takes
into account that theoretical uncertainties affect parameter estimation
gradually, which helps optimize data analysis and ensures that all available
cosmological information is extracted. | astro-ph_CO |
Interacting dark matter and cosmic acceleration: We study the effect of an explicit interaction between two scalar fields
components describing dark matter in the context of a recent proposal framework
for interaction. We find that, even assuming a very small coupling, it is
sufficient to explain the observational effects of a cosmological constant, and
also overcome the problems of the $\Lambda$CDM model without assuming an exotic
dark energy. | astro-ph_CO |
Simulation of Primordial Black Holes with large negative non-Gaussianity: In this work, we have performed numerical simulations of primordial black
hole (PBH) formation in the Friedman-Lema\^itre-Robertson-Walker universe
filled by radiation fluid, introducing the local-type non-Gaussianity to the
primordial curvature fluctuation. We have compared the numerical results from
simulations with previous analytical estimations on the threshold value for PBH
formation done in the previous paper arXiv:2109.00791, particularly for
negative values of the non-linearity parameter $f_{\rm NL}$. Our numerical
results show the existence of PBH formation of (the so-called) type I also in
the case $f_{\rm NL} \lesssim -0.336$, which was not found in the previous
analytical expectations using the critical averaged compaction function. In
particular, although the universal value for the averaged critical compaction
function $\bar{\mathcal{C}}_{c}=2/5$ found previously in the literature is not
satisfied for all the profiles considered in this work, an alternative direct
analytical estimate has been found to be roughly accurate to estimate the
thresholds, which gives the value of the critical averaged density with a few
$\%$ deviation from the numerical one for $f_{\rm NL}\gtrsim -1$. | astro-ph_CO |
Radio Detection of Green Peas: Implications for Magnetic Fields in Young
Galaxies: Green Peas are a new class of young, emission line galaxies that were
discovered by citizen volunteers in the Galaxy Zoo project. Their low stellar
mass, low metallicity and very high star formation rates make Green Peas the
nearby (z~0.2) analogs of the Lyman-break Galaxies (LBGs) which account for the
bulk of the star formation in the early universe (z~2-5). They thus provide
accessible laboratories in the nearby Universe for understanding star
formation, supernova feedback, particle acceleration and magnetic field
amplification in early galaxies. We report the first direct radio detection of
Green Peas with low frequency GMRT observations and our stacking detection with
archival VLA FIRST data. We show that the radio emission implies that these
extremely young galaxies already have magnetic fields (>30 muG) even larger
than that of the Milky Way. This is at odds with the present understanding of
magnetic field growth based on amplification of seed fields by dynamo action
over a galaxy's lifetime. Our observations strongly favor models with
pregalactic magnetic fields at muG levels. | astro-ph_CO |
Reheating constraints and consistency relations of the Starobinsky model
and some of its generalizations: Building on the success of the Starobinsky model in describing the
inflationary period of the universe, we investigate two simple generalizations
of this model and their constraints imposed by the reheating epoch. The first
generalization takes the form $R^{2p}$, while the second is the
$\alpha$-Starobinsky model. We first focus on the case where $p=1$ or
equivalently, $\alpha=1$, which corresponds to the original Starobinsky model.
We derive exact consistency relations between observables and cosmological
quantities, without neglecting any terms, and impose the reheating condition $0
< \omega_{re} < 0.25$, where $\omega_{re}$ is the equation of state parameter
at the end of reheating. This allows us to obtain new bounds for $n_s$ and $r$
that satisfy this condition and apply them to other observables and
cosmological quantities. We repeat this process for the cases where $p \neq 1$
and $\alpha \neq 1$ and find that these generalizations only result in minor
modifications of the Starobinsky model, including the potential and the bounds
on observables and cosmological quantities. | astro-ph_CO |
Constraining axion inflation with gravitational waves from preheating: We study gravitational wave production from gauge preheating in a variety of
inflationary models, detailing its dependence on both the energy scale and the
shape of the potential. We show that preheating into Abelian gauge fields
generically leads to a large gravitational wave background that contributes
significantly to the effective number of relativistic degrees of freedom in the
early universe, $N_\mathrm{eff}$. We demonstrate that the efficiency of
gravitational wave production is correlated with the tensor-to-scalar ratio,
$r$. In particular, we show that efficient gauge preheating in models whose
tensor-to-scalar ratio would be detected by next-generation cosmic microwave
background experiments ($r \gtrsim 10^{-3}$) will be either detected through
its contribution to $N_\mathrm{eff}$ or ruled out. Furthermore, we show that
bounds on $N_\mathrm{eff}$ provide the most sensitive probe of the possible
axial coupling of the inflaton to gauge fields regardless of the potential. | astro-ph_CO |
Determination of dark matter type by X-ray sources statistics: The current cosmological model includes cold dark matter, which consists of
massive nonrelativistic particles. There are also some observational and
theoretical evidences for warm dark matter. The existence of warm DM can be
examined by measuring of the galaxy clusters density profiles and accurate
counting of dwarf galaxies. In this work I suppose that DM haloes are well
traced by X-ray gas in clusters, groups, pairs and even single galaxies. The
type of DM is inspected with the Xgal sample of 5021 X-ray emitting galaxies
observed by XMM-Newton. The selection bias of this sample is also analyzed. | astro-ph_CO |
Cosmology and neutrino mass with the Minimum Spanning Tree: The information content of the minimum spanning tree (MST), used to capture
higher-order statistics and information from the cosmic web, is compared to
that of the power spectrum for a $\nu\Lambda$CDM model. The measurements are
made in redshift space using haloes from the Quijote simulation of mass $\geq
3.2\times 10^{13}\,h^{-1}{\rm M}_{\odot}$ in a box of length $L_{\rm
box}=1\,h^{-1}{\rm Gpc}$. The power spectrum multipoles (monopole and
quadrupole) are computed for Fourier modes in the range $0.006 < k < 0.5\,
h{\rm Mpc}^{-1}$. For comparison the MST is measured with a minimum length
scale of $l_{\min}\simeq13\,h^{-1}{\rm Mpc}$. Combining the MST and power
spectrum allows for many of the individual degeneracies to be broken; on its
own the MST provides tighter constraints on the sum of neutrino masses
$M_{\nu}$ and cosmological parameters $h$, $n_{\rm s}$, and $\Omega_{\rm b}$
but the power spectrum alone provides tighter constraints on $\Omega_{\rm m}$
and $\sigma_{8}$. Combined we find constraints that are a factor of two (or
greater) on all parameters with respect to the power spectrum (for $M_{\nu}$
there is a factor of four improvement). These improvements appear to be driven
by the MST's sensitivity to small scale clustering, where the effect of
neutrino free-streaming becomes relevant, and high-order statistical
information in the cosmic web. The MST is shown to be a powerful tool for
cosmology and neutrino mass studies, and therefore could play a pivotal role in
ongoing and future galaxy redshift surveys (such as DES, DESI, \emph{Euclid},
and Rubin-LSST). | astro-ph_CO |
Weak lensing magnification in the Dark Energy Survey Science
Verification Data: In this paper the effect of weak lensing magnification on galaxy number
counts is studied by cross-correlating the positions of two galaxy samples,
separated by redshift, using data from the Dark Energy Survey Science
Verification dataset. The analysis is carried out for two
photometrically-selected galaxy samples, with mean photometric redshifts in the
$0.2 < z < 0.4$ and $0.7 < z < 1.0$ ranges, in the riz bands. A signal is
detected with a $3.5\sigma$ significance level in each of the bands tested, and
is compatible with the magnification predicted by the $\Lambda$CDM model. After
an extensive analysis, it cannot be attributed to any known systematic effect.
The detection of the magnification signal is robust to estimated uncertainties
in the outlier rate of the pho- tometric redshifts, but this will be an
important issue for use of photometric redshifts in magnification mesurements
from larger samples. In addition to the detection of the magnification signal,
a method to select the sample with the maximum signal-to-noise is proposed and
validated with data. | astro-ph_CO |
The Effects of Local Primordial Non-Gaussianity on the Formation and
Evolution of Galaxies: Thanks to the rapid progress in precision cosmology in the last few years, we
now have access to physical observables that may constrain the theory of
inflation through the non-Gaussianity (NG) signatures in the cosmic microwave
background radiation and the distribution of large-scale structure. Numerical
modeling of the NG signals from different inflation models is essential to
correctly interpret current and near future data from large-scale structure
surveys. In this study, we use high-resolution cosmological hydrodynamical
simulations to investigate the effects of primordial NG on the formation and
evolution of galaxies from the cosmic dawn to the present day. Focusing on the
local type primordial NG, we find that it may affect the formation history of
stars and black holes in galaxies, and their distribution. Compared to the
Gaussian case, large non-Gaussian potential with $f_{NL} \gtrsim 10^3$ leads to
earlier collapse of the first structures, more massive galaxies especially at
high redshifts, stronger clustering of galaxies, and higher halo bias. However,
for smaller NG with $f_{NL} \lesssim 10^2$, the effect is significantly weaker.
Observations of the distribution and properties of high-redshift, rare objects
such as the first galaxies and quasars may provide further constraints on the
primordial NG. | astro-ph_CO |
Multiscale cosmology and structure-emerging Dark Energy: A plausibility
analysis: Cosmological backreaction suggests a link between structure formation and the
expansion history of the Universe. In order to quantitatively examine this
connection, we dynamically investigate a volume partition of the Universe into
over-- and underdense regions. This allows us to trace structure formation
using the volume fraction of the overdense regions $\lambda_{\CM}$ as its
characterizing parameter. Employing results from cosmological perturbation
theory and extrapolating the leading mode into the nonlinear regime, we
construct a three--parameter model for the effective cosmic expansion history,
involving $\lambda_{\CM_{0}}$, the matter density $\Omega_{m}^{\CD_{0}}$, and
the Hubble rate $H_{\CD_{0}}$ of today's Universe. Taking standard values for
$\Omega_{m}^{\CD_{0}}$ and $H_{\CD_{0}}$ as well as a reasonable value for
$\lambda_{\CM_{0}}$, that we derive from $N$--body simulations, we determine
the corresponding amounts of backreaction and spatial curvature. We find that
the obtained values that are sufficient to generate today's structure also lead
to a $\Lambda$CDM--like behavior of the scale factor, parametrized by the same
parameters $\Omega_{m}^{\CD_{0}}$ and $H_{\CD_{0}}$, but without a cosmological
constant. However, the temporal behavior of $\lambda_{\CM}$ does not faithfully
reproduce the structure formation history. Surprisingly, however, the model
matches with structure formation with the assumption of a low matter content,
$\Omega_{m}^{\CD_{0}}\approx3\%$, a result that hints to a different
interpretation of part of the backreaction effect as kinematical Dark Matter.
(truncated) | astro-ph_CO |
Primordial Black Hole Formation during a Strongly Coupled Crossover: The final mass distribution of primordial black holes is sensitive to the
equation of state of the Universe at the scales accessible by the power
spectrum. Motivated by the presence of phase transitions in several beyond the
Standard Model theories, some of which are strongly coupled, we analyze the
production of primordial black holes during such phase transitions, which we
model using the gauge/gravity duality. We focus in the (often regarded as
physically uninteresting) case for which the phase transition is just a smooth
crossover. We find an enhancement of primordial black hole production in the
range $M_{\rm{PBH}}\in[10^{-16},10^{-6}]M_{\odot}$. | astro-ph_CO |
Tracking the orbit of unresolved subhalos for semi-analytic models: We present a model to track the orbital evolution of "unresolved subhaloes"
(USHs) in cosmological simulations. USHs are subhaloes that are no longer
distinguished by halo finders as self-bound overdensities within their larger
host system due to limited mass resolution. These subhaloes would host "orphan
galaxies" in semi-analytic models of galaxy formation and evolution (SAMs).
Predicting the evolution of the phase-space components of USHs is crucial for
the adequate modelling of environmental processes, interactions and mergers
implemented in SAMs that affect the baryonic properties of orphan satellites.
Our model takes into account dynamical friction drag, mass loss by tidal
stripping and merger with the host halo, involving three free parameters. To
calibrate this model, we consider two DM-only simulations of different mass
resolution (MultiDark simulations). The simulation with higher-mass resolution
({\sc smdpl}; $ m_{\rm DM} = 9.6 \times 10^7 ~ h^{-1}\,\mathrm{M_{\odot}}$)
provides information about subhaloes that are not resolved in the lower-mass
resolution one ({\sc mdpl2}; $ m_{\rm DM} = 1.5 \times 10^9 ~
h^{-1}\,\mathrm{M_{\odot}}$); the orbit of those USHs is tracked by our model.
We use as constraining functions the subhalo mass function (SHMF) and the
two-point correlation function (2PCF) obtained from {\sc smdpl}, being the
latter a novel aspect of our approach. While the SHMF fails to put tight
constraints on the efficiency of dynamical friction and the merger condition,
the addition of clustering information helps to specify the parameters of the
model related to the spatial distribution of subhaloes. Our model allows to
achieve good convergence between the results of simulations of different mass
resolution, with a precision better than 10 per cent for both SHMF and 2PCF. | astro-ph_CO |
CMB at small scales: Cosmology from tSZ power spectrum: Small scale CMB angular power spectrum contains not only primordial CMB
information but also many contaminants coming from secondary anisotropies. Most
of the latter depend on the cosmological model but are often marginalised over.
We propose a new analysis of the SPT data focusing on the cosmological
contribution of the thermal Sunyaev Zel'dovich (tSZ) effect. We model the tSZ
angular spectrum with the halo model and train a random forest algorithm to
speed up its computation. We show that using the cosmological information of
the tSZ on top of the primordial CMB one contained in SPT data bring more
constraints on cosmological parameters. We also combine for the first time
Planck tSZ angular power spectrum with SPT ones to put further constraints.
This proof of concept study shows how much a proper modelling of the
foregrounds in the cosmological analyses is needed. | astro-ph_CO |
The QUIJOTE experiment: project overview and first results: QUIJOTE (Q-U-I JOint TEnerife) is a new polarimeter aimed to characterize the
polarization of the Cosmic Microwave Background and other Galactic and
extragalactic signals at medium and large angular scales in the frequency range
10-40 GHz. The multi-frequency (10-20~GHz) instrument, mounted on the first
QUIJOTE telescope, saw first light on November 2012 from the Teide Observatory
(2400~m a.s.l). During 2014 the second telescope has been installed at this
observatory. A second instrument at 30~GHz will be ready for commissioning at
this telescope during summer 2015, and a third additional instrument at 40~GHz
is now being developed. These instruments will have nominal sensitivities to
detect the B-mode polarization due to the primordial gravitational-wave
component if the tensor-to-scalar ratio is larger than r=0.05. | astro-ph_CO |
Quasar Structure Emerges from the Three Forms of Radiation Pressure: All quasar spectra show the same atomic features in the optical, UV, near-IR
and soft X-rays over all of cosmic time, luminosity black hole mass and
accretion rate. This is a puzzle. Here I show that it is possible that all of
these atomic features can be accounted for by gas from an accretion disk driven
by the three forms of radiation pressure: electron scattering, line driving and
dust driving. The locations where they successfully drive an escaping wind, and
those where they produce only a failed wind are both needed to produce the
observed features. | astro-ph_CO |
First study of reionization in tilted flat and untilted non-flat
dynamical dark energy inflation models: We examine the effects of dark energy dynamics and spatial curvature on
cosmic reionization by studying reionization in tilted spatially-flat and
untilted non-flat XCDM and $\phi$CDM dynamical dark energy inflation models
that best fit the Planck 2015 cosmic microwave background (CMB) anisotropy and
a large compilation of non-CMB data. We carry out a detailed statistical study,
based on a principal component analysis and a Markov chain Monte Carlo analysis
of a compilation of lower-redshift reionization data, to estimate the
uncertainties in the cosmological model reionization histories. We find that,
irrespective of the nature of dark energy, there are significant differences
between the reionization histories of the spatially-flat and non-flat models.
Although both the flat and non-flat models can accurately match the
low-redshift ($z\lesssim6$) reionization observations, there is a clear
discrepancy between high-redshift ($z>7$) Lyman-$\alpha$ emitter data and the
predictions from non-flat models. This is solely due to the fact that the
non-flat models have a significantly larger electron scattering optical depth,
$\tau_{\rm el}$, compared to the flat models, which requires an extended and
much earlier reionization scenario supported by more high-redshift ionizing
sources in the non-flat models. Non-flat models also require strong redshift
evolution in the photon escape fraction, that can become unrealistically high
($\gtrsim1$) at some redshifts. However, $\tau_{\rm el}$ is about 0.9-$\sigma$
lower in the tilted flat $\Lambda$CDM model when the new Planck 2018 data are
used and this reduction will partially alleviate the tension between the
non-flat model predictions and the data. | astro-ph_CO |
Differential Observation Techniques for the SZE-21cm and radio sources: The SZE-21cm has been proposed as an alternative probe for the Dark Ages (DA)
and the Epoch of Reionization (EoR). The effect is produced when photons of the
21cm background are inverse Compton (up-)scattered by electrons residing in hot
plasma of cosmic structures and can be studied through differential
observations of the large-scale structure, towards and away a region of the
radio sky containing the cosmic structure of interest. This work makes use of
the 21cmFAST code to simulate low frequency radio observations of a galaxy
cluster from which we then extract the SZE-21cm signal. We further explore uses
of the differential technique to radio observations of active radio galaxies
using radio observations from the MWA GLEAM survey. The differential techniques
this work studies enable us to extract the SZE-21cm signal from simulated
galaxy cluster observations, which can then be used to obtain the global
features of the 21cm signal during the DA and EoR. The technique shows further
benefits in source extraction and characterisation, and feature enhancement in
radio observations particularly for low-surface brightness and extended radio
sources. | astro-ph_CO |
Constraining Big Bang lithium production with recent solar neutrino data: The 3He({\alpha},{\gamma})7Be reaction affects not only the production of 7Li
in Big Bang nucleosynthesis, but also the fluxes of 7Be and 8B neutrinos from
the Sun. This double role is exploited here to constrain the former by the
latter. A number of recent experiments on 3He({\alpha},{\gamma})7Be provide
precise cross section data at E = 0.5-1.0 MeV center-of-mass energy. However,
there is a scarcity of precise data at Big Bang energies, 0.1-0.5 MeV, and
below. This problem can be alleviated, based on precisely calibrated 7Be and 8B
neutrino fluxes from the Sun that are now available, assuming the neutrino
flavour oscillation framework to be correct. These fluxes and the standard
solar model are used here to determine the 3He(alpha,gamma)7Be astrophysical
S-factor at the solar Gamow peak, S(23+6-5 keV) = 0.548+/-0.054 keVb. This new
data point is then included in a re-evaluation of the 3He({\alpha},{\gamma})7Be
S-factor at Big Bang energies, following an approach recently developed for
this reaction in the context of solar fusion studies. The re-evaluated S-factor
curve is then used to re-determine the 3He({\alpha},{\gamma})7Be thermonuclear
reaction rate at Big Bang energies. The predicted primordial lithium abundance
is 7Li/H = 5.0e-10, far higher than the Spite plateau. | astro-ph_CO |
Creation of cosmic structure in the complex galaxy cluster merger Abell
2744: We present a detailed strong lensing, weak lensing and X-ray analysis of
Abell 2744 (z = 0.308), one of the most actively merging galaxy clusters known.
It appears to have unleashed `dark', `ghost', `bullet' and `stripped'
substructures, each ~10^14 solar masses. The phenomenology is complex and will
present a challenge for numerical simulations to reproduce. With new, multiband
HST imaging, we identify 34 strongly-lensed images of 11 galaxies around the
massive Southern `core'. Combining this with weak lensing data from HST, VLT
and Subaru, we produce the most detailed mass map of this cluster to date. We
also perform an independent analysis of archival Chandra X-ray imaging. Our
analyses support a recent claim that the Southern core and Northwestern
substructure are post-merger and exhibit morphology similar to the Bullet
Cluster viewed from an angle. From the separation between X-ray emitting gas
and lensing mass in the Southern core, we derive a new and independent
constraint on the self-interaction cross section of dark matter particles
sigma/m <~ 3 \pm 1 cm^2 g^-1. In the Northwestern substructure, the gas, dark
matter, and galaxy components have become separated by much larger distances.
Most curiously, the `ghost' clump (primarily gas) leads the `dark' clump
(primarily dark matter) by more than 150 kpc. We propose an enhanced
`ram-pressure slingshot' scenario which may have yielded this reversal of
components with such a large separation, but needs further confirmation by
follow-up observations and numerical simulations. A secondary merger involves a
second `bullet' clump in the North and an extremely `stripped' clump to the
West. The latter appears to exhibit the largest separation between dark matter
and X-ray emitting baryons detected to date in our sky. | astro-ph_CO |
Non-parametric modeling of the intra-cluster gas using APEX-SZ bolometer
imaging data: We demonstrate the usability of mm-wavelength imaging data obtained from the
APEX-SZ bolometer array to derive the radial temperature profile of the hot
intra-cluster gas out to radius r_500 and beyond. The goal is to study the
physical properties of the intra-cluster gas by using a non-parametric
de-projection method that is, aside from the assumption of spherical symmetry,
free from modeling bias. We use publicly available X-ray imaging data from the
XMM-Newton observatory and our Sunyaev-Zel'dovich Effect (SZE) imaging data
from the APEX-SZ experiment at 150 GHz to de-project the density and
temperature profiles for the relaxed cluster Abell 2204. We derive the gas
density, temperature and entropy profiles assuming spherical symmetry, and
obtain the total mass profile under the assumption of hydrostatic equilibrium.
For comparison with X-ray spectroscopic temperature models, a re-analysis of
the recent Chandra observation is done with the latest calibration updates.
Using the non-parametric modeling we demonstrate a decrease of gas temperature
in the cluster outskirts, and also measure the gas entropy profile. These
results are obtained for the first time independently of X-ray spectroscopy,
using SZE and X-ray imaging data. The contribution of the SZE systematic
uncertainties in measuring T_e at large radii is shown to be small compared to
the Chandra systematic spectroscopic errors. The upper limit on M_200 derived
from the non-parametric method is consistent with the NFW model prediction from
weak lensing analysis. | astro-ph_CO |
Do Cosmological Perturbations Have Zero Mean?: A central assumption in our analysis of cosmic structure is that cosmological
perturbations have zero ensemble mean. This property is one of the consequences
of statistically homogeneity, the invariance of correlation functions under
spatial translations. In this article we explore whether cosmological
perturbations indeed have zero mean, and thus test one aspect of statistical
homogeneity. We carry out a classical test of the zero mean hypothesis against
a class of alternatives in which perturbations have non-vanishing means, but
homogeneous and isotropic covariances. Apart from Gaussianity, our test does
not make any additional assumptions about the nature of the perturbations and
is thus rather generic and model-independent. The test statistic we employ is
essentially Student's t statistic, applied to appropriately masked,
foreground-cleaned cosmic microwave background anisotropy maps produced by the
WMAP mission. We find evidence for a non-zero mean in a particular range of
multipoles, but the evidence against the zero mean hypothesis goes away when we
correct for multiple testing. We also place constraints on the mean of the
temperature multipoles as a function of angular scale. On angular scales
smaller than four degrees, a non-zero mean has to be at least an order of
magnitude smaller than the standard deviation of the temperature anisotropies. | astro-ph_CO |
The WIRCAM Deep Infrared Cluster Survey I: Groups and Clusters at z >
1.1: We use CFHTLS deep optical data, WIRCam Deep Survey (WIRDS) NIR data and XMM
data to identify z>1.1 clusters in the CFHTLS D1 and D4 fields. Counterparts to
such clusters can not be identified without deep NIR data and as such the total
of =1deg2 of J , H & Ks band imaging provided by WIRDS is an indispensable tool
in such work. Using public XMM X-ray data, we identify extended X-ray sources
in the two fields. The resulting catalogue of extended X-ray sources was
analyzed for optical/NIR counterparts, using a red-sequence algorithm.
Redshifts of candidate groups and clusters were estimated using the median
photometric redshifts of detected counterparts and where available
spectroscopic data. Additionally, we surveyed X-ray point sources for potential
group systems at the limit of our detection range in the X-ray data. A
catalogue of z > 1.1 cluster candidates in the two fields has been compiled and
cluster masses, radii and temperatures have been estimated using the scaling
relations. The catalogue consists of 15 z > 1.1 candidates. Three of the
detections are previously published extended X-ray sources. Of note is JKSC 041
for which we identify possible structures at z = 0.8, z = 0.96, z = 1.13 and z
= 1.49. We also make an independent detection of the massive cluster, XMMXCS
J2215.9-1738. We use the z > 1.1 catalogue to compare the cluster number counts
in these fields with models based on WMAP 7-year cosmology and find that the
models slightly over-predict the observations, whilst at z>1.5 we do not detect
any clusters. We note that cluster number counts at z > 1.1 are highly
sensitive to the cosmological model, however a significant reduction in present
statistical (due to available survey area) and systematic (due to cluster
scaling relations) uncertainties is required in order to confidently constrain
cosmological parameters using cluster number counts at high redshift. | astro-ph_CO |
The age-redshift relation for Luminous Red Galaxies in the Sloan Digital
Sky Survey: We present a detailed analysis of 17,852 quiescent, Luminous Red Galaxies
(LRGs) selected from Sloan Digital Sky Survey (SDSS) Data Release Seven (DR7)
spanning a redshift range of 0.0 < z < 0.4. These galaxies are co-added into
four equal bins of velocity dispersion and luminosity to produce high
signal-to-noise spectra (>100A^{-1}), thus facilitating accurate measurements
of the standard Lick absorption-line indices. In particular, we have carefully
corrected and calibrated these indices onto the commonly used Lick/IDS system,
thus allowing us to compare these data with other measurements in the
literature, and derive realistic ages, metallicities ([Z/H]) and alpha-element
abundance ratios ([alpha/Fe]) for these galaxies using Simple Stellar
Population (SSP) models. We use these data to study the relationship of these
galaxy parameters with redshift, and find little evidence for evolution in
metallicity or alpha-elements (especially for our intermediate mass samples).
This demonstrates that our subsamples are consistent with pure passive evolving
(i.e. no chemical evolution) and represent a homogeneous population over this
redshift range. We also present the age-redshift relation for these LRGs and
clearly see a decrease in their age with redshift (5 Gyrs over the redshift
range studied here) which is fully consistent with the cosmological lookback
times in a concordance Lambda CDM universe. We also see that our most massive
sample of LRGs is the youngest compared to the lower mass galaxies. We provide
these data now to help future cosmological and galaxy evolution studies of
LRGs, and provide in the appendices of this paper the required methodology and
information to calibrate SDSS spectra onto the Lick/IDS system. | astro-ph_CO |
The extended HI halo of NGC 4945 as seen by MeerKAT: Observations of the neutral atomic hydrogen (HI) in the nuclear starburst
galaxy NGC 4945 with MeerKAT are presented. We find a large amount of halo gas,
previously missed by HI observations, accounting for 6.8% of the total HI mass.
This is most likely gas blown into the halo by star formation. Our maps go down
to a $3\sigma$ column density level of $5\times10^{18} cm^{-2}$ . We model the
HI distribution using tilted-ring fitting techniques and find a warp on the
galaxy's approaching and receding sides. The HI in the northern side of the
galaxy appears to be suppressed. This may be the result of ionisation by the
starburst activity in the galaxy, as suggested by a previous study. The origin
of the warp is unclear but could be due to past interactions or ram pressure
stripping. Broad, asymmetric HI absorption lines extending beyond the HI
emission velocity channels are present towards the nuclear region of NGC 4945.
Such broad lines suggest the existence of a nuclear ring moving at a high
circular velocity. This is supported by the clear rotation patterns in the HI
absorption velocity field. The asymmetry of the absorption spectra can be
caused by outflows or inflows of gas in the nuclear region of NGC 4945. The
continuum map shows small extensions on both sides of the galaxy's major axis
that might be signs of outflows resulting from the starburst activity. | astro-ph_CO |
Mass and metal ejection efficiency in disk galaxies driven by young
stellar clusters of nuclear starburst: We present results from models of galactic winds driven by energy injected by
nuclear starbursts. The total energy of the starburst is provided by young
central stellar clusters and parts of the galactic interstellar medium are
pushed out as part of the galactic wind (in some cases the galactic wind
contains an important part of the metals produced in the new generation of
stars). We have performed adiabatic and radiative 3D N-Body/Smooth Particle
Hydrodynamics simulations of galactic winds using the GADGET-2 code. The
numerical models cover a wide range of starburst (from $\sim10^2$ to $\sim10^7$
M$_\odot$) and galactic gas masses (from $\sim6\times10^6$ to $\sim10^{11}$
M$_\odot$). The concentrated central starburst regions are an efficient engine
for producing of the mass and metal loss in galaxies, and also for driving the
metal redistribution in the galaxies. | astro-ph_CO |
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