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the determination of exoplanet properties and occurrence rates using kepler data critically depends on our knowledge of the fundamental properties (such as temperature, radius, and mass) of the observed stars. we present revised stellar properties for 197,096 kepler targets observed between quarters 1-17 (q1-17), which were used for the final transiting planet search run by the kepler mission (data release 25, dr25). similar to the q1-16 catalog by huber et al., the classifications are based on conditioning published atmospheric parameters on a grid of dartmouth isochrones, with significant improvements in the adopted method and over 29,000 new sources for temperatures, surface gravities, or metallicities. in addition to fundamental stellar properties, the new catalog also includes distances and extinctions, and we provide posterior samples for each stellar parameter of each star. typical uncertainties are ∼27% in radius, ∼17% in mass, and ∼51% in density, which is somewhat smaller than previous catalogs because of the larger number of improved {log}g constraints and the inclusion of isochrone weighting when deriving stellar posterior distributions. on average, the catalog includes a significantly larger number of evolved solar-type stars, with an increase of 43.5% in the number of subgiants. we discuss the overall changes of radii and masses of kepler targets as a function of spectral type, with a particular focus on exoplanet host stars. | revised stellar properties of kepler targets for the q1-17 (dr25) transit detection run |
we present observations with the cosmic origins spectrograph (cos) onboard the hubble space telescope of five star-forming galaxies at redshifts z in the range 0.2993-0.4317 and with high emission-line flux ratios o32 = [o iii] λ5007/[o ii] λ3727 ∼ 8-27 aiming to detect the lyman continuum (lyc) emission. we detect lyc emission in all galaxies with the escape fractions fesc(lyc) in a range of 2-72 per cent. a narrow lyα emission line with two peaks in four galaxies and with three peaks in one object is seen in medium-resolution cos spectra with a velocity separation between the peaks vsep varying from ∼153 to ∼345 km s-1. we find a general increase of the lyc escape fraction with increasing o32 and decreasing stellar mass m⋆, but with a large scatter of fesc(lyc). a tight anticorrelation is found between fesc(lyc) and vsep making vsep a good parameter for the indirect determination of the lyc escape fraction. we argue that one possible source driving the escape of ionizing radiation is stellar winds and radiation from hot massive stars. | low-redshift lyman continuum leaking galaxies with high [o iii]/[o ii] ratios |
we present the second data release (dr2) of the skymapper southern survey, a hemispheric survey carried out with the skymapper telescope at siding spring observatory in australia, using six optical filters: u, v, g, r, i, z. dr2 is the first release to go beyond the ∼18 mag (10σ) limit of the shallow survey released in the first data release (dr1), and includes portions of the sky at full survey depth that reach > 21 mag in g and r filters. the dr2 photometry has a precision as measured by internal reproducibility of 1% in u and v, and 0.7% in griz. more than 21 000 ° have data in some filters (at either shallow or main survey depth) and over 7 000 ° have deep main survey coverage in all six filters. finally, about 18 000 ° have main survey data in i and z filters, albeit not yet at full depth. the release contains over 120 000 images, as well as catalogues with over 500 million unique astrophysical objects and nearly 5 billion individual detections. it also contains cross-matches with a range of external catalogues such as gaia dr2, pan-starrs1 dr1, galex guvcat, 2mass, and allwise, as well as spectroscopic surveys such as 2mrs, galah, 6dfgs, and 2dflens. | skymapper southern survey: second data release (dr2) |
transmission spectra are differential measurements that utilize stellar illumination to probe transiting exoplanet atmospheres. any spectral difference between the illuminating light source and the disk-integrated stellar spectrum due to starspots and faculae will be imprinted in the observed transmission spectrum. however, few constraints exist for the extent of photospheric heterogeneities in m dwarfs. here we model spot and faculae covering fractions consistent with observed photometric variabilities for m dwarfs and the associated 0.3-5.5 μm stellar contamination spectra. we find that large ranges of spot and faculae covering fractions are consistent with observations and corrections assuming a linear relation between variability amplitude, and covering fractions generally underestimate the stellar contamination. using realistic estimates for spot and faculae covering fractions, we find that stellar contamination can be more than 10× larger than the transit depth changes expected for atmospheric features in rocky exoplanets. we also find that stellar spectral contamination can lead to systematic errors in radius and therefore the derived density of small planets. in the case of the trappist-1 system, we show that trappist-1's rotational variability is consistent with spot covering fractions {f}{spot}={8}-7+18 % and faculae covering fractions {f}{fac}={54}-46+16 % . the associated stellar contamination signals alter the transit depths of the trappist-1 planets at wavelengths of interest for planetary atmospheric species by roughly 1-15× the strength of planetary features, significantly complicating jwst follow-up observations of this system. similarly, we find that stellar contamination can lead to underestimates of the bulk densities of the trappist-1 planets of {{δ }}(ρ )=-{8}-20+7 % , thus leading to overestimates of their volatile contents. | the transit light source effect: false spectral features and incorrect densities for m-dwarf transiting planets |
double neutron stars (dnss) have been observed as galactic radio pulsars, and the recent discovery of gravitational waves from the dns merger gw170817 adds to the known dns population. we perform rapid population synthesis of massive binary stars and discuss model predictions, including dns formation rates, mass distributions, and delay time distributions. we vary assumptions and parameters of physical processes such as mass transfer stability criteria, supernova natal kick distributions, remnant mass prescriptions, and common-envelope energetics. we compute the likelihood of observing the orbital period-eccentricity distribution of the galactic dns population under each of our population synthesis models, allowing us to quantitatively compare the models. we find that mass transfer from a stripped post-helium-burning secondary (case bb) on to a neutron star is most likely dynamically stable. we also find that a natal kick distribution composed of both low (maxwellian σ =30 km s^{-1}) and high (σ =265 km s^{-1}) components is preferred over a single high-kick component. we conclude that the observed dns mass distribution can place strong constraints on model assumptions. | on the formation history of galactic double neutron stars |
a new star has exploded back onto the climate scene: hydrogen. it offers possibilities to move away from fossil fuels, but it brings its own challenges. | the hydrogen solution? |
we present uv-extended e-miles stellar population synthesis models covering the spectral range λλ 1680-50 000 å at moderately high resolution. we employ the ngsl space-based stellar library to compute spectra of single-age, single-metallicity stellar populations in the wavelength range from 1680 to 3540 å. these models represent a significant improvement in resolution and age/metallicity coverage over previous studies based on earlier space-based libraries. these model spectra were joined with those we computed in the visible using miles, and other empirical libraries for redder wavelengths. the models span the metallicity range -1.79≤ [m/h]≤ +0.26 and ages above 30 myr, for a suite of initial mass function types with varying slopes. we focus on the behaviour of colours, spectra and line-strength indices in the uv range as a function of relevant stellar population parameters. whereas some indices strengthen with increasing age and metallicity, as most metallicity indicators in the visible, other indices peak around 3 gyr for metal-rich stellar populations, such as mg at 2800 å. our models provide reasonably good fits to the integrated colours and most line strengths of the stellar clusters of the milky way and large magellanic cloud. our full spectrum fits in the uv range for a representative set of early-type galaxies (etgs) of varying mass yield age and metallicity estimates in very good agreement with those obtained in the optical range. the comparison of uv colours and line strengths of massive etgs with our models reveals the presence of young stellar components, with ages in the range 0.1-0.5 gyr and mass fractions 0.1-0.5 per cent, on the top of an old stellar population. | uv-extended e-miles stellar population models: young components in massive early-type galaxies |
we present the sphinx suite of cosmological adaptive mesh refinement simulations, the first radiation-hydrodynamical simulations to simultaneously capture large-scale reionization and the escape of ionizing radiation from thousands of resolved galaxies. our 5 and 10 co-moving mpc volumes resolve haloes down to the atomic cooling limit and model the interstellar medium with better than ≈10 pc resolution. the project has numerous goals in improving our understanding of reionization and making predictions for future observations. in this first paper, we study how the inclusion of binary stars in computing stellar luminosities impacts reionization, compared to a model that includes only single stars. owing to the suppression of galaxy growth via strong feedback, our galaxies are in good agreement with observational estimates of the galaxy luminosity function. we find that binaries have a significant impact on the timing of reionization: with binaries, our boxes are 99.9 percent ionized by volume at z ≈ 7, while without them our volumes fail to reionize by z = 6. these results are robust to changes in volume size, resolution, and feedback efficiency. the escape of ionizing radiation from individual galaxies varies strongly and frequently. on average, binaries lead to escape fractions of ≈7-10 percent, about three times higher than with single stars only. the higher escape fraction is a result of a shallower decline in ionizing luminosity with age, and is the primary reason for earlier reionization, although the higher integrated luminosity with binaries also plays a subdominant role. | the sphinx cosmological simulations of the first billion years: the impact of binary stars on reionization |
we introduce the automatic learning for the rapid classification of events (alerce) broker, an astronomical alert broker designed to provide a rapid and self-consistent classification of large etendue telescope alert streams, such as that provided by the zwicky transient facility (ztf) and, in the future, the vera c. rubin observatory legacy survey of space and time (lsst). alerce is a chilean-led broker run by an interdisciplinary team of astronomers and engineers working to become intermediaries between survey and follow-up facilities. alerce uses a pipeline that includes the real-time ingestion, aggregation, cross-matching, machine-learning (ml) classification, and visualization of the ztf alert stream. we use two classifiers: a stamp-based classifier, designed for rapid classification, and a light curve-based classifier, which uses the multiband flux evolution to achieve a more refined classification. we describe in detail our pipeline, data products, tools, and services, which are made public for the community (see https://alerce.science). since we began operating our real-time ml classification of the ztf alert stream in early 2019, we have grown a large community of active users around the globe. we describe our results to date, including the real-time processing of 1.5 × 108 alerts, the stamp classification of 3.4 × 107 objects, the light-curve classification of 1.1 × 106 objects, the report of 6162 supernova candidates, and different experiments using lsst-like alert streams. finally, we discuss the challenges ahead in going from a single stream of alerts such as ztf to a multistream ecosystem dominated by lsst. | the automatic learning for the rapid classification of events (alerce) alert broker |
as the only dark matter candidate that does not invoke a new particle that survives to the present day, primordial black holes (pbhs) have drawn increasing attention recently. up to now, various observations have strongly constrained most of the mass range for pbhs, leaving only small windows where pbhs could make up a substantial fraction of the dark matter. here we revisit the pbh constraints for the asteroid-mass window, i.e., the mass range 3.5× 10-17msolar < mpbh < 4× 10-12msolar. we revisit 3 categories of constraints. (1) for optical microlensing, we analyze the finite source size and diffractive effects and discuss the scaling relations between the event rate, mpbh and the event duration. we argue that it will be difficult to push the existing optical microlensing constraints to much lower mpbh. (2) for dynamical capture of pbhs in stars, we derive a general result on the capture rate based on phase space arguments. we argue that survival of stars does not constrain pbhs, but that disruption of stars by captured pbhs should occur and that the asteroid-mass pbh hypothesis could be constrained if we can work out the observational signature of this process. (3) for destruction of white dwarfs by pbhs that pass through the white dwarf without getting gravitationally captured, but which produce a shock that ignites carbon fusion, we perform a 1+1d hydrodynamic simulation to explore the post-shock temperature and relevant timescales, and again we find this constraint to be ineffective. in summary, we find that the asteroid-mass window, which was previously constrained due to femtolensing, wd survival, optical microlensing, and neutron star capture is no longer constrained. hence, the asteroid-mass window remains open for pbhs to account for all the dark matter. | revisiting constraints on asteroid-mass primordial black holes as dark matter candidates |
we analyze the near infrared ($\sim0.8-1\mu$m) rest-frame morphologies of galaxies with $\log m_*/m_\odot>9$ in the redshift range $0<z<6$, compare with previous hst-based results and release the first jwst-based morphological catalog of $\sim20,000$ galaxies in the ceers survey. galaxies are classified into four main broad classes -- spheroid, disk+spheroid, disk, and disturbed -- based on imaging with four filters -- $f150w$, $f200w$, $f356w$, and $f444w$ -- using convolutional neural networks trained on hst/wfc3 labeled images and domain-adapted to jwst/nircam. we find that $\sim90\%$ and $\sim75\%$ of galaxies at $z<3$ have the same early/late and regular/irregular classification, respectively, in jwst and hst imaging when considering similar wavelengths. for small (large) and faint objects, jwst-based classifications tend to systematically present less bulge-dominated systems (peculiar galaxies) than hst-based ones, but the impact on the reported evolution of morphological fractions is less than $\sim10\%$. using jwst-based morphologies at the same rest-frame wavelength ($\sim0.8-1\mu$m), we confirm an increase in peculiar galaxies and a decrease in bulge-dominated galaxies with redshift, as reported in previous hst-based works, suggesting that the stellar mass distribution, in addition to light distribution, is more disturbed in the early universe. however, we find that undisturbed disk-like systems already dominate the high-mass end of the late-type galaxy population ($\log m_*/m_\odot>10.5$) at $z\sim5$, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies $\sim1$ gyr after the big bang. finally, we find that the morphology-quenching relation is already in place for massive galaxies at $z>3$, with massive quiescent galaxies ($\log m_*/m_\odot>10.5$) being predominantly bulge-dominated. | galaxy morphology from $z\\sim6$ through the eyes of jwst |
early jwst observations that targeted so-called double-break sources (attributed to lyman and balmer breaks at $z>7$), reported a previously unknown population of very massive, evolved high-redshift galaxies. this surprising discovery led to a flurry of attempts to explain these objects' unexpected existence including invoking alternatives to the standard $\lambda$cdm cosmological paradigm. to test these early results, we adopted the same double-break candidate galaxy selection criteria to search for such objects in the jwst images of the canadian niriss unbiased cluster survey (canucs), and found a sample of 19 sources over five independent canucs fields that cover a total effective area of $\sim60\,$arcmin$^2$ at $z\sim8$. however, (1) our sed fits do not yield exceptionally high stellar masses for our candidates, while (2) spectroscopy of five of the candidates shows that while all five are at high redshifts, their red colours are due to high-ew emission lines in star-forming galaxies rather than balmer breaks in massive, evolved systems. additionally, (3) field-to-field variance leads to differences of $\sim 1.5$ dex in the maximum stellar masses measured in the different fields, suggesting that the early single-field jwst observations may have suffered from cosmic variance and/or sample bias. finally, (4) we show that the presence of even a single massive outlier can dominate conclusions from small samples such as those in early jwst observations. in conclusion, we find that the double-break sources in canucs are not sufficiently massive or numerous to warrant questioning the standard $\lambda$cdm paradigm. | $\\lambda$cdm not dead yet: massive high-z balmer break galaxies are less common than previously reported |
we present a new-generation tool to model and interpret spectral energy distributions (seds) of galaxies, which incorporates in a consistent way the production of radiation and its transfer through the interstellar and intergalactic media. this flexible tool, named beagle (for bayesian analysis of galaxy seds), allows one to build mock galaxy catalogues as well as to interpret any combination of photometric and spectroscopic galaxy observations in terms of physical parameters. the current version of the tool includes versatile modelling of the emission from stars and photoionized gas, attenuation by dust and accounting for different instrumental effects, such as spectroscopic flux calibration and line spread function. we show a first application of the beagle tool to the interpretation of broad-band seds of a published sample of ∼ 10^4 galaxies at redshifts 0.1 ≲ z ≲ 8. we find that the constraints derived on photometric redshifts using this multipurpose tool are comparable to those obtained using public, dedicated photometric-redshift codes and quantify this result in a rigorous statistical way. we also show how the post-processing of beagle output data with the python extension pyp-beagle allows the characterization of systematic deviations between models and observations, in particular through posterior predictive checks. the modular design of the beagle tool allows easy extensions to incorporate, for example, the absorption by neutral galactic and circumgalactic gas, and the emission from an active galactic nucleus, dust and shock-ionized gas. information about public releases of the beagle tool will be maintained on http://www.jacopochevallard.org/beagle. | modelling and interpreting spectral energy distributions of galaxies with beagle |
in this work we implement the minimal geometric deformation decoupling method to obtain general static interior solutions for a btz vacuum from the most general isotropic solution in 2+1 dimensions including the cosmological constant λ. we obtain that the general solution can be generated only by the energy density of the original isotropic sector, so that this quantity plays the role of a generating function. although as a particular example we study the static star with constant density, the method here developed can be easily applied to more complex situations described by other energy density profiles. | a general interior anisotropic solution for a btz vacuum in the context of the minimal geometric deformation decoupling approach |
the interaction of λ and σ hyperons (y) with nucleons (n) is strongly influenced by the coupled-channel dynamics. due to the small mass difference of the nλ and nς systems, the sizable coupling strength of the nς ↔ nλ processes constitutes a crucial element in the determination of the nλ interaction. in this letter we present the most precise measurements on the interaction of pλ pairs, from zero relative momentum up to the opening of the nς channel. the correlation function in the relative momentum space for pλ ⊕ p ‾ λ ‾ pairs measured in high-multiplicity triggered pp collisions at √{ s } = 13 tev at the lhc is reported. the opening of the inelastic nς channels is visible in the extracted correlation function as a cusp-like structure occurring at relative momentum k⁎ = 289mev/ c. this represents the first direct experimental observation of the nς ↔ nλ coupled channel in the pλ system. the correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the nς ↔ nλ transition potential. a weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body nnλ interaction for a proper description of the λ in-medium properties, which has implications on the nuclear equation of state and for the presence of hyperons inside neutron stars. | exploring the nλ-nς coupled system with high precision correlation techniques at the lhc |
i review holographic models for (dense and cold) nuclear matter, neutron stars, and their mergers. i start by a brief general discussion on current knowledge of cold qcd matter and neutron stars, and go on discussing various approaches to model cold nuclear and quark matter by using gauge/gravity duality, pointing out their strengths and weaknesses. then i focus on recent results for a complex bottom-up holographic framework (v-qcd), which also takes input from lattice qcd results, effective field theory, and perturbative qcd. dense nuclear matter is modeled in v-qcd through a homogeneous non-abelian bulk gauge field. feasible "hybrid" equations of state for cold nuclear (and quark) matter can be constructed by using traditional methods (e.g., effective field theory) at low densities and the holographic v-qcd model at higher densities. i discuss the constraints from this approach to the properties of the nuclear to quark matter transition as well as to properties of neutron stars. using such hybrid equations of state as an input for numerical simulations of neutron star mergers, i also derive predictions for the spectrum of produced gravitational waves. | holographic modeling of nuclear matter and neutron stars |
the phangs collaboration has been building a reference data set for the multiscale, multiphase study of star formation and the interstellar medium (ism) in nearby galaxies. with the successful launch and commissioning of jwst, we can now obtain high-resolution infrared imaging to probe the youngest stellar populations and dust emission on the scales of star clusters and molecular clouds (~5-50 pc). in cycle 1, phangs is conducting an eight-band imaging survey from 2 to 21 μm of 19 nearby spiral galaxies. optical integral field spectroscopy, co(2-1) mapping, and uv-optical imaging for all 19 galaxies have been obtained through large programs with alma, vlt-muse, and hubble. phangs-jwst enables a full inventory of star formation, accurate measurement of the mass and age of star clusters, identification of the youngest embedded stellar populations, and characterization of the physical state of small dust grains. when combined with hubble catalogs of ~10,000 star clusters, muse spectroscopic mapping of ~20,000 h ii regions, and ~12,000 alma-identified molecular clouds, it becomes possible to measure the timescales and efficiencies of the earliest phases of star formation and feedback, build an empirical model of the dependence of small dust grain properties on local ism conditions, and test our understanding of how dust-reprocessed starlight traces star formation activity, all across a diversity of galactic environments. here we describe the phangs-jwst treasury survey, present the remarkable imaging obtained in the first few months of science operations, and provide context for the initial results presented in the first series of phangs-jwst publications. | the phangs-jwst treasury survey: star formation, feedback, and dust physics at high angular resolution in nearby galaxies |
observing a supernova explosion shortly after it occurs can reveal important information about the physics of stellar explosions and the nature of the progenitor stars of supernovae (sne). when a star with a well-defined edge explodes in vacuum, the first photons to escape from its surface appear as a brief shock-breakout flare. the duration of this flare can extend to at most a few hours even for nonspherical breakouts from supergiant stars, after which the explosion ejecta should expand and cool. alternatively, for stars exploding within a distribution of sufficiently dense optically thick circumstellar material, the first photons escape from the material beyond the stellar edge, and the duration of the initial flare can extend to several days, during which the escaping emission indicates photospheric heating. the difficulty in detecting sn explosions promptly after the event has so far limited data regarding supergiant stellar explosions mostly to serendipitous observations that, owing to the lack of ultraviolet (uv) data, were unable to determine whether the early emission is heating or cooling, and hence the nature of the early explosion event. here, we report observations of sn 2023ixf in the nearby galaxy m101, covering the early days of the event. using uv spectroscopy from the hubble space telescope (hst) as well as a comprehensive set of additional multiwavelength observations, we trace the photometric and spectroscopic evolution of the event and are able to temporally resolve the emergence and evolution of the sn emission. | resolving the explosion of supernova 2023ixf in messier 101 within its complex circumstellar environment |
emergent bulk properties of matter governed by the strong nuclear force give rise to physical phenomena across vastly different scales, ranging from the shape of atomic nuclei to the masses and radii of neutron stars. they can be accessed on earth by measuring the spatial extent of the outer skin made of neutrons that characterizes the surface of heavy nuclei. the isotope 208pb, owing to its simple structure and neutron excess, has been in this context the target of many dedicated efforts. here, we determine the neutron skin from measurements of particle distributions and their collective flow in 208pb + 208pb collisions at ultrarelativistic energy performed at the large hadron collider, which are mediated by interactions of gluons and thus sensitive to the overall size of the colliding 208pb ions. by means of state-of-the-art global analysis tools within the hydrodynamic model of heavy-ion collisions, we infer a neutron skin δ rn p=0.217 ±0.058 fm , consistent with nuclear theory predictions, and competitive in accuracy with a recent determination from parity-violating asymmetries in polarized electron scattering. we establish thus a new experimental method to systematically measure neutron distributions in the ground state of atomic nuclei. | determination of the neutron skin of 208pb from ultrarelativistic nuclear collisions |
turbulent rayleigh-bénard convection displays a large-scale order in the form of rolls and cells on lengths larger than the layer height once the fluctuations of temperature and velocity are removed. these turbulent superstructures are reminiscent of the patterns close to the onset of convection. here we report numerical simulations of turbulent convection in fluids at different prandtl number ranging from 0.005 to 70 and for rayleigh numbers up to 107. we identify characteristic scales and times that separate the fast, small-scale turbulent fluctuations from the gradually changing large-scale superstructures. the characteristic scales of the large-scale patterns, which change with prandtl and rayleigh number, are also correlated with the boundary layer dynamics, and in particular the clustering of thermal plumes at the top and bottom plates. our analysis suggests a scale separation and thus the existence of a simplified description of the turbulent superstructures in geo- and astrophysical settings. | turbulent superstructures in rayleigh-bénard convection |
this year marks the 30th anniversary of the only supernova from which we have detected neutrinos—sn 1987a. the 20 or so neutrinos that were detected were mined to great depth in order to determine the events that occurred in the explosion and to place limits upon all manner of neutrino properties. since 1987 the scale and sensitivity of the detectors capable of identifying neutrinos from a galactic supernova have grown considerably so that current generation detectors are capable of detecting of order 10 000 neutrinos for a supernova at the galactic center. next generation detectors will increase that yield by another order of magnitude. simultaneous with the growth of neutrino detection capability, our understanding of how massive stars explode and how the neutrino interacts with hot and dense matter has also increased by a tremendous degree. the neutrino signal will contain much information on all manner of physics of interest to a wide community. in this review we describe the expected features of the neutrino signal, the detectors which will detect it, and the signatures one might try to look for in order to get at this physics. | what can be learned from a future supernova neutrino detection? |
we estimate the 21 cm radio background from accretion onto the first intermediate-mass black holes between z ≈ 30 and z ≈ 16. combining potentially optimistic, but plausible, scenarios for black hole formation and growth with empirical correlations between luminosity and radio emission observed in low-redshift active galactic nuclei, we find that a model of black holes forming in molecular cooling halos is able to produce a 21 cm background that exceeds the cosmic microwave background (cmb) at z ≈ 17, though models involving larger halo masses are not entirely excluded. such a background could explain the surprisingly large amplitude of the 21 cm absorption feature recently reported by the edges collaboration. such black holes would also produce significant x-ray emission and contribute to the 0.5-2 kev soft x-ray background at the level of ≈10-13-10-12 erg s-1 cm-2 deg-2, consistent with existing constraints. in order to avoid heating the intergalactic medium (igm) over the edges trough, these black holes would need to be obscured by hydrogen column depths of n h ∼ 5 × 1023 cm-2. such black holes would avoid violating constraints on the cmb optical depth from planck if their uv photon escape fractions were below f esc ≲ 0.1, which would be a natural result of n h ∼ 5 × 1023 cm-2 being imposed by an unheated igm. | modeling the radio background from the first black holes at cosmic dawn: implications for the 21 cm absorption amplitude |
we present the redshift evolution of the galaxy effective radius re obtained from the hubble space telescope (hst) samples of ∼190,000 galaxies at z = 0-10. our hst samples consist of 176,152 photo-z galaxies at z = 0-6 from the 3d-hst+candels catalog and 10,454 lyman break galaxies (lbgs) at z = 4-10 identified in the cosmic assembly near-infrared deep extragalactic legacy survey (candels), hudf 09/12, and hff parallel fields, providing the largest data set to date for galaxy size evolution studies. we derive re with the same technique over the wide redshift range of z = 0-10, evaluating the optical-to-uv morphological k correction and the selection bias of photo-z galaxies+lbgs as well as the cosmological surface-brightness dimming effect. we find that re values at a given luminosity significantly decrease toward high z, regardless of statistics choices (e.g., {r}{{e}}\propto {(1+z)}-1.10+/- 0.06 for median). for star-forming galaxies, there is no evolution of the power-law slope of the size-luminosity relation and the median sérsic index (n∼ 1.5). moreover, the re distribution is well represented by log-normal functions whose standard deviation {σ }{ln{r}{{e}}} does not show significant evolution within the range of {σ }{ln{r}{{e}}}∼ 0.45-0.75. we calculate the stellar-to-halo size ratio from our re measurements and the dark-matter halo masses estimated from the abundance-matching study, and we obtain a nearly constant value of {r}{{e}}/{r}{vir}=1.0%-3.5% at z = 0-8. the combination of the re-distribution shape+standard deviation, the constant {r}{{e}}/{r}{vir}, and n∼ 1.5 suggests a picture in which typical high-z star-forming galaxies have disk-like stellar components in a sense of dynamics and morphology over cosmic time of z∼ 0-6. if high-z star-forming galaxies are truly dominated by disks, the {r}{{e}}/{r}{vir} value and the disk-formation model indicate that the specific angular momentum of the disk normalized by the host halo is {j}{{d}}/{m}{{d}}≃ 0.5-1. these are statistical results for major stellar components of galaxies, and the detailed study of clumpy subcomponents is presented in the paper ii. | morphologies of ∼190,000 galaxies at z = 0-10 revealed with hst legacy data. i. size evolution |
galaxies and their dark-matter haloes have posed several challenges to the dark energy plus cold dark matter (λcdm) cosmological model. these discrepancies between observations and theory intensify for the lowest-mass (`dwarf') galaxies. λcdm predictions for the number, spatial distribution and internal structure of low-mass dark-matter haloes have historically been at odds with observed dwarf galaxies, but this is partially expected, because many predictions modelled only the dark-matter component. any robust λcdm prediction must include, hand in hand, a model for galaxy formation to understand how baryonic matter populates and affects dark-matter haloes. in this review, we consider the most notable challenges to λcdm regarding dwarf galaxies, and we discuss how recent cosmological numerical simulations have pinpointed baryonic solutions to these challenges. we identify remaining tensions, including the diversity of the inner dark-matter content, planes of satellites, stellar morphologies and star-formation quenching. their resolution, or validation as actual problems with λcdm, will probably require both refining of galaxy-formation models and improving numerical accuracy in simulations. | baryonic solutions and challenges for cosmological models of dwarf galaxies |
we study a suite of extremely high-resolution cosmological feedback in realistic environments simulations of dwarf galaxies (m_halo ≲ 10^{10} m_{\odot }), run to z = 0 with 30 m_{\odot } resolution, sufficient (for the first time) to resolve the internal structure of individual supernovae remnants within the cooling radius. every halo with m_halo ≳ 10^{8.6} m_{\odot } is populated by a resolved stellar galaxy, suggesting very low-mass dwarfs may be ubiquitous in the field. our ultra-faint dwarfs (ufds; m_{\ast }< 105 m_{\odot }) have their star formation (sf) truncated early (z ≳ 2), likely by reionization, while classical dwarfs (m_{\ast }> 105 m_{\odot }) continue forming stars to z < 0.5. the systems have bursty star formation histories, forming most of their stars in periods of elevated sf strongly clustered in both space and time. this allows our dwarf with m*/mhalo > 10-4 to form a dark matter core {>}200 pc, while lower mass ufds exhibit cusps down to {≲}100 pc, as expected from energetic arguments. our dwarfs with m_{\ast }> 104 m_{\odot } have half-mass radii (r1/2) in agreement with local group (lg) dwarfs (dynamical mass versus r1/2 and stellar rotation also resemble observations). the lowest mass ufds are below surface brightness limits of current surveys but are potentially visible in next-generation surveys (e.g. lsst). the stellar metallicities are lower than in lg dwarfs; this may reflect pre-enrichment of the lg by the massive hosts or pop-iii stars. consistency with lower resolution studies implies that our simulations are numerically robust (for a given physical model). | be it therefore resolved: cosmological simulations of dwarf galaxies with 30 solar mass resolution |
we compute a new generation of standard solar models (ssms) that includes recent updates on some important nuclear reaction rates and a more consistent treatment of the equation of state. models also include a novel and flexible treatment of opacity uncertainties based on opacity kernels, required in light of recent theoretical and experimental works on radiative opacity. two large sets of ssms, each based on a different canonical set of solar abundances with high and low metallicity (z), are computed to determine model uncertainties and correlations among different observables. we present detailed comparisons of high- and low-z models against different ensembles of solar observables, including solar neutrinos, surface helium abundance, depth of the convective envelope, and sound speed profile. a global comparison, including all observables, yields a p-value of 2.7σ for the high-z model and 4.7σ for the low-z one. when the sound speed differences in the narrow region of 0.65< r/{r}⊙ < 0.70 are excluded from the analysis, results are 0.9σ and 3.0σ for high- and low-z models respectively. these results show that high-z models agree well with solar data but have a systematic problem right below the bottom of the convective envelope linked to steepness of molecular weight and temperature gradients, and that low-z models lead to a much more general disagreement with solar data. we also show that, while simple parametrizations of opacity uncertainties can strongly alleviate the solar abundance problem, they are insufficient to substantially improve the agreement of ssms with helioseismic data beyond that obtained for high-z models due to the intrinsic correlations of theoretical predictions. | a new generation of standard solar models |
we present a first sample of 117 [o iii] λλ4960, 5008-selected star-forming galaxies at 5.33 < z < 6.93 detected in jwst/nircam 3.5 μm slitless spectroscopy of a $6\buildrel{\,\prime}\over{.} 5\,\times \,3\buildrel{\,\prime}\over{.} 4$ field centered on the hyperluminous quasar sdss j0100+2802, obtained as part of the emission-line galaxies and intergalactic gas in the epoch of reionization (eiger) survey. three prominent galaxy overdensities are observed, one of them at the redshift of the quasar. galaxies are found within 200 pkpc and 105 km s-1 of four known metal absorption-line systems. we focus on the role of the galaxies in ionizing the intergalactic medium (igm) during the later stages of cosmic reionization and construct the mean lyα and lyβ transmission as a function of distance from the galaxies. at the lowest redshifts in our study, 5.3 < z < 5.7, the igm transmission rises monotonically with distance from the galaxies, as seen previously at lower redshifts. in contrast, at 5.7 < z < 6.14, the transmission of both lyα and lyβ first increases with distance but then peaks at a distance of 5 cmpc before declining. finally, in the region 6.15 < z < 6.26, where the additional ionizing radiation from the quasar dominates, the monotonic increase in transmission with distance is reestablished. this result is interpreted to represent evidence that the transmission of the igm at z ~ 5.9 toward j0100+2802 results from the "local" ionizing radiation of galaxies that dominates over the much-reduced cosmic background. | eiger. i. a large sample of [o iii]-emitting galaxies at 5.3 < z < 6.9 and direct evidence for local reionization by galaxies |
we describe the creation, content, and validation of the dark energy survey (des) internal year-one cosmology data set, y1a1 gold, in support of upcoming cosmological analyses. the y1a1 gold data set is assembled from multiple epochs of des imaging and consists of calibrated photometric zero-points, object catalogs, and ancillary data products—e.g., maps of survey depth and observing conditions, star-galaxy classification, and photometric redshift estimates—that are necessary for accurate cosmological analyses. the y1a1 gold wide-area object catalog consists of ∼ 137 million objects detected in co-added images covering ∼ 1800 {\deg }2 in the des grizy filters. the 10σ limiting magnitude for galaxies is g=23.4, r=23.2, i=22.5, z=21.8, and y=20.1. photometric calibration of y1a1 gold was performed by combining nightly zero-point solutions with stellar locus regression, and the absolute calibration accuracy is better than 2% over the survey area. des y1a1 gold is the largest photometric data set at the achieved depth to date, enabling precise measurements of cosmic acceleration at z ≲ 1. | dark energy survey year 1 results: the photometric data set for cosmology |
context. the heating of the solar corona by small heating events requires an increasing number of such events at progressively smaller scales, with the bulk of the heating occurring at scales that are currently unresolved.aims: the goal of this work is to study the smallest brightening events observed in the extreme-uv quiet sun.methods: we used commissioning data taken by the extreme ultraviolet imager (eui) on board the recently launched solar orbiter mission. on 30 may 2020, the eui was situated at 0.556 au from the sun. its high resolution euv telescope (hrieuv, 17.4 nm passband) reached an exceptionally high two-pixel spatial resolution of 400 km. the size and duration of small-scale structures was determined by the hrieuv data, while their height was estimated from triangulation with simultaneous images from the atmospheric imaging assembly (aia) on board the solar dynamics observatory mission. this is the first stereoscopy of small-scale brightenings at high resolution.results: we observed small localised brightenings, also known as `campfires', in a quiet sun region with length scales between 400 km and 4000 km and durations between 10 s and 200 s. the smallest and weakest of these hrieuv brightenings have not been previously observed. simultaneous observations from the eui high-resolution lyman-α telescope (hrilya) do not show localised brightening events, but the locations of the hrieuv events clearly correspond to the chromospheric network. comparisons with simultaneous aia images shows that most events can also be identified in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of aia, although they appear weaker and blurred. our differential emission measure analysis indicated coronal temperatures peaking at log t ≈ 6.1 − 6.15. we determined the height for a few of these campfires to be between 1000 and 5000 km above the photosphere.conclusions: we find that `campfires' are mostly coronal in nature and rooted in the magnetic flux concentrations of the chromospheric network. we interpret these events as a new extension to the flare-microflare-nanoflare family. given their low height, the eui `campfires' could stand as a new element of the fine structure of the transition region-low corona, that is, as apexes of small-scale loops that undergo internal heating all the way up to coronal temperatures. | extreme-uv quiet sun brightenings observed by the solar orbiter/eui |
we show that the deep underground neutrino experiment (dune), with significant but feasible new efforts, has the potential to deliver world-leading results in solar neutrinos. with a 100 kton -yr exposure, dune could detect ≳105 signal events above 5 mev electron energy. separate precision measurements of neutrino-mixing parameters and the 8b flux could be made using two detection channels (νe+40ar and νe ,μ ,τ+e- ) and the day-night effect (>10 σ ). new particle physics may be revealed through the comparison of solar neutrinos (with matter effects) and reactor neutrinos (without), which is discrepant by ∼2 σ (and could become 5.6 σ ). new astrophysics may be revealed through the most precise measurement of the 8b flux (to 2.5%) and the first detection of the hep flux (to 11%). dune is required: no other experiment, even proposed, has been shown capable of fully realizing these discovery opportunities. | dune as the next-generation solar neutrino experiment |
studying the formation and evolution of black hole binaries (bhbs) is essential for the interpretation of current and forthcoming gravitational wave (gw) detections. we investigate the statistics of bhbs that form from isolated binaries, by means of a new version of the sevn population-synthesis code. sevn integrates stellar evolution by interpolation over a grid of stellar evolution tracks. we upgraded sevn to include binary stellar evolution processes and we used it to evolve a sample of 1.5 × 108 binary systems, with metallicity in the range [10-4; 4 × 10-2]. from our simulations, we find that the mass distribution of black holes (bhs) in double compact-object binaries is remarkably similar to the one obtained considering only single stellar evolution. the maximum bh mass we obtain is ∼30, 45, and 55 m_{⊙} at metallicity z = 2 × 10-2, 6 × 10-3, and 10-4, respectively. a few massive single bhs may also form (≲ 0.1 per cent of the total number of bhs), with mass up to ∼65, 90, and 145 m_{⊙} at z = 2 × 10-2, 6 × 10-3, and 10-4, respectively. these bhs fall in the mass gap predicted from pair-instability supernovae. we also show that the most massive bhbs are unlikely to merge within a hubble time. in our simulations, merging bhs like gw151226 and gw170608, form at all metallicities, the high-mass systems (like gw150914, gw170814, and gw170104) originate from metal-poor (z ≲ 6 × 10-3) progenitors, whereas gw170729-like systems are hard to form, even at z = 10-4. the bhb merger rate in the local universe obtained from our simulations is ∼90gpc-3yr-1, consistent with the rate inferred from ligo-virgo data. | merging black hole binaries with the sevn code |
i show that a recently discovered star cluster near the center of the ultra-faint dwarf galaxy eridanus ii provides strong constraints on massive compact halo objects (machos) of ≳5 m ⊙ as the main component of dark matter. macho dark matter will dynamically heat the cluster, driving it to larger sizes and higher velocity dispersions until it dissolves into its host galaxy. the stars in compact ultra-faint dwarf galaxies themselves will be subject to the same dynamical heating; the survival of at least 10 such galaxies places independent limits on macho dark matter of masses ≳10 m ⊙. both eri ii’s cluster and the compact ultra-faint dwarfs are characterized by stellar masses of just a few thousand m ⊙ and half-light radii of 13 pc (for the cluster) and ∼30 pc (for the ultra-faint dwarfs). these systems close the ∼20-100 m ⊙ window of allowed macho dark matter and combine with existing constraints from microlensing, wide binaries, and disk kinematics to rule out dark matter composed entirely of machos from ∼10-7 m ⊙ up to arbitrarily high masses. | constraints on macho dark matter from compact stellar systems in ultra-faint dwarf galaxies |
high-redshift quasi-stellar object (qso) spectra show large spatial fluctuations in the ly α opacity of the intergalactic medium on surprisingly large scales at z ≳ 5.5. we present a radiative transfer simulation of cosmic reionization driven by galaxies that reproduces this large scatter and the rapid evolution of the ly α opacity distribution at 5 < z < 6. the simulation also reproduces the low thomson scattering optical depth reported by the latest cosmic microwave background (cmb) measurement and is consistent with the observed short near-zones and strong red damping wings in the highest redshift qsos. it also matches the rapid disappearance of observed ly α emission by galaxies at z ≳ 6. reionization is complete at z = 5.3 in our model, and 50 per cent of the volume of the universe is ionized at z = 7. agreement with the ly α forest data in such a late reionization model requires a rapid evolution of the ionizing emissivity of galaxies that peaks at z ∼ 6.8. the late end of reionization results in a large scatter in the photoionization rate and the neutral hydrogen fraction at redshifts as low as z ≲ 5.5 with large residual neutral `islands' that can produce very long gunn-peterson troughs resembling those seen in the data. | large ly α opacity fluctuations and low cmb τ in models of late reionization with large islands of neutral hydrogen extending to z < 5.5 |
the study of the development of structures on multiple scales in the cold interstellar medium has experienced rapid expansion in the past decade, on both the observational and the theoretical front. spectral line studies at (sub-)millimeter wavelengths over a wide range of physical scales have provided unique probes of the kinematics of dense gas in star-forming regions, and have been complemented by extensive, high dynamic range dust continuum surveys of the column density structure of molecular cloud complexes, while dust polarization maps have highlighted the role of magnetic fields. this has been accompanied by increasingly sophisticated numerical simulations including new physics (e.g., supernova driving, cosmic rays, non-ideal magneto-hydrodynamics, radiation pressure) and new techniques such as zoom-in simulations allowing multi-scale studies. taken together, these new data have emphasized the anisotropic growth of dense structures on all scales, from giant ism bubbles driven by stellar feedback on ∼50–100 pc scales through parsec-scale molecular filaments down to < 0.1 pc dense cores and < 1000 au protostellar disks. combining observations and theory, we present a coherent picture for the formation and evolution of these structures and synthesize a comprehensive physical scenario for the initial conditions and early stages of star and disk formation. | from bubbles and filaments to cores and disks: gas gathering and growth of structure leading to the formation of stellar systems |
in this first of a series of papers, we utilize results for around 2000 star cluster models simulated using the mocca code for star cluster evolution (survey database i) to determine the astrophysical properties and local merger rate densities for coalescing binary black holes (bbhs) originating from globular clusters (gcs). we extracted information for all coalescing bbhs that escape the cluster models and subsequently merge within a hubble time along with bbhs that are retained in our gc models and merge inside the cluster via gravitational wave emission. by obtaining results from a substantial number of realistic star cluster models that cover different initial parameters, we have an extremely large statistical sample of bbhs with stellar mass and massive stellar bh (≲100 m⊙) components that merge within a hubble time. using these data, we estimate local merger rate densities for these bbhs originating from gcs to be at least 5.4 gpc-3 yr-1. | mocca-survey database - i. coalescing binary black holes originating from globular clusters |
the predicted rate of binary black hole mergers from galactic fields can vary over several orders of magnitude and is extremely sensitive to the assumptions of stellar evolution. but in dense stellar environments such as globular clusters, binary black holes form by well-understood gravitational interactions. in this letter, we study the formation of black hole binaries in an extensive collection of realistic globular cluster models. by comparing these models to observed milky way and extragalactic globular clusters, we find that the mergers of dynamically formed binaries could be detected at a rate of ∼100 per year, potentially dominating the binary black hole merger rate. we also find that a majority of cluster-formed binaries are more massive than their field-formed counterparts, suggesting that advanced ligo could identify certain binaries as originating from dense stellar environments. | binary black hole mergers from globular clusters: implications for advanced ligo |
the kepler mission was designed to identify and characterize transiting planets in the kepler field of view and to determine their occurrence rates. emphasis was placed on identification of earth-size planets orbiting in the habitable zone of their host stars. science data were acquired for a period of four years. long-cadence data with 29.4 min sampling were obtained for ∼200,000 individual stellar targets in at least one observing quarter in the primary kepler mission. light curves for target stars are extracted in the kepler science data processing pipeline, and are searched for transiting planet signatures. a threshold crossing event is generated in the transit search for targets where the transit detection threshold is exceeded and transit consistency checks are satisfied. these targets are subjected to further scrutiny in the data validation (dv) component of the pipeline. transiting planet candidates are characterized in dv, and light curves are searched for additional planets after transit signatures are modeled and removed. a suite of diagnostic tests is performed on all candidates to aid in discrimination between genuine transiting planets and instrumental or astrophysical false positives. data products are generated per target and planet candidate to document and display transiting planet model fit and diagnostic test results. these products are exported to the exoplanet archive at the nasa exoplanet science institute, and are available to the community. we describe the dv architecture and diagnostic tests, and provide a brief overview of the data products. transiting planet modeling and the search for multiple planets on individual targets are described in a companion paper. the final revision of the kepler pipeline code base is available to the general public through github. the kepler pipeline has also been modified to support the transiting exoplanet survey satellite (tess) mission which is expected to commence in 2018. | kepler data validation i—architecture, diagnostic tests, and data products for vetting transiting planet candidates |
there has been a striking realization that physics resolving the black hole information paradox could imply postmerger gravitational wave echoes. we here report on evidence for echoes from the ligo compact binary merger events, gw151226, gw170104, gw170608, gw170814, as well as the neutron star merger gw170817. there is a signal for each event with a p -value of order 1% or sometimes significantly less. our study begins with the comparison of echoes from a variety of horizonless exotic compact objects. next we investigate the effects of spin. the identification of the more generic features of echoes then leads to the development of relatively simple windowing methods, in both time and frequency space, to extract a signal from noise. the time delay between echoes is inversely related to the spacing between the spectral resonances, and it is advantageous to look directly for this resonance structure. we find time delays for the first four events that are consistent with a simple model that accounts for mass and spin of the final object, while for the neutron star merger the final mass and spin are constrained. | gravitational wave echoes through new windows |
the possibility that primordial black holes (pbhs) represent all of the dark matter (dm) in the universe and explain the coalescences of binary black holes detected by ligo/virgo has attracted a lot of attention. pbhs are generated by the enhancement of scalar perturbations which inevitably produce the induced gravitational waves (gws). we calculate the induced gws up to the third-order correction which not only enhances the amplitude of induced gws, but also extends the cutoff frequency from 2 k* to 3 k*. such effects of the third-order correction lead to an around 10% increase of the signal-to-noise ratio (snr) for both lisa and pulsar timing array (pta) observations, and significantly widen the mass range of pbhs in the stellar mass window accompanying detectable induced gws for pta observations including ipta, fast and ska. on the other hand, the null detections of the induced gws by lisa and pta experiments will exclude the possibility that all of the dm is comprised of pbhs and the gw events detected by ligo/virgo are generated by pbhs. | probing primordial-black-hole dark matter with scalar induced gravitational waves |
over a decade ago, a group of supernova explosions with peak luminosities far exceeding (often by >100 times) those of normal events has been identified. these superluminous supernovae (slsne) have been a focus of intensive study. i review the accumulated observations and discuss the implications for the physics of these extreme explosions. slsne can be classified into hydrogen-poor (slsne-i) and hydrogen-rich (slsne-ii) events. combining photometric and spectroscopic analysis of samples of nearby slsne-i and lower-luminosity events, a threshold of mag at peak appears to separate slsne-i from the normal population. slsn-i light curves can be quite complex, presenting both early bumps and late postpeak undulations. slsne-i spectroscopically evolve from an early hot photospheric phase with a blue continuum and weak absorption lines, through a cool photospheric phase resembling spectra of sne ic, and into the late nebular phase. slsne-ii are not nearly as well studied, lacking information based on large-sample studies. proposed models for the slsn power source are challenged to explain all the observations. slsne arise from massive progenitors, with some events associated with very massive stars ( m). host galaxies of slsne in the nearby universe tend to have low mass and subsolar metallicity. slsne are rare, with rates <100 times lower than ordinary supernovae. slsn cosmology and their use as beacons to study the high-redshift universe offer exciting prospects. | the most luminous supernovae |
the nature of dark matter (dm) remains unknown despite very precise knowledge of its abundance in the universe. an alternative to new elementary particles postulates dm as made of macroscopic compact halo objects (macho) such as black holes formed in the very early universe. stellar-mass primordial black holes (pbhs) are subject to less robust constraints than other mass ranges and might be connected to gravitational-wave signals detected by the laser interferometer gravitational-wave observatory (ligo). new methods are therefore necessary to constrain the viability of compact objects as a dm candidate. here we report bounds on the abundance of compact objects from gravitational lensing of type ia supernovae (sne). current sne data sets constrain compact objects to represent less than 35.2% (joint lightcurve analysis) and 37.2% (union 2.1) of the total matter content in the universe, at 95% confidence level. the results are valid for masses larger than ∼0.01 m⊙ (solar masses), limited by the size sne relative to the lens einstein radius. we demonstrate the mass range of the constraints by computing magnification probabilities for realistic sne sizes and different values of the pbh mass. our bounds are sensitive to the total abundance of compact objects with m ≳0.01 m⊙ and complementary to other observational tests. these results are robust against cosmological parameters, outlier rejection, correlated noise, and selection bias. pbhs and other machos are therefore ruled out as the dominant form of dm for objects associated to ligo gravitational wave detections. these bounds constrain early-universe models that predict stellar-mass pbh production and strengthen the case for lighter forms of dm, including new elementary particles. | limits on stellar-mass compact objects as dark matter from gravitational lensing of type ia supernovae |
accounting for nebular emission when modeling galaxy spectral energy distributions (seds) is important, as both line and continuum emissions can contribute significantly to the total observed flux. in this work, we present a new nebular emission model integrated within the flexible stellar population synthesis code that computes the line and continuum emission for complex stellar populations using the photoionization code cloudy. the self-consistent coupling of the nebular emission to the matched ionizing spectrum produces emission line intensities that correctly scale with the stellar population as a function of age and metallicity. this more complete model of galaxy seds will improve estimates of global gas properties derived with diagnostic diagrams, star formation rates based on hα, and physical properties derived from broadband photometry. our models agree well with results from other photoionization models and are able to reproduce observed emission from h ii regions and star-forming galaxies. our models show improved agreement with the observed h ii regions in the ne iii/o ii plane and show satisfactory agreement with he ii emission from z = 2 galaxies, when including rotating stellar models. models including post-asymptotic giant branch stars are able to reproduce line ratios consistent with low-ionization emission regions. the models are integrated into current versions of fsps and include self-consistent nebular emission predictions for mist and padova+geneva evolutionary tracks. | nebular continuum and line emission in stellar population synthesis models |
context. the chemical composition of the sun is required in the context of various studies in astrophysics, among them in the calculation of standard solar models (ssms) used to describe the evolution of the sun from the pre-main-sequence to its present age.aims: in this work, we provide a critical re-analysis of the solar chemical abundances and corresponding ssms.methods: for the photospheric values, we employed new high-quality solar observational data collected with the iag facility, state-of-the art non-equilibrium modelling, new oscillator strengths, and different atmospheric models, including the marcs model, along with averages based on stagger and co5bold 3d radiation-hydrodynamics simulations of stellar convection. we performed new calculations of oscillator strengths for transitions in o i and n i. for o i, which is a critical element with regard to the interior models, calculations were carried out using several independent methods. we investigated our results in comparison with the previous estimates.results: we find an unprecedented agreement between the new estimates of transition probabilities, thus supporting our revised solar oxygen abundance value. we also provide new estimates of the noble gas ne abundance. in addition, we discuss the consistency of our photospheric measurements with meteoritic values, taking into account the systematic and correlated errors. finally, we provide revised chemical abundances, leading to a new value proposed for the solar photospheric present-day metallicity of z/x = 0.0225, which we then employed in ssm calculations. we find that the puzzling mismatch between the helioseismic constraints on the solar interior structure and the model can be resolved thanks to this new chemical composition. | observational constraints on the origin of the elements. iv. standard composition of the sun |
we study the compatibility of recursive techniques with the classical limit of scattering amplitudes through the construction of the classical compton amplitude for general spinning compact objects. this is done using bcfw recursion on three-point amplitudes expressed in terms of the classical spin vector and tensor, and expanded to next-to-leading-order in ћ by using the heavy on-shell spinors. matching to the result of classical computations, we find that lower-point quantum contributions are, in general, required for the recursive construction of classical, spinning, higher-point amplitudes with massive propagators. we are thus led to conclude that bcfw recursion and the classical limit do not commute. in possession of the classical compton amplitude, we remove non-localities to all orders in spin for opposite graviton helicities, and to fifth order in the same-helicity case. finally, all possible on-shell contact terms potentially relevant to black-hole scattering at the second post-minkowskian order are enumerated and written explicitly. | recursion in the classical limit and the neutron-star compton amplitude |
we perform three-dimensional general-relativistic magnetohydrodynamic simulations with weak interactions of binary neutron-star (bns) mergers resulting in a long-lived remnant neutron star, with properties typical of galactic bns and consistent with those inferred for the first observed bns merger gw170817. we demonstrate self-consistently that within ≲30 ms postmerger magnetized (σ ∼5 - 10 ) incipient jets emerge with asymptotic lorentz factor γ ∼5 - 10 , which successfully break out from the merger debris within ≲20 ms . a fast (v ≲0.6 c ), magnetized (σ ∼0.1 ) wind surrounds the jet core and generates a uv/blue kilonova precursor on timescales of hours, similar to the precursor signal due to free neutron decay in fast dynamical ejecta. postmerger ejecta are quickly dominated by magnetohydrodynamically driven outflows from an accretion disk. we demonstrate that, within only 50 ms postmerger, ≳2 ×10-2m⊙ of lanthanide-free, quasispherical ejecta with velocities ∼0.1 - 0.2 c is launched, yielding a kilonova signal consistent with gw170817 on timescales of ≲5 d . | jets from neutron-star merger remnants and massive blue kilonovae |
we present the highest fidelity spectrum to date of a planetary-mass object. vhs 1256 b is a <20 m jup widely separated (~8″, a = 150 au), young, planetary-mass companion that shares photometric colors and spectroscopic features with the directly imaged exoplanets hr 8799c, d, and e. as an l-to-t transition object, vhs 1256 b exists along the region of the color-magnitude diagram where substellar atmospheres transition from cloudy to clear. we observed vhs 1256 b with jwst's nirspec ifu and miri mrs modes for coverage from 1 to 20 μm at resolutions of ~1000-3700. water, methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in several portions of the jwst spectrum based on comparisons from template brown dwarf spectra, molecular opacities, and atmospheric models. the spectral shape of vhs 1256 b is influenced by disequilibrium chemistry and clouds. we directly detect silicate clouds, the first such detection reported for a planetary-mass companion. | the jwst early-release science program for direct observations of exoplanetary systems ii: a 1 to 20 μm spectrum of the planetary-mass companion vhs 1256-1257 b |
we make use of deep 1.2 mm continuum observations (12.7 μjy beam-1 rms) of a 1 arcmin2 region in the hubble ultra deep field to probe dust-enshrouded star formation from 330 lyman-break galaxies spanning the redshift range z = 2-10 (to ∼2-3 m ⊙ yr-1 at 1σ over the entire range). given the depth and area of aspecs, we would expect to tentatively detect 35 galaxies, extrapolating the meurer z ∼ 0 irx-β relation to z ≥ 2 (assuming dust temperature td∼ 35 k). however, only six tentative detections are found at z ≳ 2 in aspecs, with just three at >3σ. subdividing our z = 2-10 galaxy samples according to stellar mass, uv luminosity, and uv-continuum slope and stacking the results, we find a significant detection only in the most massive (>109.75 m ⊙) subsample, with an infrared excess (irx = l ir/l uv) consistent with previous z ∼ 2 results. however, the infrared excess we measure from our large selection of sub-l ∗ (<109.75 m ⊙) galaxies is {0.11}-0.42+0.32 ± 0.34 (bootstrap and formal uncertainties) and {0.14}-0.14+0.15 ± 0.18 at z = 2-3 and z = 4-10, respectively, lying below even an irx-β relation for the small magellanic cloud (95% confidence). these results demonstrate the relevance of stellar mass for predicting the ir luminosity of z ≳ 2 galaxies. we find that the evolution of the irx-stellar mass relationship depends on the evolution of the dust temperature. if the dust temperature increases monotonically with redshift (\propto {(1+z)}0.32) such that td∼ 44-50 k at z ≥ 4, current results are suggestive of little evolution in this relationship to z ∼ 6. we use these results to revisit recent estimates of the z ≥ 3 star formation rate density. | alma spectroscopic survey in the hubble ultra deep field: the infrared excess of uv-selected z = 2-10 galaxies as a function of uv-continuum slope and stellar mass |
we compute the expected x-ray diffuse background and radiative feedback on the intergalactic medium (igm) from x-ray binaries prior to and during the epoch of reionization. the cosmic evolution of compact binaries is followed using a population synthesis technique that treats separately neutron stars and black hole binaries in different spectral states and is calibrated to reproduce the observed x-ray properties of galaxies at z ≲ 4. together with an updated empirical determination of the cosmic history of star formation, recent modeling of the stellar mass-metallicity relation, and a scheme for absorption by the igm that accounts for the presence of ionized h ii bubbles during the epoch of reionization, our detailed calculations provide refined predictions of the x-ray volume emissivity and filtered radiation background from “normal” galaxies at z ≳ 6. radiative transfer effects modulate the background spectrum, which shows a characteristic peak between 1 and 2 kev. because of the energy dependence of photoabsorption, soft x-ray photons are produced by local sources, while more energetic radiation arrives unattenuated from larger cosmological volumes. while the filtering of x-ray radiation through the igm slightly increases the mean excess energy per photoionization, it also weakens the radiation intensity below 1 kev, lowering the mean photoionization and heating rates. numerical integration of the rate and energy equations shows that the contribution of x-ray binaries to the ionization of the bulk igm is negligible, with the electron fraction never exceeding 1%. direct he i photoionizations are the main source of igm heating, and the temperature of the largely neutral medium in between h ii cavities increases above the temperature of the cosmic microwave background (cmb) only at z ≲ 10, when the volume filling factor of h ii bubbles is already ≳0.1. therefore, in this scenario, it is only at relatively late epochs that neutral intergalactic hydrogen may be observable in 21 cm emission against the cmb. | radiation backgrounds at cosmic dawn: x-rays from compact binaries |
a stochastic background of gravitational waves could be created by the superposition of a large number of independent sources. the physical processes occurring at the earliest moments of the universe certainly created a stochastic background that exists, at some level, today. this is analogous to the cosmic microwave background, which is an electromagnetic record of the early universe. the recent observations of gravitational waves by the advanced ligo and advanced virgo detectors imply that there is also a stochastic background that has been created by binary black hole and binary neutron star mergers over the history of the universe. whether the stochastic background is observed directly, or upper limits placed on it in specific frequency bands, important astrophysical and cosmological statements about it can be made. this review will summarize the current state of research of the stochastic background, from the sources of these gravitational waves to the current methods used to observe them. | stochastic gravitational wave backgrounds |
knowledge of the ages of the stars formed over a galaxy's lifetime is fundamental to an understanding of its formation and evolution. however, stellar ages are difficult to obtain since they cannot be measured from observations, but require comparison with stellar models1. alternatively, age distributions can be derived by applying the robust technique of colour-magnitude diagram fitting2, which until now has been used primarily to study nearby galaxies. accurate distances to individual milky way stars now provided by the gaia spacecraft mission3 have allowed us to derive ages from a thick-disk colour-magnitude diagram and from the two-sequenced colour-magnitude diagram of the kinematically hot local halo4, whose blue sequence has been linked to a major accretion event, gaia-enceladus5,6. because accurate stellar ages were lacking, the time of the merger and its role in our galaxy's early evolution remained unclear. here we show that the stars in both halo sequences share identical age distributions, and are older than most of the thick-disk stars. the sharp halo age distribution cutoff at ten billion years ago can be identified with the time of accretion of gaia-enceladus to the milky way. together with state-of-the-art cosmological simulations of galaxy formation7, these robust ages allow us to order the early sequence of events that shaped our galaxy. we identify the red-sequence stars as the first stars formed within the milky way progenitor, and their kinematics indicate that these stars constitute the long-sought in situ halo of the milky way. | uncovering the birth of the milky way through accurate stellar ages with gaia |
fast radio bursts (frbs) are extragalactic astrophysical transients1 whose brightness requires emitters that are highly energetic yet compact enough to produce the short, millisecond-duration bursts. frbs have thus far been detected at frequencies from 8 gigahertz (ref. 2) down to 300 megahertz (ref. 3), but lower-frequency emission has remained elusive. some frbs repeat4-6, and one of the most frequently detected, frb 20180916b7, has a periodicity cycle of 16.35 days (ref. 8). using simultaneous radio data spanning a wide range of wavelengths (a factor of more than 10), here we show that frb 20180916b emits down to 120 megahertz, and that its activity window is frequency dependent (that is, chromatic). the window is both narrower and earlier at higher frequencies. binary wind interaction models predict a wider window at higher frequencies, the opposite of our observations. our full-cycle coverage shows that the 16.3-day periodicity is not aliased. we establish that low-frequency frb emission can escape the local medium. for bursts of the same fluence, frb 20180916b is more active below 200 megahertz than at 1.4 gigahertz. combining our results with previous upper limits on the all-sky frb rate at 150 megahertz, we find there are 3-450 frbs in the sky per day above 50 jy ms. our chromatic results strongly disfavour scenarios in which absorption from strong stellar winds causes frb periodicity. we demonstrate that some frbs are found in `clean' environments that do not absorb or scatter low-frequency radiation. | chromatic periodic activity down to 120 megahertz in a fast radio burst |
gravitational-wave detectors are starting to reveal the redshift evolution of the binary black hole (bbh) merger rate, r bbh(z). we make predictions for r bbh(z) as a function of black hole mass for systems originating from isolated binaries. to this end, we investigate correlations between the delay time and black hole mass by means of the suite of binary population synthesis simulations, compas. we distinguish two channels: the common envelope (ce), and the stable roche-lobe overflow (rlof) channel, characterized by whether the system has experienced a common envelope or not. we find that the ce channel preferentially produces bhs with masses below about 30 m ⊙ and short delay times (t delay ≲ 1 gyr), while the stable rlof channel primarily forms systems with bh masses above 30 m ⊙ and long delay times (t delay ≳ 1 gyr). we provide a new fit for the metallicity-dependent specific star formation rate density based on the illustris tng simulations, and use this to convert the delay time distributions into a prediction of r bbh(z). this leads to a distinct redshift evolution of r bbh(z) for high and low primary bh masses. we furthermore find that, at high redshift, r bbh(z) is dominated by the ce channel, while at low redshift, it contains a large contribution (~40%) from the stable rlof channel. our results predict that, for increasing redshifts, bbhs with component masses above 30 m ⊙ will become increasingly scarce relative to less massive bbh systems. evidence of this distinct evolution of r bbh(z) for different bh masses can be tested with future detectors. | the redshift evolution of the binary black hole merger rate: a weighty matter |
determinations of the ultraviolet (uv) luminosity function of active galactic nuclei (agn) at high redshifts are important for constraining the agn contribution to reionization and understanding the growth of supermassive black holes. recent inferences of the luminosity function suffer from inconsistencies arising from inhomogeneous selection and analysis of data. we address this problem by constructing a sample of more than 80 000 colour-selected agn from redshift z = 0 to 7.5 using multiple data sets homogenized to identical cosmologies, intrinsic agn spectra, and magnitude systems. using this sample, we derive the agn uv luminosity function from redshift z = 0 to 7.5. the luminosity function has a double power-law form at all redshifts. the break magnitude m* shows a steep brightening from m* ∼ -24 at z = 0.7 to m* ∼ -29 at z = 6. the faint-end slope β significantly steepens from -1.9 at z < 2.2 to -2.4 at z ≃ 6. in spite of this steepening, the contribution of agn to the hydrogen photoionization rate at z ∼ 6 is subdominant (<3 per cent), although it can be non-negligible (∼10 per cent) if these luminosity functions hold down to m1450 = -18. under reasonable assumptions, agn can reionize he ii by redshift z = 2.9. at low redshifts (z < 0.5), agn can produce about half of the hydrogen photoionization rate inferred from the statistics of h i absorption lines in the intergalactic medium. our analysis also reveals important systematic errors in the data, which need to be addressed and incorporated in the agn selection function in future in order to improve our results. we make various fitting functions, codes, and data publicly available. | evolution of the agn uv luminosity function from redshift 7.5 |
in this work we construct an ultracompact star configuration in the framework of gravitational decoupling by the minimal geometric deformation approach. we use the complexity factor as a complementary condition to close the system of differential equations. it is shown that for a polynomial complexity the resulting solution can be matched with two different modified-vacuum geometries. | ultracompact stars with polynomial complexity by gravitational decoupling |
we define various types of "phantom" stars that may appear in the tess input catalog (tic), and provide examples and lists of currently known cases. we present a methodology that can be used to check for phantoms around any object of interest in the tic, and we present an approach for correcting the tic-reported flux contamination factors accordingly. we checked all 2077 tess objects of interest (tois) known as of july 21st 2020 (sectors 1 to 24) and sent corrections for 291 stars to mast where they are integrated into the publicly available tic-8, updating it to tic 8.1. we used the experience gained to construct an all-sky algorithm searching for "phantoms" which led to 34 million updates integrated into tic 8.2. | tess input catalog versions 8.1 and 8.2: phantoms in the 8.0 catalog and how to handle them |
we describe a public data release of the fire-2 cosmological zoom-in simulations of galaxy formation (available at http://flathub.flatironinstitute.org/fire) from the feedback in realistic environments (fire) project. fire-2 simulations achieve parsec-scale resolution to explicitly model the multiphase interstellar medium while implementing direct models for stellar evolution and feedback, including stellar winds, core-collapse and type ia supernovae, radiation pressure, photoionization, and photoelectric heating. we release complete snapshots from three suites of simulations. the first comprises 20 simulations that zoom in on 14 milky way (mw)-mass galaxies, five smc/lmc-mass galaxies, and four lower-mass galaxies including one ultrafaint; we release 39 snapshots across z = 0-10. the second comprises four massive galaxies, with 19 snapshots across z = 1-10. finally, a high-redshift suite comprises 22 simulations, with 11 snapshots across z = 5-10. each simulation also includes dozens of resolved lower-mass (satellite) galaxies in its zoom-in region. snapshots include all stored properties for all dark matter, gas, and star particles, including 11 elemental abundances for stars and gas, and formation times (ages) of star particles. we also release accompanying (sub)halo catalogs, which include galaxy properties and member star particles. for the simulations to z = 0, including all mw-mass galaxies, we release the formation coordinates and an "ex situ" flag for all star particles, pointers to track particles across snapshots, catalogs of stellar streams, and multipole basis expansions for the halo mass distributions. we describe publicly available python packages for reading and analyzing these simulations. | public data release of the fire-2 cosmological zoom-in simulations of galaxy formation |
gravitational waves from ~90 black hole binary systems have been detected and their progenitors' properties inferred1 so far by the laser interferometer gravitational-wave observatory2 and virgo3 experiments. this has allowed the scientific community to draw conclusions on the formation channels of black holes in binaries, informing population models and at times defying our understanding of black hole astrophysics. the most challenging event detected so far is the short-duration gravitational-wave transient gw190521 (refs. 4,5). we analyse this signal under the hypothesis that it was generated by the merger of two nonspinning black holes on hyperbolic orbits. the configuration best matching the data corresponds to two black holes of source-frame masses of 8 1−25+62m⊙ and 5 2−32+32m⊙ undergoing two encounters and then merging into an intermediate-mass black hole. we find that the hyperbolic merger hypothesis is favoured with respect to a quasi-circular merger with precessing spins with bayes' factors larger than 4,300 to 1, although this number will be reduced by the currently uncertain prior odds. our results suggest that gw190521 might be the first gravitational wave detection from the dynamical capture of two stellar-mass nonspinning black holes. | gw190521 as a dynamical capture of two nonspinning black holes |
axions are some of the best motivated particles beyond the standard model. we show how the attractive self-interactions of dark matter (dm) axions over a broad range of masses, from 10-22 ev to 107 gev , can lead to nongravitational growth of density fluctuations and the formation of bound objects. this structure formation enhancement is driven by parametric resonance when the initial field misalignment is large, and it affects axion density perturbations on length scales of order the hubble horizon when the axion field starts oscillating, deep inside the radiation-dominated era. this effect can turn an otherwise nearly scale-invariant spectrum of adiabatic perturbations into one that has a spike at the aforementioned scales, producing objects ranging from dense dm halos to scalar-field configurations such as solitons and oscillons. we call this class of cosmological scenarios for axion dm production "the large-misalignment mechanism." we explore observational consequences of this mechanism for axions with masses up to 10 ev. for axions heavier than 10-5 ev , the compact axion halos are numerous enough to significantly impact earth-bound direct detection experiments, yielding intermittent but coherent signals with repetition rates exceeding one per decade and crossing times less than a day. these episodic increases in the axion density and kinematic coherence suggest new approaches for axion dm searches, including for the qcd axion. dense structures made up of axions from 10-22 ev to 10-5 ev are detectable through gravitational lensing searches, and their gravitational interactions can also perturb baryonic structures and alter star formation. at very high misalignment amplitudes, the axion field can undergo self-interaction-induced implosions long before matter-radiation equality, producing potentially-detectable low-frequency stochastic gravitational waves. | large-misalignment mechanism for the formation of compact axion structures: signatures from the qcd axion to fuzzy dark matter |
in the past decade, observations from space and the ground have found water to be the most abundant molecular species, after hydrogen, in the atmospheres of hot, gaseous extrasolar planets1-5. being the main molecular carrier of oxygen, water is a tracer of the origin and the evolution mechanisms of planets. for temperate, terrestrial planets, the presence of water is of great importance as an indicator of habitable conditions. being small and relatively cold, these planets and their atmospheres are the most challenging to observe, and therefore no atmospheric spectral signatures have so far been detected6. super-earths—planets lighter than ten earth masses—around later-type stars may provide our first opportunity to study spectroscopically the characteristics of such planets, as they are best suited for transit observations. here, we report the detection of a spectroscopic signature of water in the atmosphere of k2-18 b—a planet of eight earth masses in the habitable zone of an m dwarf7—with high statistical confidence (atmospheric detectability index5 = 5.0, ~3.6σ (refs. 8,9)). in addition, the derived mean molecular weight suggests an atmosphere still containing some hydrogen. the observations were recorded with the hubble space telescope/wide field camera 3 and analysed with our dedicated, publicly available, algorithms5,9. although the suitability of m dwarfs to host habitable worlds is still under discussion10-13, k2-18 b offers an unprecedented opportunity to gain insight into the composition and climate of habitable-zone planets. | water vapour in the atmosphere of the habitable-zone eight-earth-mass planet k2-18 b |
networks have advanced the study of nonlocality beyond bell's theorem. here, we introduce the concept of full network nonlocality, which describes correlations that necessitate all links in a network to distribute nonlocal resources. showcasing that this notion is stronger than standard network nonlocality, we prove that the most well-known network bell test does not witness full network nonlocality. in contrast, we demonstrate that its generalization to star networks is capable of detecting full network nonlocality in quantum theory. more generally, we point out that established methods for analyzing local and theory-independent correlations in networks can be combined in order to systematically deduce sufficient conditions for full network nonlocality in any network and input-output scenario. we demonstrate the usefulness of these methods by constructing polynomial witnesses of full network nonlocality for the bilocal scenario. then, we show that these inequalities can be violated via quantum elegant joint measurements. | full network nonlocality |
we present a survey of the [c ii] 158 μm line and underlying far-infrared (fir) dust continuum emission in a sample of 27 z≳ 6 quasars using the atacama large millimeter array (alma) at ∼ 1\prime\prime resolution. the [c ii] line was significantly detected (at > 5-σ) in 23 sources (85%). we find typical line luminosities of {l}[{{c}{{ii}}]}={10}9-10 {l}⊙ , and an average line width of ∼385 {km} {{{s}}}-1. the [c ii]-to-far-infrared luminosity ratios ([c ii]/fir) in our sources span one order of magnitude, highlighting a variety of conditions in the star-forming medium. four quasar host galaxies are clearly resolved in their [c ii] emission on a few kpc scales. basic estimates of the dynamical masses of the host galaxies give masses between 2 × 1010 and 2 × 1011 {m}⊙ , i.e., more than an order of magnitude below what is expected from local scaling relations, given the available limits on the masses of the central black holes (> 3× {10}8 {m}⊙ , assuming eddington-limited accretion). in stacked alma [c ii] spectra of individual sources in our sample, we find no evidence of a deviation from a single gaussian profile. the quasar luminosity does not strongly correlate with either the [c ii] luminosity or equivalent width. this survey (with typical on-source integration times of 8 minutes) showcases the unparalleled sensitivity of alma at millimeter wavelengths, and offers a unique reference sample for the study of the first massive galaxies in the universe. | an alma [c ii] survey of 27 quasars at z > 5.94 |
a new final endpoint of complete gravitational collapse is proposed. by extending the concept of bose–einstein condensation to gravitational systems, a static, spherically symmetric solution to einstein's equations is obtained, characterized by an interior de sitter region of p=‑ρ gravitational vacuum condensate and an exterior schwarzschild geometry of arbitrary total mass m. these are separated by a phase boundary with a small but finite thickness ℓ, replacing both the schwarzschild and de sitter classical horizons. the resulting collapsed cold, compact object has no singularities, no event horizons, and a globally defined killing time. its entropy is maximized under small fluctuations and is given by the standard hydrodynamic entropy of the thin shell, which is of order kbℓmc/ℏ, instead of the bekenstein–hawking entropy, sbh=4πkbgm2/ℏc. unlike bhs, a collapsed star of this kind is consistent with quantum theory, thermodynamically stable, and suffers from no information paradox. | gravitational condensate stars: an alternative to black holes |
we follow our first paper with an analysis of the ensemble of the extensive pre-explosion ground- and space-based infrared observations of the red supergiant (rsg) progenitor candidate for the nearby core-collapse supernova sn 2023ixf in messier 101, together with optical data prior to explosion obtained with the hubble space telescope (hst). we have confirmed the association of the progenitor candidate with the sn, as well as constrained the metallicity at the sn site, based on sn observations with instruments at gemini-north. the internal host extinction to the sn has also been confirmed from a high-resolution keck spectrum. we fit the observed spectral energy distribution (sed) for the star, accounting for its intrinsic variability, with dust radiative-transfer modeling, which assume a silicate-rich dust shell ahead of the underlying stellar photosphere. the star is heavily dust-obscured, likely the dustiest progenitor candidate yet encountered. we found maximum-likelihood estimates of the star's effective temperature and luminosity of 3450 k and 9.3e4 l_sun, with 68% credible intervals of 2370--3700 k and (7.6--10.8)e4 l_sun. the candidate may have a galactic rsg analog, irc -10414, with a strikingly similar sed and luminosity. via comparison with single-star evolutionary models we have constrained the initial mass of the progenitor candidate from 12 m_sun to as high as 15 m_sun. we have had available to us an extraordinary view of the sn 2023ixf progenitor candidate, which should be further followed up in future years with hst and the james webb space telescope. | the sn 2023ixf progenitor in m101: ii. properties |
the formation of galaxies by gradual hierarchical co-assembly of baryons and cold dark matter halos is a fundamental paradigm underpinning modern astrophysics. a key test of this paradigm is via the observations of massive galaxies at early times as the evolution of the masses and abundances of dark matter halos is straight forward to simulate and massive halos should contain the universal cosmic baryon fraction at high redshift. extremely massive quiescent galaxies > $10^{11}$ m$_\odot$ have now been observed as early as 1-2 billions years after the big bang producing tension with theoretical models and driving significant revisions. typical spectroscopic ages of these objects are 300-500 myr. here we report on the spectroscopic observations with the james webb space telescope of one of these objects that is quite different from the rest; selected by it having much redder colours. we see spectral features typical of much older stellar populations and detailed modeling shows that they formed at least 1.5 billion years earlier in time $z \gtrsim 11$ in a rapid star formation event. dark matter halos massive enough to host these ancestors ought not to have assembled at this time. this observation may point to a significant gap in our understanding of early stellar populations, galaxy formation and/or the nature of dark matter. | an extraordinarily massive galaxy that formed its stars at $z \\gtrsim 11$ |
we have established precise planet radii, semimajor axes, incident stellar fluxes, and stellar masses for 909 planets in 355 multi-planet systems discovered by kepler. in this sample, we find that planets within a single multi-planet system have correlated sizes: each planet is more likely to be the size of its neighbor than a size drawn at random from the distribution of observed planet sizes. in systems with three or more planets, the planets tend to have a regular spacing: the orbital period ratios of adjacent pairs of planets are correlated. furthermore, the orbital period ratios are smaller in systems with smaller planets, suggesting that the patterns in planet sizes and spacing are linked through formation and/or subsequent orbital dynamics. yet, we find that essentially no planets have orbital period ratios smaller than 1.2, regardless of planet size. using empirical mass-radius relationships, we estimate the mutual hill separations of planet pairs. we find that 93% of the planet pairs are at least 10 mutual hill radii apart, and that a spacing of ∼20 mutual hill radii is most common. we also find that when comparing planet sizes, the outer planet is larger in 65% ± 0.4% of cases, and the typical ratio of the outer to inner planet size is positively correlated with the temperature difference between the planets. this could be the result of photo-evaporation. based on observations obtained at the w. m. keck observatory, which is operated jointly by the university of california and the california institute of technology. keck time has been granted by the university of california, and california institute of technology, and the university of hawaii. | the california-kepler survey. v. peas in a pod: planets in a kepler multi-planet system are similar in size and regularly spaced |
we introduce a new model for the structure and evolution of the gas in galactic discs. in the model the gas is in vertical pressure and energy balance. star formation feedback injects energy and momentum, and non-axisymmetric torques prevent the gas from becoming more than marginally gravitationally unstable. from these assumptions we derive the relationship between galaxies' bulk properties (gas surface density, stellar content, and rotation curve) and their star formation rates, gas velocity dispersions, and rates of radial inflow. we show that the turbulence in discs can be powered primarily by star formation feedback, radial transport, or a combination of the two. in contrast to models that omit either radial transport or star formation feedback, the predictions of this model yield excellent agreement with a wide range of observations, including the star formation law measured in both spatially resolved and unresolved data, the correlation between galaxies' star formation rates and velocity dispersions, and observed rates of radial inflow. the agreement holds across a wide range of galaxy mass and type, from local dwarfs to extreme starbursts to high-redshift discs. we apply the model to galaxies on the star-forming main sequence, and show that it predicts a transition from mostly gravity-driven turbulence at high redshift to star-formation-driven turbulence at low redshift. this transition and the changes in mass transport rates that it produces naturally explain why galaxy bulges tend to form at high redshift and discs at lower redshift, and why galaxies tend to quench inside-out. | a unified model for galactic discs: star formation, turbulence driving, and mass transport |
the new era of gravitational wave astronomy truly began on september 14, 2015, with the detection of gw150914, the sensational first direct observation of gravitational waves from the inspiral and merger of two black holes by the two advanced ligo detectors. in the subsequent first three observing runs of the ligo-virgo network, gravitational waves from ∼50 compact binary mergers have been announced, with more results to come. the events have mostly been produced by binary black holes, but two binary neutron star mergers have been observed thus far, as well as the mergers of two neutron star-black hole systems. furthermore, gravitational waves emitted by core-collapse supernovae, pulsars, and the stochastic gravitational wave background are within the ligo-virgo-kagra sensitivity band and are likely to be observed in future observation runs. beyond signal detection, a major challenge has been the development of statistical and computational methodology for estimating the physical waveform parameters and quantifying their uncertainties in order to accurately characterize the emitting system. these methods depend on the sources of the gravitational waves and the gravitational waveform model that is used. this review examines the main waveform models and parameter estimation methods used to extract physical parameters from gravitational wave signals detected to date by ligo and virgo and from those expected to be observed in the future, which will include kagra, and how these methods interface with various aspects of ligo-virgo-kagra science. also presented are the statistical methods used by ligo and virgo to estimate detector noise, test general relativity, and draw conclusions about the rates of compact binary mergers in the universe. furthermore, a summary of major publicly available gravitational wave parameter estimation software packages is given. | parameter estimation with gravitational waves |
previous studies based on the analysis of gaia dr2 data have revealed that accreted stars, possibly originating from a single progenitor satellite, are a significant component of the halo of our galaxy, potentially constituting most of the halo stars at [fe/h] < -1 within a few kpc from the sun and beyond. in this paper, we couple astrometric data from gaia dr2 with elemental abundances from apogee dr14 to characterise the kinematics and chemistry of in-situ and accreted populations up to [fe/h] ∼ -2. accreted stars appear to significantly impact the galactic chemo-kinematic relations, not only at [fe/h] < -1, but also at metallicities typical of the thick and metal-poor thin discs. they constitute about 60% of all stars at [fe/h] < -1, the remaining 40% being made of (metal-weak) thick-disc stars. we find that the stellar kinematic fossil record shows the imprint left by this accretion event, which heated the old galactic disc. we are able to age-date this kinematic imprint, showing that the accretion occurred between nine and 11 gyr ago, and that it led to the last significant heating of the galactic disc. an important fraction of stars with abundances typical of the (metal-rich) thick disc, and heated by this interaction, is now found in the galactic halo. indeed, about half of the kinematically defined halo at few kpc from the sun is composed of metal-rich thick-disc stars. moreover, we suggest that this metal-rich thick-disc component dominates the stellar halo of the inner galaxy. the new picture that emerges from this study is one where the standard, non-rotating in-situ halo population, the collapsed halo, seems to be more elusive than ever. | the milky way has no in-situ halo other than the heated thick disc. composition of the stellar halo and age-dating the last significant merger with gaia dr2 and apogee |
globular clusters are large and dense agglomerate of stars. at variance with smaller clusters of stars, they exhibit signs of some chemical evolution. at least for this reason, they are intermediate between open clusters and massive objects such as nuclear clusters or compact galaxies. while some facts are well established, the increasing amount of observational data are revealing a complexity that has so far defied the attempts to interpret the whole data set in a simple scenario. we review this topic focusing on the main observational features of clusters in the milky way and its satellites. we find that most of the observational facts related to the chemical evolution in globular clusters are described as being primarily a function of the initial mass of the clusters, tuned by further dependence on the metallicity—that mainly affects specific aspects of the nucleosynthesis processes involved—and on the environment, that likely determines the possibility of independent chemical evolution of the fragments or satellites, where the clusters form. we review the impact of multiple populations on different regions of the colour-magnitude diagram and underline the constraints related to the observed abundances of lithium, to the cluster dynamics, and to the frequency of binaries in stars of different chemical composition. we then re-consider the issues related to the mass budget and the relation between globular cluster and field stars. any successful model of globular cluster formation should explain these facts. | what is a globular cluster? an observational perspective |
in the context of the massive secondary object recently observed in the compact-star merger gw190814, we investigate the possibility of producing massive neutron stars from a few different equation of state models that contain exotic degrees of freedom, such as hyperons and quarks. our work shows that state-of-the-art relativistic mean-field models can generate massive stars reaching ≳2.05 msun , while being in good agreement with gravitational-wave events and x-ray pulsar observations, when quark vector interactions and nonstandard self-vector interactions are introduced. in particular, we present a new version of the chiral mean field (cmf) model in which a different quark-deconfinement potential allows for stable stars with a pure quark core. when rapid rotation is considered, our models generate stellar masses that approach, and in some cases surpass 2.5 msun . we find that in such cases fast rotation does not necessarily suppress exotic degrees of freedom due to changes in stellar central density, but require a larger amount of baryons than what is allowed in the nonrotating stars. this is not the case for pure quark stars, which can easily reach 2.5 msun and still possess approximately the same amount of baryons as stable nonrotating stars. we also briefly discuss possible origins for fast rotating stars with a large amount of baryons and their stability, showing how the event gw190814 can be associated with a star containing quarks as one of its progenitors. | gw190814 as a massive rapidly rotating neutron star with exotic degrees of freedom |
we investigate the internal structure and density profiles of haloes of mass 1010-1014 m⊙ in the evolution and assembly of galaxies and their environment (eagle) simulations. these follow the formation of galaxies in a λ cold dark matter universe and include a treatment of the baryon physics thought to be relevant. the eagle simulations reproduce the observed present-day galaxy stellar mass function, as well as many other properties of the galaxy population as a function of time. we find significant differences between the masses of haloes in the eagle simulations and in simulations that follow only the dark matter component. nevertheless, haloes are well described by the navarro-frenk-white density profile at radii larger than ∼5 per cent of the virial radius but, closer to the centre, the presence of stars can produce cuspier profiles. central enhancements in the total mass profile are most important in haloes of mass 1012-1013 m⊙, where the stellar fraction peaks. over the radial range where they are well resolved, the resulting galaxy rotation curves are in very good agreement with observational data for galaxies with stellar mass m* < 5 × 1010 m⊙. we present an empirical fitting function that describes the total mass profiles and show that its parameters are strongly correlated with halo mass. | baryon effects on the internal structure of λcdm haloes in the eagle simulations |
we present a critical assessment of the sn1987a supernova cooling bound on axions and other light particles. core collapse simulations used in the literature to substantiate the bound omitted from the calculation the envelope exterior to the proto-neutron star (pns). as a result, the only source of neutrinos in these simulations was, by construction, a cooling pns. we show that if the canonical delayed neutrino mechanism failed to explode sn1987a, and if the precollapse star was rotating, then an accretion disk would form that could explain the late-time (t ≳5 sec ) neutrino events. such accretion disk would be a natural feature if sn1987a was a collapse-induced thermonuclear explosion. axions do not cool the disk and do not affect its neutrino output, provided the disk is optically thin to neutrinos, as it naturally is. these considerations cast doubt on the supernova cooling bound. | is there a supernova bound on axions? |
stellar dynamos generate magnetic fields that are of fundamental importance to the variability and evolution of sun-like and low-mass stars, and for the development of their planetary systems. as a key to understanding stellar dynamos, empirical relations between stellar parameters and magnetic fields are required for comparison to ab initio predictions from dynamo models. we report measurements of surface-average magnetic fields in 292 m dwarfs from a comparison with radiative transfer calculations; for 260 of them, this is the first measurement of this kind. our data were obtained from more than 15 000 high-resolution spectra taken during the carmenes project. they reveal a relation between average field strength, ⟨b⟩, and rossby number, ro, resembling the well-studied rotation-activity relation. among the slowly rotating stars, we find that magnetic flux, φb, is proportional to rotation period, p, and among the rapidly rotating stars that average surface fields do not grow significantly beyond the level set by the available kinetic energy. furthermore, we find close relations between nonthermal coronal x-ray emission, chromospheric hα and ca h&k emission, and magnetic flux. taken together, these relations demonstrate empirically that the rotation-activity relation can be traced back to a dependence of the magnetic dynamo on rotation. we advocate the picture that the magnetic dynamo generates magnetic flux on the stellar surface proportional to rotation rate with a saturation limit set by the available kinetic energy, and we provide relations for average field strengths and nonthermal emission that are independent of the choice of the convective turnover time. we also find that ca h&k emission saturates at average field strengths of ⟨b⟩≈800 g while hα and x-ray emission grow further with stronger fields in the more rapidly rotating stars. this is in conflict with the coronal stripping scenario predicting that in the most rapidly rotating stars coronal plasma would be cooled to chromospheric temperatures. table b.1 is 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/662/a41 | magnetism, rotation, and nonthermal emission in cool stars. average magnetic field measurements in 292 m dwarfs |
pair instabilities in supernovae might prevent the formation of black holes with masses between ∼50 m⊙ and ∼130 m⊙ . multiple generations of black-hole mergers provide a possible way to populate this "mass gap" from below. however this requires an astrophysical environment with a sufficiently large escape speed to retain merger remnants, and prevent them from being ejected by gravitational-wave recoils. we show that, if the mass gap is indeed populated by multiple mergers, the observation of a single black-hole binary component in the mass gap implies that its progenitors grew in an environment with escape speed vesc≳50 km /s . this is larger than the escape speeds of most globular clusters, requiring denser and heavier environments such as nuclear star clusters or disks-assisted migration in galactic nuclei. a single detection in the upper mass gap would hint at the existence of a much larger population of first-generation events from the same environment, thus providing a tool to disentangle the contribution of different formation channels to the observed merger rate. | escape speed of stellar clusters from multiple-generation black-hole mergers in the upper mass gap |
the recent detection of gw190814 featured the merger of a binary with a primary having a mass of $\sim 23\, \mathrm{ m}_{\odot }$ and a secondary with a mass of $\sim 2.6\, \mathrm{ m}_{\odot }$ . while the primary was most likely a black hole, the secondary could be interpreted as either the lightest black hole or the most massive neutron star ever observed, but also as the indication of a novel class of exotic compact objects. we here argue that although the secondary in gw190814 is most likely a black hole at merger, it needs not be an ab-initio black hole nor an exotic object. rather, based on our current understanding of the nuclear-matter equation of state, it can be a rapidly rotating neutron star that collapsed to a rotating black hole at some point before merger. using universal relations connecting the masses and spins of uniformly rotating neutron stars, we estimate the spin, $0.49_{-0.05}^{+0.08} \lesssim \chi \lesssim 0.68_{-0.05}^{+0.11}$ , of the secondary - a quantity not constrained so far by the detection - and a novel strict lower bound on the maximum mass, $m_{_{\mathrm{tov}}}\gt 2.08^{+0.04}_{-0.04}\, \, \mathrm{ m}_{\odot }$ and an optimal bound of $m_{_{\mathrm{tov}}}\gt 2.15^{+0.04}_{-0.04}\, \, \mathrm{ m}_{\odot }$ , of non-rotating neutron stars, consistent with recent observations of a very massive pulsar. the new lower bound also remains valid even in the less likely scenario in which the secondary neutron star never collapsed to a black hole. | a lower bound on the maximum mass if the secondary in gw190814 was once a rapidly spinning neutron star |
solar probe cup (spc) is a faraday cup instrument on board nasa's parker solar probe (psp) spacecraft designed to make rapid measurements of thermal coronal and solar wind plasma. the spacecraft is in a heliocentric orbit that takes it closer to the sun than any previous spacecraft, allowing measurements to be made where the coronal and solar wind plasma is being heated and accelerated. the spc instrument was designed to be pointed directly at the sun at all times, allowing the solar wind (which is flowing primarily radially away from the sun) to be measured throughout the orbit. the instrument is capable of measuring solar wind ions with an energy between 100 and 6000 v (protons with speeds from 139 to 1072 km s-1). it also measures electrons with an energy/charge between 100 and 1500 v. spc has been designed to have a wide dynamic range that is capable of measuring protons and alpha particles at the closest perihelion (9.86 solar radii from the center of the sun) and out to 0.25 au. initial observations from the first orbit of psp indicate that the instrument is functioning well. | the solar probe cup on the parker solar probe |
contact. the star formation rate (sfr) in high-redshift galaxies is expected due to competing physical processes. this stochastic variability might boost the luminosity of galaxies and might explain the over-abundance seen at z ≳ 10 by the james webb space telescope.aims: we quantify the amplitude and timescales of this variability and identify the key physical processes.methods: we selected 245 z = 7.7 galaxies with stellar mass 5 × 106 ≲ m⋆/m⊙ ≲ 5 × 1010 from serra, which is a suite of high-resolution radiation-hydrodynamic cosmological simulations. after fitting the average sfr trend, ⟨sfr⟩, we quantified the time-dependent variation, δ(t)≡log[sfr/⟨sfr⟩], for each system and performed a periodogram analysis to search for periodicity modulations.results: we find that δ(t) is distributed as a zero-mean gaussian, with standard deviation σδ ≃ 0.24 (corresponding to a uv magnitude s.d. σuv ≃ 0.61) that is independent of m⋆. however, the modulation timescale increases with stellar mass: tδ ∼ (9, 50, 100) myr for m⋆ ∼ (0.1, 1, 5)×109 m⊙, respectively. these timescales are imprinted on the sfr by different processes: (i) photoevaporation, (ii) supernova explosions, and (iii) cosmological accretion/merging dominating in low-, intermediate-, and high-mass systems, respectively.conclusions: the predicted sfr variations cannot account for the required z ≳ 10 uv luminosity function boost. other processes, such as radiation-driven outflows clearing the dust, must then be invoked to explain the enhanced luminosity of super-early systems. | stochastic star formation in early galaxies: implications for the james webb space telescope |
in this work we have extended the maurya-gupta isotropic fluid solution to einstein field equations to an aniso-tropic domain. to do so, we have employed the gravitational decoupling via the minimal geometric deformation approach. the present model is representing the strange star candidate lmc x-4. a mathematical, physical and graphical analysis, shown that the obtained model fulfills all the criteria to be an admissible solution of the einstein field equations. specifically, we have analyzed the regularity of the metric potentials and the effective density, radial and tangential pressures within the object, causality condition, energy conditions, equilibrium via tolman-oppenheimer-volkoff equation and the stability of the model by means of the adiabatic index and the square of subliminal sound speeds. | generalized relativistic anisotropic compact star models by gravitational decoupling |
organic–inorganic hybrid perovskite materials are receiving increasing attention and becoming star materials on account of their unique and intriguing optical and electrical properties, such as high molar extinction coefficient, wide absorption spectrum, low excitonic binding energy, ambipolar carrier transport property, long carrier diffusion length, and high defects tolerance. although a high power conversion efficiency (pce) of up to 22.7% is certified for perovskite solar cells (pscs), it is still far from the theoretical shockley–queisser limit efficiency (30.5%). obviously, trap‑assisted nonradiative (also called shockley–read–hall, srh) recombination in perovskite films and interface recombination should be mainly responsible for the above efficiency distance. here, recent research advancements in suppressing bulk srh recombination and interface recombination are systematically investigated. for reducing srh recombination in the films, engineering perovskite composition, additives, dimensionality, grain orientation, nonstoichiometric approach, precursor solution, and post‑treatment are explored. the focus herein is on the recombination at perovskite/electron‑transporting material and perovskite/hole‑transporting material interfaces in normal or inverted pscs. strategies for suppressing bulk and interface recombination are described. additionally, the effect of trap‑assisted nonradiative recombination on hysteresis and stability of pscs is discussed. finally, possible solutions and reasonable prospects for suppressing recombination losses are presented. | causes and solutions of recombination in perovskite solar cells |
the radius distribution of small, close-in exoplanets has recently been shown to be bimodal. the photoevaporation model predicted this bimodality. in the photoevaporation scenario, some planets are completely stripped of their primordial h/he atmospheres, whereas others retain them. comparisons between the photoevaporation model and observed planetary populations have the power to unveil details of the planet population inaccessible by standard observations, such as the core mass distribution and core composition. in this work, we present a hierarchical inference analysis on the distribution of close-in exoplanets using forward models of photoevaporation evolution. we use this model to constrain the planetary distributions for core composition, core mass, and initial atmospheric mass fraction. we find that the core-mass distribution is peaked, with a peak-mass of ~4m⊕. the bulk core-composition is consistent with a rock/iron mixture that is ice-poor and 'earth-like'; the spread in core-composition is found to be narrow ($\lesssim 16{{\ \rm per\ cent}}$ variation in iron-mass fraction at the 2σ level) and consistent with zero. this result favours core formation in a water/ice poor environment. we find the majority of planets accreted a h/he envelope with a typical mass fraction of $\sim 4{{\ \rm per\ cent}}$; only a small fraction did not accrete large amounts of h/he and were 'born-rocky'. we find four times as many super-earths were formed through photoevaporation, as formed without a large h/he atmosphere. finally, we find core-accretion theory overpredicts the amount of h/he cores would have accreted by a factor of ~5, pointing to additional mass-loss mechanisms (e.g. 'boil-off') or modifications to core-accretion theory. | unveiling the planet population at birth |
the phangs program is building the first data set to enable the multiphase, multiscale study of star formation across the nearby spiral galaxy population. this effort is enabled by large survey programs with the atacama large millimeter/submillimeter array (alma), muse on the very large telescope, and the hubble space telescope (hst), with which we have obtained co(2-1) imaging, optical spectroscopic mapping, and high-resolution uv-optical imaging, respectively. here, we present phangs-hst, which has obtained nuv-u-b-v-i imaging of the disks of 38 spiral galaxies at distances of 4-23 mpc, and parallel v- and i-band imaging of their halos, to provide a census of tens of thousands of compact star clusters and multiscale stellar associations. the combination of hst, alma, and vlt/muse observations will yield an unprecedented joint catalog of the observed and physical properties of ~100,000 star clusters, associations, h ii regions, and molecular clouds. with these basic units of star formation, phangs will systematically chart the evolutionary cycling between gas and stars across a diversity of galactic environments found in nearby galaxies. we discuss the design of the phangs-hst survey and provide an overview of the hst data processing pipeline and first results. we highlight new methods for selecting star cluster candidates, morphological classification of candidates with convolutional neural networks, and identification of stellar associations over a range of physical scales with a watershed algorithm. we describe the cross-observatory imaging, catalogs, and software products to be released. the phangs high-level science products will seed a broad range of investigations, in particular, the study of embedded stellar populations and dust with the james webb space telescope, for which a phangs cycle 1 treasury program to obtain eight-band 2-21 μm imaging has been approved. | the phangs-hst survey: physics at high angular resolution in nearby galaxies with the hubble space telescope |
the gaia early data release 3 has delivered exquisite astrometric data for 1.47 billion sources, which is revolutionizing many fields in astronomy. for a small fraction of these sources, the astrometric solutions are poor, and the reported values and uncertainties may not apply. before any analysis, it is important to recognize and excise these spurious results - this is commonly done by means of quality flags in the gaia catalogue. here, we devise a means of separating 'good' from 'bad' astrometric solutions that is an order of magnitude cleaner than any single flag: 99.3 per cent pure and 97.3 per cent complete, as validated on our test data. we devise an extensive sample of manifestly bad astrometric solutions, with parallax that is negative at ≥4.5σ; and a corresponding sample of presumably good solutions, including sources in healpix pixels on the sky that do not contain such negative parallaxes, and sources that fall on the main sequence in a colour-absolute magnitude diagram. we then train a neural network that uses 17 pertinent gaia catalogue entries and information about nearby sources to discriminate between these two samples, captured in a single 'astrometric fidelity' parameter. a diverse set of verification tests shows that our approach works very cleanly, including for sources with positive parallaxes. the main limitations of our approach are in the very low signal-to-noise ratio and the crowded regime. our astrometric fidelities for all of edr3 can be queried via the virtual observatory, our code and data are public. | a classifier for spurious astrometric solutions in gaia edr3 |
using numerical hydrodynamics calculations and a novel method for densely sampling parameter space, we measure the accretion and torque on a binary system from a circumbinary disk. in agreement with some earlier studies, we find that the net torque on the binary is positive for mass ratios close to unity, and that accretion always drives the binary toward equal mass. accretion variability depends sensitively on the numerical sink prescription, but the torque and relative accretion onto each component do not depend on the sink timescale. positive torque and highly variable accretion occurs only for mass ratios greater than around 0.05. this means that for mass ratios below 0.05, the binary would migrate inward until the secondary accreted sufficient mass, after which it would execute a u-turn and migrate outward. we explore a range of viscosities, from α = 0.03 to α = 0.15, and find that this outward torque is proportional to the viscous torque, so that torque per unit accreted mass is independent of α. dependence of accretion and torque on mass ratio is explored in detail, densely sampling mass ratios between 0.01 and unity. for mass ratio q > 0.2, accretion variability is found to exhibit a distinct sawtooth pattern, typically with a five-orbit cycle that provides a smoking gun prediction for variable quasars observed over long periods, as a potential means to confirm the presence of a binary. | circumbinary disks: accretion and torque as a function of mass ratio and disk viscosity |
we present a measurement of the hubble constant h0 from surface brightness fluctuation (sbf) distances for 63 bright, mainly early-type galaxies out to 100 mpc observed with the wfc3/ir on the hubble space telescope (hst). the sample is drawn from several independent hst imaging programs using the f110w bandpass, with the majority of the galaxies being selected from the massive survey. the distances reach the hubble flow with a median statistical uncertainty per measurement of 4%. we construct the hubble diagram with these ir sbf distances and constrain h0 using four different treatments of the galaxy velocities. for the sbf zero-point calibration, we use both the existing tie to cepheid variables, updated for consistency with the latest determination of the distance to the large magellanic cloud from detached eclipsing binaries, and a new tie to the tip of the red giant branch (trgb) calibrated from the maser distance to ngc 4258. these two sbf calibrations are consistent with each other and with theoretical predictions from stellar population models. from a weighted average of the cepheid and trgb calibrations, we derive h0 = 73.3 ± 0.7 ± 2.4 km s-1 mpc-1, where the error bars reflect the statistical and systematic uncertainties. this result accords well with recent measurements of h0 from type ia supernovae, time delays in multiply lensed quasars, and water masers. the systematic uncertainty could be reduced to below 2% by calibrating the sbf method with precision trgb distances for a statistical sample of massive early-type galaxies out to the virgo cluster measured with the james webb space telescope. * based on observations with the nasa/esa hubble space telescope, obtained at the space telescope science institute, which is operated by aura, inc., under nasa contract nas5-26555. these observations come from go programs #11711, #11712, #12450, #14219, #14654, #14771, #14804, #15265, #15329. | the hubble constant from infrared surface brightness fluctuation distances |
we report our spitzer space telescope observations and detections of the binary neutron star merger gw170817. at 4.5 μm, gw170817 is detected at 21.9 mag ab at +43 days and 23.9 mag ab at +74 days after merger. at 3.6 μm, gw170817 is not detected to a limit of 23.2 mag ab at +43 days and 23.1 mag ab at +74 days. our detections constitute the latest and reddest constraints on the kilonova/macronova emission and composition of heavy elements. the 4.5 μm luminosity at this late phase cannot be explained by elements exclusively from the first abundance peak of the r-process. moreover, the steep decline in the spitzer band, with a power-law index of 3.4 ± 0.2, can be explained by a few of the heaviest isotopes with half-life around 14 d dominating the luminosity (e.g. 140ba, 143pr, 147nd, 156eu, 191os, 223ra, 225ra, 233pa, 234th) or a model with lower deposition efficiency. this data offers evidence that the heaviest elements in the second and third r-process abundance peak were indeed synthesized. our conclusion is verified by both analytics and network simulations and robust despite intricacies and uncertainties in the nuclear physics. future observations with spitzer and james webb space telescope will further illuminate the relative abundance of the synthesized heavy elements. | spitzer mid-infrared detections of neutron star merger gw170817 suggests synthesis of the heaviest elements |
we present results from the first population synthesis study of protostellar discs. we analyse the evolution and properties of a large sample of protostellar discs formed in a radiation hydrodynamical simulation of star cluster formation. due to the chaotic nature of the star formation process, we find an enormous diversity of young protostellar discs, including misaligned discs, and discs whose orientations vary with time. star-disc interactions truncate discs and produce multiple systems. discs may be destroyed in dynamical encounters and/or through ram-pressure stripping, but reform by later gas accretion. we quantify the distributions of disc mass and radii for protostellar ages up to ≈105 yr. for low-mass protostars, disc masses tend to increase with both age and protostellar mass. disc radii range from of order 10 to a few hundred au, grow in size on time-scales ≲ 104 yr, and are smaller around lower mass protostars. the radial surface density profiles of isolated protostellar discs are flatter than the minimum mass solar nebula model, typically scaling as σ ∝ r-1. disc to protostar mass ratios rarely exceed two, with a typical range of md/m* = 0.1-1 to ages ≲ 104 yr and decreasing thereafter. we quantify the relative orientation angles of circumstellar discs and the orbit of bound pairs of protostars, finding a preference for alignment that strengths with decreasing separation. we also investigate how the orientations of the outer parts of discs differ from the protostellar and inner disc spins for isolated protostars and pairs. | on the diversity and statistical properties of protostellar discs |
we present galaxy stellar mass functions (gsmfs) at z = 4-8 from a rest-frame ultraviolet (uv) selected sample of ∼4500 galaxies, found via photometric redshifts over an area of ∼280 arcmin2 in the cosmic assembly near-infrared deep extragalactic legacy survey (candels)/great observatories origins deep survey (goods) fields and the hubble ultra deep field. the deepest spitzer/irac data to date and the relatively large volume allow us to place a better constraint at both the low- and high-mass ends of the gsmfs compared to previous space-based studies from pre-candels observations. supplemented by a stacking analysis, we find a linear correlation between the rest-frame uv absolute magnitude at 1500 å ({m}{{uv}}) and logarithmic stellar mass ({log}{m}* ) that holds for galaxies with {log}({m}* /{m}⊙ )≲ 10. we use simulations to validate our method of measuring the slope of the {log}{m}* -m uv relation, finding that the bias is minimized with a hybrid technique combining photometry of individual bright galaxies with stacked photometry for faint galaxies. the resultant measured slopes do not significantly evolve over z = 4-8, while the normalization of the trend exhibits a weak evolution toward lower masses at higher redshift. we combine the {log}{m}* -m uv distribution with observed rest-frame uv luminosity functions at each redshift to derive the gsmfs, finding that the low-mass-end slope becomes steeper with increasing redshift from α =-{1.55}-0.07+0.08 at z = 4 to α =-{2.25}-0.35+0.72 at z = 8. the inferred stellar mass density, when integrated over {m}* ={10}8-1013 m ⊙, increases by a factor of {10}-2+30 between z = 7 and z = 4 and is in good agreement with the time integral of the cosmic star formation rate density. | the evolution of the galaxy stellar mass function at z = 4-8: a steepening low-mass-end slope with increasing redshift |
we include a fully coupled treatment of metal and dust enrichment into the delphi semi-analytic model of galaxy formation to explain the dust content of 13 lyman break galaxies (lbgs) detected by the atacama large millimetre array (alma) rebels large program at z ≃ 7. we find that the galaxy dust mass, md, is regulated by the combination of type ii supernova dust production, astration, shock destruction, and ejection in outflows; grain growth (with a standard time-scale τ0 = 30 myr) plays a negligible role. the model predicts a dust-to-stellar mass ratio of $\sim 0.07\!-\!0.1{{\ \rm per\ cent}}$ and a uv-to-total star formation rate relation such that log(ψuv) = -0.05 [log(ψ)]2 + 0.86 log(ψ) - 0.05 (implying that 55-80 per cent of the star formation is obscured) for rebels galaxies with stellar mass $m_* = 10^{9}\!-\!10^{10} \rm m_\odot$. this relation reconciles the intrinsic uv luminosity of lbgs with their observed luminosity function at z = 7. however, 2 out of the 13 systems show dust-to-stellar mass ratios ($\sim 0.94\!-\!1.1{{\ \rm per\ cent}}$) that are up to 18 times larger than expected from the fiducial relation. due to the physical coupling between dust and metal enrichment, even decreasing τ0 to very low values (0.3 myr) only increases the dust-to-stellar mass ratio by a factor of ~2. given that grain growth is not a viable explanation for such high observed ratios of the dust-to-stellar mass, we propose alternative solutions. | the alma rebels survey: the dust content of z 7 lyman break galaxies |
the california-kepler survey (cks) is an observational program developed to improve our knowledge of the properties of stars found to host transiting planets by nasa’s kepler mission. the improvement stems from new high-resolution optical spectra obtained using hires at the w. m. keck observatory. the cks stellar sample comprises 1305 stars classified as kepler objects of interest, hosting a total of 2075 transiting planets. the primary sample is magnitude-limited ({kp}< 14.2) and contains 960 stars with 1385 planets. the sample was extended to include some fainter stars that host multiple planets, ultra-short period planets, or habitable zone planets. the spectroscopic parameters were determined with two different codes, one based on template matching and the other on direct spectral synthesis using radiative transfer. we demonstrate a precision of 60 k in {t}{eff}, 0.10 dex in {log}g, 0.04 dex in [{fe}/{{h}}], and 1.0 {km} {{{s}}}-1 in v\sin i. in this paper, we describe the cks project and present a uniform catalog of spectroscopic parameters. subsequent papers in this series present catalogs of derived stellar properties such as mass, radius, and age; revised planet properties; and statistical explorations of the ensemble. cks is the largest survey to determine the properties of kepler stars using a uniform set of high-resolution, high signal-to-noise ratio spectra. the hires spectra are available to the community for independent analyses. based on observations obtained at the w. m. keck observatory, which is operated jointly by the university of california and the california institute of technology. keck time was granted for this project by the university of california, and california institute of technology, the university of hawaii, and nasa. | the california-kepler survey. i. high-resolution spectroscopy of 1305 stars hosting kepler transiting planets |
in this article, we attempt to find a singularity free solution of einstein's field equations for compact stellar objects, precisely strange (quark) stars, considering schwarzschild metric as the exterior spacetime. to this end, we consider that the stellar object is spherically symmetric, static and anisotropic in nature and follows the density profile given by mak and harko (2002) , which satisfies all the physical conditions. to investigate different properties of the ultra-dense strange stars we have employed the mit bag model for the quark matter. our investigation displays an interesting feature that the anisotropy of compact stars increases with the radial coordinate and attains its maximum value at the surface which seems an inherent property for the singularity free anisotropic compact stellar objects. in this connection we also perform several tests for physical features of the proposed model and show that these are reasonably acceptable within certain range. further, we find that the model is consistent with the energy conditions and the compact stellar structure is stable with the validity of the tov equation and herrera cracking concept. for the masses below the maximum mass point in mass vs radius curve the typical behavior achieved within the framework of general relativity. we have calculated the maximum mass and radius of the strange stars for the three finite values of bag constant bg. | relativistic model for anisotropic strange stars |
i review the spatially resolved spectroscopic properties of low-redshift star-forming galaxies (and their retired counterparts) using results from the most recent optical integral field spectroscopy galaxy surveys. first, i briefly summarize the global spectroscopic properties of these galaxies, discussing the main ionization processes and the global relations described by the star-formation rates, gas-phase oxygen abundances, and average properties of their stellar populations (age and metallicity) in comparison with the stellar mass. second, i present the local distribution of the ionizing processes down to kiloparsec scales, and i show how the global scaling relations found using integrated parameters (like the star-formation main sequence, mass-metallicity relation, and schmidt-kennicutt law) have local/resolved counterparts, with the global ones being, for the most part, just integrated/average versions of the local ones. i discuss the local/resolved star-formation histories (sfhs) and chemical-enrichment histories and their implications on the inside-out growth of galaxies. third, i present the radial distributions of the surface densities of the properties explored globally and how they depend on the integrated galaxy properties. in conclusion, i find that the evolution of galaxies is mostly governed by local processes but clearly affected by global ones: many global scaling relations present resolved counterparts (verified down to kiloparsec scales) that can explain them as well as the observed radial gradients in galaxies. these relations are consequences of the local sfhs, the narrow range of the depletion times, and a local metal enrichment. deviations from these relations are due to dynamical and mixing processes, local exchange of gas (inflows, outflows, and fountains), depletion time differences, and/or differences in the resolved sfhs. ionization happens at local scales that may be driven by different physical processes, and it cannot be clearly understood using purely integrated quantities. the dominant ionization in galaxies has a stellar origin. | spatially resolved spectroscopic properties of low-redshift star-forming galaxies |
the merger of neutron stars drives a relativistic jet which can be observed as a short gamma-ray burst. a strong large-scale magnetic field is necessary to launch the relativistic jet. however, the magnetohydrodynamical mechanism to build up this magnetic field remains uncertain. here we show that the $\alpha\omega$ dynamo mechanism driven by the magnetorotational instability builds up the large-scale magnetic field inside the long-lived binary neutron star merger remnant by performing an {\it ab initio} super-high resolution neutrino-radiation magnetohydrodynamics merger simulation in full general relativity. as a result, the magnetic field induces the poynting-flux dominated relativistic outflow with the luminosity $\sim 10^{51}$\,erg/s and magnetically-driven post-merger mass ejection with the mass $\sim 0.1m_\odot$. therefore, the magnetar scenario in binary neutron star mergers is possible. these can be the engines of short-hard gamma-ray bursts and very bright kilonovae. therefore, this scenario is testable in future observation. | a large-scale magnetic field via $\\alpha\\omega$ dynamo in binary neutron star mergers |
we present results of a spectroscopic survey for new k- and m-type members of scorpius-centaurus (sco-cen), the nearest ob association (∼100-200 pc). using an x-ray, proper motion and colour-magnitude selected sample, we obtained spectra for 361 stars, for which we report spectral classifications and li and hα equivalent widths. we identified 156 new members of sco-cen, and recovered 51 previously published members. we have combined these with previously known members to form a sample of 493 solar-mass (∼0.7-1.3 m⊙) members of sco-cen. we investigated the star formation history of this sample, and re-assessed the ages of the massive main-sequence turn-off and the g-type members in all three subgroups. we performed a census for circumstellar discs in our sample using wise infrared data and find a protoplanetary disc fraction for k-type stars of 4.4^{+1.6}_{-0.9} per cent for upper centaurus-lupus and lower centaurus-crux at ∼16 myr and 9.0^{+4.0}_{-2.2} per cent for upper scorpius at ∼10 myr. these data are consistent with a protoplanetary disc e-folding time-scale of ∼4-5 myr for ∼1 m⊙ stars, twice that previously quoted, but consistent with the bell et al. revised age scale of young clusters. finally, we construct an age map of scorpius-centaurus which clearly reveals substructure consisting of concentrations of younger and older stars. we find evidence for strong age gradients within all three subgroups. none of the subgroups are consistent with being simple, coeval populations which formed in single bursts, but likely represents a multitude of smaller star formation episodes of hundreds to tens of stars each. | the star formation history and accretion-disc fraction among the k-type members of the scorpius-centaurus ob association |
the galaxy evolution explorer (galex) imaged the sky in two ultraviolet (uv) bands, far-uv (fuv, λ eff ∼ 1528 å), and near-uv (nuv, λ eff ∼ 2310 å), delivering the first comprehensive sky surveys at these wavelengths. the galex database contains fuv and nuv images, ∼500 million source measurements and over 100,000 low-resolution uv spectra. the uv surveys are a unique resource for statistical studies of hot stellar objects, z ≲ 2 qsos, star-forming galaxies, nebulae and the interstellar medium, and provide a roadmap for planning future uv instrumentation and follow-up observing programs. we present science-enhanced, “clean” catalogs of galex uv sources, with useful tags to facilitate scientific investigations. the catalogs are an improved and expanded version of our previous catalogs of uv sources (bcscat). with respect to bcscat, we have patched 640 fields for which the pipeline had improperly coadded non-overlapping observations, and we provide a version with a larger sky coverage (about 10%) by relaxing the restriction to the central area of the galex field to 1.°1 diameter (guvcat_ais_fov055), as well as the cleaner, more restrictive version using only the 1° central portion of each field as in bcscat (guvcat_ais_fov050). we added new tags to facilitate selection and cleaning of statistical samples for science applications: we flag sources within the footprint of extended objects (nearby galaxies, stellar clusters) so that these regions can be excluded for estimating source density. as in our previous catalogs, in guvcat duplicate measurements of the same source are removed, so that each astrophysical object has only one entry. such a unique-source catalog is needed to study the density and distributions of sources, and to match uv sources with catalogs at other wavelengths. the catalog includes all observations from the all-sky imaging survey (ais), the survey with the largest area coverage, with both fuv and nuv detectors exposed: over 28,700 fields, made up of a total of 57,000 observations (“visits”). the total area covered, when overlaps are removed and gaps are accounted for, is 24,790 square degrees for guvcat_ais_fov055 (guvcat_ais_fov055) and 22,125 square degrees for (guvcat_ais_fov050). the total numbers of “unique” ais sources (eliminating duplicate measurements) are 82,992,086 ({guvcat}\ais\fov055) and 69,772,677 ({guvcat}\ais\fov050). the typical depth of the guvcat_ais catalog is fuv = 19.9, nuv = 20.8 ab mag. | revised catalog of galex ultraviolet sources. i. the all-sky survey: guvcat_ais |
a wealth of extragalactic populations completely missed at uv-optical wavelengths has been identified in the last decade, combining the deepest hst and spitzer observations. these dark sources are thought to be dusty and star-forming systems at 3 < z < 5, and major contributors to the stellar mass build up. in this letter, we report an investigation of the deep jwst survey in the smacs0723 cluster, analysing nircam and miri images. we search for sources in the f444w band that are undetected in the f200w catalogues. we characterize the properties of these sources via detailed spectral energy distribution (sed) modelling, accounting for a wide set of parameters and star formation histories, after a careful determination of their photometry. among a robust sample of 20 candidates, we identify a mixed population of very red sources. we highlight the identification of evolved systems, with stellar masses m* ~ 109-11 m⊙ at 8 < z < 13 characterized by unexpectedly important dust content at those epochs (av up to ~5.8 mag), challenging current model predictions. we further identify an extremely red source (f200w-f440w ~ 7 mag) that can be reproduced only by the spectrum of a passive, quenched galaxy of m* ~ 1011.56 m⊙ at z ~ 5, filled of dust (av ~ 5 mag). | jwst unveils heavily obscured (active and passive) sources up to z 13 |
we present a catalog of uniformly determined stellar properties and abundances for 1,617 f, g, and k stars using an automated spectral synthesis modeling procedure. all stars were observed using the hires spectrograph at keck observatory. our procedure used a single line list to fit model spectra to observations of all stars to determine effective temperature, surface gravity, metallicity, projected rotational velocity, and the abundances of 15 elements (c, n, o, na, mg, al, si, ca, ti, v, cr, mn, fe, ni, and y). sixty percent of the sample had hipparcos parallaxes and v-band photometry, which we combined with the spectroscopic results to obtain mass, radius, and luminosity. additionally, we used the luminosity, effective temperature, metallicity and α-element enhancement to interpolate in the yonsei-yale isochrones to derive mass, radius, gravity, and age ranges for those stars. finally, we determined new relations between effective temperature and macroturbulence for dwarfs and subgiants. our analysis achieved precisions of 25 k in {t}{eff}, 0.01 dex in [m/h], 0.028 dex for {log}g, and 0.5 km s-1 in v\sin i based on multiple observations of the same stars. the abundance results were similarly precise, between ∼0.01 and ∼0.04 dex, though trends with respect to {t}{eff} remained for which we derived empirical corrections. the trends, though small, were much larger than our uncertainties and are shared with published abundances. we show that changing our model atmosphere grid accounts for most of the trend in [m/h] between 5000 and 5500 k, indicating a possible problem with the atmosphere models or opacities. | spectral properties of cool stars: extended abundance analysis of 1,617 planet-search stars |
we present teobresums, a new effective-one-body (eob) waveform model for nonprecessing (spin-aligned) and tidally interacting compact binaries. spin-orbit and spin-spin effects are blended together by making use of the concept of centrifugal eob radius. the point-mass sector through merger and ringdown is informed by numerical relativity (nr) simulations of binary black holes (bbhs) computed with the spec and bam codes. an improved, nr-based phenomenological description of the postmerger waveform is developed. the tidal sector of teobresums describes the dynamics of neutron star binaries up to merger and incorporates a resummed attractive potential motivated by recent advances in the post-newtonian and gravitational self-force description of relativistic tidal interactions. equation-of-state-dependent self-spin interactions (monopole-quadrupole effects) are incorporated in the model using leading order post-newtonian results in a new expression of the centrifugal radius. teobresums is compared to 135 spec and 19 bam bbh waveforms. the maximum unfaithfulness to spec data f ¯—at design advanced ligo sensitivity and evaluated with total mass m with a variance of 10 m⊙≤m ≤200 m⊙—is always below 2.5 ×10-3 except for a single outlier that grazes the 7.1 ×10-3 level. when compared to bam data, f ¯ is smaller than 0.01 except for a single outlier in one of the corners of the nr-covered parameter space that reaches the 0.052 level. teobresums is also compatible, up to merger, to high-end nr waveforms from binary neutron stars with spin effects and reduced initial eccentricity computed with the bam and thc codes. the data quality of binary neutron star waveforms is assessed via rigorous convergence tests from multiple resolution runs and takes into account systematic effects estimated by using the two independent high-order nr codes. the model is designed to generate accurate templates for the analysis of ligo-virgo data through merger and ringdown. we demonstrate its use by analyzing the publicly available data for gw150914. | time-domain effective-one-body gravitational waveforms for coalescing compact binaries with nonprecessing spins, tides, and self-spin effects |
a central challenge in gravitational wave astronomy is identifying weak signals in the presence of non-stationary and non-gaussian noise. the separation of gravitational wave signals from noise requires good models for both. when accurate signal models are available, such as for binary neutron star systems, it is possible to make robust detection statements even when the noise is poorly understood. in contrast, searches for 'un-modeled' transient signals are strongly impacted by the methods used to characterize the noise. here we take a bayesian approach and introduce a multi-component, variable dimension, parameterized noise model that explicitly accounts for non-stationarity and non-gaussianity in data from interferometric gravitational wave detectors. instrumental transients (glitches) and burst sources of gravitational waves are modeled using a morlet-gabor continuous wavelet frame. the number and placement of the wavelets is determined by a trans-dimensional reversible jump markov chain monte carlo algorithm. the gaussian component of the noise and sharp line features in the noise spectrum are modeled using the bayesline algorithm, which operates in concert with the wavelet model. | bayeswave: bayesian inference for gravitational wave bursts and instrument glitches |
we report on the detailed analysis of a gravitationally lensed y-band dropout, a2744_yd4, selected from deep hubble space telescope imaging in the frontier field cluster abell 2744. band 7 observations with the atacama large millimeter/submillimeter array (alma) indicate the proximate detection of a significant 1 mm continuum flux suggesting the presence of dust for a star-forming galaxy with a photometric redshift of z≃ 8. deep x-shooter spectra confirms the high-redshift identity of a2744_yd4 via the detection of lyα emission at a redshift z = 8.38. the association with the alma detection is confirmed by the presence of [o iii] 88 μm emission at the same redshift. although both emission features are only significant at the 4σ level, we argue their joint detection and the positional coincidence with a high-redshift dropout in the hubble space telescope images confirms the physical association. analysis of the available photometric data and the modest gravitational magnification (μ ≃ 2) indicates a2744_yd4 has a stellar mass of ∼2 × 109 {m}⊙ , a star formation rate of ∼20 {m}⊙yr-1 and a dust mass of ∼6 × 106 {m}⊙ . we discuss the implications of the formation of such a dust mass only ≃ 200 {myr} after the onset of cosmic reionization. | dust in the reionization era: alma observations of a z = 8.38 gravitationally lensed galaxy |
we study the formation and the subsequent mass growth of axion stars inside axion miniclusters. numerically solving the schrödinger-poisson equations with realistic initial conditions we find that the axion stars exhibit similar properties to solitonic cores in ultralight bosonic dark matter halos in terms of their radial density profiles and large-amplitude oscillations. a merger of two axion stars confirms a previously found empirical law for the mass of the merged axion star. monitoring the axion star masses over time, we observe a mass growth consistent with the mass increase of bose stars in the kinetic regime reported by levkov et al., confirming that the mass evolution of axion stars can be understood in terms of wave condensation. based on this result, we predict a saturation of mass growth in relation to the minicluster mass consistent with the core-halo mass relation previously found for ultralight bosonic dark matter halos. | formation and mass growth of axion stars in axion miniclusters |
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