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using deep jwst imaging from jades, jems and smiles, we characterize optically-faint and extremely red galaxies at $z>3$ that were previously missing from galaxy census estimates. the data indicate the existence of abundant, dusty and post-starburst-like galaxies down to $10^8$m$_\odot$, below the sensitivity limit of spitzer and alma. modeling the nircam and hst photometry of these red sources can result in extreme, high values for both stellar mass and star formation rate (sfr); however, including 7 miri filters out to 21$\mu$m results in decreased mass (median 0.6 dex for log$_{10}$m$^*$/m$_{\odot}>$10), and sfr (median 10$\times$ for sfr$>$100 m$_{\odot}$/yr). at $z>6$, our sample includes a high fraction of little red dots (lrds; nircam-selected dust-reddened agn candidates). we significantly measure older stellar populations in the lrds out to rest-frame 3$\mu$m (the stellar bump) and rule out a dominant contribution from hot dust emission, a signature of agn contamination to stellar population measurements. this allows us to measure their contribution to the cosmic census at $z>3$, below the typical detection limits of alma ($l_{\rm ir}<10^{12}l_\odot$). we find that these sources, which are overwhelmingly missed by hst and alma, could effectively double the obscured fraction of the star formation rate density at $4<z<6$ compared to some estimates, showing that prior to jwst, the obscured contribution from fainter sources could be underestimated. finally, we identify five sources with evidence for balmer breaks and high stellar masses at $5.5<z<7.7$. while spectroscopy is required to determine their nature, we discuss possible measurement systematics to explore with future data. | the galaxies missed by hubble and alma: the contribution of extremely red galaxies to the cosmic census at 3<z<8 |
here we provide the most comprehensive determinations of the rest-frame uv luminosity function (lf) available to date with the hubble space telescope (hst) at z ~ 2-9. essentially all of the noncluster extragalactic legacy fields are utilized, including the hubble ultra deep field, the hubble frontier fields parallel fields, and all five candels fields, for a total survey area of 1136 arcmin2. our determinations include galaxies at z ~ 2-3 leveraging the deep hduv, uvudf, and ers wfc3/uvis observations available over an ~150 arcmin2 area in the goods-north and goods-south regions. all together, our collective samples include >24,000 sources, >2.3× larger than previous selections with hst. we identify 5766, 6332, 7240, 3449, 1066, 601, 246, and 33 sources at z ~ 2, 3, 4, 5, 6, 7, 8, and 9, respectively. combining our results with an earlier z ~ 10 lf determination by oesch et al., we quantify the evolution of the uv lf. our results indicate that there is (1) a smooth flattening of the faint-end slope α from α ~ -2.4 at z ~ 10 to α ~ -1.5 at z ~ 2, (2) minimal evolution in the characteristic luminosity m* at z ≥ 2.5, and (3) a monotonic increase in the normalization ${\mathrm{log}}_{10}{\phi }^{* }$ from z ~ 10 to 2, which can be well described by a simple second-order polynomial, consistent with an "accelerated" evolution scenario. we find that each of these trends (from z ~ 10 to 2.5 at least) can be readily explained on the basis of the evolution of the halo mass function and a simple constant star formation efficiency model. | new determinations of the uv luminosity functions from z 9 to 2 show a remarkable consistency with halo growth and a constant star formation efficiency |
mergers of binary neutron stars and black hole-neutron star binaries are among the most promising sources for ground-based gravitational-wave (gw) detectors and are also high-energy astrophysical phenomena, as illustrated by the observations of gws and electromagnetic (em) waves in the event of gw170817. mergers of these neutron star binaries are also the most promising sites for r-process nucleosynthesis. numerical simulation in full general relativity (numerical relativity) is a unique approach to the theoretical prediction of the merger process, gws emitted, mass ejection process, and resulting em emission. we summarize the current understanding of the processes of neutron star mergers and subsequent mass ejection based on the results of the latest numerical-relativity simulations. we emphasize that the predictions of the numerical-relativity simulations agree broadly with the optical and ir observations of gw170817. | merger and mass ejection of neutron star binaries |
over the past decade, increasingly robust estimates of the dense molecular gas content in galaxy populations between redshift z = 0 and the peak of cosmic galaxy/star formation (z ∼ 1-3) have become available. this rapid progress has been possible due to the advent of powerful ground- and space-based telescopes for the combined study of several millimeter to far-ir, line or continuum tracers of the molecular gas and dust components. the main conclusions of this review are as follows: star-forming galaxies contained much more molecular gas at earlier cosmic epochs than at the present time. the galaxy-integrated depletion timescale for converting the gas into stars depends primarily on z or hubble time and, at a given z, on the vertical location of a galaxy along the star-formation rate versus stellar mass main sequence (ms) correlation. global rates of galaxy gas accretion primarily control the evolution of the cold molecular gas content and star-formation rates of the dominant ms galaxy population, which in turn vary with cosmological expansion. another key driver may be global disk fragmentation in high-z, gas-rich galaxies, which ties local free-fall timescales to galactic orbital times and leads to rapid radial matter transport and bulge growth. the low star-formation efficiency inside molecular clouds is plausibly set by supersonic streaming motions and internal turbulence, which in turn may be driven by conversion of gravitational energy at high z and/or by local feedback from massive stars at low z. a simple gas regulator model is remarkably successful in predicting the combined evolution of molecular gas fractions, star-formation rates, galactic winds, and gas-phase metallicities. | the evolution of the star-forming interstellar medium across cosmic time |
fast radio bursts (frbs) are brief, bright, extragalactic radio flashes1,2. their physical origin remains unknown, but dozens of possible models have been postulated3. some frb sources exhibit repeat bursts4-7. although over a hundred frb sources have been discovered8, only four have been localized and associated with a host galaxy9-12, and just one of these four is known to emit repeating frbs9. the properties of the host galaxies, and the local environments of frbs, could provide important clues about their physical origins. the first known repeating frb, however, was localized to a low-metallicity, irregular dwarf galaxy, and the apparently non-repeating sources were localized to higher-metallicity, massive elliptical or star-forming galaxies, suggesting that perhaps the repeating and apparently non-repeating sources could have distinct physical origins. here we report the precise localization of a second repeating frb source6, frb 180916.j0158+65, to a star-forming region in a nearby (redshift 0.0337 ± 0.0002) massive spiral galaxy, whose properties and proximity distinguish it from all known hosts. the lack of both a comparably luminous persistent radio counterpart and a high faraday rotation measure6 further distinguish the local environment of frb 180916.j0158+65 from that of the single previously localized repeating frb source, frb 121102. this suggests that repeating frbs may have a wide range of luminosities, and originate from diverse host galaxies and local environments. | a repeating fast radio burst source localized to a nearby spiral galaxy |
this paper presents the second data release of the hyper suprime-cam subaru strategic program, a wide-field optical imaging survey using the 8.2 m subaru telescope. the release includes data from 174 nights of observation through 2018 january. the wide layer data cover about 300 deg^2 in all five broad-band filters (grizy) to the nominal survey exposure (10 min in gr and 20 min in izy). partially observed areas are also included in the release; about 1100 deg^2 is observed in at least one filter and one exposure. the median seeing in the i-band is {0.^' ' }6}, demonstrating the superb image quality of the survey. the deep (26 deg^2) and ultradeep (4 deg^2) data are jointly processed and the ultradeep-cosmos field reaches an unprecedented depth of i∼ 28 at 5 σ for point sources. in addition to the broad-band data, narrow-band data are also available in the deep and ultradeep fields. this release includes a major update to the processing pipeline, including improved sky subtraction, psf modeling, object detection, and artifact rejection. the overall data quality has been improved, but this release is not without problems; there is a persistent deblender problem as well as new issues with masks around bright stars. the user is encouraged to review the issue list before utilizing the data for scientific explorations. all the image products as well as catalog products are available for download. the catalogs are also loaded into a database, which provides an easy interface for users to retrieve data for objects of interest. in addition to these main data products, detailed galaxy shape measurements withheld from public data release 1 (pdr1) are now available to the community. the shape catalog is drawn from the s16a internal release, which has a larger area than pdr1 (160 deg^2). all products are available at the data release site, https://hsc-release.mtk.nao.ac.jp/. | second data release of the hyper suprime-cam subaru strategic program |
physics-informed neural networks (pinn) are neural networks (nns) that encode model equations, like partial differential equations (pde), as a component of the neural network itself. pinns are nowadays used to solve pdes, fractional equations, integral-differential equations, and stochastic pdes. this novel methodology has arisen as a multi-task learning framework in which a nn must fit observed data while reducing a pde residual. this article provides a comprehensive review of the literature on pinns: while the primary goal of the study was to characterize these networks and their related advantages and disadvantages. the review also attempts to incorporate publications on a broader range of collocation-based physics informed neural networks, which stars form the vanilla pinn, as well as many other variants, such as physics-constrained neural networks (pcnn), variational hp-vpinn, and conservative pinn (cpinn). the study indicates that most research has focused on customizing the pinn through different activation functions, gradient optimization techniques, neural network structures, and loss function structures. despite the wide range of applications for which pinns have been used, by demonstrating their ability to be more feasible in some contexts than classical numerical techniques like finite element method (fem), advancements are still possible, most notably theoretical issues that remain unresolved. | scientific machine learning through physics-informed neural networks: where we are and what's next |
the properties of neutron stars are determined by the nature of the matter that they contain. these properties can be constrained by measurements of the star's size. we obtain stringent constraints on neutron-star radii by combining multimessenger observations of the binary neutron-star merger gw170817 with nuclear theory that best accounts for density-dependent uncertainties in the equation of state. we construct equations of state constrained by chiral effective field theory and marginalize over these using the gravitational-wave observations. combining this with the electromagnetic observations of the merger remnant that imply the presence of a short-lived hypermassive neutron star, we find that the radius of a 1.4 m⊙ neutron star is r1.4 m⊙=11.0-0.6+0.9km ? (90% credible interval). using this constraint, we show that neutron stars are unlikely to be disrupted in neutron star-black hole mergers; subsequently, such events will not produce observable electromagnetic emission. | stringent constraints on neutron-star radii from multimessenger observations and nuclear theory |
we review numerous arguments for primordial black holes (pbhs) based on observational evidence from a variety of lensing, dynamical, accretion and gravitational-wave effects. this represents a shift from the usual emphasis on pbh constraints and provides what we term a positivist perspective. microlensing observations of stars and quasars suggest that pbhs of around $1\,m_{\odot}$ could provide much of the dark matter in galactic halos, this being allowed by the large magellanic cloud microlensing observations if the pbhs have an extended mass function. more generally, providing the mass and dark matter fraction of the pbhs is large enough, the associated poisson fluctuations could generate the first bound objects at a much earlier epoch than in the standard cosmological scenario. this simultaneously explains the recent detection of high-redshift dwarf galaxies, puzzling correlations of the source-subtracted infrared and x-ray cosmic backgrounds, the size and the mass-to-light ratios of ultra-faint-dwarf galaxies, the dynamical heating of the galactic disk, and the binary coalescences observed by ligo/virgo/kagra in a mass range not usually associated with stellar remnants. even if pbhs provide only a small fraction of the dark matter, they could explain various other observational conundra, and sufficiently large ones could seed the supermassive black holes in galactic nuclei or even early galaxies themselves. we argue that pbhs would naturally have formed around the electroweak, quantum chromodynamics and electron-positron annihilation epochs, when the sound-speed inevitably dips. this leads to an extended pbh mass function with a number of distinct bumps, the most prominent one being at around $1\,m_{\odot}$, and this would allow pbhs to explain many of the observations in a unified way. | observational evidence for primordial black holes: a positivist perspective |
we present atacama large millimeter and submillimeter array observations of the protoplanetary disk around the herbig ae star hd 163296 that trace the spatial distribution of millimeter-sized particles and cold molecular gas on spatial scales as small as 25 astronomical units (a.u.). the image of the disk recorded in the 1.3 mm continuum emission reveals three dark concentric rings that indicate the presence of dust depleted gaps at about 60, 100, and 160 a.u. from the central star. the maps of the 12co, 13co, and c 18o j =2 -1 emission do not show such structures but reveal a change in the slope of the radial intensity profile across the positions of the dark rings in the continuum image. by comparing the observations with theoretical models for the disk emission, we find that the density of co molecules is reduced inside the middle and outer dust gaps. however, in the inner ring there is no evidence of co depletion. from the measurements of the dust and gas densities, we deduce that the gas-to-dust ratio varies across the disk and, in particular, it increases by at least a factor 5 within the inner dust gap compared to adjacent regions of the disk. the depletion of both dust and gas suggests that the middle and outer rings could be due to the gravitational torque exerted by two saturn-mass planets orbiting at 100 and 160 a.u. from the star. on the other hand, the inner dust gap could result from dust accumulation at the edge of a magnetorotational instability dead zone, or from dust opacity variations at the edge of the co frost line. observations of the dust emission at higher angular resolution and of molecules that probe dense gas are required to establish more precisely the origins of the dark rings observed in the hd 163296 disk. | ringed structures of the hd 163296 protoplanetary disk revealed by alma |
neutron stars and quark stars are ideal laboratories to study fundamental physics at supra nuclear densities and strong gravitational fields. astrophysical observables, however, depend strongly on the star's internal structure, which is currently unknown due to uncertainties in the equation of state. universal relations, however, exist among certain stellar observables that do not depend sensitively on the star's internal structure. one such set of relations is between the star's moment of inertia (i), its tidal love number (love) and its quadrupole moment (q), the so-called i-love-q relations. similar relations hold among the star's multipole moments, which resemble the well-known black hole no-hair theorems. universal relations break degeneracies among astrophysical observables, leading to a variety of applications: (i) x-ray measurements of the nuclear matter equation of state, (ii) gravitational wave measurements of the intrinsic spin of inspiraling compact objects, and (iii) gravitational and astrophysical tests of general relativity that are independent of the equation of state. we here review how the universal relations come about and all the applications that have been devised to date. | approximate universal relations for neutron stars and quark stars |
we present jwst/nirspec prism spectroscopy of macs0647-jd, the triply-lensed $z \sim 11$ candidate discovered in hst imaging and spatially resolved by jwst imaging into two components a and b. spectroscopy of component a yields a spectroscopic redshift $z=10.17$ based on 7 detected emission lines: ciii] $\lambda\lambda$1907,1909, [oii] $\lambda$3727, [neiii] $\lambda$3869, [neiii] $\lambda$3968, h$\delta$ $\lambda$4101, h$\gamma$ $\lambda$4340, and [oiii] $\lambda$4363. these are the second-most distant detections of these emission lines to date, in a galaxy observed just 460 million years after the big bang. based on observed and extrapolated line flux ratios we derive a gas-phase metallicity $z =$ log(o/h) = $7.5 - 8.0$, or $(0.06 - 0.2)$ $z_\odot$, ionization parameter log($u$) $\sim -1.9\pm0.2$, and an ionizing photon production efficiency ${\rm log}(\xi_{\rm ion})=25.2\pm0.2\,$erg$^{-1}$ hz. the spectrum has a softened lyman-$\alpha$ break, evidence for a strong ly$\alpha$ damping wing, suggesting that macs0647-jd was unable to ionize its surroundings beyond its immediate vicinity ($r_{\text{hii}} \ll 1$ pmpc). the ly$\alpha$ damping wing also suppresses the f150w photometry, explaining the slightly overestimated photometric redshift $z = 10.6 \pm 0.3$. macs0647-jd has a stellar mass log($m/m_\odot$) = $8.1 \pm 0.3$, including $\sim$ 6$\times 10^7 m_\odot$ in component a, most of which formed recently (within $\sim$ 20 myr) with a star formation rate $2\pm1 m_\odot$ / yr, all within an effective radius $70\pm24\,$pc. the smaller component b ($r \sim 20$) pc is likely older ($\sim$100 myr) with more dust ($a_v \sim 0.1$ mag), as found previously. spectroscopy of a fainter companion galaxy c separated by a distance of \about\ 3$\,$kpc reveals a lyman break consistent with $z = 10.17$. macs0647-jd is likely the most distant galaxy merger known. | jwst nirspec spectroscopy of the triply-lensed $z = 10.17$ galaxy macs0647$-$jd |
the tip of the red giant branch (trgb) method provides one of the most accurate and precise means of measuring the distances to nearby galaxies. here we present a multi-wavelength, vijhk absolute calibration of the trgb based on observations of trgb stars in the large magellanic cloud (lmc), grounded on a geometric distance, determined by detached eclipsing binaries (debs). this paper presents a more detailed description of the method first presented by freedman et al. for measuring corrections for the total line-of-sight extinction and reddening to the lmc. in this method, we use a differential comparison of the red giant population in the lmc, first with red giants in the local group galaxy ic 1613, and then with those in the small magellanic cloud (smc). as a consistency check, we derive an independent calibration of the trgb sequence using the smc alone, invoking its geometric distance also calibrated by debs. an additional consistency check comes from near-infrared observations of galactic globular clusters covering a wide range of metallicities. in all cases we find excellent agreement in the zero-point calibration. we then examine the recent claims by yuan et al., demonstrating that, in the case of the smc, they corrected for extinction alone while neglecting the essential correction for reddening. in the case of ic 1613, we show that their analysis contains an incorrect treatment of (over-correction for) metallicity. using our revised (and direct) measurement of the lmc trgb extinction, we find a value of h0 = 69.6 ± 0.8 (±1.1% stat) ± 1.7 (±2.4% sys) km s-1 mpc-1. | calibration of the tip of the red giant branch |
the binary neutron-star merger gw170817 was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy ngc 4993 at a distance of about 41 megaparsecs from earth. the radio and x-ray afterglows of gw170817 exhibited delayed onset, a gradual increase in the emission with time (proportional to t0.8) to a peak about 150 days after the merger event, followed by a relatively rapid decline. so far, various models have been proposed to explain the afterglow emission, including a choked-jet cocoon and a successful-jet cocoon (also called a structured jet). however, the observational data have remained inconclusive as to whether gw170817 launched a successful relativistic jet. here we report radio observations using very long-baseline interferometry. we find that the compact radio source associated with gw170817 exhibits superluminal apparent motion between 75 days and 230 days after the merger event. this measurement breaks the degeneracy between the choked- and successful-jet cocoon models and indicates that, although the early-time radio emission was powered by a wide-angle outflow (a cocoon), the late-time emission was most probably dominated by an energetic and narrowly collimated jet (with an opening angle of less than five degrees) and observed from a viewing angle of about 20 degrees. the imaging of a collimated relativistic outflow emerging from gw170817 adds substantial weight to the evidence linking binary neutron-star mergers and short γ-ray bursts. | superluminal motion of a relativistic jet in the neutron-star merger gw170817 |
the ultraviolet transient astronomy satellite (ultrasat) is scheduled to be launched to geostationary orbit in 2026. it will carry a telescope with an unprecedentedly large field of view (204 deg$^2$) and nuv (230-290nm) sensitivity (22.5 mag, 5$\sigma$, at 900s). ultrasat will conduct the first wide-field survey of transient and variable nuv sources and will revolutionize our ability to study the hot transient universe: it will explore a new parameter space in energy and time-scale (months long light-curves with minutes cadence), with an extra-galactic volume accessible for the discovery of transient sources that is $>$300 times larger than that of galex and comparable to that of lsst. ultrasat data will be transmitted to the ground in real-time, and transient alerts will be distributed to the community in $<$15 min, enabling a vigorous ground-based follow-up of ultrasat sources. ultrasat will also provide an all-sky nuv image to $>$23.5 ab mag, over 10 times deeper than the galex map. two key science goals of ultrasat are the study of mergers of binaries involving neutron stars, and supernovae: with a large fraction ($>$50%) of the sky instantaneously accessible, fast (minutes) slewing capability and a field-of-view that covers the error ellipses expected from gw detectors beyond 2025, ultrasat will rapidly detect the electromagnetic emission following bns/ns-bh mergers identified by gw detectors, and will provide continuous nuv light-curves of the events; ultrasat will provide early (hour) detection and continuous high (minutes) cadence nuv light curves for hundreds of core-collapse supernovae, including for rarer supernova progenitor types. | ultrasat: a wide-field time-domain uv space telescope |
the family of metallic kagome compounds a v3sb5 (a =k ,rb ,cs ) was recently discovered to exhibit both superconductivity and charge order. the nature of the charge density wave (cdw) phase is presently unsettled, which complicates the interpretation of the superconducting ground state. in this paper, we use group theory and density functional theory (dft) to derive and solve a phenomenological landau model for this cdw state. the dft results reveal three unstable phonon modes with the same in-plane momentum but different out-of-plane momenta, whose frequencies depend strongly on the electronic temperature. this is indicative of an electronically driven cdw, stabilized by features of the in-plane electronic dispersion. motivated by the dft analysis, we construct a landau free-energy expansion for coupled cdw order parameters with wave vectors at the m and l points of the hexagonal brillouin zone. we find an unusual trilinear term coupling these different order parameters, which can promote the simultaneous condensation of both cdws even if the two modes are not nearly degenerate. we classify the different types of coupled multi-q cdw orders, focusing on those that break the sixfold rotational symmetry and lead to a unit-cell doubling along all three crystallographic directions, as suggested by experiments. we determine a region in parameter space, characterized by large nonlinear landau coefficients, where these phases—dubbed staggered trihexagonal and staggered star of david—are the leading instabilities of the system. finally, we discuss the implications of our results for the kagome metals. | theory of the charge density wave in a v3sb5 kagome metals |
the large sky area multi-object fiber spectroscopic telescope (lamost) general survey is a spectroscopic survey that will eventually cover approximately half of the celestial sphere and collect 10 million spectra of stars, galaxies and qsos. objects in both the pilot survey and the first year regular survey are included in the lamost dr1. the pilot survey started in october 2011 and ended in june 2012, and the data have been released to the public as the lamost pilot data release in august 2012. the regular survey started in september 2012, and completed its first year of operation in june 2013. the lamost dr1 includes a total of 1202 plates containing 2 955 336 spectra, of which 1 790 879 spectra have observed signal-to-noise ratio (snr) ≥ 10. all data with snr ≥ 2 are formally released as lamost dr1 under the lamost data policy. this data release contains a total of 2 204 696 spectra, of which 1 944 329 are stellar spectra, 12 082 are galaxy spectra and 5017 are quasars. the dr1 not only includes spectra, but also three stellar catalogs with measured parameters: late a,fgk-type stars with high quality spectra (1061 918 entries), a-type stars (100 073 entries), and m-type stars (121 522 entries). this paper introduces the survey design, the observational and instrumental limitations, data reduction and analysis, and some caveats. a description of the fits structure of spectral files and parameter catalogs is also provided. | the first data release (dr1) of the lamost regular survey |
we demonstrate in a general and analytic way how high-density information about the equation of state (eos) of strongly interacting matter obtained using perturbative quantum chromodynamics constrains the same eos at densities reachable in physical neutron stars. our approach is based on utilizing the full information of the thermodynamic potentials at the high-density limit together with thermodynamic stability and causality. this requires considering the pressure as a function of chemical potential p (μ ) instead of the commonly used pressure as a function of energy density p (ε ). the results can be used to propagate the perturbative quantum chromodynamics calculations reliable around 40 ns to lower densities in the most conservative way possible. we constrain the eos starting from only a few times the nuclear saturation density n ≳2.2 ns , and at n =5 ns we exclude at least 65% of otherwise allowed area in the ε -p plane. this provides information complementary to astrophysical observations that should be taken into account in any complete statistical inference study of the eos. these purely theoretical results are independent of astrophysical neutron-star input, and hence, they can also be used to test theories of modified gravity and beyond the standard model physics in neutron stars. | how perturbative qcd constrains the equation of state at neutron-star densities |
the hydrogen epoch of reionization array (hera) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (igm) throughout cosmic reionization (z = 6-12), and to explore earlier epochs of our cosmic dawn (z ∼ 30). during these epochs, early stars and black holes heated and ionized the igm, introducing fluctuations in 21 cm emission. hera is designed to characterize the evolution of the 21 cm power spectrum to constrain the timing and morphology of reionization, the properties of the first galaxies, the evolution of large-scale structure, and the early sources of heating. the full hera instrument will be a 350-element interferometer in south africa consisting of 14 m parabolic dishes observing from 50 to 250 mhz. currently, 19 dishes have been deployed on site and the next 18 are under construction. hera has been designated as an ska precursor instrument. in this paper, we summarize hera’s scientific context and provide forecasts for its key science results. after reviewing the current state of the art in foreground mitigation, we use the delay-spectrum technique to motivate high-level performance requirements for the hera instrument. next, we present the hera instrument design, along with the subsystem specifications that ensure that hera meets its performance requirements. finally, we summarize the schedule and status of the project. we conclude by suggesting that, given the realities of foreground contamination, current-generation 21 cm instruments are approaching their sensitivity limits. hera is designed to bring both the sensitivity and the precision to deliver its primary science on the basis of proven foreground filtering techniques, while developing new subtraction techniques to unlock new capabilities. the result will be a major step toward realizing the widely recognized scientific potential of 21 cm cosmology. | hydrogen epoch of reionization array (hera) |
gravitational waves detected from the binary neutron star (ns) merger gw170817 constrained the ns equation of state by placing an upper bound on certain parameters, describing the binary’s tidal interactions. we show that the interpretation of the uv/optical/infrared counterpart of gw170817 with kilonova models, combined with new numerical-relativity results, imply a complementary lower bound on the tidal deformability parameter. the joint constraints tentatively rule out both extremely stiff and soft ns equations of state. | gw170817: joint constraint on the neutron star equation of state from multimessenger observations |
the precise localization of the repeating fast radio burst (frb 121102) has provided the first unambiguous association (chance coincidence probability p ≲ 3 × 10-4) of an frb with an optical and persistent radio counterpart. we report on optical imaging and spectroscopy of the counterpart and find that it is an extended (0.″6-0.″8) object displaying prominent balmer and [o iii] emission lines. based on the spectrum and emission line ratios, we classify the counterpart as a low-metallicity, star-forming, mr‧ = 25.1 ab mag dwarf galaxy at a redshift of z = 0.19273(8), corresponding to a luminosity distance of 972 mpc. from the angular size, the redshift, and luminosity, we estimate the host galaxy to have a diameter ≲4 kpc and a stellar mass of m * ∼ (4-7) × 107 m ⊙, assuming a mass-to-light ratio between 2 to 3 m ⊙ l ⊙ -1. based on the hα flux, we estimate the star formation rate of the host to be 0.4 m ⊙ yr-1 and a substantial host dispersion measure (dm) depth ≲324 pc cm-3. the net dm contribution of the host galaxy to frb 121102 is likely to be lower than this value depending on geometrical factors. we show that the persistent radio source at frb 121102’s location reported by marcote et al. is offset from the galaxy’s center of light by ∼200 mas and the host galaxy does not show optical signatures for agn activity. if frb 121102 is typical of the wider frb population and if future interferometric localizations preferentially find them in dwarf galaxies with low metallicities and prominent emission lines, they would share such a preference with long gamma-ray bursts and superluminous supernovae. | the host galaxy and redshift of the repeating fast radio burst frb 121102 |
while tidal disruption events (tdes) have long been heralded as laboratories for the study of quiescent black holes, the small number of known tdes and uncertainties in their emission mechanism have hindered progress toward this promise. here we present 17 new tdes that have been detected recently by the zwicky transient facility along with swift uv and x-ray follow-up observations. our homogeneous analysis of the optical/uv light curves, including 22 previously known tdes from the literature, reveals a clean separation of light-curve properties with spectroscopic class. the tdes with bowen fluorescence features in their optical spectra have smaller blackbody radii, lower optical luminosities, and higher disruption rates compared to the rest of the sample. the small subset of tdes that show only helium emission lines in their spectra have the longest rise times, the highest luminosities, and the lowest rates. a high detection rate of bowen lines in tdes with small photometric radii could be explained by the high density that is required for this fluorescence mechanism. the stellar debris can provide a source for this dense material. diffusion of photons through this debris may explain why the rise and fade timescale of the tdes in our sample are not correlated. we also report, for the first time, the detection of soft x-ray flares from a tde on ∼day timescales. based on the fact that the x-ray flares peak at a luminosity similar to the optical/uv blackbody luminosity, we attribute them to brief glimpses through a reprocessing layer that otherwise obscures the inner accretion flow. | seventeen tidal disruption events from the first half of ztf survey observations: entering a new era of population studies |
the h0licow collaboration inferred via strong gravitational lensing time delays a hubble constant value of h0 = 73.3-1.8+1.7 km s-1 mpc-1, describing deflector mass density profiles by either a power-law or stars (constant mass-to-light ratio) plus standard dark matter halos. the mass-sheet transform (mst) that leaves the lensing observables unchanged is considered the dominant source of residual uncertainty in h0. we quantify any potential effect of the mst with a flexible family of mass models, which directly encodes it, and they are hence maximally degenerate with h0. our calculation is based on a new hierarchical bayesian approach in which the mst is only constrained by stellar kinematics. the approach is validated on mock lenses, which are generated from hydrodynamic simulations. we first applied the inference to the tdcosmo sample of seven lenses, six of which are from h0licow, and measured h0 = 74.5-6.1+5.6 km s-1 mpc-1. secondly, in order to further constrain the deflector mass density profiles, we added imaging and spectroscopy for a set of 33 strong gravitational lenses from the sloan lens acs (slacs) sample. for nine of the 33 slac lenses, we used resolved kinematics to constrain the stellar anisotropy. from the joint hierarchical analysis of the tdcosmo+slacs sample, we measured h0 = 67.4-3.2+4.1 km s-1 mpc-1. this measurement assumes that the tdcosmo and slacs galaxies are drawn from the same parent population. the blind h0licow, tdcosmo-only and tdcosmo+slacs analyses are in mutual statistical agreement. the tdcosmo+slacs analysis prefers marginally shallower mass profiles than h0licow or tdcosmo-only. without relying on the form of the mass density profile used by h0licow, we achieve a ∼5% measurement of h0. while our new hierarchical analysis does not statistically invalidate the mass profile assumptions by h0licow - and thus the h0 measurement relying on them - it demonstrates the importance of understanding the mass density profile of elliptical galaxies. the uncertainties on h0 derived in this paper can be reduced by physical or observational priors on the form of the mass profile, or by additional data. array(0x2329100) | tdcosmo. iv. hierarchical time-delay cosmography - joint inference of the hubble constant and galaxy density profiles |
we present 2241 exoplanet candidates identified with data from the transiting exoplanet survey satellite (tess) during its 2 yr prime mission. we list these candidates in the tess objects of interest (toi) catalog, which includes both new planet candidates found by tess and previously known planets recovered by tess observations. we describe the process used to identify tois, investigate the characteristics of the new planet candidates, and discuss some notable tess planet discoveries. the toi catalog includes an unprecedented number of small planet candidates around nearby bright stars, which are well suited for detailed follow-up observations. the tess data products for the prime mission (sectors 1-26), including the toi catalog, light curves, full-frame images, and target pixel files, are publicly available at the mikulski archive for space telescopes. | the tess objects of interest catalog from the tess prime mission |
the second ligo-virgo catalog of gravitational-wave (gw) transients has more than quadrupled the observational sample of binary black holes. we analyze this catalog using a suite of five state-of-the-art binary black hole population models covering a range of isolated and dynamical formation channels and infer branching fractions between channels as well as constraints on uncertain physical processes that impact the observational properties of mergers. given our set of formation models, we find significant differences between the branching fractions of the underlying and detectable populations, and the diversity of detections suggests that multiple formation channels are at play. a mixture of channels is strongly preferred over any single channel dominating the detected population: an individual channel does not contribute to more than ≃70% of the observational sample of binary black holes. we calculate the preference between the natal spin assumptions and common-envelope efficiencies in our models, favoring natal spins of isolated black holes of ≲0.1 and marginally preferring common-envelope efficiencies of ≳2.0 while strongly disfavoring highly inefficient common envelopes. we show that it is essential to consider multiple channels when interpreting gw catalogs, as inference on branching fractions and physical prescriptions becomes biased when contributing formation scenarios are not considered or incorrect physical prescriptions are assumed. although our quantitative results can be affected by uncertain assumptions in model predictions, our methodology is capable of including models with updated theoretical considerations and additional formation channels. | one channel to rule them all? constraining the origins of binary black holes using multiple formation pathways |
the basic geometry of the solar system-the shapes, spacings, and orientations of the planetary orbits-has long been a subject of fascination as well as inspiration for planet-formation theories. for exoplanetary systems, those same properties have only recently come into focus. here we review our current knowledge of the occurrence of planets around other stars, their orbital distances and eccentricities, the orbital spacings and mutual inclinations in multiplanet systems, the orientation of the host star's rotation axis, and the properties of planets in binary-star systems. | the occurrence and architecture of exoplanetary systems |
the distribution of planet sizes encodes details of planet formation and evolution. we present the most precise planet size distribution to date based on gaia parallaxes, kepler photometry, and spectroscopic temperatures from the california-kepler survey. previously, we measured stellar radii to 11% precision using high-resolution spectroscopy; by adding gaia astrometry, the errors are now 3%. planet radius measurements are, in turn, improved to 5% precision. with a catalog of ∼1000 planets with precise properties, we probed in fine detail the gap in the planet size distribution that separates two classes of small planets, rocky super-earths and gas-dominated sub-neptunes. our previous study and others suggested that the gap may be observationally under-resolved and inherently flat-bottomed, with a band of forbidden planet sizes. analysis based on our new catalog refutes this; the gap is partially filled in. two other important factors that sculpt the distribution are a planet’s orbital distance and its host-star mass, both of which are related to a planet’s x-ray/uv irradiation history. for lower-mass stars, the bimodal planet distribution shifts to smaller sizes, consistent with smaller stars producing smaller planet cores. details of the size distribution including the extent of the “sub-neptune desert” and the width and slope of the gap support the view that photoevaporation of low-density atmospheres is the dominant evolutionary determinant of the planet size distribution. | the california-kepler survey. vii. precise planet radii leveraging gaia dr2 reveal the stellar mass dependence of the planet radius gap |
general relativity has shown an outstanding observational success in the scales where it has been directly tested. however, modifications have been intensively explored in the regimes where it seems either incomplete or signals its own limit of validity. in particular, the breakdown of unitarity near the planck scale strongly suggests that general relativity needs to be modified at high energies and quantum gravity effects are expected to be important. this is related to the existence of spacetime singularities when the solutions of general relativity are extrapolated to regimes where curvatures are large. in this sense, born-infeld inspired modifications of gravity have shown an extraordinary ability to regularise the gravitational dynamics, leading to non-singular cosmologies and regular black hole spacetimes in a very robust manner and without resorting to quantum gravity effects. this has boosted the interest in these theories in applications to stellar structure, compact objects, inflationary scenarios, cosmological singularities, and black hole and wormhole physics, among others. we review the motivations, various formulations, and main results achieved within these theories, including their observational viability, and provide an overview of current open problems and future research opportunities. | born-infeld inspired modifications of gravity |
gamma-ray bursts (grbs) are divided into two populations1,2; long grbs that derive from the core collapse of massive stars (for example, ref. 3) and short grbs that form in the merger of two compact objects4,5. although it is common to divide the two populations at a gamma-ray duration of 2 s, classification based on duration does not always map to the progenitor. notably, grbs with short (≲2 s) spikes of prompt gamma-ray emission followed by prolonged, spectrally softer extended emission (ee-sgrbs) have been suggested to arise from compact object mergers6-8. compact object mergers are of great astrophysical importance as the only confirmed site of rapid neutron capture (r-process) nucleosynthesis, observed in the form of so-called kilonovae9-14. here we report the discovery of a possible kilonova associated with the nearby (350 mpc), minute-duration grb 211211a. the kilonova implies that the progenitor is a compact object merger, suggesting that grbs with long, complex light curves can be spawned from merger events. the kilonova of grb 211211a has a similar luminosity, duration and colour to that which accompanied the gravitational wave (gw)-detected binary neutron star (bns) merger gw170817 (ref. 4). further searches for gw signals coincident with long grbs are a promising route for future multi-messenger astronomy. | a kilonova following a long-duration gamma-ray burst at 350 mpc |
most supernova explosions accompany the death of a massive star. these explosions give birth to neutron stars and black holes, and eject solar masses of heavy elements. however, determining the mechanism of explosion has been a half-century journey of great numerical and physical complexity. here we present the status of this theoretical quest and the physics and astrophysics upon which its resolution seems to depend. the delayed neutrino-heating mechanism is emerging as the key driver of supernova explosions, but there remain many issues to address, such as the chaos of the involved dynamics. | core-collapse supernova explosion theory |
preface; 1. convexity, colours, and statistics; 2. geometry of probability distributions; 3. much ado about spheres; 4. complex projective spaces; 5. outline of quantum mechanics; 6. coherent states and group actions; 7. the stellar representation; 8. the space of density matrices; 9. purification of mixed quantum states; 10. quantum operations; 11. duality: maps versus states; 12. discrete structures in hilbert space; 13. density matrices and entropies; 14. distinguishability measures; 15. monotone metrics and measures; 16. quantum entanglement; 17. multipartite entanglement; appendix 1. basic notions of differential geometry; appendix 2. basic notions of group theory; appendix 3. geometry - do it yourself; appendix 4. hints and answers to the exercises; bibliography; index. | geometry of quantum states |
we review recent progress and future prospects for harnessing powerful tools from theoretical high-energy physics, such as scattering amplitudes and effective field theory, to develop a precise and systematically improvable framework for calculating gravitational-wave signals from binary systems composed of black holes and/or neutron stars. this effort aims to provide state-of-the-art predictions that will enable high-precision measurements at future gravitational-wave detectors. in turn, applying the tools of quantum field theory in this new arena will uncover theoretical structures that can transform our understanding of basic phenomena and lead to new tools that will further the cycle of innovation. while still in a nascent stage, this research direction has already derived new analytic results in general relativity, and promises to advance the development of highly accurate waveform models for ever more sensitive detectors. | snowmass white paper: gravitational waves and scattering amplitudes |
freeze-out of the gas-phase elements onto cold grains in dense interstellar and circumstellar media builds up ice mantles consisting of molecules that are mostly formed in situ (h2o, nh3, co2, co, ch3oh, and more). this review summarizes the detected infrared spectroscopic ice features and compares the abundances across galactic, extragalactic, and solar system environments. a tremendous amount of information is contained in the ice band profiles. laboratory experiments play a critical role in the analysis of the observations. strong evidence is found for distinct ice formation stages, separated by co freeze-out at high densities. the ice bands have proven to be excellent probes of the thermal history of their environment. the evidence for the long-held idea that processing of ices by energetic photons and cosmic rays produces complex molecules is weak. recent state-of-the-art observations show promise for much progress in this area with planned infrared facilities. | observations of the icy universe. |
the recent detection by advanced ligo of gravitational waves (gw) from the merging of a binary black hole system sets new limits on the merging rates of massive primordial black holes (pbh) that could be a significant fraction or even the totality of the dark matter in the universe. aligo opens the way to the determination of the distribution and clustering of such massive pbh. if pbh clusters have a similar density to the one observed in ultra-faint dwarf galaxies, we find merging rates comparable to aligo expectations. massive pbh dark matter predicts the existence of thousands of those dwarf galaxies where star formation is unlikely because of gas accretion onto pbh, which would possibly provide a solution to the missing satellite and too-big-to-fail problems. finally, we study the possibility of using aligo and future gw antennas to measure the abundance and mass distribution of pbh in the range [5-200] m⊙ to 10% accuracy. | the clustering of massive primordial black holes as dark matter: measuring their mass distribution with advanced ligo |
the prediction of a supersonic solar wind1 was first confirmed by spacecraft near earth2,3 and later by spacecraft at heliocentric distances as small as 62 solar radii4. these missions showed that plasma accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the sun before depositing it in the wind. alfvénic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy5-7. magnetic tension forces the corona to co-rotate with the sun, but any residual rotation far from the sun reported until now has been much smaller than the amplitude of waves and deflections from interacting wind streams8. here we report observations of solar-wind plasma at heliocentric distances of about 35 solar radii9-11, well within the distance at which stream interactions become important. we find that alfvén waves organize into structured velocity spikes with duration of up to minutes, which are associated with propagating s-like bends in the magnetic-field lines. we detect an increasing rotational component to the flow velocity of the solar wind around the sun, peaking at 35 to 50 kilometres per second—considerably above the amplitude of the waves. these flows exceed classical velocity predictions of a few kilometres per second, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age12-14. | alfvénic velocity spikes and rotational flows in the near-sun solar wind |
the astrophysics of the cosmic dawn, when star formation commenced in the first collapsed objects, is predicted to be revealed by spectral and spatial signatures in the cosmic radio background at long wavelengths. the sky-averaged redshifted 21 cm absorption line of neutral hydrogen is a probe of the cosmic dawn. the line profile is determined by the evolving thermal state of the gas, radiation background, lyman α radiation from stars scattering off cold primordial gas, and relative populations of the hyperfine spin levels in neutral hydrogen atoms. we report a radiometer measurement of the spectrum of the radio sky in the 55-85 mhz band, which shows that the profile found by bowman et al. in data taken with the experiment to detect the global epoch of reionization signature (edges) low-band instrument is not of astrophysical origin; their best-fitting profile is rejected with 95.3% confidence. the profile was interpreted to be a signature of the cosmic dawn; however, its amplitude was substantially higher than that predicted by standard cosmological models. our non-detection bears out earlier concerns and suggests that the profile found by bowman et al. is not evidence for new astrophysics or non-standard cosmology. | on the detection of a cosmic dawn signal in the radio background |
spitzer/infrared array camera (irac) imaging has revealed that the brightest z ~ 7-8 galaxies often exhibit young ages and strong nebular line emission, hinting at high ionizing efficiency among early galaxies. however, irac's limited sensitivity has long hindered efforts to study the fainter, more numerous population often thought largely responsible for reionization. here, we use cosmic evolution early release science (ceers) jwst/nircam data to characterize 116 ultraviolet (uv)-faint (median muv = -19.5) z ~ 6.5-8 galaxies. the spectral energy distributions are typically dominated by young (~10-50 myr), low-mass (m* ~ 108 m⊙) stellar populations, and we find no need for extremely high stellar masses (~1011 m⊙). considering previous studies of uv-bright (muv ~ -22) z ~ 7-8 galaxies, we find evidence for a strong (5-10 times) increase in specific star formation rate (ssfr) toward lower luminosities (median ssfr = 103 gyr-1 in ceers). the larger ssfrs imply a more dominant contribution from ob stars in the relatively numerous uv-faint population, perhaps suggesting that these galaxies are very efficient ionizing agents (median ξion = 1025.7 erg-1 hz). in spite of the much larger ssfrs, we find little increase in [o iii] + h β equivalent widths towards fainter muv (median ≈780 $\mathrm{\mathring{a}}$). if confirmed, this may indicate that a substantial fraction of our ceers galaxies possess extremely low metallicities (≲3 per cent z⊙) where [o iii] emission is suppressed. alternatively, high ionizing photon escape fractions or bursty star formation histories can also weaken the nebular lines in a subset of our sample. while the majority of galaxies in our sample are very blue (median β = -2.0), we identify a significant tail of very dusty galaxies (β ~ -1) at ≈0.5$l_\mathrm{uv}^\ast$ which may contribute significantly to the z ~ 7-8 star formation rate density. | a jwst/nircam study of key contributors to reionization: the star-forming and ionizing properties of uv-faint z 7-8 galaxies |
numerical simulations have become a major tool for understanding galaxy formation and evolution. over the decades the field has made significant progress. it is now possible to simulate the formation of individual galaxies and galaxy populations from well-defined initial conditions with realistic abundances and global properties. an essential component of the calculation is to correctly estimate the inflow to and outflow from forming galaxies because observations indicating low formation efficiency and strong circumgalactic presence of gas are persuasive. energetic "feedback" from massive stars and accreting supermassive black holes - generally unresolved in cosmological simulations - plays a major role in driving galactic outflows, which have been shown to regulate many aspects of galaxy evolution. a surprisingly large variety of plausible subresolution models succeeds in this exercise. they capture the essential characteristics of the problem, i.e., outflows regulating galactic gas flows, but their predictive power is limited. in this review, we focus on one major challenge for galaxy formation theory: to understand the underlying physical processes that regulate the structure of the interstellar medium, star formation, and the driving of galactic outflows. this requires accurate physical models and numerical simulations, which can precisely describe the multiphase structure of the interstellar medium on the currently unresolved few hundred parsec scales of large-scale cosmological simulations. such models ultimately require the full accounting for the dominant cooling and heating processes, the radiation and winds from massive stars and accreting black holes, and an accurate treatment of supernova explosions as well as the nonthermal components of the interstellar medium like magnetic fields and cosmic rays. | theoretical challenges in galaxy formation |
a review is given of the theory and phenomenology of neutrino electromagnetic interactions, which provide powerful tools to probe the physics beyond the standard model. after a derivation of the general structure of the electromagnetic interactions of dirac and majorana neutrinos in the one-photon approximation, the effects of neutrino electromagnetic interactions in terrestrial experiments and in astrophysical environments are discussed. the experimental bounds on neutrino electromagnetic properties are presented and the predictions of theories beyond the standard model are confronted. | neutrino electromagnetic interactions: a window to new physics |
the disks that orbit young stars are the essential conduits and reservoirs of material for star and planet formation. their structures, meaning the spatial variations of the disk physical conditions, reflect the underlying mechanisms that drive those formation processes. observations of the solids and gas in these disks, particularly at high resolution, provide fundamental insights on their mass distributions, dynamical states, and evolutionary behaviors. over the past decade, rapid developments in these areas have largely been driven by observations with the atacama large millimeter/submillimeter array (alma). this review highlights the state of observational research on disk structures, emphasizing the following three key conclusions that reflect the main branches of the field: relationships among disk structure properties are also linked to the masses, environments, and evolutionary states of their stellar hosts. there is clear, qualitative evidence for the growth and migration of disk solids, although the implied evolutionary timescales suggest the classical assumption of a smooth gas disk is inappropriate. small-scale substructures with a variety of morphologies, locations, scales, and amplitudes—presumably tracing local gas pressure maxima—broadly influence the physical and observational properties of disks.the last point especially is reshaping the field, with the recognition that these disk substructures likely trace active sites of planetesimal growth or are the hallmarks of planetary systems at their formation epoch. | observations of protoplanetary disk structures |
the second gaia data release (gaia dr2) contains, beyond the astrometry, three-band photometry for 1.38 billion sources. one band is the g band, the other two were obtained by integrating the gaia prism spectra (bp and rp). we have used these three broad photometric bands to infer stellar effective temperatures, teff, for all sources brighter than g = 17 mag with teff in the range 3000-10 000 k (some 161 million sources). using in addition the parallaxes, we infer the line-of-sight extinction, ag, and the reddening, e(bp - rp), for 88 million sources. together with a bolometric correction we derive luminosity and radius for 77 million sources. these quantities as well as their estimated uncertainties are part of gaia dr2. here we describe the procedures by which these quantities were obtained, including the underlying assumptions, comparison with literature estimates, and the limitations of our results. typical accuracies are of order 324 k (teff), 0.46 mag (ag), 0.23 mag (e(bp - rp)), 15% (luminosity), and 10% (radius). being based on only a small number of observable quantities and limited training data, our results are necessarily subject to some extreme assumptions that can lead to strong systematics in some cases (not included in the aforementioned accuracy estimates). one aspect is the non-negativity contraint of our estimates, in particular extinction, which we discuss. yet in several regions of parameter space our results show very good performance, for example for red clump stars and solar analogues. large uncertainties render the extinctions less useful at the individual star level, but they show good performance for ensemble estimates. we identify regimes in which our parameters should and should not be used and we define a "clean" sample. despite the limitations, this is the largest catalogue of uniformly-inferred stellar parameters to date. more precise and detailed astrophysical parameters based on the full bp/rp spectrophotometry are planned as part of the third gaia data release. | gaia data release 2. first stellar parameters from apsis |
we analyze 24 binary radio pulsars in the north american nanohertz observatory for gravitational waves (nanograv) nine-year data set. we make 14 significant measurements of the shapiro delay, including new detections in four pulsar-binary systems (psrs j0613-0200, j2017+0603, j2302+4442, and j2317+1439), and derive estimates of the binary-component masses and orbital inclination for these msp-binary systems. we find a wide range of binary pulsar masses, with values as low as {m}{{p}}={1.18}-0.09+0.10 {m}⊙for psr j1918-0642 and as high as {m}{{p}}={1.928}-0.017+0.017 {m}⊙for psr j1614-2230 (both 68.3% credibility). we make an improved measurement of the shapiro timing delay in the psr j1918-0642 and j2043+1711 systems, measuring the pulsar mass in the latter system to be {m}{{p}}={1.41}-0.18+0.21 {m}⊙(68.3% credibility) for the first time. we measure secular variations of one or more orbital elements in many systems, and use these measurements to further constrain our estimates of the pulsar and companion masses whenever possible. in particular, we used the observed shapiro delay and periastron advance due to relativistic gravity in the psr j1903+0327 system to derive a pulsar mass of {m}{{p}}={1.65}-0.02+0.02 {m}⊙(68.3% credibility). we discuss the implications that our mass measurements have on the overall neutron-star mass distribution, and on the “mass/orbital-period” correlation due to extended mass transfer. | the nanograv nine-year data set: mass and geometric measurements of binary millisecond pulsars |
many neutron star properties, such as the proton fraction, reflect the symmetry energy contributions to the equation of state that dominate when neutron and proton densities differ strongly. to constrain these contributions at suprasaturation densities, we measure the spectra of charged pions produced by colliding rare isotope tin (sn) beams with isotopically enriched sn targets. using ratios of the charged pion spectra measured at high transverse momenta, we deduce the slope of the symmetry energy to be 42 <l <117 mev . this value is slightly lower but consistent with the l values deduced from a recent measurement of the neutron skin thickness of 208pb. | probing the symmetry energy with the spectral pion ratio |
we investigate the application of an equation of state that incorporates corrections derived from the snyder model (and the generalized uncertainty principle) to describe the behaviour of matter in a low-mass star. remarkably, the resulting equations exhibit striking similarities to those arising from modified einstein gravity theories. by modeling matter with realistic considerations, we are able to more effectively constrain the theory parameters, surpassing the limitations of existing astrophysical bounds. the bound we obtain is β0≤4.5 ×1047 . we underline the significance of realistic matter modeling in order to enhance our understanding of effects arising in quantum gravity phenomenology and implications of quantum gravitational corrections in astrophysical systems. | constraining snyder and gup models with low-mass stars |
in the recent years, primordial black holes (pbhs) have emerged as one of the most interesting and hotly debated topics in cosmology. among other possibilities, pbhs could explain both some of the signals from binary black hole mergers observed in gravitational wave detectors and an important component of the dark matter in the universe. significant progress has been achieved both on the theory side and from the point of view of observations, including new models and more accurate calculations of pbh formation, evolution, clustering, merger rates, as well as new astrophysical and cosmological probes. in this work, we review, analyse and combine the latest developments in order to perform end-to-end calculations of the various gravitational wave signatures of pbhs. different ways to distinguish pbhs from stellar black holes are emphasized. finally, we discuss their detectability with lisa, the first planned gravitational-wave observatory in space. | primordial black holes and their gravitational-wave signatures |
aims: we produce a clean and well-characterised catalogue of objects within 100 pc of the sun from the gaia early data release 3. we characterise the catalogue through comparisons to the full data release, external catalogues, and simulations. we carry out a first analysis of the science that is possible with this sample to demonstrate its potential and best practices for its use.methods: theselection of objects within 100 pc from the full catalogue used selected training sets, machine-learning procedures, astrometric quantities, and solution quality indicators to determine a probability that the astrometric solution is reliable. the training set construction exploited the astrometric data, quality flags, and external photometry. for all candidates we calculated distance posterior probability densities using bayesian procedures and mock catalogues to define priors. any object with reliable astrometry and a non-zero probability of being within 100 pc is included in the catalogue.results: we have produced a catalogue of 331 312 objects that we estimate contains at least 92% of stars of stellar type m9 within 100 pc of the sun. we estimate that 9% of the stars in this catalogue probably lie outside 100 pc, but when the distance probability function is used, a correct treatment of this contamination is possible. we produced luminosity functions with a high signal-to-noise ratio for the main-sequence stars, giants, and white dwarfs. we examined in detail the hyades cluster, the white dwarf population, and wide-binary systems and produced candidate lists for all three samples. we detected local manifestations of several streams, superclusters, and halo objects, in which we identified 12 members of gaia enceladus. we present the first direct parallaxes of five objects in multiple systems within 10 pc of the sun.conclusions: we provide the community with a large, well-characterised catalogue of objects in the solar neighbourhood. this is a primary benchmark for measuring and understanding fundamental parameters and descriptive functions in astronomy. tables are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/649/a6 | gaia early data release 3. the gaia catalogue of nearby stars |
we present jwst nirspec spectroscopy for 11 galaxy candidates with photometric redshifts of z ≃ 9 - 13 and m uv ∈ [ -21, -18] newly identified in nircam images in the cosmic evolution early release science survey. we confirm emission line redshifts for 7 galaxies at z = 7.762-8.998 using spectra at ~1-5 μm either with the nirspec prism or its three medium-resolution (r ~ 1000) gratings. for z ≃ 9 photometric candidates, we achieve a high confirmation rate of ≃90%, which validates the classical dropout selection from nircam photometry. no robust emission lines are identified in three galaxy candidates at z > 10, where the strong [o iii] and hβ lines would be redshifted beyond the wavelength range observed by nirspec, and the lyα continuum break is not detected with the sensitivity of the current data. compared with hubble space telescope-selected bright galaxies (m uv ≃ -22) that are similarly spectroscopically confirmed at z ≃ 8 - 9, these nircam-selected galaxies are characterized by lower star formation rates (sfrs; sfr ≃ 4 m ⊙ yr-1) and lower stellar masses (≃108 m ⊙), but with higher specific sfr (≃40 gyr-1), higher [o iii]+hβ equivalent widths (≃1100 å), and elevated production efficiency of ionizing photons ( $\mathrm{log}({\xi }_{\mathrm{ion}}/\mathrm{hz}\,{\mathrm{erg}}^{-1})\simeq 25.8$ ) induced by young stellar populations (<10 myr) accounting for ≃20% of the galaxy mass, highlighting the key contribution of faint galaxies to cosmic reionization. taking advantage of the homogeneous selection and sensitivity, we also investigate metallicity and ism conditions with empirical calibrations using the [o iii]5008/hβ ratio. we find that galaxies at z ≃ 8 - 9 have higher sfrs and lower metallicities than galaxies at similar stellar masses at z ≃ 2 - 6, which is generally consistent with the current galaxy formation and evolution models. | ceers spectroscopic confirmation of nircam-selected z ≳ 8 galaxy candidates with jwst/nirspec: initial characterization of their properties |
finding the first generation of stars formed out of pristine gas in the early universe, known as population iii (popiii) stars, is one of the most important goals of modern astrophysics. recent models suggest that popiii stars may form in pockets of pristine gas in the halo of more evolved galaxies. here we present nirspec-ifu and nirspec-msa observations of the region around gn-z11, an exceptionally luminous galaxy at $z=10.6$, which reveal a $>$5$\sigma$ detection of a feature consistent with being heii$\lambda$1640 emission at the redshift of gn-z11. the very high equivalent width of the putative heii emission in this clump (170 a), and the lack of metal lines, can be explained in terms of photoionisation by popiii stars, while photoionisation by popii stars is inconsistent with the data. it would also indicate that the putative popiii stars likely have a top-heavy initial mass function (imf), with an upper cutoff reaching at least 500 m$_\odot$. the popiii bolometric luminosity inferred from the heii line would be $\sim 2\times 10^{10}~l_\odot$, which (with a top-heavy imf) would imply a total stellar mass formed in the burst of $\sim 6\times 10^{5}~m_\odot$. we find that photoionisation by the active galactic nucleus (agn) in gn-z11 cannot account for the heii luminosity observed in the clump, but can potentially be responsible for additional heii emission observed closer to gn-z11. we also consider the possibility of in-situ photoionisation by an accreting direct collapse black hole (dcbh) hosted by the heii clump; we find that this scenario is less favoured, but it remains a possible alternative interpretation. we also report the detection of a ly$\alpha$ halo stemming out of gn-z11 and extending out to $\sim$2 kpc, as well as resolved, funnel-shaped ciii] emission, likely tracing the ionisation cone of the agn. | jwst-jades. possible population iii signatures at z=10.6 in the halo of gn-z11 |
the noise in millisecond pulsar (msp) timing data can include contributions from observing instruments, the interstellar medium, the solar wind, solar system ephemeris errors, and the pulsars themselves. the noise environment must be accurately characterized in order to form the null hypothesis from which signal models can be compared, including the signature induced by nanohertz-frequency gravitational waves (gws). here we describe the noise models developed for each of the msps in the parkes pulsar timing array (ppta) third data release, which have been used as the basis of a search for the isotropic stochastic gw background. we model pulsar spin noise, dispersion measure variations, scattering variations, events in the pulsar magnetospheres, solar wind variability, and instrumental effects. we also search for new timing model parameters and detected shapiro delays in psr j0614-3329 and psr j1902-5105. the noise and timing models are validated by testing the normalized and whitened timing residuals for gaussianity and residual correlations with time. we demonstrate that the choice of noise models significantly affects the inferred properties of a common-spectrum process. using our detailed models, the recovered common-spectrum noise in the ppta is consistent with a power law with a spectral index of γ = 13/3, the value predicted for a stochastic gw background from a population of supermassive black hole binaries driven solely by gw emission. | the gravitational-wave background null hypothesis: characterizing noise in millisecond pulsar arrival times with the parkes pulsar timing array |
the cosmic radio-frequency spectrum is expected to show a strong absorption signal corresponding to the 21-centimetre-wavelength transition of atomic hydrogen around redshift 20, which arises from lyman-α radiation from some of the earliest stars. by observing this 21-centimetre signal—either its sky-averaged spectrum or maps of its fluctuations, obtained using radio interferometers—we can obtain information about cosmic dawn, the era when the first astrophysical sources of light were formed. the recent detection of the global 21-centimetre spectrum reveals a stronger absorption than the maximum predicted by existing models, at a confidence level of 3.8 standard deviations. here we report that this absorption can be explained by the combination of radiation from the first stars and excess cooling of the cosmic gas induced by its interaction with dark matter. our analysis indicates that the spatial fluctuations of the 21-centimetre signal at cosmic dawn could be an order of magnitude larger than previously expected and that the dark-matter particle is no heavier than several proton masses, well below the commonly predicted mass of weakly interacting massive particles. our analysis also confirms that dark matter is highly non-relativistic and at least moderately cold, and primordial velocities predicted by models of warm dark matter are potentially detectable. these results indicate that 21-centimetre cosmology can be used as a dark-matter probe. | possible interaction between baryons and dark-matter particles revealed by the first stars |
neutral-atomic and molecular outflows are a common occurrence in galaxies, near and far. they operate over the full extent of their galaxy hosts, from the innermost regions of galactic nuclei to the outermost reaches of galaxy halos. they carry a substantial amount of material that would otherwise have been used to form new stars. these cool outflows may have a profound impact on the evolution of their host galaxies and environments. this article provides an overview of the basic physics of cool outflows, a comprehensive assessment of the observational techniques and diagnostic tools used to characterize them, a detailed description of the best-studied cases, and a more general discussion of the statistical properties of these outflows in the local and distant universe. the remaining outstanding issues that have not yet been resolved are summarized at the end of the review to inspire new research directions. | cool outflows in galaxies and their implications |
the gaia sausage is the major accretion event that built the stellar halo of the milky way galaxy. here, we provide dynamical and chemical evidence for a second substantial accretion episode, distinct from the gaia sausage. the sequoia event provided the bulk of the high-energy retrograde stars in the stellar halo, as well as the recently discovered globular cluster fsr 1758. there are up to six further globular clusters, including ω centauri, as well as many of the retrograde substructures in myeong et al., associated with the progenitor dwarf galaxy, named the sequoia. the stellar mass in the sequoia galaxy is ∼5 × 10 m⊙ , whilst the total mass is ∼1010 m⊙ , as judged from abundance matching or from the total sum of the globular cluster mass. although clearly less massive than the sausage, the sequoia has a distinct chemodynamical signature. the strongly retrograde sequoia stars have a typical eccentricity of ∼0.6, whereas the sausage stars have no clear net rotation and move on predominantly radial orbits. on average, the sequoia stars have lower metallicity by ∼0.3 dex and higher abundance ratios as compared to the sausage. we conjecture that the sausage and the sequoia galaxies may have been associated and accreted at a comparable epoch. | evidence for two early accretion events that built the milky way stellar halo |
the coalescence of double neutron star (ns-ns) and black hole (bh)-ns binaries are prime sources of gravitational waves (gw) for advanced ligo/virgo and future ground-based detectors. neutron-rich matter released from such events undergoes rapid neutron capture (r-process) nucleosynthesis as it decompresses into space, enriching our universe with rare heavy elements like gold and platinum. radioactive decay of these unstable nuclei powers a rapidly evolving, approximately isotropic thermal transient known as a "kilonova", which probes the physical conditions during the merger and its aftermath. here i review the history and physics of kilonovae, leading to the current paradigm of day-timescale emission at optical wavelengths from lanthanide-free components of the ejecta, followed by week-long emission with a spectral peak in the near-infrared (nir). these theoretical predictions, as compiled in the original version of this review, were largely confirmed by the transient optical/nir counterpart discovered to the first ns-ns merger, gw170817, discovered by ligo/virgo. using a simple light curve model to illustrate the essential physical processes and their application to gw170817, i then introduce important variations about the standard picture which may be observable in future mergers. these include ∼hour-long uv precursor emission, powered by the decay of free neutrons in the outermost ejecta layers or shock-heating of the ejecta by a delayed ultra-relativistic outflow; and enhancement of the luminosity from a long-lived central engine, such as an accreting bh or millisecond magnetar. joint gw and kilonova observations of gw170817 and future events provide a new avenue to constrain the astrophysical origin of the r-process elements and the equation of state of dense nuclear matter. | kilonovae |
coexisting density-wave and superconducting states along with the large anomalous hall effect in the absence of local magnetism remain intriguing and enigmatic features of the av3sb5 kagome metals (a = k, rb, cs). here, we demonstrate via optical spectroscopy and density-functional calculations that low-energy dynamics of kv3sb5 is characterized by unconventional localized carriers, which are strongly renormalized across the density-wave transition and indicative of electronic correlations. strong phonon anomalies are prominent not only below the density-wave transition, but also at high temperatures, suggesting an intricate interplay of phonons with the underlying electronic structure. we further propose the star-of-david and tri-hexagon (inverse star-of-david) configurations for the density-wave order in kv3sb5. these configurations are strongly reminiscent of p-wave states expected in the hubbard model on the kagome lattice at the filling level of the van hove singularity. the proximity to this regime should have intriguing and far-reaching implications for the physics of kv3sb5 and related materials. | optical detection of the density-wave instability in the kagome metal kv3sb5 |
we present rest-frame optical data of the compact z = 5.55 galaxy gs_3073 obtained using the integral field spectroscopy mode of the near-infrared spectrograph on board the james webb space telescope. the galaxy's prominent broad components in several hydrogen and helium lines (though absent in the forbidden lines) and v detection of a large equivalent width of he iiλ4686, ew(he ii) ∼20 å, unambiguously identify it as an active galactic nucleus (agn). we measured a gas phase metallicity of zgas/z⊙∼0.21−0.04+0.08 , which is lower than what has been inferred for both more luminous agn at a similar redshift and lower redshift agn. we empirically show that classical emission line ratio diagnostic diagrams cannot be used to distinguish between the primary ionisation source (agn or star formation) for systems with such low metallicity, though different diagnostic diagrams involving he iiλ4686 prove very useful, independent of metallicity. we measured the central black hole mass to be log(mbh/m⊙)∼8.2 ± 0.4 based on the luminosity and width of the broad line region of the hα emission. while this places gs_3073 at the lower end of known high-redshift black hole masses, it still appears to be overly massive when compared to its host galaxy's mass properties. we detected an outflow with a projected velocity ≳700 km s−1 and inferred an ionised gas mass outflow rate of about 100 m⊙ yr−1, suggesting that one billion years after the big bang, gs_3073 is able to enrich the intergalactic medium with metals. | ga-nifs: a massive black hole in a low-metallicity agn at z ∼ 5.55 revealed by jwst/nirspec ifs |
the merger of two neutron stars has been predicted to produce an optical-infrared transient (lasting a few days) known as a ‘kilonova’, powered by the radioactive decay of neutron-rich species synthesized in the merger. evidence that short γ-ray bursts also arise from neutron-star mergers has been accumulating. in models of such mergers, a small amount of mass (10-4-10-2 solar masses) with a low electron fraction is ejected at high velocities (0.1-0.3 times light speed) or carried out by winds from an accretion disk formed around the newly merged object. this mass is expected to undergo rapid neutron capture (r-process) nucleosynthesis, leading to the formation of radioactive elements that release energy as they decay, powering an electromagnetic transient. a large uncertainty in the composition of the newly synthesized material leads to various expected colours, durations and luminosities for such transients. observational evidence for kilonovae has so far been inconclusive because it was based on cases of moderate excess emission detected in the afterglows of γ-ray bursts. here we report optical to near-infrared observations of a transient coincident with the detection of the gravitational-wave signature of a binary neutron-star merger and with a low-luminosity short-duration γ-ray burst. our observations, taken roughly every eight hours over a few days following the gravitational-wave trigger, reveal an initial blue excess, with fast optical fading and reddening. using numerical models, we conclude that our data are broadly consistent with a light curve powered by a few hundredths of a solar mass of low-opacity material corresponding to lanthanide-poor (a fraction of 10-4.5 by mass) ejecta. | optical emission from a kilonova following a gravitational-wave-detected neutron-star merger |
since the science white paper of the large high altitude air shower observatory (lhaaso) published on arxiv in 2019 [e-print: 1905.02773 (astro-ph.he)], lhaaso has completed the transition from a project to an operational gamma-ray astronomical observatory lhaaso is a new generation multi-component facility located in daocheng, sichuan province of china, at an altitude of 4410 meters. it aims at measuring with unprecedented sensitivity the spectrum, composition, and anisotropy of cosmic rays in the energy range between 10$^{12}$ and 10$^{18}$~ev, and acting simultaneously as a wide aperture (one stereoradiant) continuously operating gamma-ray telescope in the energy range between 10$^{11}$ and $10^{15}$~ev with the designed sensitivity of 1.3\% of the crab unit (cu) above 100 tev. lhaaso's capability of measuring simultaneously different shower components (electrons, muons, and cherenkov/fluorescence light), will allow it to investigate the origin, acceleration, and propagation of cr through measurement of the energy spectrum, elemental composition, and anisotropy with unprecedented resolution. the remarkable sensitivity of lhaaso will play a key role in cr physics and gamma-ray astronomy for a general and comprehensive exploration of the high energy universe and will allow important studies of fundamental physics (such as indirect dark matter search, lorentz invariance violation, quantum gravity) and solar and heliospheric physics. the lhaaso collaboration organized an editorial working group and finished all editorial work of this science book, to summarize the instrumental features and outline the prospects of scientific researches with the lhaaso experiment. | the large high altitude air shower observatory (lhaaso) science book (2021 edition) |
with several dozen binary black hole events detected by ligo-virgo to date and many more expected in the next few years, gravitational-wave astronomy is shifting from individual-event analyses to population studies. using the gwtc-2 catalog, we perform a hierarchical bayesian analysis that for the first time combines several state-of-the-art astrophysical formation models with a population of primordial black holes (pbhs) and constrains the fraction of a putative subpopulation of pbhs in the data. we find that this fraction depends significantly on the set of assumed astrophysical models. while a primordial population is statistically favored against certain competitive astrophysical channels, such as globular clusters and nuclear stellar clusters, a dominant contribution from the stable-mass-transfer isolated formation channel drastically reduces the need for pbhs, except for explaining the rate of mass-gap events like gw190521. the tantalizing possibility that black holes formed after inflation are contributing to ligo-virgo observations could only be verified by further reducing uncertainties in astrophysical and primordial formation models, and it may ultimately be confirmed by third-generation interferometers. | searching for a subpopulation of primordial black holes in ligo-virgo gravitational-wave data |
the hierarchical triple-body approximation has useful applications to a variety of systems from planetary and stellar scales to supermassive black holes. in this approximation, the energy of each orbit is separately conserved, and therefore the two semimajor axes are constants. on timescales much larger than the orbital periods, the orbits exchange angular momentum, which leads to eccentricity and orientation (i.e., inclination) oscillations. the orbits' eccentricity can reach extreme values, leading to a nearly radial motion, which can further evolve into short orbit periods and merging binaries. furthermore, the orbits' mutual inclinations may change dramatically from pure prograde to pure retrograde, leading to misalignment and a wide range of inclinations. this dynamical behavior is coined the “eccentric kozai-lidov mechanism.” the behavior of such a system is exciting, rich, and chaotic in nature. furthermore, these dynamics are accessible from a large part of the triple-body parameter space and can be applied to a diverse range of astrophysical settings and used to gain insights into many puzzles. | the eccentric kozai-lidov effect and its applications |
the recent nobel-prize-winning detections of gravitational waves from merging black holes and the subsequent detection of the collision of two neutron stars in coincidence with electromagnetic observations have inaugurated a new era of multimessenger astrophysics. to enhance the scope of this emergent field of science, we pioneered the use of deep learning with convolutional neural networks, that take time-series inputs, for rapid detection and characterization of gravitational wave signals. this approach, deep filtering, was initially demonstrated using simulated ligo noise. in this article, we present the extension of deep filtering using real data from ligo, for both detection and parameter estimation of gravitational waves from binary black hole mergers using continuous data streams from multiple ligo detectors. we demonstrate for the first time that machine learning can detect and estimate the true parameters of real events observed by ligo. our results show that deep filtering achieves similar sensitivities and lower errors compared to matched-filtering while being far more computationally efficient and more resilient to glitches, allowing real-time processing of weak time-series signals in non-stationary non-gaussian noise with minimal resources, and also enables the detection of new classes of gravitational wave sources that may go unnoticed with existing detection algorithms. this unified framework for data analysis is ideally suited to enable coincident detection campaigns of gravitational waves and their multimessenger counterparts in real-time. | deep learning for real-time gravitational wave detection and parameter estimation: results with advanced ligo data |
strong constraints on the coupling of new light particles to the standard model (sm) arise from their production in the hot cores of stars, and the effects of this on stellar cooling. for new light particles which have an effective in-medium mixing with the photon, plasma effects can result in parametrically different production rates to those obtained from a naive calculation. taking these previously-neglected contributions into account, we make updated estimates for the stellar cooling bounds on light scalars and vectors with a variety of sm couplings. in particular, we improve the bounds on light ( m ≲ kev) scalars coupling to electrons or nucleons by up to 3 orders of magnitude in the coupling squared, significantly revise the supernova cooling bounds on dark photon couplings, and qualitatively change the mass dependence of stellar bounds on new vectors. scalars with mass ≲ 2 kev that couple through the higgs portal are constrained to mixing angle sin θ ≲ 3 × 10-10, which gives the dominant bound for scalar masses above ∼ 0 .2ev. | stellar cooling bounds on new light particles: plasma mixing effects |
we present emission-line ratios from a sample of 27 lyman-break galaxies from z ∼ 5.5 − 9.5 with −17.0 < m1500 < −20.4, measured from ultra-deep jwst/nirspec multi-object spectroscopy from the jwst advanced deep extragalactic survey (jades). we used a combination of 28 h deep prism/clear and 7 h deep g395m/f290lp observations to measure, or place strong constraints on, ratios of widely studied rest-frame optical emission lines including hα, hβ, [o ii] λλ3726, 3729, [ne iii] λ3869, [o iii] λ4959, [o iii] λ5007, [o i] λ6300, [n ii] λ6583, and [s ii] λλ6716, 6731 in individual z > 5.5 spectra. we find that the emission-line ratios exhibited by these z ∼ 5.5 − 9.5 galaxies occupy clearly distinct regions of line-ratio space compared to typical z ∼ 0 − 3 galaxies, instead being more consistent with extreme populations of lower-redshift galaxies. this is best illustrated by the [o iii]/[o ii] ratio, tracing interstellar medium (ism) ionisation, in which we observe more than half of our sample to have [o iii]/[o ii] > 10. our high signal-to-noise spectra reveal more than an order of magnitude of scatter in line ratios such as [o ii]/hβ and [o iii]/[o ii], indicating significant diversity in the ism conditions within the sample. we find no convincing detections of [n ii] λ6583 in our sample, either in individual galaxies, or a stack of all g395m/f290lp spectra. the emission-line ratios observed in our sample are generally consistent with galaxies with extremely high ionisation parameters (log u ∼ −1.5), and a range of metallicities spanning from ∼0.1 × z⊙ to higher than ∼0.3 × z⊙, suggesting we are probing low-metallicity systems undergoing periods of rapid star formation, driving strong radiation fields. these results highlight the value of deep observations in constraining the properties of individual galaxies, and hence probing diversity within galaxy population. | jades: probing interstellar medium conditions at z ∼ 5.5-9.5 with ultra-deep jwst/nirspec spectroscopy |
we search for excess γ-ray emission coincident with the positions of confirmed and candidate milky way satellite galaxies using six years of data from the fermi large area telescope (lat). our sample of 45 stellar systems includes 28 kinematically confirmed dark-matter-dominated dwarf spheroidal galaxies (dsphs) and 17 recently discovered systems that have photometric characteristics consistent with the population of known dsphs. for each of these targets, the relative predicted γ-ray flux due to dark matter annihilation is taken from kinematic analysis if available, and estimated from a distance-based scaling relation otherwise, assuming that the stellar systems are dm-dominated dsphs. lat data coincident with four of the newly discovered targets show a slight preference (each ∼ 2σ local) for γ-ray emission in excess of the background. however, the ensemble of derived γ-ray flux upper limits for individual targets is consistent with the expectation from analyzing random blank-sky regions, and a combined analysis of the population of stellar systems yields no globally significant excess (global significance < 1σ ). our analysis has increased sensitivity compared to the analysis of 15 confirmed dsphs by ackermann et al. the observed constraints on the dm annihilation cross section are statistically consistent with the background expectation, improving by a factor of ∼2 for large dm masses ({m}{dm,b\bar{b}}≳ 1 {tev} and {m}{dm,{τ }+{τ }-}≳ 70 {gev}) and weakening by a factor of ∼1.5 at lower masses relative to previously observed limits. | searching for dark matter annihilation in recently discovered milky way satellites with fermi-lat |
we present an analysis of the ultraviolet luminosity function (uv lf) and star formation rate density of distant galaxies ($7.5 < z < 13.5$) in the `blank' fields of the prime extragalactic areas for reionization science (pearls) survey combined with early release science (ers) data from the ceers, glass and ngdeep surveys/fields. we use a combination of sed fitting tools and quality cuts to obtain a reliable selection and characterisation of high-redshift ($z>6.5$) galaxies from a consistently processed set of deep, near-infrared imaging. within an area of 110 arcmin$^{2}$, we identify 214 candidate galaxies at redshifts $z>6.5$ and we use this sample to study the ultraviolet luminosity function (uv lf) in four redshift bins between $7.5<z<13.5$. the measured number density of galaxies at $z=8$ and $z=9$ match those of past observations undertaken by the em hubble space telescope (hst). however, towards higher redshifts we find that the evolution of the uv lf is mild, resulting in higher measured number densities of uv luminous galaxies at $z=10.5$ and $z=12.5$ compared to predictions from simulations and past hst observations. when examining the star formation rate density of galaxies at this time period, our observations are still consistent with a constant star formation efficiency, are slightly lower than previous early estimations using jwst and support galaxy driven reionization at $z\sim8$. | epochs paper ii: the ultraviolet luminosity function from $7.5<z<13.5$ using 110 square arcminutes of deep, blank-field data from the pearls survey and public science programmes |
rings are the most frequently revealed substructure in atacama large millimeter/submillimeter array (alma) dust observations of protoplanetary disks, but their origin is still hotly debated. in this paper, we identify dust substructures in 12 disks and measure their properties to investigate how they form. this subsample of disks is selected from a high-resolution (∼0.″12) alma 1.33 mm survey of 32 disks in the taurus star-forming region, which was designed to cover a wide range of brightness and to be unbiased to previously known substructures. while axisymmetric rings and gaps are common within our sample, spiral patterns and high-contrast azimuthal asymmetries are not detected. fits of disk models to the visibilities lead to estimates of the location and shape of gaps and rings, the flux in each disk component, and the size of the disk. the dust substructures occur across a wide range of stellar mass and disk brightness. disks with multiple rings tend to be more massive and more extended. the correlation between gap locations and widths, the intensity contrast between rings and gaps, and the separations of rings and gaps could all be explained if most gaps are opened by low-mass planets (super-earths and neptunes) in the condition of low disk turbulence (α = 10-4). the gap locations are not well correlated with the expected locations of co and n2 ice lines, so condensation fronts are unlikely to be a universal mechanism to create gaps and rings, though they may play a role in some cases. | gaps and rings in an alma survey of disks in the taurus star-forming region |
we present a robust measurement and analysis of the rest-frame ultraviolet (uv) luminosity functions at z = 4-8. we use deep hubble space telescope imaging over the cosmic assembly near-infrared deep extragalactic legacy survey/goods fields, the hubble ultra deep field, and the hubble frontier field deep parallel observations near the abell 2744 and macs j0416.1-2403 clusters. the combination of these surveys provides an effective volume of 0.6-1.2 × 106 mpc3 over this epoch, allowing us to perform a robust search for faint ({m}{uv}=-18) and bright (m{}{uv}\lt -21) high-redshift galaxies. we select candidate galaxies using a well-tested photometric redshift technique with careful screening of contaminants, finding a sample of 7446 candidate galaxies at 3.5 \lt z \lt 8.5, with >1000 galaxies at z ≈ 6-8. we measure both a stepwise luminosity function for candidate galaxies in our redshift samples, and a schechter function, using a markov chain monte carlo analysis to measure robust uncertainties. at the faint end, our uv luminosity functions agree with previous studies, yet we find a higher abundance of uv-bright candidate galaxies at z ≥slant 6. our best-fit value of the characteristic magnitude {m}{uv}* is consistent with -21 at z ≥slant 5, which is different than that inferred based on previous trends at lower redshift, and brighter at ∼2σ significance than previous measures at z = 6 and 7. at z = 8, a single power law provides an equally good fit to the uv luminosity function, while at z = 6 and 7 an exponential cutoff at the bright end is moderately preferred. we compare our luminosity functions to semi-analytical models, and find that the lack of evolution in {m}{uv}* is consistent with models where the impact of dust attenuation on the bright end of the luminosity function decreases at higher redshift, although a decreasing impact of feedback may also be possible. we measure the evolution of the cosmic star-formation rate (sfr) density by integrating our observed luminosity functions to {m}{uv}=-17, correcting for dust attenuation, and find that the sfr density declines proportionally to (1 +z){}-4.3+/- 0.5 at z \gt 4, which is consistent with observations at z ≥slant 9. our observed luminosity functions are consistent with a reionization history that starts at z ≳ 10, completes at z \gt 6, and reaches a midpoint (x{}{{h} {{ii}}} = 0.5) at 6.7 \lt z \lt 9.4. finally, using a constant cumulative number density selection and an empirically derived rising star-formation history, our observations predict that the abundance of bright z = 9 galaxies is likely higher than previous constraints, although consistent with recent estimates of bright z ∼ 10 galaxies. | the evolution of the galaxy rest-frame ultraviolet luminosity function over the first two billion years |
we combine gravitational wave (gw) and electromagnetic (em) data to perform a bayesian parameter estimation of the binary neutron star (ns) merger gw170817. the em likelihood is constructed from a fit to a large number of numerical relativity simulations which we combine with a lower bound on the mass of the remnant's accretion disk inferred from the modeling of the em light curve. in comparison with previous works, our analysis yields a more precise determination of the tidal deformability of the binary, for which the em data provide a lower bound, and of the mass ratio of the binary, with the em data favoring a smaller mass asymmetry. the 90% credible interval for the areal radius of a 1 .4 m⊙ ns is found to be 12 .2-0.8 +1 .0±0 .2 km (statistical and systematic uncertainties). | multimessenger parameter estimation of gw170817 |
we present the fourth open gravitational-wave catalog (4-ogc) of binary neutron star (bns), binary black hole (bbh), and neutron star-black hole (nsbh) mergers. the catalog includes observations from 2015 to 2020 covering the first through third observing runs (o1, o2, o3a, and o3b) of advanced ligo and advanced virgo. the updated catalog includes seven bbh mergers that were not previously reported with high significance during o3b for a total of 94 observations: 90 bbhs, 2 nsbhs, and 2 bnss. the most confident new detection, gw200318_191337, has component masses ${49.1}_{-12.0}^{+16.4}{m}_{\odot }$ and ${31.6}_{-11.6}^{+12.0}{m}_{\odot };$ its redshift of ${0.84}_{-0.35}^{+0.4}$ (90% credible interval) may make it the most distant merger so far. we estimate the merger rate of bbh sources, assuming a power-law mass distribution containing an additive gaussian peak, to be ${16.5}_{-6.2}^{+10.4}({25.0}_{-8.0}^{+12.6})$ gpc-3 yr-1 at a redshift of z = 0 (0.2). for bns and nsbh sources, we estimate a merger rate of ${200}_{-148}^{+309}$ gpc-3 yr-1 and ${19}_{-14}^{+30}$ gpc-3 yr-1, respectively, assuming the known sources are representative of the total population. we provide reference parameter estimates for each of these sources using an up-to-date model accounting for instrumental calibration uncertainty. the corresponding data release also includes our full set of subthreshold candidates. | 4-ogc: catalog of gravitational waves from compact binary mergers |
we introduce sparc (spitzer photometry and accurate rotation curves): a sample of 175 nearby galaxies with new surface photometry at 3.6 μm and high-quality rotation curves from previous h i/hα studies. sparc spans a broad range of morphologies (s0 to irr), luminosities (∼5 dex), and surface brightnesses (∼4 dex). we derive [3.6] surface photometry and study structural relations of stellar and gas disks. we find that both the stellar mass-h i mass relation and the stellar radius-h i radius relation have significant intrinsic scatter, while the h i mass-radius relation is extremely tight. we build detailed mass models and quantify the ratio of baryonic to observed velocity (v bar/v obs) for different characteristic radii and values of the stellar mass-to-light ratio (ϒ⋆) at [3.6]. assuming ϒ⋆ ≃ 0.5 m ⊙/l ⊙ (as suggested by stellar population models), we find that (i) the gas fraction linearly correlates with total luminosity (ii) the transition from star-dominated to gas-dominated galaxies roughly corresponds to the transition from spiral galaxies to dwarf irregulars, in line with density wave theory; and (iii) v bar/v obs varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. these basic properties are lost for low values of ϒ⋆ ≃ 0.2 m ⊙/l ⊙ as suggested by the diskmass survey. the mean maximum-disk limit in bright galaxies is ϒ⋆ ≃ 0.7 m ⊙/l ⊙ at [3.6]. the sparc data are publicly available and represent an ideal test bed for models of galaxy formation. | sparc: mass models for 175 disk galaxies with spitzer photometry and accurate rotation curves |
we present new measurements of the parallax of seven long-period (≥10 days) milky way (mw) cepheid variables (ss cma, xy car, vy car, vx per, wz sgr, x pup, and s vul) using one-dimensional astrometric measurements from spatial scanning of wide-field camera 3 on the hubble space telescope (hst). the observations were obtained at ∼6 month intervals over 4 years. the distances are 1.7-3.6 kpc, with a mean precision of 45 μas (signal-to-noise ratio (s/n) ≈ 10) and a best precision of 29 μas (s/n = 14). the accuracy of the parallaxes is demonstrated through independent analyses of >100 reference stars. this raises to 10 the number of long-period cepheids with significant parallax measurements, 8 obtained from this program. we also present high-precision mean f555w, f814w, and f160w magnitudes of these cepheids, allowing a direct, zeropoint-independent comparison to >1800 extragalactic cepheids in the hosts of 19 sne ia. this sample addresses two outstanding systematic uncertainties affecting prior comparisons of mw and extragalactic cepheids used to calibrate the hubble constant (h 0): their dissimilarity of periods and photometric systems. comparing the new parallaxes to their predicted values derived from reversing the distance ladder gives a ratio (or independent scale for h 0) of 1.037 ± 0.036, consistent with no change and inconsistent at the 3.5σ level with a ratio of 0.91 needed to match the value predicted by planck cosmic microwave background data in concert with λcdm. using these data instead to augment the riess et al. measurement of h 0 improves the precision to 2.3%, yielding 73.48 ± 1.66 km s-1 mpc-1, and the tension with planck + λcdm increases to 3.7σ. the future combination of gaia parallaxes and hst spatial scanning photometry of 50 mw cepheids can support a <1% calibration of h 0. | new parallaxes of galactic cepheids from spatially scanning the hubble space telescope: implications for the hubble constant |
we review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. einstein’s theory of general relativity (gr) has been tested accurately within the local universe i.e. the solar system, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the universe. this being said, the standard model of cosmology assumes gr on all scales. in 1998, astronomers made the surprising discovery that the expansion of the universe is accelerating, not slowing down. this late-time acceleration of the universe has become the most challenging problem in theoretical physics. within the framework of gr, the acceleration would originate from an unknown dark energy. alternatively, it could be that there is no dark energy and gr itself is in error on cosmological scales. in this review, we first give an overview of recent developments in modified gravity theories including f(r) gravity, braneworld gravity, horndeski theory and massive/bigravity theory. we then focus on common properties these models share, such as screening mechanisms they use to evade the stringent solar system tests. once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. we present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard λ cdm model. since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. the last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years. | cosmological tests of modified gravity |
we present an analysis of the deepest herschel images in four major extragalactic fields goods-north, goods-south, uds, and cosmos obtained within the goods-herschel and candels-herschel key programs. the star formation picture provided by a total of 10 497 individual far-infrared detections is supplemented by the stacking analysis of a mass complete sample of 62 361 star-forming galaxies from the hubble space telescope (hst) h band-selected catalogs of the candels survey and from two deep ground-based ks band-selected catalogs in the goods-north and the cosmos-wide field to obtain one of the most accurate and unbiased understanding to date of the stellar mass growth over the cosmic history. we show, for the first time, that stacking also provides a powerful tool to determine the dispersion of a physical correlation and describe our method called "scatter stacking", which may be easily generalized to other experiments. the combination of direct uv and far-infrared uv-reprocessed light provides a complete census on the star formation rates (sfrs), allowing us to demonstrate that galaxies at z = 4 to 0 of all stellar masses (m∗) follow a universal scaling law, the so-called main sequence of star-forming galaxies. we find a universal close-to-linear slope of the log 10(sfr)-log 10(m∗) relation, with evidence for a flattening of the main sequence at high masses (log 10(m∗/m⊙) > 10.5) that becomesless prominent with increasing redshift and almost vanishes by z ≃ 2. this flattening may be due to the parallel stellar growth of quiescent bulges in star-forming galaxies, which mostly happens over the same redshift range. within the main sequence, we measure a nonvarying sfr dispersion of 0.3 dex: at a fixed redshift and stellar mass, about 68% of star-forming galaxies form stars at a universal rate within a factor 2. the specific sfr (ssfr = sfr/m∗) of star-forming galaxies is found to continuously increase from z = 0 to 4. finally we discuss the implications of our findings on the cosmic sfr history and on the origin of present-day stars: more than two-thirds of present-day stars must have formed in a regime dominated by the "main sequence" mode. as a consequence we conclude that, although omnipresent in the distant universe, galaxy mergers had little impact in shaping the global star formation history over the last 12.5 billion years. herschel is an esa space observatory with science instruments provided by european-led principal investigator consortia and with important participation from nasa.appendices are available in electronic form at http://www.aanda.org | the herschel view of the dominant mode of galaxy growth from z = 4 to the present day |
substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. at lhc and top rhic energies, qcd matter is studied at very high temperatures and nearly vanishing net-baryon densities. there is evidence that a quark-gluon-plasma (qgp) was created at experiments at rhic and lhc. the transition from the qgp back to the hadron gas is found to be a smooth cross over. for larger net-baryon densities and lower temperatures, it is expected that the qcd phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. the discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. the compressed baryonic matter (cbm) experiment at fair will play a unique role in the exploration of the qcd phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. high-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. the goal of the cbm experiment at sis100 (√{s_{nn}}= 2.7-4.9 gev) is to discover fundamental properties of qcd matter: the phase structure at large baryon-chemical potentials ( μ_b > 500 mev), effects of chiral symmetry, and the equation of state at high density as it is expected to occur in the core of neutron stars. in this article, we review the motivation for and the physics programme of cbm, including activities before the start of data taking in 2024, in the context of the worldwide efforts to explore high-density qcd matter. | challenges in qcd matter physics -the scientific programme of the compressed baryonic matter experiment at fair |
the dispersive sweep of fast radio bursts (frbs) has been used to probe the ionized baryon content of the intergalactic medium1, which is assumed to dominate the total extragalactic dispersion. although the host-galaxy contributions to the dispersion measure appear to be small for most frbs2, in at least one case there is evidence for an extreme magneto-ionic local environment3,4 and a compact persistent radio source5. here we report the detection and localization of the repeating frb 20190520b, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. the estimated host-galaxy dispersion measure of approximately 903−111+72 parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of frb host galaxies2,6, far exceeds the dispersion-measure contribution of the intergalactic medium. caution is thus warranted in inferring redshifts for frbs without accurate host-galaxy identifications. | a repeating fast radio burst associated with a persistent radio source |
mass and radius are two of the most fundamental properties of an astronomical object. increasingly, new planet discoveries are being announced with a measurement of one of these quantities, but not both. this has led to a growing need to forecast the missing quantity using the other, especially when predicting the detectability of certain follow-up observations. we present an unbiased forecasting model built upon a probabilistic mass-radius relation conditioned on a sample of 316 well-constrained objects. our publicly available code, forecaster, accounts for observational errors, hyper-parameter uncertainties, and the intrinsic dispersions observed in the calibration sample. by conditioning our model on a sample spanning dwarf planets to late-type stars, forecaster can predict the mass (or radius) from the radius (or mass) for objects covering nine orders of magnitude in mass. classification is naturally performed by our model, which uses four classes we label as terran worlds, neptunian worlds, jovian worlds, and stars. our classification identifies dwarf planets as merely low-mass terrans (like the earth) and brown dwarfs as merely high-mass jovians (like jupiter). we detect a transition in the mass-radius relation at {2.0}-0.6+0.7 m⊕, which we associate with the divide between solid, terran worlds and neptunian worlds. this independent analysis adds further weight to the emerging consensus that rocky super-earths represent a narrower region of parameter space than originally thought. effectively, then, the earth is the super-earth we have been looking for. | probabilistic forecasting of the masses and radii of other worlds |
since the release of the 2015 long range plan in nuclear physics, major events have occurred that reshaped our understanding of quantum chromodynamics (qcd) and nuclear matter at large densities, in and out of equilibrium. the us nuclear community has an opportunity to capitalize on advances in astrophysical observations and nuclear experiments and engage in an interdisciplinary effort in the theory of dense baryonic matter that connects low- and high-energy nuclear physics, astrophysics, gravitational waves physics, and data science | long range plan: dense matter theory for heavy-ion collisions and neutron stars |
work aimed at compiling detailed catalogs of variable stars in the galaxy, which has been carried out continuously by moscow variable-star researchers since 1946 on behalf of the international astronomical union, has entered the stage of the publication of the 5th, completely electronic edition of the general catalogue of variable stars (gcvs). this paper describes the requirements for the contents of the 5th edition and the current state of the catalog in its new version, gcvs 5.1. the complete revision of information for variable stars in the constellation carina and the compilation of the 81st name-list of variable stars are considered as examples of work on the 5th edition. the gcvs 5.1 is freely accessible on the internet. we recommend the present paper as a unified reference to the 5th edition of the gcvs. | general catalogue of variable stars: version gcvs 5.1 |
the apache point observatory galactic evolution experiment (apogee) has built the largest moderately high-resolution (r ≈ 22,500) spectroscopic map of the stars across the milky way, and including dust-obscured areas. the apogee stellar parameter and chemical abundances pipeline (aspcap) is the software developed for the automated analysis of these spectra. aspcap determines atmospheric parameters and chemical abundances from observed spectra by comparing observed spectra to libraries of theoretical spectra, using χ2 minimization in a multidimensional parameter space. the package consists of a fortran90 code that does the actual minimization and a wrapper idl code for book-keeping and data handling. this paper explains in detail the aspcap components and functionality, and presents results from a number of tests designed to check its performance. aspcap provides stellar effective temperatures, surface gravities, and metallicities precise to 2%, 0.1 dex, and 0.05 dex, respectively, for most apogee stars, which are predominantly giants. it also provides abundances for up to 15 chemical elements with various levels of precision, typically under 0.1 dex. the final data release (dr12) of the sloan digital sky survey iii contains an apogee database of more than 150,000 stars. aspcap development continues in the sdss-iv apogee-2 survey. | aspcap: the apogee stellar parameter and chemical abundances pipeline |
we have derived accurate distances to galactic globular clusters by combining data from the gaia early data release 3 (edr3) with distances based on hubble space telescope (hst) data and literature-based distances. we determine distances either directly from the gaia edr3 parallaxes, or kinematically by combining line-of-sight velocity dispersion profiles with gaia edr3 and hst-based proper motion velocity dispersion profiles. we furthermore calculate cluster distances from fitting nearby subdwarfs, whose absolute luminosities we determine from their gaia edr3 parallaxes, to globular cluster main sequences. we finally use hst-based stellar number counts to determine distances. we find good agreement in the average distances derived from the different methods down to a level of about 2 per cent. combining all available data, we are able to derive distances to 162 galactic globular clusters, with the distances to about 20 nearby globular clusters determined with an accuracy of 1 per cent or better. we finally discuss the implications of our distances for the value of the local hubble constant. | accurate distances to galactic globular clusters through a combination of gaia edr3, hst, and literature data |
we present the jwst cycle 1 53.8 h medium program fresco, short for 'first reionization epoch spectroscopically complete observations'. fresco covers 62 arcmin2 in each of the two goods/candels fields for a total area of 124 arcmin2 exploiting jwst's powerful new grism spectroscopic capabilities at near-infrared wavelengths. by obtaining ~2 h deep nircam/grism observations with the f444w filter, fresco yields unprecedented spectra at r ~ 1600 covering 3.8-5.0 µm for most galaxies in the nircam field of view. this setup enables emission line measurements over most of cosmic history, from strong pah lines at z ~ 0.2-0.5, to pa α and pa β at z ~ 1-3, he i and [s iii] at z ~ 2.5-4.5, h α and [n ii] at z ~ 5-6.5, up to [o iii] and h β for z ~ 7-9 galaxies. fresco's grism observations provide total line fluxes for accurately estimating galaxy stellar masses and calibrating slit-loss corrections of nirspec/msa spectra in the same field. additionally, fresco results in a mosaic of f182m, f210m, and f444w imaging in the same fields to a depth of ~28.2 mag (5σ in 0${_{.}^{\prime\prime}}$32 diameter apertures). here, we describe the overall survey design and the key science goals that can be addressed with fresco. we also highlight several, early science results, including: spectroscopic redshifts of lyman break galaxies that were identified almost 20 yr ago, the discovery of broad-line active galactic nuclei at z > 4, and resolved pa α maps of galaxies at z ~ 1.4. these results demonstrate the enormous power for serendipitous discovery of nircam/grism observations. | the jwst fresco survey: legacy nircam/grism spectroscopy and imaging in the two goods fields |
numerical methods have become a powerful tool for research in astrophysics, but their utility depends critically on the availability of suitable simulation codes. this calls for continuous efforts in code development, which is necessitated also by the rapidly evolving technology underlying today's computing hardware. here, we discuss recent methodological progress in the gadget code, which has been widely applied in cosmic structure formation over the past two decades. the new version offers improvements in force accuracy, in time-stepping, in adaptivity to a large dynamic range in time-scales, in computational efficiency, and in parallel scalability through a special mpi/shared-memory parallelization and communication strategy, and a more-sophisticated domain decomposition algorithm. a manifestly momentum conserving fast multipole method (fmm) can be employed as an alternative to the one-sided treepm gravity solver introduced in earlier versions. two different flavours of smoothed particle hydrodynamics, a classic entropy-conserving formulation and a pressure-based approach, are supported for dealing with gaseous flows. the code is able to cope with very large problem sizes, thus allowing accurate predictions for cosmic structure formation in support of future precision tests of cosmology, and at the same time is well adapted to high dynamic range zoom-calculations with extreme variability of the particle number density in the simulated volume. the gadget-4 code is publicly released to the community and contains infrastructure for on-the-fly group and substructure finding and tracking, as well as merger tree building, a simple model for radiative cooling and star formation, a high dynamic range power spectrum estimator, and an initial condition generator based on second-order lagrangian perturbation theory. | simulating cosmic structure formation with the gadget-4 code |
the astrophysical origin of gravitational wave (gw) events discovered by ligo/virgo remains an outstanding puzzle. in active galactic nuclei (agns), compact-object binaries form, evolve, and interact with a dense star cluster and a gas disk. an important question is whether and how binaries merge in these environments. to address this question, we have performed one-dimensional n-body simulations combined with a semianalytical model that includes the formation, disruption, and evolution of binaries self-consistently. we point out that binaries can form in single-single interactions through the dissipation of kinetic energy in a gaseous medium. this "gas-capture" binary formation channel contributes up to 97% of gas-driven mergers and leads to a high merger rate in agn disks even without preexisting binaries. we find the merger rate to be in the range of ∼0.02-60 gpc-3 yr-1. the results are insensitive to the assumptions on the gaseous hardening processes: we find that once they are formed, binaries merge efficiently via binary-single interactions even if these gaseous processes are ignored. we find that the average number of mergers per black hole (bh) is 0.4, and the probability for repeated mergers in 30 myr is ∼0.21-0.45. high bh masses due to repeated mergers, high eccentricities, and a significant doppler drift of gws are promising signatures that distinguish this merger channel from others. furthermore, we find that gas-capture binaries reproduce the distribution of low-mass x-ray binaries in the galactic center, including an outer cutoff at ∼1 pc due to the competition between migration and hardening by gas torques. | formation and evolution of compact-object binaries in agn disks |
we present the first high-resolution sub-millimeter survey of both dust and gas for a large population of protoplanetary disks. characterizing fundamental properties of protoplanetary disks on a statistical level is critical to understanding how disks evolve into the diverse exoplanet population. we use the atacama large millimeter/submillimeter array (alma) to survey 89 protoplanetary disks around stars with {m}* \gt 0.1 {m}⊙in the young (1-3 myr), nearby (150-200 pc) lupus complex. our observations cover the 890 μm continuum and the 13co and c18o 3-2 lines. we use the sub-millimeter continuum to constrain {m}{{dust}} to a few martian masses (0.2-0.4 m ⊕) and the co isotopologue lines to constrain {m}{{gas}} to roughly a jupiter mass (assuming an interstellar medium (ism)-like [{co}]/[{{{h}}}2] abundance). of 89 sources, we detect 62 in continuum, 36 in 13co, and 11 in c18o at \gt 3σ significance. stacking individually undetected sources limits their average dust mass to ≲ 6 lunar masses (0.03 m ⊕), indicating rapid evolution once disk clearing begins. we find a positive correlation between {m}{{dust}} and m *, and present the first evidence for a positive correlation between {m}{{gas}} and m *, which may explain the dependence of giant planet frequency on host star mass. the mean dust mass in lupus is 3× higher than in upper sco, while the dust mass distributions in lupus and taurus are statistically indistinguishable. most detected disks have {m}{{gas}}≲ 1 {m}{{jup}} and gas-to-dust ratios \lt 100, assuming an ism-like [{co}]/[{{{h}}}2] abundance; unless co is very depleted, the inferred gas depletion indicates that planet formation is well underway by a few myr and may explain the unexpected prevalence of super-earths in the exoplanet population. | alma survey of lupus protoplanetary disks. i. dust and gas masses |
double neutron star (dns) systems represent extreme physical objects and the endpoint of an exotic journey of stellar evolution and binary interactions. large numbers of dns systems and their mergers are anticipated to be discovered using the square kilometre array searching for radio pulsars, and the high-frequency gravitational wave detectors (ligo/virgo), respectively. here we discuss all key properties of dns systems, as well as selection effects, and combine the latest observational data with new theoretical progress on various physical processes with the aim of advancing our knowledge on their formation. we examine key interactions of their progenitor systems and evaluate their accretion history during the high-mass x-ray binary stage, the common envelope phase, and the subsequent case bb mass transfer, and argue that the first-formed nss have accreted at most ∼ 0.02 {m}⊙ . we investigate dns masses, spins, and velocities, and in particular correlations between spin period, orbital period, and eccentricity. numerous monte carlo simulations of the second supernova (sn) events are performed to extrapolate pre-sn stellar properties and probe the explosions. all known close-orbit dns systems are consistent with ultra-stripped exploding stars. although their resulting ns kicks are often small, we demonstrate a large spread in kick magnitudes that may, in general, depend on the past interaction history of the exploding star and thus correlate with the ns mass. we analyze and discuss ns kick directions based on our sn simulations. finally, we discuss the terminal evolution of close-orbit dns systems until they merge and possibly produce a short γ-ray burst. | formation of double neutron star systems |
we discuss an interpretation that a peak in the sound velocity in neutron star matter, as suggested by the observational data, signifies strongly coupled conformal matter. the normalized trace anomaly is a dimensionless measure of conformality leading to the derivative and the nonderivative contributions to the sound velocity. we find that the peak in the sound velocity is attributed to the derivative contribution from the trace anomaly that steeply approaches the conformal limit. smooth continuity to the behavior of high-density qcd implies that the matter part of the trace anomaly may be positive definite. we discuss a possible implication of the positivity condition of the trace anomaly on the m -r relation of the neutron stars. | trace anomaly as signature of conformality in neutron stars |
the concept of stars being tidally ripped apart and consumed by a massive black hole (mbh) lurking in the center of a galaxy first captivated theorists in the late 1970s. the observational evidence for these rare but illuminating phenomena for probing otherwise dormant mbhs first emerged in archival searches of the soft x-ray rosat all-sky survey in the 1990s, but has recently accelerated with the increasing survey power in the optical time domain, with tidal disruption events (tdes) now regarded as a class of optical nuclear transients with distinct spectroscopic features. multiwavelength observations of tdes have revealed panchromatic emission, probing a wide range of scales, from the innermost regions of the accretion flow to the surrounding circumnuclear medium. i review the current census of 56 tdes reported in the literature, and their observed properties can be summarized as follows: the optical light curves follow a power-law decline from peak that scales with the inferred central black hole mass as expected for the fallback rate of the stellar debris, but the rise time does not. the uv-optical and soft x-ray thermal emission come from different spatial scales, and their intensity ratio has a large dynamic range and is highly variable, providing important clues as to what is powering the two components. they can be grouped into three spectral classes, and those with bowen fluorescence line emission show a preference for a hotter and more compact line-emitting region, whereas those with only heii emission lines are the rarest class. | tidal disruption events |
we present jwst nircam nine-band near-infrared imaging of the luminous z = 10.6 galaxy gn-z11 from the jwst advanced deep extragalactic survey of the goods-n field. we find a spectral energy distribution (sed) entirely consistent with the expected form of a high-redshift galaxy: a clear blue continuum from 1.5 to 4 μm with a complete dropout in f115w. the core of gn-z11 is extremely compact in jwst imaging. we analyze the image with a two-component model, using a point source and a sérsic profile that fits to a half-light radius of 200 pc and an index n = 0.9. we find a low-surface-brightness haze about 0.″4 to the northeast of the galaxy, which is most likely a foreground object but might be a more extended component of gn-z11. at a spectroscopic redshift of 10.60 (bunker et al. 2023), the comparison of the nircam f410m and f444w images spans the balmer jump. from population-synthesis modeling, here assuming no light from an active galactic nucleus, we reproduce the sed of gn-z11, finding a stellar mass of ~109 m ⊙, a star formation rate of ~20 m ⊙ yr-1, and a young stellar age of ~20 myr. since massive galaxies at high redshift are likely to be highly clustered, we search for faint neighbors of gn-z11, finding nine galaxies out to ~5 comoving mpc transverse with photometric redshifts consistent with z = 10.6, and a tenth more tentative dropout only 3″ away. this is consistent with gn-z11 being hosted by a massive dark-matter halo (≈8 × 1010 m ⊙), though lower halo masses cannot be ruled out. | jades imaging of gn-z11: revealing the morphology and environment of a luminous galaxy 430 myr after the big bang |
nearly a century ago it was recognized that radiation absorption by stellar matter controls the internal temperature profiles within stars. laboratory opacity measurements, however, have never been performed at stellar interior conditions, introducing uncertainties in stellar models. a particular problem arose when refined photosphere spectral analysis led to reductions of 30-50 per cent in the inferred amounts of carbon, nitrogen and oxygen in the sun. standard solar models using the revised element abundances disagree with helioseismic observations that determine the internal solar structure using acoustic oscillations. this could be resolved if the true mean opacity for the solar interior matter were roughly 15 per cent higher than predicted, because increased opacity compensates for the decreased element abundances. iron accounts for a quarter of the total opacity at the solar radiation/convection zone boundary. here we report measurements of wavelength-resolved iron opacity at electron temperatures of 1.9-2.3 million kelvin and electron densities of (0.7-4.0) × 1022 per cubic centimetre, conditions very similar to those in the solar region that affects the discrepancy the most: the radiation/convection zone boundary. the measured wavelength-dependent opacity is 30-400 per cent higher than predicted. this represents roughly half the change in the mean opacity needed to resolve the solar discrepancy, even though iron is only one of many elements that contribute to opacity. | a higher-than-predicted measurement of iron opacity at solar interior temperatures |
the gravitational wave event gw170817 was caused by the merger of two neutron stars (see the introduction by smith). in three papers, teams associated with the growth (global relay of observatories watching transients happen) project present their observations of the event at wavelengths from x-rays to radio waves. evans et al. used space telescopes to detect gw170817 in the ultraviolet and place limits on its x-ray flux, showing that the merger generated a hot explosion known as a blue kilonova. hallinan et al. describe radio emissions generated as the explosion slammed into the surrounding gas within the host galaxy. kasliwal et al. present additional observations in the optical and infrared and formulate a model for the event involving a cocoon of material expanding at close to the speed of light, matching the data at all observed wavelengths. | swift and nustar observations of gw170817: detection of a blue kilonova |
in the λcdm paradigm, the galactic stellar halo is predicted to harbor the accreted debris of smaller systems. to identify these systems, the h3 spectroscopic survey, combined with gaia, is gathering 6d phase-space and chemical information in the distant galaxy. here we present a comprehensive inventory of structure within 50 kpc from the galactic center using a sample of 5684 giants at $| b| \gt 40^\circ $ and $| z| \gt 2\,\mathrm{kpc}$ . we identify known structures including the high-α disk, the in situ halo (disk stars heated to eccentric orbits), sagittarius (sgr), gaia-sausage-enceladus (gse), the helmi streams, sequoia, and thamnos. additionally, we identify the following new structures: (i) aleph ([fe/h] = -0.5), a low-eccentricity structure that rises a surprising 10 kpc off the plane, (ii) and (iii) arjuna ([fe/h] = -1.2) and i'itoi ([fe/h] < -2), which comprise the high-energy retrograde halo along with sequoia, and (iv) wukong ([fe/h] = -1.6), a prograde phase-space overdensity chemically distinct from gse. for each structure, we provide [fe/h], [α/fe], and orbital parameters. stars born within the galaxy are a major component at $| z| \sim 2\,\mathrm{kpc}$ (≈60%), but their relative fraction declines sharply to ≲5% past 15 kpc. beyond 15 kpc, >80% of the halo is built by two massive (m⋆ ∼ 108-109m⊙) accreted dwarfs: gse ([fe/h] = -1.2) within 25 kpc and sgr ([fe/h] = -1.0) beyond 25 kpc. this explains the relatively high overall metallicity of the halo ([fe/h] ≈ -1.2). we attribute ≳95% of the sample to one of the listed structures, pointing to a halo built entirely from accreted dwarfs and heating of the disk. | evidence from the h3 survey that the stellar halo is entirely comprised of substructure |
following the first two annual intensity mapping workshops at stanford in march 2016 and johns hopkins in june 2017, we report on the recent advances in theory, instrumentation and observation that were presented in these meetings and some of the opportunities and challenges that were identified looking forward. with preliminary detections of co, [cii], lya and low-redshift 21cm, and a host of experiments set to go online in the next few years, the field is rapidly progressing on all fronts, with great anticipation for a flood of new exciting results. this current snapshot provides an efficient reference for experts in related fields and a useful resource for nonspecialists. we begin by introducing the concept of line-intensity mapping and then discuss the broad array of science goals that will be enabled, ranging from the history of star formation, reionization and galaxy evolution to measuring baryon acoustic oscillations at high redshift and constraining theories of dark matter, modified gravity and dark energy. after reviewing the first detections reported to date, we survey the experimental landscape, presenting the parameters and capabilities of relevant instruments such as comap, mmime, aim-co, ccat-p, time, concerto, chime, hirax, hera, starfire, meerkat/ska and spherex. finally, we describe recent theoretical advances: different approaches to modeling line luminosity functions, several techniques to separate the desired signal from foregrounds, statistical methods to analyze the data, and frameworks to generate realistic intensity map simulations. | line-intensity mapping: 2017 status report |
we review the use of emission lines for understanding galaxy evolution, focusing on excitation source, metallicity, ionization parameter, ism pressure, and electron density. we discuss the physics, benefits, and caveats of emission line diagnostics, including the effects of theoretical model uncertainties, diffuse ionized gas, and sample selection bias. in anticipation of upcoming telescope facilities, we provide new self-consistent emission line diagnostic calibrations for complete spectral coverage from the uv to the ir. these diagnostics can be used in concert to understand how fundamental galaxy properties have changed across cosmic time. we conclude the following: the uv, optical, and ir contain complementary diagnostics that can probe the conditions within different nebular ionization zones. accounting for complex density gradients and temperature profiles is critical for reliably estimating the fundamental properties of hii regions and galaxies. diffuse ionized gas can raise metallicity estimates, flatten metallicity gradients, and introduce scatter in ionization parameter measurements. new 3d emission line diagnostics successfully separate the contributions from star formation, agn, and shocks using integral field spectroscopy.we summarize with a discussion of the challenges and major opportunities for emission line diagnostics in the coming years. | understanding galaxy evolution through emission lines |
we present the dark energy camera (decam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational-wave emission, gw170817. our observations commenced 10.5 hr post-merger, as soon as the localization region became accessible from chile. we imaged 70 deg2 in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). at 11.4 hr post-merger we detected a bright optical transient located 10\buildrel{\prime\prime}\over{.} 6 from the nucleus of ngc 4993 at redshift z = 0.0098, consistent (for {h}0=70 km s-1 mpc-1) with the distance of 40 ± 8 mpc reported by the ligo scientific collaboration and the virgo collaboration (lvc). at detection the transient had magnitudes of i=17.3 and z=17.4, and thus an absolute magnitude of {m}i=-15.7, in the luminosity range expected for a kilonova. we identified 1500 potential transient candidates. applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with ngc 4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. we therefore conclude that the optical counterpart we have identified near ngc 4993 is associated with gw170817. this discovery ushers in the era of multi-messenger astronomy with gravitational waves and demonstrates the power of decam to identify the optical counterparts of gravitational-wave sources. | the electromagnetic counterpart of the binary neutron star merger ligo/virgo gw170817. i. discovery of the optical counterpart using the dark energy camera |
we investigate the extension of isotropic interior solutions for static self-gravitating systems to include the effects of anisotropic spherically symmetric gravitational sources by means of the gravitational decoupling realised via the minimal geometric deformation approach. in particular, the matching conditions at the surface of the star with the outer schwarzschild space-time are studied in great detail, and we describe how to generate, from a single physically acceptable isotropic solution, new families of anisotropic solutions whose physical acceptability is also inherited from their isotropic parent. | anisotropic solutions by gravitational decoupling |
gravitational waves have been detected from a binary neutron star merger event, gw170817. the detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy ngc 4993, at a distance of 40 megaparsecs from earth. we report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. the observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry. | a radio counterpart to a neutron star merger |
the building of planetary systems is controlled by the gas and dust dynamics of protoplanetary disks. while the gas is simultaneously accreted onto the central star and dissipated away by winds, dust grains aggregate and collapse to form planetesimals and eventually planets. this dust and gas dynamics involves instabilities, turbulence and complex non-linear interactions which ultimately control the observational appearance and the secular evolution of these disks. this chapter is dedicated to the most recent developments in our understanding of the dynamics of gaseous and dusty disks, covering hydrodynamic and magnetohydrodynamic turbulence, gas-dust instabilities, dust clumping and disk winds. we show how these physical processes have been tested from observations and highlight standing questions that should be addressed in the future. | hydro-, magnetohydro-, and dust-gas dynamics of protoplanetary disks |
in this article, i introduce ideas and techniques to extract information about the equation of state of matter at very high densities from gravitational waves emitted before, during and after the merger of binary neutron stars. i also review current work and results on the actual use of the first gravitational-wave observation of a neutron-star merger to set constraints on properties of such equation of state. in passing, i also touch on the possibility that what we observe in gravitational waves are not neutron stars, but something more exotic. in order to make this article more accessible, i also review the dynamics and gravitational-wave emission of neutron-star mergers in general, with focus on numerical simulations and on which representations of the equation of state are used for studies on binary systems. | gravitational waves from neutron star mergers and their relation to the nuclear equation of state |
fast radio bursts (frbs) are bright, millisecond-scale radio flashes of unknown physical origin1. young, highly magnetized, isolated neutron stars—magnetars—have been suggested as the most promising candidates for frb progenitors owing to their energetics and high x-ray flaring activity2,3. here we report the detection with konus-wind of a hard x-ray event of 28 april 2020 temporally coincident with a bright, two-peak radio burst4,5 in the direction of galactic magnetar sgr 1935+2154, with properties remarkably similar to those of frbs. we show that the two peaks of the double-peaked x-ray burst coincide in time with the radio peaks and infer a common source and the association of these phenomena. an unusual hardness of the x-ray spectrum strongly distinguishes the 28 april event among multiple `ordinary' flares from sgr 1935+2154. a recent non-detection5-7 of radio emission from about 100 typical soft bursts from sgr 1935+2154 favours the idea that bright, frb-like magnetar signals are associated with rare, hard-spectrum x-ray bursts. the implied rate of these hard x-ray bursts (~0.04 yr−1 magnetar−1) appears consistent with the rate estimate4 of sgr 1935+2154-like radio bursts (0.007-0.04 yr−1 magnetar−1). | a peculiar hard x-ray counterpart of a galactic fast radio burst |
the radii and orbital periods of 4,000+ confirmed/candidate exoplanets have been precisely measured by the kepler mission. the radii show a bimodal distribution, with two peaks corresponding to smaller planets (likely rocky) and larger intermediate-size planets, respectively. while only the masses of the planets orbiting the brightest stars can be determined by ground-based spectroscopic observations, these observations allow calculation of their average densities placing constraints on the bulk compositions and internal structures. however, an important question about the composition of planets ranging from 2 to 4 earth radii (r⊕) still remains. they may either have a rocky core enveloped in a h2-he gaseous envelope (gas dwarfs) or contain a significant amount of multicomponent, h2o-dominated ices/fluids (water worlds). planets in the mass range of 10-15 m⊕, if half-ice and half-rock by mass, have radii of 2.5 r⊕, which exactly match the second peak of the exoplanet radius bimodal distribution. any planet in the 2- to 4-r⊕ range requires a gas envelope of at most a few mass percentage points, regardless of the core composition. to resolve the ambiguity of internal compositions, we use a growth model and conduct monte carlo simulations to demonstrate that many intermediate-size planets are “water worlds.” | growth model interpretation of planet size distribution |
the prospects for the habitability of m-dwarf planets have long been debated, due to key differences between the unique stellar and planetary environments around these low-mass stars, as compared to hotter, more luminous sun-like stars. over the past decade, significant progress has been made by both space- and ground-based observatories to measure the likelihood of small planets to orbit in the habitable zones of m-dwarf stars. we now know that most m dwarfs are hosts to closely-packed planetary systems characterized by a paucity of jupiter-mass planets and the presence of multiple rocky planets, with roughly a third of these rocky m-dwarf planets orbiting within the habitable zone, where they have the potential to support liquid water on their surfaces. theoretical studies have also quantified the effect on climate and habitability of the interaction between the spectral energy distribution of m-dwarf stars and the atmospheres and surfaces of their planets. these and other recent results fill in knowledge gaps that existed at the time of the previous overview papers published nearly a decade ago by tarter et al. (2007) and scalo et al. (2007). in this review we provide a comprehensive picture of the current knowledge of m-dwarf planet occurrence and habitability based on work done in this area over the past decade, and summarize future directions planned in this quickly evolving field. | the habitability of planets orbiting m-dwarf stars |
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