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we study bose-einstein condensation and the formation of bose stars in virialized dark matter halos and miniclusters by universal gravitational interactions. we prove that this phenomenon does occur and it is described by a kinetic equation. we give an expression for the condensation time. our results suggest that bose stars may form kinetically in mainstream dark matter models such as invisible qcd axions and fuzzy dark matter. | gravitational bose-einstein condensation in the kinetic regime |
gravitational-wave detections are enabling measurements of the rate of coalescences of binaries composed of two compact objects—neutron stars and/or black holes. the coalescence rate of binaries containing neutron stars is further constrained by electromagnetic observations, including galactic radio binary pulsars and short gamma-ray bursts. meanwhile, increasingly sophisticated models of compact objects merging through a variety of evolutionary channels produce a range of theoretically predicted rates. rapid improvements in instrument sensitivity, along with plans for new and improved surveys, make this an opportune time to summarise the existing observational and theoretical knowledge of compact-binary coalescence rates. | rates of compact object coalescences |
we present a systematic numerical relativity study of the mass ejection and the associated electromagnetic transients and nucleosynthesis from binary neutron star (ns) mergers. we find that a few 10-3 m ⊙ of material is ejected dynamically during the mergers. the amount and the properties of these outflows depend on binary parameters and on the ns equation of state (eos). a small fraction of these ejecta, typically ∼10-6 m ⊙, is accelerated by shocks formed shortly after merger to velocities larger than 0.6c and produces bright radio flares on timescales of weeks, months, or years after merger. their observation could constrain the strength with which the nss bounce after merger and, consequently, the eos of matter at extreme densities. the dynamical ejecta robustly produce second and third r-process peak nuclei with relative isotopic abundances close to solar. the production of light r-process elements is instead sensitive to the binary mass ratio and the neutrino radiation treatment. accretion disks of up to ∼0.2 m ⊙ are formed after merger, depending on the lifetime of the remnant. in most cases, neutrino- and viscously driven winds from these disks dominate the overall outflow. finally, we generate synthetic kilonova light curves and find that kilonovae depend on the merger outcome and could be used to constrain the ns eos. | binary neutron star mergers: mass ejection, electromagnetic counterparts, and nucleosynthesis |
banyan σ is a new bayesian algorithm to identify members of young stellar associations within 150 pc of the sun. it includes 27 young associations with ages in the range ∼1-800 myr, modeled with multivariate gaussians in six-dimensional (6d) xyzuvw space. it is the first such multi-association classification tool to include the nearest sub-groups of the sco-cen ob star-forming region, the ic 2602, ic 2391, pleiades and platais 8 clusters, and the ρ ophiuchi, corona australis, and taurus star formation regions. a model of field stars is built from a mixture of multivariate gaussians based on the besançon galactic model. the algorithm can derive membership probabilities for objects with only sky coordinates and proper motion, but can also include parallax and radial velocity measurements, as well as spectrophotometric distance constraints from sequences in color-magnitude or spectral type-magnitude diagrams. banyan σ benefits from an analytical solution to the bayesian marginalization integrals over unknown radial velocities and distances that makes it more accurate and significantly faster than its predecessor banyan ii. a contamination versus hit rate analysis is presented and demonstrates that banyan σ achieves a better classification performance than other moving group tools available in the literature, especially in terms of cross-contamination between young associations. an updated list of bona fide members in the 27 young associations, augmented by the gaia-dr1 release, as well as all parameters for the 6d multivariate gaussian models for each association and the galactic field neighborhood within 300 pc are presented. this new tool will make it possible to analyze large data sets such as the upcoming gaia-dr2 to identify new young stars. idl and python versions of banyan σ are made available with this publication, and a more limited online web tool is available at http://www.exoplanetes.umontreal.ca/banyan/banyansigma.php. | banyan. xi. the banyan σ multivariate bayesian algorithm to identify members of young associations with 150 pc |
interpreting high-energy, astrophysical phenomena, such as supernova explosions or neutron-star collisions, requires a robust understanding of matter at supranuclear densities. however, our knowledge about dense matter explored in the cores of neutron stars remains limited. fortunately, dense matter is not probed only in astrophysical observations, but also in terrestrial heavy-ion collision experiments. here we use bayesian inference to combine data from astrophysical multi-messenger observations of neutron stars1-9 and from heavy-ion collisions of gold nuclei at relativistic energies10,11 with microscopic nuclear theory calculations12-17 to improve our understanding of dense matter. we find that the inclusion of heavy-ion collision data indicates an increase in the pressure in dense matter relative to previous analyses, shifting neutron-star radii towards larger values, consistent with recent observations by the neutron star interior composition explorer mission5-8,18. our findings show that constraints from heavy-ion collision experiments show a remarkable consistency with multi-messenger observations and provide complementary information on nuclear matter at intermediate densities. this work combines nuclear theory, nuclear experiment and astrophysical observations, and shows how joint analyses can shed light on the properties of neutron-rich supranuclear matter over the density range probed in neutron stars. | constraining neutron-star matter with microscopic and macroscopic collisions |
this report addresses topics and questions of common interest in the fields of ultra-cold gases and nuclear physics in the context of the bcs-bec crossover. by this crossover, the phenomena of bardeen-cooper-schrieffer (bcs) superfluidity and bose-einstein condensation (bec), which share the same kind of spontaneous symmetry breaking, are smoothly connected through the progressive reduction of the size of the fermion pairs involved as the fundamental entities in both phenomena. this size ranges, from large values when cooper pairs are strongly overlapping in the bcs limit of a weak inter-particle attraction, to small values when composite bosons are non-overlapping in the bec limit of a strong inter-particle attraction, across the intermediate unitarity limit where the size of the pairs is comparable with the average inter-particle distance. the bcs-bec crossover has recently been realized experimentally, and essentially in all of its aspects, with ultra-cold fermi gases. this realization, in turn, has raised the interest of the nuclear physics community in the crossover problem, since it represents an unprecedented tool to test fundamental and unanswered questions of nuclear many-body theory. here, we focus on the several aspects of the bcs-bec crossover, which are of broad joint interest to both ultra-cold fermi gases and nuclear matter, and which will likely help to solve in the future some open problems in nuclear physics (concerning, for instance, neutron stars). similarities and differences occurring in ultra-cold fermi gases and nuclear matter will then be emphasized, not only about the relative phenomenologies but also about the theoretical approaches to be used in the two contexts. common to both contexts is the fact that at zero temperature the bcs-bec crossover can be described at the mean-field level with reasonable accuracy. at finite temperature, on the other hand, inclusion of pairing fluctuations beyond mean field represents an essential ingredient of the theory, especially in the normal phase where they account for precursor pairing effects. after an introduction to present the key concepts of the bcs-bec crossover, this report discusses the mean-field treatment of the superfluid phase, both for homogeneous and inhomogeneous systems, as well as for symmetric (spin- or isospin-balanced) and asymmetric (spin- or isospin-imbalanced) matter. pairing fluctuations in the normal phase are then considered, with their manifestations in thermodynamic and dynamic quantities. the last two sections provide a more specialized discussion of the bcs-bec crossover in ultra-cold fermi gases and nuclear matter, respectively. the separate discussion in the two contexts aims at cross communicating to both communities topics and aspects which, albeit arising in one of the two fields, share a strong common interest. | the bcs-bec crossover: from ultra-cold fermi gases to nuclear systems |
the evolution of the milky way disk, which contains most of the stars in the galaxy, is affected by several phenomena. for example, the bar and the spiral arms of the milky way induce radial migration of stars1 and can trap or scatter stars close to orbital resonances2. external perturbations from satellite galaxies can also have a role, causing dynamical heating of the galaxy3, ring-like structures in the disk4 and correlations between different components of the stellar velocity5. these perturbations can also cause `phase wrapping' signatures in the disk6-9, such as arched velocity structures in the motions of stars in the galactic plane. some manifestations of these dynamical processes have already been detected, including kinematic substructure in samples of nearby stars10-12, density asymmetries and velocities across the galactic disk that differ from the axisymmetric and equilibrium expectations13, especially in the vertical direction11,14-16, and signatures of incomplete phase mixing in the disk7,12,17,18. here we report an analysis of the motions of six million stars in the milky way disk. we show that the phase-space distribution contains different substructures with various morphologies, such as snail shells and ridges, when spatial and velocity coordinates are combined. we infer that the disk must have been perturbed between 300 million and 900 million years ago, consistent with estimates of the previous pericentric passage of the sagittarius dwarf galaxy. our findings show that the galactic disk is dynamically young and that modelling it as time-independent and axisymmetric is incorrect. | a dynamically young and perturbed milky way disk |
the general theory of relativity predicts that a star passing close to a supermassive black hole should exhibit a relativistic redshift. in this study, we used observations of the galactic center star s0-2 to test this prediction. we combined existing spectroscopic and astrometric measurements from 1995-2017, which cover s0-2’s 16-year orbit, with measurements from march to september 2018, which cover three events during s0-2’s closest approach to the black hole. we detected a combination of special relativistic and gravitational redshift, quantified using the redshift parameter ϒ. our result, ϒ = 0.88 ± 0.17, is consistent with general relativity (ϒ = 1) and excludes a newtonian model (ϒ = 0) with a statistical significance of 5σ. | relativistic redshift of the star s0-2 orbiting the galactic center supermassive black hole |
the presence of excess scatter in the ly-α forest at z ~ 5.5, together with the existence of sporadic extended opaque gunn-peterson troughs, has started to provide robust evidence for a late end of hydrogen reionization. however, low data quality and systematic uncertainties complicate the use of ly-α transmission as a precision probe of reionization's end stages. in this paper, we assemble a sample of 67 quasar sightlines at z > 5.5 with high signal-to-noise ratios of >10 per ≤15 km s-1 spectral pixel, relying largely on the new xqr-30 quasar sample. xqr-30 is a large program on vlt/x-shooter which obtained deep (snr > 20 per pixel) spectra of 30 quasars at z > 5.7. we carefully account for systematics in continuum reconstruction, instrumentation, and contamination by damped ly-α systems. we present improved measurements of the mean ly-α transmission over 4.9 < z < 6.1. using all known systematics in a forward modelling analysis, we find excellent agreement between the observed ly-α transmission distributions and the homogeneous-uvb simulations sherwood and nyx up to z ≤ 5.2 (<1σ), and mild tension (~2.5σ) at z = 5.3. homogeneous uvb models are ruled out by excess ly-α transmission scatter at z ≥ 5.4 with high confidence (>3.5σ). our results indicate that reionization-related fluctuations, whether in the uvb, residual neutral hydrogen fraction, and/or igm temperature, persist in the intergalactic medium until at least z = 5.3 (t = 1.1 gyr after the big bang). this is further evidence for a late end to reionization. | hydrogen reionization ends by z = 5.3: lyman-α optical depth measured by the xqr-30 sample |
the stellar initial mass function (imf) impacts nearly all observable properties of galaxies, controls the production rate of heavy elements, and governs how much energy is available to regulate galaxy growth. theoretical work predicts that the high-redshift imf may be more top-heavy compared to the local universe, due to higher gas pressures, a higher cosmic microwave background temperature, and lower metallicities. however, direct observational evidence for a top-heavy imf at high-redshift remains elusive. here we report the detection of two lyman-$\alpha$-emitting galaxies at redshift $5.9$ and $7.9$ that show evidence for exceptionally top-heavy imfs. our analysis of jwst/nirspec data demonstrates that these galaxies exhibit spectra which are completely dominated by the nebular continuum. alongside a clear balmer jump, we observe a steep turnover in the ultraviolet continuum. although this feature can be produced by an extremely thick damped lyman-$\alpha$ system with holes, we show instead that this turnover is two-photon emission from neutral hydrogen. two-photon emission can only dominate if the ionizing emissivity is $\gtrsim10\times$ that of a typical star-forming galaxy. while weak he~{\sc~ii} emission disfavours ionizing contributions from agn or x-ray binaries, such radiation fields can be produced in star clusters dominated by low-metallicity stars of $\gtrsim50\ {\rm m_{\odot}}$, where the imf is $10-30\times$ more top-heavy than typically assumed. such a top-heavy imf implies our understanding of star formation in the early universe and the sources of reionization may need revision. | nebular dominated galaxies in the early universe with top-heavy stellar initial mass functions |
we present bayesian analysis of galaxies for physical inference and parameter estimation, or bagpipes, a new python tool that can be used to rapidly generate complex model galaxy spectra and to fit these to arbitrary combinations of spectroscopic and photometric data using the multinest nested sampling algorithm. we extensively test our ability to recover realistic star formation histories (sfhs) by fitting mock observations of quiescent galaxies from the mufasa simulation. we then perform a detailed analysis of the sfhs of a sample of 9289 quiescent galaxies from ultravista with stellar masses, m* > 1010 m⊙ and redshifts 0.25 < z < 3.75. the majority of our sample exhibit sfhs that rise gradually then quench relatively rapidly over 1-2 gyr. this behaviour is consistent with recent cosmological hydrodynamic simulations, where agn-driven feedback in the low-accretion (jet) mode is the dominant quenching mechanism. at z > 1, we also find a class of objects with sfhs that rise and fall very rapidly, with quenching time-scales of <1 gyr, consistent with quasar-mode agn feedback. finally, at z < 1 we find a population with sfhs which quench more slowly than they rise, over >3 gyr, which we speculate to be the result of diminishing overall cosmic gas supply. we confirm the mass-accelerated evolution (downsizing) trend, and a trend towards more rapid quenching at higher stellar masses. however, our results suggest that the latter is a natural consequence of mass-accelerated evolution, rather than a change in quenching physics with stellar mass. we find 61 ± 8 per cent of z > 1.5 massive-quenched galaxies undergo significant further evolution by z = 0.5. bagpipes is available at bagpipes.readthedocs.io. | inferring the star formation histories of massive quiescent galaxies with bagpipes: evidence for multiple quenching mechanisms |
the earliest jwst observations have revealed an unexpected abundance of super-early (z > 10), massive ($m_*\, \approx 10^9 {\rm m}_{\odot }$ ) galaxies at the bright-end (muv ≈ -21) of the ultraviolet luminosity function (uv lf). we present a minimal physical model that explains the observed galaxy abundance at z = 10-14. the model primarily combines (i) the halo mass function, with (ii) an obscured star formation fraction prescription that is consistent with findings of the alma rebels dusty galaxy survey. it has been successfully tested on well-known uv lfs up to z = 7. we argue that the weak evolution from z = 7 to z ≈ 14 of the lf bright-end can arise from a conspiracy between a decreasing dust attenuation, making galaxies brighter, that almost exactly compensates for the increasing shortage of their host halos. our minimal model naturally reproduces the z = 10-14 lf if galaxies at $z\lower.5ex\rm{\,\, \buildrel\gt \over \sim \,\,}11$ contain a negligible amounts of dust. we speculate that dust could have been efficiently ejected during the very first phases of galaxy build-up. | on the stunning abundance of super-early, luminous galaxies revealed by jwst |
the galactic archaeology with hermes (galah) survey is a large high-resolution spectroscopic survey using the newly commissioned high efficiency and resolution multi-element spectrograph (hermes) on the anglo-australian telescope. the hermes spectrograph provides high-resolution (r ∼ 28 000) spectra in four passbands for 392 stars simultaneously over a 2 deg field of view. the goal of the survey is to unravel the formation and evolutionary history of the milky way, using fossil remnants of ancient star formation events which have been disrupted and are now dispersed throughout the galaxy. chemical tagging seeks to identify such dispersed remnants solely from their common and unique chemical signatures; these groups are unidentifiable from their spatial, photometric or kinematic properties. to carry out chemical tagging, the galah survey will acquire spectra for a million stars down to v ∼ 14. the hermes spectra of fgk stars contain absorption lines from 29 elements including light proton-capture elements, α-elements, odd-z elements, iron-peak elements and n-capture elements from the light and heavy s-process and the r-process. this paper describes the motivation and planned execution of the galah survey, and presents some results on the first-light performance of hermes. | the galah survey: scientific motivation |
we explore the kinematic gas properties of six $5.5<z<7.4$ galaxies in the jwst advanced deep extragalactic survey (jades), using high-resolution jwst/nirspec multi-object spectroscopy of the rest-frame optical emission lines [oiii] and h$\alpha$. the objects are small and of low stellar mass ($\sim 1\,$kpc; $m_*\sim10^{7-9}\,{\rm m_\odot}$), less massive than any galaxy studied kinematically at $z>1$ thus far. the cold gas masses implied by the observed star formation rates are $\sim 10\times$ larger than the stellar masses. we find that their ionised gas is spatially resolved by jwst, with evidence for broadened lines and spatial velocity gradients. using a simple thin-disc model, we fit these data with a novel forward modelling software that accounts for the complex geometry, point spread function, and pixellation of the nirspec instrument. we find the sample to include both rotation- and dispersion-dominated structures, as we detect velocity gradients of $v(r_{\rm e})\approx100-150\,{\rm km\,s^{-1}}$, and find velocity dispersions of $\sigma_0\approx 30-70\,{\rm km\,s^{-1}}$ that are comparable to those at cosmic noon. the dynamical masses implied by these models ($m_{\rm dyn}\sim10^{9-10}\,{\rm m_\odot}$) are larger than the stellar masses by up to a factor 40, and larger than the total baryonic mass (gas + stars) by a factor of $\sim 3$. qualitatively, this result is robust even if the observed velocity gradients reflect ongoing mergers rather than rotating discs. unless the observed emission line kinematics is dominated by outflows, this implies that the centres of these galaxies are dark-matter dominated or that star formation is $3\times$ less efficient, leading to higher inferred gas masses. | ionised gas kinematics and dynamical masses of $z\\gtrsim6$ galaxies from jades/nirspec high-resolution spectroscopy |
we report the discovery of 15 exceptionally luminous $10\lesssim z\lesssim14$ candidate galaxies discovered in the first 0.28 deg$^2$ of jwst/nircam imaging from the cosmos-web survey. these sources span rest-frame uv magnitudes of $-20.5>m_{\rm uv}>-22$, and thus constitute the most intrinsically luminous $z\gtrsim10$ candidates identified by jwst to-date. selected via nircam imaging with hubble acs/f814w, deep ground-based observations corroborate their detection and help significantly constrain their photometric redshifts. we analyze their spectral energy distributions using multiple open-source codes and evaluate the probability of low-redshift solutions; we conclude that 12/15 (80%) are likely genuine $z\gtrsim10$ sources and 3/15 (20%) likely low-redshift contaminants. three of our $z\sim12$ candidates push the limits of early stellar mass assembly: they have estimated stellar masses $\sim5\times10^{9}\,m_\odot$, implying an effective stellar baryon fraction of $\epsilon_{\star}\sim0.2-0.5$, where $\epsilon_{\star}\equiv m_{\star}/(f_{b}m_{halo})$. the assembly of such stellar reservoirs is made possible due to rapid, burst-driven star formation on timescales $<$100\,myr where the star-formation rate may far outpace the growth of the underlying dark matter halos. this is supported by the similar volume densities inferred for $m_\star\sim10^{10}\,m_\odot$ galaxies relative to $m_\star\sim10^{9}\,m_\odot$ -- both about $10^{-6}$ mpc$^{-3}$ -- implying they live in halos of comparable mass. at such high redshifts, the duty cycle for starbursts would be of order unity, which could cause the observed change in the shape of the uvlf from a double powerlaw to schechter at $z\approx8$. spectroscopic redshift confirmation and ensuing constraints of their masses will be critical to understanding how, and if, such early massive galaxies push the limits of galaxy formation in $\lambda$cdm. | cosmos-web: intrinsically luminous z$\\gtrsim$10 galaxy candidates test early stellar mass assembly |
the disk substructures at high angular resolution project (dsharp) used alma to map the 1.25 mm continuum of protoplanetary disks at a spatial resolution of ∼5 au. we present a systematic analysis of annular substructures in the 18 single-disk systems targeted in this survey. no dominant architecture emerges from this sample; instead, remarkably diverse morphologies are observed. annular substructures can occur at virtually any radius where millimeter continuum emission is detected and range in widths from a few astronomical units to tens of astronomical units. intensity ratios between gaps and adjacent rings range from near-unity to just a few percent. in a minority of cases, annular substructures coexist with other types of substructures, including spiral arms (3/18) and crescent-like azimuthal asymmetries (2/18). no clear trend is observed between the positions of the substructures and stellar host properties. in particular, the absence of an obvious association with stellar host luminosity (and hence the disk thermal structure) suggests that substructures do not occur preferentially near major molecular snowlines. annular substructures like those observed in dsharp have long been hypothesized to be due to planet-disk interactions. a few disks exhibit characteristics particularly suggestive of this scenario, including substructures in possible mean-motion resonance and “double gap” features reminiscent of hydrodynamical simulations of multiple gaps opened by a planet in a low-viscosity disk. | the disk substructures at high angular resolution project (dsharp). ii. characteristics of annular substructures |
the 2017 event horizon telescope (eht) observations of the central source in m87 have led to the first measurement of the size of a black-hole shadow. this observation offers a new and clean gravitational test of the black-hole metric in the strong-field regime. we show analytically that spacetimes that deviate from the kerr metric but satisfy weak-field tests can lead to large deviations in the predicted black-hole shadows that are inconsistent with even the current eht measurements. we use numerical calculations of regular, parametric, non-kerr metrics to identify the common characteristic among these different parametrizations that control the predicted shadow size. we show that the shadow-size measurements place significant constraints on deviation parameters that control the second post-newtonian and higher orders of each metric and are, therefore, inaccessible to weak-field tests. the new constraints are complementary to those imposed by observations of gravitational waves from stellar-mass sources. | gravitational test beyond the first post-newtonian order with the shadow of the m87 black hole |
we present a near-infrared spectral sequence of the electromagnetic counterpart to the binary neutron star merger gw170817 detected by advanced laser interferometer gravitational-wave observatory (ligo)/virgo. our data set comprises seven epochs of j+h spectra taken with flamingos-2 on gemini-south between 1.5 and 10.5 days after the merger. in the initial epoch, the spectrum is dominated by a smooth blue continuum due to a high-velocity, lanthanide-poor blue kilonova component. starting the following night, all of the subsequent spectra instead show features that are similar to those predicted in model spectra of material with a high concentration of lanthanides, including spectral peaks near 1.07 and 1.55 μm. our fiducial model with 0.04 m ⊙ of ejecta, an ejection velocity of v = 0.1c, and a lanthanide concentration of x lan = 10-2 provides a good match to the spectra taken in the first five days, although it over-predicts the late-time fluxes. we also explore models with multiple fitting components, in each case finding that a significant abundance of lanthanide elements is necessary to match the broad spectral peaks that we observe starting at 2.5 days after the merger. these data provide direct evidence that binary neutron star mergers are significant production sites of even the heaviest r-process elements. | the electromagnetic counterpart of the binary neutron star merger ligo/virgo gw170817. iv. detection of near-infrared signatures of r-process nucleosynthesis with gemini-south |
the kepler mission, combined with ground-based radial velocity (rv) follow-up and dynamical analyses of transit timing variations, has revolutionized the observational constraints on sub-neptune-sized planet compositions. the results of an extensive kepler follow-up program including multiple doppler measurements for 22 planet-hosting stars more than doubles the population of sub-neptune-sized transiting planets that have rv mass constraints. this unprecedentedly large and homogeneous sample of planets with both mass and radius constraints opens the possibility of a statistical study of the underlying population of planet compositions. we focus on the intriguing transition between rocky exoplanets (comprised of iron and silicates) and planets with voluminous layers of volatiles (h/he and astrophysical ices). applying a hierarchical bayesian statistical approach to the sample of kepler transiting sub-neptune planets with keck rv follow-up, we constrain the fraction of close-in planets (with orbital periods less than ∼50 days) that are sufficiently dense to be rocky, as a function of planet radius. we show that the majority of 1.6 {{r}\oplus } planets have too low density to be comprised of fe and silicates alone. at larger radii, the constraints on the fraction of rocky planets are even more stringent. these insights into the size demographics of rocky and volatile-rich planets offer empirical constraints to planet formation theories, and guide the range of planet radii to be considered in studies of the occurrence rate of “earth-like” planets, {{η }\oplus }. | most 1.6 earth-radius planets are not rocky |
we introduce a suite of 30 cosmological magneto-hydrodynamical zoom simulations of the formation of galaxies in isolated milky way mass dark haloes. these were carried out with the moving mesh code arepo, together with a comprehensive model for galaxy formation physics, including active galactic nuclei (agn) feedback and magnetic fields, which produces realistic galaxy populations in large cosmological simulations. we demonstrate that our simulations reproduce a wide range of present-day observables, in particular, two-component disc-dominated galaxies with appropriate stellar masses, sizes, rotation curves, star formation rates and metallicities. we investigate the driving mechanisms that set present-day disc sizes/scalelengths, and find that they are related to the angular momentum of halo material. we show that the largest discs are produced by quiescent mergers that inspiral into the galaxy and deposit high-angular momentum material into the pre-existing disc, simultaneously increasing the spin of dark matter and gas in the halo. more violent mergers and strong agn feedback play roles in limiting disc size by destroying pre-existing discs and by suppressing gas accretion on to the outer disc, respectively. the most important factor that leads to compact discs, however, is simply a low angular momentum for the halo. in these cases, agn feedback plays an important role in limiting central star formation and the formation of a massive bulge. | the auriga project: the properties and formation mechanisms of disc galaxies across cosmic time |
the advent of the second data release of the gaia mission, in combination with data from large spectroscopic surveys, is revolutionizing our understanding of the galaxy. thanks to these transformational data sets and the knowledge accumulated thus far, a new, more mature picture of the evolution of the early milky way is currently emerging. two of the traditional galactic components, namely, the stellar halo and the thick disk, appear to be intimately linked: stars with halo-like kinematics originate in similar proportions from a heated (thick) disk and from debris from a system named gaia-enceladus. gaia-enceladus was the last big merger event experienced by the milky way and was completed around 10 gyr ago. the puffed-up stars now present in the halo as a consequence of the merger have thus exposed the existence of a disk component at z ∼ 1.8. this is likely related to the previously known metal-weak thick disk and may be traceable to metallicities [fe/h] [formula: see text] -4. as importantly, there is evidence that the merger with gaia-enceladus triggered star formation in the early milky way, plausibly leading to the appearance of the thick disk as we know it. other merger events have been characterized better, and new ones have been uncovered. these include, for example, the helmi streams, sequoia, and thamnos, which add to the list of those discovered in wide-field photometric surveys, such as the sagittarius streams. current knowledge of their progenitors' properties, star formation, and chemical evolutionary histories is still incomplete. debris from different objects shows different degrees of overlap in phase-space. this sometimes confusing situation can be improved by determining membership probabilities via quantitative statistical methods. a task for the next few years will be to use ongoing and planned spectroscopic surveys for chemical labeling and to disentangle events from one another using dimensions other than phase-space, metallicity, or [α/fe]. these large surveys will also provide line-of-sight velocities missing for faint stars in gaia releases and more accurate distance determinations for distant objects, which in combination with other surveys could also lead to more accurate age dating. the resulting samples of stars will cover a much wider volume of the galaxy, allowing, for example, the linking of kinematic substructures found in the inner halo to spatial overdensities in the outer halo. all the results obtained so far are in line with the expectations of current cosmological models. nonetheless, tailored hydrodynamical simulations to reproduce in detail the properties of the merger debris, as well as constrained cosmological simulations of the milky way, are needed. such simulations will undoubtedly unravel more connections between the different galactic components and their substructures, and will aid in pushing our knowledge of the assembly of the milky way to the earliest times. | streams, substructures, and the early history of the milky way |
we present the first effort to aggregate, homogenize, and uniformly model the combined ultraviolet, optical, and near-infrared data set for the electromagnetic counterpart of the binary neutron star merger gw170817. by assembling all of the available data from 18 different papers and 46 different instruments, we are able to identify and mitigate systematic offsets between individual data sets and to identify clear outlying measurements, with the resulting pruned and adjusted data set offering an opportunity to expand the study of the kilonova. the unified data set includes 647 individual flux measurements, spanning 0.45-29.4 days post-merger, and thus has greater constraining power for physical models than any single data set. we test a number of semi-analytical models and find that the data are well modeled with a three-component kilonova model: a “blue” lanthanide-poor component (κ =0.5 cm2 g-1) with {m}{ej}≈ 0.020 {m}⊙and {v}{ej}≈ 0.27c; an intermediate opacity “purple” component (κ =3 cm2 g-1) with {m}{ej}≈ 0.047 {m}⊙and {v}{ej}≈ 0.15c; and a “red” lanthanide-rich component (κ =10 cm2 g-1) with {m}{ej}≈ 0.011 {m}⊙and {v}{ej}≈ 0.14c. we further explore the possibility of ejecta asymmetry and its impact on the estimated parameters. from the inferred parameters we draw conclusions about the physical mechanisms responsible for the various ejecta components, the properties of the neutron stars, and, combined with an up-to-date merger rate, the implications for r-process enrichment via this channel. to facilitate future studies of this keystone event we make the unified data set and our modeling code public. | the combined ultraviolet, optical, and near-infrared light curves of the kilonova associated with the binary neutron star merger gw170817: unified data set, analytic models, and physical implications |
we revisit constraints on dark photons with masses below ∼ 100 mev from the observations of supernova 1987a. if dark photons are produced in sufficient quantity, they reduce the amount of energy emitted in the form of neutrinos, in conflict with observations. for the first time, we include the effects of finite temperature and density on the kinetic-mixing parameter, ɛ, in this environment. this causes the constraints on ɛ to weaken with the dark-photon mass below ∼ 15 mev. for large-enough values of ɛ, it is well known that dark photons can be reabsorbed within the supernova. since the rates of reabsorption processes decrease as the dark-photon energy increases, we point out that dark photons with energies above the wien peak can escape without scattering, contributing more to energy loss than is possible assuming a blackbody spectrum. furthermore, we estimate the systematic uncertainties on the cooling bounds by deriving constraints assuming one analytic and four different simulated temperature and density profiles of the proto-neutron star. finally, we estimate also the systematic uncertainty on the bound by varying the distance across which dark photons must propagate from their point of production to be able to affect the star. this work clarifies the bounds from sn1987a on the dark-photon parameter space. | revisiting supernova 1987a constraints on dark photons |
we search for an isotropic stochastic gravitational-wave background (gwb) in the newly released 11 year data set from the north american nanohertz observatory for gravitational waves (nanograv). while we find no evidence for a gwb, we place constraints on a population of inspiraling supermassive black hole (smbh) binaries, a network of decaying cosmic strings, and a primordial gwb. for the first time, we find that the gwb constraints are sensitive to the solar system ephemeris (sse) model used and that sse errors can mimic a gwb signal. we developed an approach that bridges systematic sse differences, producing the first pulsar-timing array (pta) constraints that are robust against sse errors. we thus place a 95% upper limit on the gw-strain amplitude of a gwb < 1.45 × 10-15 at a frequency of f = 1 yr-1 for a fiducial f -2/3 power-law spectrum and with interpulsar correlations modeled. this is a factor of ∼2 improvement over the nanograv nine-year limit calculated using the same procedure. previous pta upper limits on the gwb (as well as their astrophysical and cosmological interpretations) will need revision in light of sse systematic errors. we use our constraints to characterize the combined influence on the gwb of the stellar mass density in galactic cores, the eccentricity of smbh binaries, and smbh-galactic-bulge scaling relationships. we constrain the cosmic-string tension using recent simulations, yielding an sse-marginalized 95% upper limit of gμ < 5.3 × 10-11—a factor of ∼2 better than the published nanograv nine-year constraints. our sse-marginalized 95% upper limit on the energy density of a primordial gwb (for a radiation-dominated post-inflation universe) is ωgwb(f) h 2 < 3.4 × 10-10. | the nanograv 11 year data set: pulsar-timing constraints on the stochastic gravitational-wave background |
we introduce the public version of the cosmological magnetohydrodynamical moving-mesh simulation code arepo. this version contains a finite-volume magnetohydrodynamics algorithm on an unstructured, dynamic voronoi tessellation coupled to a tree-particle-mesh algorithm for the poisson equation either on a newtonian or cosmologically expanding spacetime. time integration is performed adopting local time step constraints for each cell individually, solving the fluxes only across active interfaces, and calculating gravitational forces only between active particles, using an operator-splitting approach. this allows simulations with high dynamic range to be performed efficiently. arepo is a massively distributed-memory parallel code, using the message passing interface (mpi) communication standard and employing a dynamical workload and memory balancing scheme to allow for optimal use of multi-node parallel computers. the employed parallelization algorithms of arepo are deterministic and produce binary-identical results when rerun on the same machine and with the same number of mpi ranks. a simple primordial cooling and star formation model is included as an example of sub-resolution models commonly used in simulations of galaxy formation. arepo also contains a suite of computationally inexpensive test problems, ranging from idealized tests for automated code verification to scaled-down versions of cosmological galaxy formation simulations, and is extensively documented in order to assist adoption of the code by new scientific users. | the arepo public code release |
we have collected transit times for the trappist-1 system with the spitzer space telescope over four years. we add to these ground-based, hst, and k2 transit-time measurements, and revisit an n-body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. we next carry out a photodynamical analysis of the spitzer light curves to derive the density of the host star and the planet densities. we find that all seven planets' densities may be described with a single rocky mass-radius relation which is depleted in iron relative to earth, with fe 21 wt% versus 32 wt% for earth, and otherwise earth-like in composition. alternatively, the planets may have an earth-like composition but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. we measure planet masses to a precision of 3%-5%, equivalent to a radial-velocity (rv) precision of 2.5 cm s-1, or two orders of magnitude more precise than current rv capabilities. we find the eccentricities of the planets are very small, the orbits are extremely coplanar, and the system is stable on 10 myr timescales. we find evidence of infrequent timing outliers, which we cannot explain with an eighth planet; we instead account for the outliers using a robust likelihood function. we forecast jwst timing observations and speculate on possible implications of the planet densities for the formation, migration, and evolution of the planet system. | refining the transit-timing and photometric analysis of trappist-1: masses, radii, densities, dynamics, and ephemerides |
we report the discovery of a luminous quasar, j1007+2115 at z = 7.515 ("pōniuā'ena"), from our wide-field reionization-era quasar survey. j1007+2115 is the second quasar now known at z > 7.5, deep into the reionization epoch. the quasar is powered by a (1.5 ± 0.2) × 109 m⊙ supermassive black hole (smbh), based on its broad mg ii emission-line profile from gemini and keck near-ir spectroscopy. the smbh in j1007+2115 is twice as massive as that in quasar j1342+0928 at z = 7.54, the current quasar redshift record holder. the existence of such a massive smbh just 700 million years after the big bang significantly challenges models of the earliest smbh growth. model assumptions of eddington-limited accretion and a radiative efficiency of 0.1 require a seed black hole of ≳104 m⊙ at z = 30. this requirement suggests either a massive black hole seed as a result of direct collapse or earlier periods of rapid black hole growth with hyper-eddington accretion and/or a low radiative efficiency. we measure the damping wing signature imprinted by neutral hydrogen absorption in the intergalactic medium (igm) on j1007+2115's lyα line profile, and find that it is weaker than that of j1342+0928 and two other z ≳ 7 quasars. we estimate an igm volume-averaged neutral fraction $\langle {x}_{{\rm{h}}{\rm{i}}}\rangle ={0.39}_{-0.13}^{+0.22}$ . this range of values suggests a patchy reionization history toward different igm sightlines. we detect the 158 μm [c ii] emission line in j1007+2115 with the atacama large millimeter/submillimeter array; this line centroid yields a systemic redshift of z = 7.5149 ± 0.0004 and indicates a star formation rate of ∼210 m⊙ yr-1 in its host galaxy. | pōniuā'ena: a luminous z = 7.5 quasar hosting a 1.5 billion solar mass black hole |
we present the properties of 16 faint lyman-$\alpha$ emitting galaxies (laes) at $z>5.8$ from the jwst advanced deep extragalactic survey (jades) spectroscopic data in the hubble ultra deep field/goods-s. these laes span a redshift range $z\approx5.8-8.0$ and uv magnitude range $m_{\textrm{uv}} \approx -17$ to $-20.6$, with ly$\alpha$ equivalent width (ew) in the range $\approx 25-350$ å. the detection of other rest-optical emission lines in the spectra of these laes enables the determination of accurate systemic redshifts and ly$\alpha$ velocity offsets, as well as the physical and chemical composition of their stars and interstellar media. these faint laes are consistent with metal-poor systems with high ionization parameters, similar to the general galaxy population at $z>6$. we measure an average ionizing photon production efficiency, log($\xi_{\textrm{ion}}$/erg$^{-1}$ hz) $\approx 25.56$ across our laes, which does not evolve strongly with redshift. we report an anti-correlation between ly$\alpha$ escape fraction and velocity offset from systemic, consistent with model expectations. we further find that the strength and velocity offset of ly$\alpha$ are not correlated with galaxy spectroscopic properties nor with $\xi_{\textrm{ion}}$. we find a decrease in ly$\alpha$ escape fractions with redshift, indicative of decreasing sizes of ionized bubbles around laes at high redshifts. we use a range of galaxy properties to predict lyman continuum escape fractions for our laes, finding that the ionizing photon output into the intergalactic medium from our laes remains roughly constant across the observed uv magnitude and ly$\alpha$ equivalent width, showing a mild increase with redshift. we derive correlations between the ionizing photon output from laes and uv magnitude ly$\alpha$ strengths and redshift, which can be used to build realistic reionization models. | jades: the production and escape of ionizing photons from faint lyman-alpha emitters in the epoch of reionization |
born in the aftermath of core-collapse supernovae, neutron stars contain matter under extraordinary conditions of density and temperature that are difficult to reproduce in the laboratory. in recent years, neutron star observations have begun to yield novel insights into the nature of strongly interacting matter in the high-density regime where current theoretical models are challenged. at the same time, chiral effective field theory has developed into a powerful framework to study nuclear matter properties with quantified uncertainties in the moderate-density regime for modeling neutron stars. in this article, we review recent developments in chiral effective field theory and focus on many-body perturbation theory as a computationally efficient tool for calculating the properties of hot and dense nuclear matter. we also demonstrate how effective field theory enables statistically meaningful comparisons among nuclear theory predictions, nuclear experiments, and observational constraints on the nuclear equation of state. | chiral effective field theory and the high-density nuclear equation of state |
jwst observations indicate a surprising excess of luminous galaxies at z ~ 10 and above, consistent with efficient conversion of the accreted gas into stars, unlike the suppression of star formation by feedback at later times. we show that the high densities and low metallicities at this epoch guarantee a high star formation efficiency (sfe) in the most massive dark-matter haloes. feedback-free starbursts (ffbs) occur when the free-fall time is shorter than ~$1\, {\rm myr}$, below the time for low-metallicity massive stars to develop winds and supernovae. this corresponds to a characteristic density of ~$3\!\times \!10^3\, {\rm cm}^{-3}$. a comparable threshold density permits a starburst by allowing cooling to star-forming temperatures in a free-fall time. the galaxies within ~1011 m⊙ haloes at z ~ 10 are expected to have ffb densities. the halo masses allow efficient gas supply by cold streams in a halo crossing time ~$80\, {\rm myr}$. the ffbs gradually turn all the accreted gas into stars in clusters of ~104-7 m⊙ within galaxies that are rotating discs or shells. the starbursting clouds are insensitive to radiative feedback and are shielded against feedback from earlier stars. we predict high sfe above thresholds in redshift and halo mass, where the density is $10^{3\!-\!4}\, {\rm cm}^{-3}$. the z ~ 10 haloes of ~1010.8 m⊙ are predicted to host galaxies of ~1010 m⊙ with star formation rate ~$65\,\mathrm{ m}_\odot \, {\rm yr}^{-1}$, blue colours, and sub-kpc sizes. the metallicity is ≤0.1 z⊙ with little dust, gas, outflows, and hot circumgalactic gas, allowing a top-heavy initial mass function but not requiring it. the compact galaxies with thousands of young ffb clusters may have implications on reionization, black hole growth, and globular clusters. | efficient formation of massive galaxies at cosmic dawn by feedback-free starbursts |
twenty years have passed since first light for the sloan digital sky survey (sdss). here, we release data taken by the fourth phase of sdss (sdss-iv) across its first three years of operation (2014 july-2017 july). this is the third data release for sdss-iv, and the 15th from sdss (data release fifteen; dr15). new data come from manga—we release 4824 data cubes, as well as the first stellar spectra in the manga stellar library (mastar), the first set of survey-supported analysis products (e.g., stellar and gas kinematics, emission-line and other maps) from the manga data analysis pipeline, and a new data visualization and access tool we call “marvin.” the next data release, dr16, will include new data from both apogee-2 and eboss; those surveys release no new data here, but we document updates and corrections to their data processing pipelines. the release is cumulative; it also includes the most recent reductions and calibrations of all data taken by sdss since first light. in this paper, we describe the location and format of the data and tools and cite technical references describing how it was obtained and processed. the sdss website (www.sdss.org) has also been updated, providing links to data downloads, tutorials, and examples of data use. although sdss-iv will continue to collect astronomical data until 2020, and will be followed by sdss-v (2020-2025), we end this paper by describing plans to ensure the sustainability of the sdss data archive for many years beyond the collection of data. | the fifteenth data release of the sloan digital sky surveys: first release of manga-derived quantities, data visualization tools, and stellar library |
we present a new 3d map of interstellar dust reddening, covering three quarters of the sky (declinations of δ ≳ -30°) out to a distance of several kiloparsecs. the map is based on high-quality stellar photometry of 800 million stars from pan-starrs 1 and 2mass. we divide the sky into sightlines containing a few hundred stars each, and then infer stellar distances and types, along with the line-of-sight dust distribution. our new map incorporates a more accurate average extinction law and an additional 1.5 yr of pan-starrs 1 data, tracing dust to greater extinctions and at higher angular resolutions than our previous map. out of the plane of the galaxy, our map agrees well with 2d reddening maps derived from far-infrared dust emission. after accounting for a 25 per cent difference in scale, we find a mean scatter of ∼10 per cent between our map and the planck far-infrared emission-based dust map, out to a depth of 0.8 mag in e(gp1 - rp1), with the level of agreement varying over the sky. our map can be downloaded at http://argonaut.skymaps.info, or from the harvard dataverse (green 2017). | galactic reddening in 3d from stellar photometry - an improved map |
context. the second gaia data release (gaia dr2) contains high-precision positions, parallaxes, and proper motions for 1.3 billion sources as well as line-of-sight velocities for 7.2 million stars brighter than grvs = 12 mag. both samples provide a full sky coverage.aims: to illustrate the potential of gaia dr2, we provide a first look at the kinematics of the milky way disc, within a radius of several kiloparsecs around the sun.methods: we benefit for the first time from a sample of 6.4 million f-g-k stars with full 6d phase-space coordinates, precise parallaxes (σϖ/ϖ ≤ 20%), and precise galactic cylindrical velocities (median uncertainties of 0.9-1.4 km s-1 and 20% of the stars with uncertainties smaller than 1 km s-1 on all three components). from this sample, we extracted a sub-sample of 3.2 million giant stars to map the velocity field of the galactic disc from 5 kpc to 13 kpc from the galactic centre and up to 2 kpc above and below the plane. we also study the distribution of 0.3 million solar neighbourhood stars (r < 200 pc), with median velocity uncertainties of 0.4 km s-1, in velocity space and use the full sample to examine how the over-densities evolve in more distant regions.results: gaia dr2 allows us to draw 3d maps of the galactocentric median velocities and velocity dispersions with unprecedented accuracy, precision, and spatial resolution. the maps show the complexity and richness of the velocity field of the galactic disc. we observe streaming motions in all the components of the velocities as well as patterns in the velocity dispersions. for example, we confirm the previously reported negative and positive galactocentric radial velocity gradients in the inner and outer disc, respectively. here, we see them as part of a non-axisymmetric kinematic oscillation, and we map its azimuthal and vertical behaviour. we also witness a new global arrangement of stars in the velocity plane of the solar neighbourhood and in distant regions in which stars are organised in thin substructures with the shape of circular arches that are oriented approximately along the horizontal direction in the u - v plane. moreover, in distant regions, we see variations in the velocity substructures more clearly than ever before, in particular, variations in the velocity of the hercules stream.conclusions: gaia dr2 provides the largest existing full 6d phase-space coordinates catalogue. it also vastly increases the number of available distances and transverse velocities with respect to gaia dr1. gaia dr2 offers a great wealth of information on the milky way and reveals clear non-axisymmetric kinematic signatures within the galactic disc, for instance. it is now up to the astronomical community to explore its full potential. | gaia data release 2. mapping the milky way disc kinematics |
for stars with unresolved companions, motions of the centre of light and that of mass decouple, causing a single-source astrometric model to perform poorly. we show that such stars can be easily detected with the reduced χ2 statistic, or renormalized unit weight error (ruwe), provided as part of gaia dr2. we convert ruwe into the amplitude of the image centroid wobble, which, if scaled by the source distance, is proportional to the physical separation between companions (for periods up to several years). we test this idea on a sample of known spectroscopic binaries and demonstrate that the amplitude of the centroid perturbation scales with the binary period and the mass ratio as expected. we apply this technique to the gaia dr2 data and show how the binary fraction evolves across the hertzsprung-russell diagram. the observed incidence of unresolved companions is high for massive young stars and drops steadily with stellar mass, reaching its lowest levels for white dwarfs. we highlight the elevated binary fraction for the nearby blue stragglers and blue horizontal branch stars. we also illustrate how unresolved hierarchical triples inflate the relative velocity signal in wide binaries. finally, we point out a hint of evidence for the existence of additional companions to the hosts of extrasolar hot jupiters. | unresolved stellar companions with gaia dr2 astrometry |
transmission spectroscopy1-3 of exoplanets has revealed signatures of water vapour, aerosols and alkali metals in a few dozen exoplanet atmospheres4,5. however, these previous inferences with the hubble and spitzer space telescopes were hindered by the observations' relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species—in particular the primary carbon-bearing molecules6,7. here we report a broad-wavelength 0.5-5.5 µm atmospheric transmission spectrum of wasp-39b8, a 1,200 k, roughly saturn-mass, jupiter-radius exoplanet, measured with the jwst nirspec's prism mode9 as part of the jwst transiting exoplanet community early release science team program10-12. we robustly detect several chemical species at high significance, including na (19σ), h2o (33σ), co2 (28σ) and co (7σ). the non-detection of ch4, combined with a strong co2 feature, favours atmospheric models with a super-solar atmospheric metallicity. an unanticipated absorption feature at 4 µm is best explained by so2 (2.7σ), which could be a tracer of atmospheric photochemistry. these observations demonstrate jwst's sensitivity to a rich diversity of exoplanet compositions and chemical processes. | early release science of the exoplanet wasp-39b with jwst nirspec prism |
we present a new grid of presupernova models of massive stars extending in mass between 13 and 120 {m}⊙ , covering four metallicities (i.e., [fe/h] = 0, -1, -2, and -3) and three initial rotation velocities (i.e., 0, 150, and 300 km s-1). the explosion has been simulated following three different assumptions in order to show how the yields depend on the remnant mass-initial mass relation. an extended network from h to bi is fully coupled to the physical evolution of the models. the main results can be summarized as follows. (a) at solar metallicity, the maximum mass exploding as a red supergiant (rsg) is of the order of 17 {m}⊙in the nonrotating case, with the more massive stars exploding as wolf-rayet (wr) stars. all rotating models, conversely, explode as wr stars. (b) the interplay between the core he-burning and the h-burning shell, triggered by the rotation-induced instabilities, drives the synthesis of a large primary amount of all the products of cno, not just {}14{{n}}. a fraction of them greatly enriches the radiative part of the he core (and is responsible for the large production of f), and a fraction enters the convective core, leading therefore to an important primary neutron flux able to synthesize heavy nuclei up to pb. (c) in our scenario, remnant masses of the order of those inferred from the first detections of gravitational waves (gw 150914, gw 151226, gw 170104, gw 170814) are predicted at all metallicities for none or moderate initial rotation velocities. | presupernova evolution and explosive nucleosynthesis of rotating massive stars in the metallicity range -3 ≤ [fe/h] ≤ 0 |
low-mass “dwarf” galaxies represent the most significant challenges to the cold dark matter (cdm) model of cosmological structure formation. because these faint galaxies are (best) observed within the local group (lg) of the milky way (mw) and andromeda (m31), understanding their formation in such an environment is critical. we present first results from the latte project: the milky way on feedback in realistic environments (fire). this simulation models the formation of an mw-mass galaxy to z=0 within λcdm cosmology, including dark matter, gas, and stars at unprecedented resolution: baryon particle mass of 7070 {m}⊙with gas kernel/softening that adapts down to 1 {pc} (with a median of 25{--}60 {pc} at z=0). latte was simulated using the gizmo code with a mesh-free method for accurate hydrodynamics and the fire-2 model for star formation and explicit feedback within a multi-phase interstellar medium. for the first time, latte self-consistently resolves the spatial scales corresponding to half-light radii of dwarf galaxies that form around an mw-mass host down to {m}{star}≳ {10}5 {m}⊙ . latte’s population of dwarf galaxies agrees with the lg across a broad range of properties: (1) distributions of stellar masses and stellar velocity dispersions (dynamical masses), including their joint relation; (2) the mass-metallicity relation; and (3) diverse range of star formation histories, including their mass dependence. thus, latte produces a realistic population of dwarf galaxies at {m}{star}≳ {10}5 {m}⊙that does not suffer from the “missing satellites” or “too big to fail” problems of small-scale structure formation. we conclude that baryonic physics can reconcile observed dwarf galaxies with standard λcdm cosmology. | reconciling dwarf galaxies with λcdm cosmology: simulating a realistic population of satellites around a milky way-mass galaxy |
the launch of the james webb space telescope (jwst) in late 2021 marks a new start for studies of galaxy formation at high redshift (z ≳ 6) during the era of cosmic reionization. jwst can capture sensitive, high-resolution images and multiobject spectroscopy in the ir that will transform our view of galaxy formation during the first billion years of cosmic history. this review summarizes our current knowledge of the role of galaxies in reionizing intergalactic hydrogen ahead of jwst, achieved through observations with the hubble space telescope and ground-based facilities including keck, the very large telescope, subaru, and the atacama large millimeter/submillimeter array. we identify outstanding questions in the field that jwst can address during its mission lifetime, including with the planned jwst cycle 1 programs. these findings include the following: surveys with jwst have sufficient sensitivity and area to complete the census of galaxy formation at the current redshift frontier (z ∼ 8-10). rest-frame optical spectroscopy with jwst of galaxies will newly enable measures of star-formation rate, metallicity, and ionization at z ∼ 8-9, allowing for the astrophysics of early galaxies to be constrained. the presence of evolved stellar populations at z ∼ 8-10 can be definitively tested by jwst, which would provide evidence of star formation out to z ∼ 15. | galaxy formation and reionization: key unknowns and expected breakthroughs by the james webb space telescope |
gaia data release 3 contains a wealth of new data products for the community. astrophysical parameters are a major component of this release, and were produced by the astrophysical parameters inference system (apsis) within the gaia data processing and analysis consortium (dpac). the aim of this paper is to describe the overall content of the astrophysical parameters in gaia dr3 and how they were produced. in apsis, we use the mean bp/rp and mean rvs spectra along with astrometry and photometry, and we derive the following parameters: source classification and probabilities for 1.6 billion objects; interstellar medium characterisation and distances for up to 470 million sources, including a 2d total galactic extinction map; 6 million redshifts of quasar candidates; 1.4 million redshifts of galaxy candidates; and an analysis of 50 million outlier sources through an unsupervised classification. the astrophysical parameters also include many stellar spectroscopic and evolutionary parameters for up to 470 million sources. these comprise teff, log g, and [m/h] (470 million using bp/rp, 6 million using rvs), radius (470 million), mass (140 million), age (120 million), chemical abundances (up to 5 million), diffuse interstellar band analysis (0.5 million), activity indices (2 million), hα equivalent widths (200 million), and further classification of spectral types (220 million) and emission-line stars (50 000). this paper is the first in a series of three papers, and focusses on describing the global content of the parameters in gaia dr3. the accompanying papers ii and iii focus on the validation and use of the stellar and non-stellar products, respectively. this catalogue is the most extensive homogeneous database of astrophysical parameters to date, and is based uniquely on gaia data. it will only be superseded by gaia data release 4, and will therefore remain a key reference over the next four years, providing astrophysical parameters independent of other ground- and space-based data. | gaia data release 3. astrophysical parameters inference system (apsis). i. methods and content overview |
we present a statistical analysis of the first 300 stars observed by the gemini planet imager exoplanet survey. this subsample includes six detected planets and three brown dwarfs; from these detections and our contrast curves we infer the underlying distributions of substellar companions with respect to their mass, semimajor axis, and host stellar mass. we uncover a strong correlation between planet occurrence rate and host star mass, with stars m * > 1.5 m ⊙ more likely to host planets with masses between 2 and 13m jup and semimajor axes of 3-100 au at 99.92% confidence. we fit a double power-law model in planet mass (m) and semimajor axis (a) for planet populations around high-mass stars (m * > 1.5 m ⊙) of the form {d}2n/({dm} {da})\propto {m}α{a}β , finding α = -2.4 ± 0.8 and β = -2.0 ± 0.5, and an integrated occurrence rate of {9}-4+5% between 5-13m jup and 10-100 au. a significantly lower occurrence rate is obtained for brown dwarfs around all stars, with {0.8}-0.5+0.8% of stars hosting a brown dwarf companion between 13-80m jup and 10-100 au. brown dwarfs also appear to be distributed differently in mass and semimajor axis compared to giant planets; whereas giant planets follow a bottom-heavy mass distribution and favor smaller semimajor axes, brown dwarfs exhibit just the opposite behaviors. comparing to studies of short-period giant planets from the radial velocity method, our results are consistent with a peak in occurrence of giant planets between ∼1 and 10 au. we discuss how these trends, including the preference of giant planets for high-mass host stars, point to formation of giant planets by core/pebble accretion, and formation of brown dwarfs by gravitational instability. | the gemini planet imager exoplanet survey: giant planet and brown dwarf demographics from 10 to 100 au |
recent jwst observations suggest an excess of z ≳ 10 galaxy candidates above most theoretical models. here, we explore how the interplay between halo formation time-scales, star formation efficiency, and dust attenuation affects the properties and number densities of galaxies observed in the early universe. to guide intuition, we calculate the theoretical upper limit on the uv luminosity function (lf), assuming star formation is 100 per cent efficient and all gas in haloes is converted into stars, and that galaxies are at the peak age for uv emission (~10 myr). this upper limit is ~4 orders of magnitude greater than current observations, implying no formal tension with star formation in lambda cold dark matter cosmology. in a more realistic model, we use the distribution of halo formation time-scales derived from extended press-schechter theory as a proxy for star formation rate (sfr). we predict that the galaxies observed so far at z ≳ 10 are dominated by those with the fastest formation time-scales, and thus most extreme sfrs and young ages. these galaxies can be upscattered by ~1.5 mag compared to the median uv magnitude versus halo mass relation. this likely introduces a selection effect at high redshift whereby only the youngest (≲10 myr), most highly star-forming galaxies (specific sfr$\gtrsim 30\, \mathrm{gyr}^{-1}$) have been detected so far. furthermore, our modelling suggests that redshift evolution at the bright end of the uv lf is substantially affected by the build-up of dust attenuation. we predict that deeper jwst observations (reaching m ~ 30) will reveal more typical galaxies with relatively older ages (~100 myr) and less extreme specific sfrs ($\sim 10\, \mathrm{gyr}^{-1}$ for a muv ~ -20 galaxy at z ~ 10). | the brightest galaxies at cosmic dawn |
newly forming protoplanets are expected to create cavities and substructures in young, gas-rich protoplanetary disks1-3, but they are difficult to detect as they could be confused with disk features affected by advanced image analysis techniques4,5. recently, a planet was discovered inside the gap of the transitional disk of the t tauri star pds 706,7. here, we report on the detection of strong hα emission from two distinct locations in the pds 70 system, one corresponding to the previously discovered planet pds 70 b, which confirms the earlier hα detection8, and another located close to the outer edge of the gap, coinciding with a previously identified bright dust spot in the disk and with a small opening in a ring of molecular emission6,7,9. we identify this second hα peak as a second protoplanet in the pds 70 system. the hα emission spectra of both protoplanets indicate ongoing accretion onto the protoplanets10,11, which appear to be near a 2:1 mean motion resonance. our observations show that adaptive-optics-assisted, medium-resolution integral field spectroscopy with muse12 targeting accretion signatures will be a powerful way to trace ongoing planet formation in transitional disks at different stages of their evolution. finding more young planetary systems in mean motion resonance would give credibility to the grand tack hypothesis in which jupiter and saturn migrated in a resonance orbit during the early formation period of our solar system13. | two accreting protoplanets around the young star pds 70 |
quasars at cosmic dawn provide powerful probes of the formation and growth of the earliest supermassive black holes (smbhs) in the universe, their connections to galaxy and structure formation, and the evolution of the intergalactic medium (igm) at the epoch of reionization (eor). hundreds of quasars have been discovered in the first billion years of cosmic history, with the quasar redshift frontier extended to z ∼ 7.6. observations of quasars at cosmic dawn show the following: <label>■</label>the number density of luminous quasars declines exponentially at z > 5, suggesting that the earliest quasars emerge at z ∼ 10; the lack of strong evolution in their average spectral energy distribution indicates a rapid buildup of the active galactic nucleus environment.<label>■</label>billion-solar-mass black holes (bhs) already exist at z > 7.5; they must form and grow in less than 700 myr, by a combination of massive early bh seeds with highly efficient and sustained accretion.<label>■</label>the rapid quasar growth is accompanied by strong star formation and feedback activity in their host galaxies, which show diverse morphological and kinetic properties, with typical dynamical mass lower than that implied by the local bh/galaxy scaling relations.<label>■</label>hi absorption in quasar spectra probes the tail end of cosmic reionization at z ∼ 5.3-6 and indicates the eor midpoint at 6.9 < z < 7.6, with large spatial fluctuations in igm ionization. observations of heavy element absorption lines suggest that the circumgalactic medium also experiences evolution in its ionization structure and metal enrichment during the eor. | quasars and the intergalactic medium at cosmic dawn |
we present an analysis of the galaxy-scale gaseous outflows from the feedback in realistic environments (fire) simulations. this suite of hydrodynamic cosmological zoom simulations resolves formation of star-forming giant molecular clouds to z = 0, and features an explicit stellar feedback model on small scales. our simulations reveal that high-redshift galaxies undergo bursts of star formation followed by powerful gusts of galactic outflows that eject much of the interstellar medium and temporarily suppress star formation. at low redshift, however, sufficiently massive galaxies corresponding to l* progenitors develop stable discs and switch into a continuous and quiescent mode of star formation that does not drive outflows far into the halo. mass-loading factors for winds in l* progenitors are η ≈ 10 at high redshift, but decrease to η ≪ 1 at low redshift. although lower values of η are expected as haloes grow in mass over time, we show that the strong suppression of outflows with decreasing redshift cannot be explained by mass evolution alone. circumgalactic outflow velocities are variable and broadly distributed, but typically range between one and three times the circular velocity of the halo. much of the ejected material builds a reservoir of enriched gas within the circumgalactic medium, some of which could be later recycled to fuel further star formation. however, a fraction of the gas that leaves the virial radius through galactic winds is never regained, causing most haloes with mass mh ≤ 1012 m⊙ to be deficient in baryons compared to the cosmic mean by z = 0. | gusty, gaseous flows of fire: galactic winds in cosmological simulations with explicit stellar feedback |
the existence of neutron star mergers has been supported since the discovery of the binary pulsar and the observation of its orbital energy loss, consistent with general relativity. they are considered nucleosynthesis sites of the rapid neutron-capture process (r-process), which is responsible for creating approximately half of all heavy elements beyond fe and is the only source of elements beyond pb and bi. detailed nucleosynthesis calculations based on the decompression of neutron star matter are consistent with solar r-process abundances of heavy nuclei. neutron star mergers have also been identified with short-duration [formula: see text]-ray bursts via their ir afterglow. the high neutron densities in ejected matter permit a violent r-process, leading to fission cycling of the heaviest nuclei in regions far from (nuclear) stability. uncertainties in several nuclear properties affect the abundance distributions. the modeling of astrophysical events also depends on the hydrodynamic treatment, the occurrence of a neutrino wind after the merger and before the possible emergence of a black hole, and the properties of black hole accretion disks. we discuss the effect of nuclear and modeling uncertainties and conclude that binary compact mergers are probably a (or the) dominant site of the production of r-process nuclei in our galaxy. | neutron star mergers and nucleosynthesis of heavy elements |
half of all of the elements in the universe that are heavier than iron were created by rapid neutron capture. the theory underlying this astrophysical r-process was worked out six decades ago, and requires an enormous neutron flux to make the bulk of the elements1. where this happens is still debated2. a key piece of evidence would be the discovery of freshly synthesized r-process elements in an astrophysical site. existing models3-5 and circumstantial evidence6 point to neutron-star mergers as a probable r-process site; the optical/infrared transient known as a `kilonova' that emerges in the days after a merger is a likely place to detect the spectral signatures of newly created neutron-capture elements7-9. the kilonova at2017gfo—which was found following the discovery of the neutron-star merger gw170817 by gravitational-wave detectors10—was the first kilonova for which detailed spectra were recorded. when these spectra were first reported11,12, it was argued that they were broadly consistent with an outflow of radioactive heavy elements; however, there was no robust identification of any one element. here we report the identification of the neutron-capture element strontium in a reanalysis of these spectra. the detection of a neutron-capture element associated with the collision of two extreme-density stars establishes the origin of r-process elements in neutron-star mergers, and shows that neutron stars are made of neutron-rich matter13. | identification of strontium in the merger of two neutron stars |
galaxies living in rich environments are suffering different perturbations able to drastically affect their evolution. among these, ram pressure stripping, i.e. the pressure exerted by the hot and dense intracluster medium (icm) on galaxies moving at high velocity within the cluster gravitational potential well, is a key process able to remove their interstellar medium (ism) and quench their activity of star formation. this review is aimed at describing this physical mechanism in different environments, from rich clusters of galaxies to loose and compact groups. we summarise the effects of this perturbing process on the baryonic components of galaxies, from the different gas phases (cold atomic and molecular, ionised, hot) to magnetic fields and cosmic rays, and describe their induced effects on the different stellar populations, with a particular attention to its role in the quenching episode generally observed in high-density environments. we also discuss on the possible fate of the stripped material once removed from the perturbed galaxies and mixed with the icm, and we try to estimate its contribution to the pollution of the surrounding environment. finally, combining the results of local and high-redshift observations with the prediction of tuned models and simulations, we try to quantify the importance of this process on the evolution of galaxies of different mass, from dwarfs to giants, in various environments and at different epochs. | ram pressure stripping in high-density environments |
orbiting planets induce a weak radial velocity (rv) shift in the host star that provides a powerful method of planet detection. importantly, the rv technique provides information about the exoplanet mass, which is unavailable with the complementary technique of transit photometry. however, rv detection of an earth-like planet in the `habitable zone'1 requires extreme spectroscopic precision that is only possible using a laser frequency comb (lfc)2. conventional lfcs require complex filtering steps to be compatible with astronomical spectrographs, but a new chip-based microresonator device, the kerr soliton microcomb3-8, is an ideal match for astronomical spectrograph resolution and can eliminate these filtering steps. here, we demonstrate an atomic/molecular line-referenced soliton microcomb for calibration of astronomical spectrographs. these devices can ultimately provide lfc systems that would occupy only a few cubic centimetres9,10, thereby greatly expanding implementation of these technologies into remote and mobile environments beyond the research lab. | searching for exoplanets using a microresonator astrocomb |
context. the third gaia data release (dr3) provides a wealth of new data products. the early part of the release, gaia edr3, already provided the astrometric and photometric data for nearly two billion sources. the full release now adds improved parameters compared to gaia dr2 for radial velocities, astrophysical parameters, variability information, light curves, and orbits for solar system objects. the improvements are in terms of the number of sources, the variety of parameter information, precision, and accuracy. for the first time, gaia dr3 also provides a sample of spectrophotometry and spectra obtained with the radial velocity spectrometer, binary star solutions, and a characterisation of extragalactic object candidates.aims: before the publication of the catalogue, these data have undergone a dedicated transversal validation process. the aim of this paper is to highlight limitations of the data that were found during this process and to provide recommendations for the usage of the catalogue.methods: the validation was obtained through a statistical analysis of the data, a confirmation of the internal consistency of different products, and a comparison of the values to external data or models.results: gaia dr3 is a new major step forward in terms of the number, diversity, precision, and accuracy of the gaia products. as always in such a large and complex catalogue, however, issues and limitations have also been found. detailed examples of the scientific quality of the gaia dr3 release can be found in the accompanying data-processing papers as well as in the performance verification papers. here we focus only on the caveats that the user should be aware of to scientifically exploit the data. | gaia data release 3. catalogue validation |
a key legacy of the recently launched the transiting exoplanet survey satellite (tess) mission will be to provide the astronomical community with many of the best transiting exoplanet targets for atmospheric characterization. however, time is of the essence to take full advantage of this opportunity. the james webb space telescope (jwst), although delayed, will still complete its nominal five year mission on a timeline that motivates rapid identification, confirmation, and mass measurement of the top atmospheric characterization targets from tess. beyond jwst, future dedicated missions for atmospheric studies such as the atmospheric remote-sensing infrared exoplanet large-survey (ariel) require the discovery and confirmation of several hundred additional sub-jovian size planets (rp< 10 r ⊕) orbiting bright stars, beyond those known today, to ensure a successful statistical census of exoplanet atmospheres. ground-based extremely large telescopes (elts) will also contribute to surveying the atmospheres of the transiting planets discovered by tess. here we present a set of two straightforward analytic metrics, quantifying the expected signal-to-noise in transmission and thermal emission spectroscopy for a given planet, that will allow the top atmospheric characterization targets to be readily identified among the tess planet candidates. targets that meet our proposed threshold values for these metrics would be encouraged for rapid follow-up and confirmation via radial velocity mass measurements. based on the catalog of simulated tess detections by sullivan et al., we determine appropriate cutoff values of the metrics, such that the tess mission will ultimately yield a sample of ∼300 high-quality atmospheric characterization targets across a range of planet size bins, extending down to earth-size, potentially habitable worlds. | a framework for prioritizing the tess planetary candidates most amenable to atmospheric characterization |
the hyper suprime-cam (hsc) is an 870 megapixel prime focus optical imaging camera for the 8.2 m subaru telescope. the wide-field corrector delivers sharp images of 0{^''.}2 (fwhm) in the hsc-i band over the entire 1.5° diameter field of view. the collimation of the camera with respect to the optical axis of the primary mirror is done with hexapod actuators, the mechanical accuracy of which is a few microns. analysis of the remaining wavefront error in off-focus stellar images reveals that the collimation of the optical components meets design specifications. while there is a flexure of mechanical components, it also is within the design specification. as a result, the camera achieves its seeing-limited imaging on maunakea during most of the time; the median seeing over several years of observing is 0.67" (fwhm) in the i band. the sensors use p-channel, fully depleted ccds of 200 μm thickness (2048 × 4176 15 μm square pixels) and we employ 116 of them to pave the 50 cm diameter focal plane. the minimum interval between exposures is 34 s, including the time to read out arrays, to transfer data to the control computer, and to save them to the hard drive. hsc on subaru uniquely features a combination of a large aperture, a wide field of view, sharp images and a high sensitivity especially at longer wavelengths, which makes the hsc one of the most powerful observing facilities in the world. | hyper suprime-cam: system design and verification of image quality |
we present the cosmology and astrophysics with machine learning simulations (camels) project. camels is a suite of 4233 cosmological simulations of ${\left(25{h}^{-1}\mathrm{mpc}\right)}^{3}$ volume each: 2184 state-of-the-art (magneto)hydrodynamic simulations run with the arepo and gizmo codes, employing the same baryonic subgrid physics as the illustristng and simba simulations, and 2049 n-body simulations. the goal of the camels project is to provide theory predictions for different observables as a function of cosmology and astrophysics, and it is the largest suite of cosmological (magneto)hydrodynamic simulations designed to train machine-learning algorithms. camels contains thousands of different cosmological and astrophysical models by way of varying ωm, σ8, and four parameters controlling stellar and active galactic nucleus feedback, following the evolution of more than 100 billion particles and fluid elements over a combined volume of ${(400{h}^{-1}\mathrm{mpc})}^{3}$ . we describe the simulations in detail and characterize the large range of conditions represented in terms of the matter power spectrum, cosmic star formation rate density, galaxy stellar mass function, halo baryon fractions, and several galaxy scaling relations. we show that the illustristng and simba suites produce roughly similar distributions of galaxy properties over the full parameter space but significantly different halo baryon fractions and baryonic effects on the matter power spectrum. this emphasizes the need for marginalizing over baryonic effects to extract the maximum amount of information from cosmological surveys. we illustrate the unique potential of camels using several machine-learning applications, including nonlinear interpolation, parameter estimation, symbolic regression, data generation with generative adversarial networks, dimensionality reduction, and anomaly detection. | the camels project: cosmology and astrophysics with machine-learning simulations |
the lhcb collaboration announced two pentaquark-like structures in the j /ψ p invariant mass distribution. we show that the current information on the narrow structure at 4.45 gev is compatible with kinematical effects of the rescattering from χc 1p to j /ψ p : first, it is located exactly at the χc 1p threshold. second, the mass of the four-star well-established λ (1890 ) is such that a leading landau singularity from a triangle diagram can coincidentally appear at the χc 1p threshold, and third, there is a narrow structure at the χc 1p threshold but not at the χc 0p and χc 2p thresholds. in order to check whether that structure corresponds to a real exotic resonance, one can measure the process λb0→k-χc 1p . if the pc(4450 ) structure exists in the χc 1p invariant mass distribution as well, then the structure cannot be just a kinematical effect but is a real resonance; otherwise, one cannot conclude that pc(4450 ) is another exotic hadron. in addition, it is also worthwhile to measure the decay ϒ (1 s )→j /ψ p p ¯ : a narrow structure at 4.45 gev but not at the χc 0p and χc 2p thresholds would exclude the possibility of a pure kinematical effect. | how to reveal the exotic nature of the pc(4450 ) |
the binary neutron star merger event gw170817 was detected through both electromagnetic radiation and gravitational waves. its afterglow emission may have been produced by either a narrow relativistic jet or an isotropic outflow. high-spatial-resolution measurements of the source size and displacement can discriminate between these scenarios. we present very-long-baseline interferometry observations, performed 207.4 days after the merger by using a global network of 32 radio telescopes. the apparent source size is constrained to be smaller than 2.5 milli-arc seconds at the 90% confidence level. this excludes the isotropic outflow scenario, which would have produced a larger apparent size, indicating that gw170817 produced a structured relativistic jet. our rate calculations show that at least 10% of neutron star mergers produce such a jet. | compact radio emission indicates a structured jet was produced by a binary neutron star merger |
one of the most compelling tasks of modern cosmology is to constrain the expansion history of the universe, since this measurement can give insights on the nature of dark energy and help to estimate cosmological parameters. in this letter are presented two new measurements of the hubble parameter h(z) obtained with the cosmic chronometer method up to z ∼ 2. taking advantage of near-infrared spectroscopy of the few very massive and passive galaxies observed at z > 1.4 available in literature, the differential evolution of this population is estimated and calibrated with different stellar population synthesis models to constrain h(z), including in the final error budget all possible sources of systematic uncertainties (star formation history, stellar metallicity, model dependences). this analysis is able to extend significantly the redshift range coverage with respect to present-day constraints, crossing for the first time the limit at z ∼ 1.75. the new h(z) data are used to estimate the gain in accuracy on cosmological parameters with respect to previous measurements in two cosmological models, finding a small but detectable improvement (∼5 per cent) in particular on ωm and w0. finally, a simulation of a euclid-like survey has been performed to forecast the expected improvement with future data. the provided constraints have been obtained just with the cosmic chronometers approach, without any additional data, and the results show the high potentiality of this method to constrain the expansion history of the universe at these redshifts. | raising the bar: new constraints on the hubble parameter with cosmic chronometers at z ~ 2. |
we investigate constraints on cosmic reionization extracted from the planck cosmic microwave background (cmb) data. we combine the planck cmb anisotropy data in temperature with the low-multipole polarization data to fit λcdm models with various parameterizations of the reionization history. we obtain a thomson optical depth τ = 0.058 ± 0.012 for the commonly adopted instantaneous reionization model. this confirms, with data solely from cmb anisotropies, the low value suggested by combining planck 2015 results with other data sets, and also reduces the uncertainties. we reconstruct the history of the ionization fraction using either a symmetric or an asymmetric model for the transition between the neutral and ionized phases. to determine better constraints on the duration of the reionization process, we also make use of measurements of the amplitude of the kinetic sunyaev-zeldovich (ksz) effect using additional information from the high-resolution atacama cosmology telescope and south pole telescope experiments. the average redshift at which reionization occurs is found to lie between z = 7.8 and 8.8, depending on the model of reionization adopted. using ksz constraints and a redshift-symmetric reionization model, we find an upper limit to the width of the reionization period of δz < 2.8. in all cases, we find that the universe is ionized at less than the 10% level at redshifts above z ≃ 10. this suggests that an early onset of reionization is strongly disfavoured by the planck data. we show that this result also reduces the tension between cmb-based analyses and constraints from other astrophysical sources. | planck intermediate results. xlvii. planck constraints on reionization history |
context. the chemo-physical parametrisation of stellar spectra is essential for understanding the nature and evolution of stars and of galactic stellar populations. a worldwide observational effort from the ground has provided, in one century, an extremely heterogeneous collection of chemical abundances for about two million stars in total, with fragmentary sky coverage.aims: this situation is revolutionised by the gaia third data release (dr3), which contains the parametrisation of radial velocity spectrometer (rvs) data performed by the general stellar parametriser-spectroscopy, gsp-spec, module. here we describe the parametrisation of the first 34 months of gaia rvs observations.methods: gsp-spec estimates the chemo-physical parameters from combined rvs spectra of single stars, without additional inputs from astrometric, photometric, or spectro-photometric bp/rp data. the main analysis workflow described here, matissegauguin, is based on projection and optimisation methods and provides the stellar atmospheric parameters; the individual chemical abundances of n, mg, si, s, ca, ti, cr, fe i, fe ii, ni, zr, ce and nd; the differential equivalent width of a cyanogen line; and the parameters of a diffuse interstellar band (dib) feature. another workflow, based on an artificial neural network (ann) and referred to with the same acronym, provides a second set of atmospheric parameters that are useful for classification control. for both workflows, we implement a detailed quality flag chain considering different error sources.results: with about 5.6 million stars, the gaia dr3 gsp-spec all-sky catalogue is the largest compilation of stellar chemo-physical parameters ever published and the first one from space data. internal and external biases have been studied taking into account the implemented flags. in some cases, simple calibrations with low degree polynomials are suggested. the homogeneity and quality of the estimated parameters enables chemo-dynamical studies of galactic stellar populations, interstellar extinction studies from individual spectra, and clear constraints on stellar evolution models. we highly recommend that users adopt the provided quality flags for scientific exploitation.conclusions: the gaia dr3 gsp-spec catalogue is a major step in the scientific exploration of milky way stellar populations. it will be followed by increasingly large and higher quality catalogues in future data releases, confirming the gaia promise of a new galactic vision. | gaia data release 3. analysis of rvs spectra using the general stellar parametriser from spectroscopy |
there is some weak evidence that the black hole merger named gw190521 had a non-zero eccentricity1,2. in addition, the masses of the component black holes exceeded the limit predicted by stellar evolution3. the large masses can be explained by successive mergers4,5, which may be efficient in gas disks surrounding active galactic nuclei, but it is difficult to maintain an eccentric orbit all the way to the merger, as basic physics would argue for circularization6. here we show that active galactic nuclei disk environments can lead to an excess of eccentric mergers, if the interactions between single and binary black holes are frequent5 and occur with mutual inclinations of less than a few degrees. we further illustrate that this eccentric population has a different distribution of the inclination between the spin vectors of the black holes and their orbital angular momentum at merger7, referred to as the spin-orbit tilt, compared with the remaining circular mergers. | agn as potential factories for eccentric black hole mergers |
neutron star interior composition explorer has a comparatively low background rate, but it is highly variable, and its spectrum must be predicted using measurements unaffected by the science target. we describe an empirical, three-parameter model based on observations of seven pointing directions that are void of detectable sources. two model parameters track different types of background events, while the third is used to predict a low-energy excess tied to observations conducted in sunlight. an examination of 3556 good time intervals (gtis), averaging 570 s, yields a median rate (0.4-12 kev; 50 detectors) of 0.87 c s-1, but in 5% (1%) of cases, the rate exceeds 10 (300) c s-1. model residuals persist at 20%-30% of the initial rate for the brightest gtis, implying one or more missing model parameters. filtering criteria are given to flag gtis likely to have unsatisfactory background predictions. with such filtering, we estimate a detection limit, 1.20 c s-1 (3σ, single gti) at 0.4-12 kev, equivalent to 3.6 × 10-12 erg cm-2 s-1 for a crab-like spectrum. the corresponding limit for soft x-ray sources is 0.51 c s-1 at 0.3-2.0 kev, or 4.3 × 10-13 erg cm-2 s-1 for a 100 ev blackbody. these limits would be four times lower if exploratory gtis accumulate 10 ks of data after filtering at the level prescribed for faint sources. such filtering selects background gtis 85% of the time. an application of the model to a 1 s timescale makes it possible to distinguish source flares from possible surges in the background. | an empirical background model for the nicer x-ray timing instrument |
we present uv and/or optical observations and models of sn 2023ixf, a type ii supernova (sn) located in messier 101 at 6.9 mpc. early time (flash) spectroscopy of sn 2023ixf, obtained primarily at lick observatory, reveals emission lines of h i, he i/ii, c iv, and n iii/iv/v with a narrow core and broad, symmetric wings arising from the photoionization of dense, close-in circumstellar material (csm) located around the progenitor star prior to shock breakout. these electron-scattering broadened line profiles persist for ~8 days with respect to first light, at which time doppler broadened the features from the fastest sn ejecta form, suggesting a reduction in csm density at r ≳ 1015 cm. the early time light curve of sn 2023ixf shows peak absolute magnitudes (e.g., mu= -18.6 mag, mg= -18.4 mag) that are ≳2 mag brighter than typical type ii sne, this photometric boost also being consistent with the shock power supplied from csm interaction. comparison of sn 2023ixf to a grid of light-curve and multiepoch spectral models from the non-lte radiative transfer code cmfgen and the radiation-hydrodynamics code heracles suggests dense, solar-metallicity csm confined to r = (0.5-1) × 1015 cm, and a progenitor mass-loss rate of $\dot{m}={10}^{-2}\,{m}_{\odot }$ yr-1. for the assumed progenitor wind velocity of vw= 50 km s-1, this corresponds to enhanced mass loss (i.e., superwind phase) during the last ~3-6 yr before explosion. | sn 2023ixf in messier 101: photo-ionization of dense, close-in circumstellar material in a nearby type ii supernova |
we introduce the virgo consortium's flamingo suite of hydrodynamical simulations for cosmology and galaxy cluster physics. to ensure the simulations are sufficiently realistic for studies of large-scale structure, the subgrid prescriptions for stellar and agn feedback are calibrated to the observed low-redshift galaxy stellar mass function and cluster gas fractions. the calibration is performed using machine learning, separately for each of flamingo's three resolutions. this approach enables specification of the model by the observables to which they are calibrated. the calibration accounts for a number of potential observational biases and for random errors in the observed stellar masses. the two most demanding simulations have box sizes of 1.0 and 2.8 gpc on a side and baryonic particle masses of 1 × 108 and $1\times 10^9\, \text{m}_\odot$, respectively. for the latter resolution, the suite includes 12 model variations in a 1 gpc box. there are 8 variations at fixed cosmology, including shifts in the stellar mass function and/or the cluster gas fractions to which we calibrate, and two alternative implementations of agn feedback (thermal or jets). the remaining 4 variations use the unmodified calibration data but different cosmologies, including different neutrino masses. the 2.8 gpc simulation follows 3 × 1011 particles, making it the largest ever hydrodynamical simulation run to z = 0. light-cone output is produced on-the-fly for up to 8 different observers. we investigate numerical convergence, show that the simulations reproduce the calibration data, and compare with a number of galaxy, cluster, and large-scale structure observations, finding very good agreement with the data for converged predictions. finally, by comparing hydrodynamical and 'dark-matter-only' simulations, we confirm that baryonic effects can suppress the halo mass function and the matter power spectrum by up to ≈20 per cent. | the flamingo project: cosmological hydrodynamical simulations for large-scale structure and galaxy cluster surveys |
gamma-ray bursts (grbs) are flashes of high-energy radiation arising from energetic cosmic explosions. bursts of long (greater than two seconds) duration are produced by the core-collapse of massive stars1, and those of short (less than two seconds) duration by the merger of compact objects, such as two neutron stars2. a third class of events with hybrid high-energy properties was identified3, but never conclusively linked to a stellar progenitor. the lack of bright supernovae rules out typical core-collapse explosions4-6, but their distance scales prevent sensitive searches for direct signatures of a progenitor system. only tentative evidence for a kilonova has been presented7,8. here we report observations of the exceptionally bright grb 211211a, which classify it as a hybrid event and constrain its distance scale to only 346 megaparsecs. our measurements indicate that its lower-energy (from ultraviolet to near-infrared) counterpart is powered by a luminous (approximately 1042 erg per second) kilonova possibly formed in the ejecta of a compact object merger. | a nearby long gamma-ray burst from a merger of compact objects |
lyman-break galaxy (lbg) candidates at z ≳ 10 are rapidly being identified in james webb space telescope (jwst)/nircam observations. due to the (redshifted) break produced by neutral hydrogen absorption of rest-frame uv photons, these sources are expected to drop out in the bluer filters while being well detected in redder filters. however, here we show that dust-enshrouded star-forming galaxies at lower redshifts (z ≲ 7) may also mimic the near-infrared (near-ir) colors of z > 10 lbgs, representing potential contaminants in lbg candidate samples. first, we analyze ceers-dsfg-1, a nircam dropout undetected in the f115w and f150w filters but detected at longer wavelengths. combining the jwst data with (sub)millimeter constraints, including deep noema interferometric observations, we show that this source is a dusty star-forming galaxy (dsfg) at z ≈ 5.1. we also present a tentative 2.6σ scuba-2 detection at 850 μm around a recently identified z ≈ 16 lbg candidate in the same field and show that, if the emission is real and associated with this candidate, the available photometry is consistent with a z ~ 5 dusty galaxy with strong nebular emission lines despite its blue near-ir colors. further observations on this candidate are imperative to mitigate the low confidence of this tentative submillimeter emission and its positional uncertainty. our analysis shows that robust (sub)millimeter detections of nircam dropout galaxies likely imply z ~ 4-6 redshift solutions, where the observed near-ir break would be the result of a strong rest-frame optical balmer break combined with high dust attenuation and strong nebular line emission, rather than the rest-frame uv lyman break. this provides evidence that dsfgs may contaminate searches for ultra-high redshift lbg candidates from jwst observations. | dusty starbursts masquerading as ultra-high redshift galaxies in jwst ceers observations |
various theoretical models treating the effect of stellar irradiation on planetary envelopes predict the presence of a radius valley, i.e. a bimodal distribution of planet radii, with super-earths and sub-neptune planets separated by a valley at around {≈ } 2 r_\oplus. such a valley has been observed recently, owing to an improvement in the precision of stellar and therefore planetary radii. here, we investigate the presence, location, and shape of such a valley using a small sample with highly accurate stellar parameters determined from asteroseismology, which includes 117 planets with a median uncertainty on the radius of 3.3 per cent. we detect a clear bimodal distribution, with super-earths ({≈ } 1.5 r_\oplus) and sub-neptunes (≈2.5 r⊕) separated by a deficiency around 2 r_\oplus. we furthermore characterize the slope of the valley as a power law r∝pγ with γ = {-0.09^{+0.02}_{-0.04}}. a negative slope is consistent with models of photoevaporation, but not with the late formation of rocky planets in a gas-poor environment, which would lead to a slope of opposite sign. the exact location of the gap further points to planet cores consisting of a significant fraction of rocky material. | an asteroseismic view of the radius valley: stripped cores, not born rocky |
in a single process, the merger of binary neutron star systems combines extreme gravity, the copious emission of gravitational waves, complex microphysics and electromagnetic processes, which can lead to astrophysical signatures observable at the largest redshifts. we review here the recent progress in understanding what could be considered einstein’s richest laboratory, highlighting in particular the numerous significant advances of the last decade. although special attention is paid to the status of models, techniques and results for fully general-relativistic dynamical simulations, a review is also offered on the initial data and advanced simulations with approximate treatments of gravity. finally, we review the considerable amount of work carried out on the post-merger phase, including black-hole formation, torus accretion onto the merged compact object, the connection with gamma-ray burst engines, ejected material, and its nucleosynthesis. | binary neutron star mergers: a review of einstein’s richest laboratory |
the historical first detection of a binary neutron star merger by the ligo-virgo collaboration [b. p. abbott et al., phys. rev. lett. 119, 161101 (2017), 10.1103/physrevlett.119.161101] is providing fundamental new insights into the astrophysical site for the r process and on the nature of dense matter. a set of realistic models of the equation of state (eos) that yield an accurate description of the properties of finite nuclei, support neutron stars of two solar masses, and provide a lorentz covariant extrapolation to dense matter are used to confront its predictions against tidal polarizabilities extracted from the gravitational-wave data. given the sensitivity of the gravitational-wave signal to the underlying eos, limits on the tidal polarizability inferred from the observation translate into constraints on the neutron-star radius. based on these constraints, models that predict a stiff symmetry energy, and thus large stellar radii, can be ruled out. indeed, we deduce an upper limit on the radius of a 1.4 m⊙ neutron star of r⋆1.4<13.76 km . given the sensitivity of the neutron-skin thickness of <mml:mmultiscripts>pb 208 </mml:mmultiscripts> to the symmetry energy, albeit at a lower density, we infer a corresponding upper limit of about rskin208≲0.25 fm . however, if the upcoming prex-ii experiment measures a significantly thicker skin, this may be evidence of a softening of the symmetry energy at high densities—likely indicative of a phase transition in the interior of neutron stars. | neutron skins and neutron stars in the multimessenger era |
we have determined masses, stellar mass functions, and structural parameters of 112 milky way globular clusters by fitting a large set of n-body simulations to their velocity dispersion and surface density profiles. the velocity dispersion profiles were calculated based on a combination of more than 15000 high-precision radial velocities which we derived from archival eso/vlt and keck spectra together with ∼20000 published radial velocities from the literature. our fits also include the stellar mass functions of the globular clusters, which are available for 47 clusters in our sample, allowing us to self-consistently take the effects of mass segregation and ongoing cluster dissolution into account. we confirm the strong correlation between the global mass functions of globular clusters and their relaxation times recently found by sollima & baumgardt (2017). we also find a correlation of the escape velocity from the centre of a globular cluster and the fraction of first generation stars (fg) in the cluster recently derived for 57 globular clusters by milone et al. (2017), but no correlation between the fg star fraction and the global mass function of a globular cluster. this could indicate that the ability of a globular cluster to keep the wind ejecta from the polluting star(s) is the crucial parameter determining the presence and fraction of second-generation stars and not its later dynamical mass loss. | a catalogue of masses, structural parameters, and velocity dispersion profiles of 112 milky way globular clusters |
the solar cycle is reviewed. the 11-year cycle of solar activity is characterized by the rise and fall in the numbers and surface area of sunspots. a number of other solar activity indicators also vary in association with the sunspots including; the 10.7 cm radio flux, the total solar irradiance, the magnetic field, flares and coronal mass ejections, geomagnetic activity, galactic cosmic ray fluxes, and radioisotopes in tree rings and ice cores. individual solar cycles are characterized by their maxima and minima, cycle periods and amplitudes, cycle shape, the equatorward drift of the active latitudes, hemispheric asymmetries, and active longitudes. cycle-to-cycle variability includes the maunder minimum, the gleissberg cycle, and the gnevyshev-ohl (even-odd) rule. short-term variability includes the 154-day periodicity, quasi-biennial variations, and double-peaked maxima. we conclude with an examination of prediction techniques for the solar cycle and a closer look at cycles 23 and 24. | the solar cycle |
the local group galaxies offer some of the most discriminating tests of models of cosmic structure formation. for example, observations of the milky way (mw) and andromeda satellite populations appear to be in disagreement with n-body simulations of the `lambda cold dark matter' (λcdm) model: there are far fewer satellite galaxies than substructures in cdm haloes (the `missing satellites' problem); dwarf galaxies seem to avoid the most massive substructures (the `too-big-to-fail' problem); and the brightest satellites appear to orbit their host galaxies on a thin plane (the `planes of satellites' problem). here we present results from apostle (a project of simulating the local environment), a suite of cosmological hydrodynamic simulations of 12 volumes selected to match the kinematics of the local group (lg) members. applying the eagle code to the lg environment, we find that our simulations match the observed abundance of lg galaxies, including the satellite galaxies of the mw and andromeda. due to changes to the structure of haloes and the evolution in the lg environment, the simulations reproduce the observed relation between stellar mass and velocity dispersion of individual dwarf spheroidal galaxies without necessitating the formation of cores in their dark matter profiles. satellite systems form with a range of spatial anisotropies, including one similar to the mws, confirming that such a configuration is not unexpected in λcdm. finally, based on the observed velocity dispersion, size, and stellar mass, we provide estimates of the maximum circular velocity for the haloes of nine mw dwarf spheroidals. | the apostle simulations: solutions to the local group's cosmic puzzles |
we present a catalogue of white dwarf candidates selected from the second data release of gaia (dr2). we used a sample of spectroscopically confirmed white dwarfs from the sloan digital sky survey (sdss) to map the entire space spanned by these objects in the gaia hertzsprung-russell diagram. we then defined a set of cuts in absolute magnitude, colour, and a number of gaia quality flags to remove the majority of contaminating objects. finally, we adopt a method analogous to the one presented in our earlier sdss photometric catalogues to calculate a probability of being a white dwarf (pwd) for all gaia sources that passed the initial selection. the final catalogue is composed of 486 641 stars with calculated pwd from which it is possible to select a sample of {∼eq } 260 000 high-confidence white dwarf candidates in the magnitude range 8 < g < 21. by comparing this catalogue with a sample of sdss white dwarf candidates, we estimate an upper limit in completeness of 85 per cent for white dwarfs with g ≤ 20 mag and teff >7000 k, at high galactic latitudes (|b| > 20°). however, the completeness drops at low galactic latitudes, and the magnitude limit of the catalogue varies significantly across the sky as a function of gaia's scanning law. we also provide the list of objects within our sample with available sdss spectroscopy. we use this spectroscopic sample to characterize the observed structure of the white dwarf distribution in the h-r diagram. | a gaia data release 2 catalogue of white dwarfs and a comparison with sdss |
recent numerical simulations in general relativistic magnetohydrodynamics (grmhd) provide useful constraints for the interpretation of the gw170817 discovery. combining the observed data with these simulations leads to a bound on the maximum mass of a cold, spherical neutron star (the tov limit): mmaxsph≲2.74 /β , where β is the ratio of the maximum mass of a uniformly rotating neutron star (the supramassive limit) over the maximum mass of a nonrotating star. causality arguments allow β to be as high as 1.27, while most realistic candidate equations of state predict β to be closer to 1.2, yielding mmaxsph in the range 2.16 - 2.28 m⊙ . a minimal set of assumptions based on these simulations distinguishes this analysis from previous ones, but leads a to similar estimate. there are caveats, however, and they are enumerated and discussed. the caveats can be removed by further simulations and analysis to firm up the basic argument. | gw170817, general relativistic magnetohydrodynamic simulations, and the neutron star maximum mass |
detections of gravitational waves are now starting to probe the mass distribution of stellar mass black holes (bhs). robust predictions from stellar models are needed to interpret these. theory predicts the existence of a gap in the bh mass distribution because of pair-instability supernovae. the maximum bh mass below the gap is the result of pulsational mass loss. we evolve massive helium stars through their late hydrodynamical phases of evolution using the open-source mesa stellar evolution code. we find that the location of the lower edge of the mass gap at 45 {m}⊙is remarkably robust against variations in the metallicity (≈3 {m}⊙ ), the treatment of internal mixing (≈1 {m}⊙ ), and stellar wind mass loss (≈4 {m}⊙ ), making it the most robust predictor for the final stages of the evolution of massive stars. the reason is that the onset of the instability is dictated by the near-final core mass, which in turn sets the resulting bh mass. however, varying the {}12{{c}}{≤ft(α ,γ \right)}16{{o}} reaction rate within its 1σ uncertainties shifts the location of the gap between 40 {m}⊙and 56 {m}⊙ . we provide updated analytic fits for population synthesis simulations. our results imply that the detection of merging bhs can provide constraints on nuclear astrophysics. furthermore, the robustness against metallicity suggests that there is a universal maximum for the location of the lower edge of the gap, which is insensitive to the formation environment and redshift for first-generation bhs. this is promising for the possibility to use the location of the gap as a “standard siren” across the universe. | mind the gap: the location of the lower edge of the pair-instability supernova black hole mass gap |
we present the third open gravitational-wave catalog (3-ogc) of compact-binary coalescences, based on the analysis of the public ligo and virgo data from 2015 through 2019 (o1, o2, o3a). our updated catalog includes a population of 57 observations, including 4 binary black hole mergers that had not been previously reported. this consists of 55 binary black hole mergers and the 2 binary neutron star mergers, gw170817 and gw190425. we find no additional significant binary neutron star or neutron star-black hole merger events. the most confident new detection is the binary black hole merger gw190925_232845, which was observed by the ligo-hanford and virgo observatories with ${{ \mathcal p }}_{\mathrm{astro}}\gt 0.99;$ its primary and secondary component masses are ${20.2}_{-2.5}^{+3.9}\,{m}_{\odot }$ and ${15.6}_{-2.6}^{+2.1}\,{m}_{\odot }$ , respectively. we estimate the parameters of all binary black hole events using an up-to-date waveform model that includes both subdominant harmonics and precession effects. to enable deep follow up as our understanding of the underlying populations evolves, we make available our comprehensive catalog of events, including the subthreshold population of candidates, and the posterior samples of our source parameter estimates. | 3-ogc: catalog of gravitational waves from compact-binary mergers |
gravitational-wave observation together with a large number of electromagnetic observations shows that the source of the latest gravitational-wave event, gw170817, detected primarily by advanced ligo, is the merger of a binary neutron star. we attempt to interpret this observational event based on our results of numerical-relativity simulations performed so far, paying particular attention to the optical and infrared observations. we finally reach a conclusion that this event is described consistently by the presence of a long-lived hypermassive or supramassive neutron star as the merger remnant because (i) significant contamination by lanthanide elements along our line of sight to this source can be avoided by the strong neutrino irradiation from it and (ii) it could play a crucial role in producing an ejecta component of appreciable mass with fast motion in the postmerger phase. we also point out that (i) the neutron-star equation of state has to be sufficiently stiff (i.e., the maximum mass of cold spherical neutron stars, mmax, has to be appreciably higher than 2 m⊙) in order for a long-lived massive neutron star to be formed as the merger remnant for the binary systems of gw170817, for which the initial total mass is ≳2.73 m⊙ , and (ii) the absence of optical counterparts associated with relativistic ejecta suggests a not-extremely-high value of mmax approximately as 2.15 - 2.25 m⊙ . | modeling gw170817 based on numerical relativity and its implications |
we construct closed-form gravitational waveforms (gws) with tidal effects for the coalescence of binary neutron stars. the method relies on a new set of eccentricity-reduced and high-resolution numerical relativity (nr) simulations and is composed of three steps. first, tidal contributions to the gw phase are extracted from the time-domain nr data. second, those contributions are employed to fix high-order coefficients in an effective and resummed post-newtonian expression. third, frequency-domain tidal approximants are built using the stationary phase approximation. our tidal approximants are valid from the low frequencies to the strong-field regime. they can be analytically added to any binary black hole gw model to obtain a binary neutron star waveform, either in the time or in the frequency domain. this work provides simple, flexible, and accurate models ready to be used in both searches and parameter estimation of binary neutron star events. | closed-form tidal approximants for binary neutron star gravitational waveforms constructed from high-resolution numerical relativity simulations |
we have derived the mean proper motions and space velocities of 154 galactic globular clusters and the velocity dispersion profiles of 141 globular clusters based on a combination of gaia dr2 proper motions with ground-based line-of-sight velocities. combining the velocity dispersion profiles derived here with new measurements of the internal mass functions allows us to model the internal kinematics of 144 clusters, more than 90 per cent of the currently known galactic globular cluster population. we also derive the initial cluster masses by calculating the cluster orbits backwards in time applying suitable recipes to account for mass-loss and dynamical friction. we find a correlation between the stellar mass function of a globular cluster and the amount of mass lost from the cluster, pointing to dynamical evolution as one of the mechanisms shaping the mass function of stars in clusters. the mass functions also show strong evidence that globular clusters started with a bottom-light initial mass function. our simulations show that the currently surviving globular cluster population has lost about 80 per cent of its mass since the time of formation. if globular clusters started from a lognormal mass function, we estimate that the milky way contained about 500 globular clusters initially, with a combined mass of about 2.5 × 108 m⊙. for a power-law initial mass function, the initial mass in globular clusters could have been a factor of three higher. | mean proper motions, space orbits, and velocity dispersion profiles of galactic globular clusters derived from gaia dr2 data |
the space-based laser interferometer space antenna (lisa) will be able to observe the gravitational-wave signals from systems comprised of a massive black hole and a stellar-mass compact object. these systems are known as extreme-mass-ratio inspirals (emris) and are expected to complete ∼1 04- 1 05 cycles in band, thus allowing exquisite measurements of their parameters. in this work, we attempt to quantify the astrophysical uncertainties affecting the predictions for the number of emris detectable by lisa, and find that competing astrophysical assumptions produce a variance of about three orders of magnitude in the expected intrinsic emri rate. however, we find that irrespective of the astrophysical model, at least a few emris per year should be detectable by the lisa mission, with up to a few thousands per year under the most optimistic astrophysical assumptions. we also investigate the precision with which lisa will be able to extract the parameters of these sources. we find that typical fractional statistical errors with which the intrinsic parameters (redshifted masses, massive black hole spin and orbital eccentricity) can be recovered are ∼10-6- 10-4 . luminosity distance (which is required to infer true masses) is inferred to about 10% precision and sky position is localized to a few square degrees, while tests of the multipolar structure of the kerr metric can be performed to percent-level precision or better. | science with the space-based interferometer lisa. v. extreme mass-ratio inspirals |
over the past decade, the existence of a substantial population of optically invisible, massive galaxies at $z\gtrsim3$ has been implied from mid-infrared to millimeter observations. with the unprecedented sensitivity of the jwst, such extremely massive galaxy candidates have immediately been identified even at $z>7$, in much larger numbers than expected. these discoveries raised a hot debate. if confirmed, early, high-mass galaxies challenge the current models of galaxy formation. however, the lack of spectroscopic confirmations leads to uncertain stellar mass ($m_{\star}$) estimates, and the possible presence of active galactic nuclei (agn) adds further uncertainty. here, we present the first sample of 36 dust-obscured galaxies with robust spectroscopic redshifts at $z_{\rm spec}=5-9$ from the jwst fresco survey. the three most extreme sources at $z\sim5-6$ ($\sim$1 billion years after the big bang) are so massive (log$m_{\star}/m_{\odot}$ $\gtrsim11.0$) that they would require, on average, about 50% of the baryons in their halos to be converted into stars -- two to three times higher than even the most efficient galaxies at later times. the extended emission of these galaxies suggests limited contribution by agn. this population of ultra-massive galaxies accounts for 20% of the total cosmic star formation rate density at $z\sim5-6$, suggesting a substantial proportion of extremely efficient star formation in the early universe. | massive optically dark galaxies unveiled by jwst challenge galaxy formation models |
star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ‘ultracool dwarfs’. this heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the sun. core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them—ranging from metal-rich mercury-sized planets to more hospitable volatile-rich earth-sized planets. here we report observations of three short-period earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. the inner two planets receive four times and two times the irradiation of earth, respectively, placing them close to the inner edge of the habitable zone of the star. our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by earth. the infrared brightness of the host star, combined with its jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system. | temperate earth-sized planets transiting a nearby ultracool dwarf star |
deep images and near-ir spectra of galaxies in the field of the lensing cluster smacs j0723.3−7327 were recently taken as part of the early release observations (eros) program of the james webb space telescope (jwst). among these, two nirspec spectra of galaxies, at z = 7.7 and at z = 8.5, were obtained, revealing, for the first time, the rest-frame optical emission line spectra of galaxies in the epoch of reionization, including the detection of the important [o iii]λ4363 auroral line (see jwst pr 2022-035). we present an analysis of the emission line properties of these galaxies, finding that these galaxies have a high excitation (as indicated by high ratios of [o iii]λ5007/[o ii] λ3727, [ne iii] λ3869/[o ii] λ3727), strong [o iii]λ4363, high equivalent widths, and other properties typical of low-metallicity star-forming galaxies. using the direct method, we determined oxygen abundances of 12 + log(o/h)≈7.9 in two z = 7.7 galaxies and a lower metallicity of 12 + log(o/h)≈7.4 − 7.5 (∼5% solar) in the z = 8.5 galaxy using different strong line methods. more accurate metallicity determinations will require better data. with stellar masses estimated from spectral energy distribution (sed) fits, we find that the three galaxies lie close to or below the z ∼ 2 mass-metallicity relation. overall, these first galaxy spectra at z ∼ 8 show a strong resemblance in their the emission line properties of galaxies in the epoch of reionization with those of relatively rare local analogs previously studied with the sdss. clearly, the first jwst observations demonstrate already the incredible power of spectroscopy to reveal the properties of galaxies in the early universe. | first look with jwst spectroscopy: resemblance among z ∼ 8 galaxies and local analogs |
the laser interferometer gravitational-wave observatory (ligo) found direct evidence for double black hole binaries emitting gravitational waves. galactic nuclei are expected to harbor the densest population of stellar-mass black holes. a significant fraction (∼ 30 % ) of these black holes can reside in binaries. we examine the fate of the black hole binaries in active galactic nuclei, which get trapped in the inner region of the accretion disk around the central supermassive black hole. we show that binary black holes can migrate into and then rapidly merge within the disk well within a salpeter time. the binaries may also accrete a significant amount of gas from the disk, well above the eddington rate. this could lead to detectable x-ray or gamma-ray emission, but would require hyper-eddington accretion with a few percent radiative efficiency, comparable to thin disks. we discuss implications for gravitational-wave observations and black hole population studies. we estimate that advanced ligo may detect ∼20 such gas-induced binary mergers per year. | rapid and bright stellar-mass binary black hole mergers in active galactic nuclei |
we present the survey design, implementation, and outlook for cosmos-web, a 255 hr treasury program conducted by the james webb space telescope in its first cycle of observations. cosmos-web is a contiguous 0.54 deg2 nircam imaging survey in four filters (f115w, f150w, f277w, and f444w) that will reach 5σ point-source depths ranging ~27.5-28.2 mag. in parallel, we will obtain 0.19 deg2 of miri imaging in one filter (f770w) reaching 5σ point-source depths of ~25.3-26.0 mag. cosmos-web will build on the rich heritage of multiwavelength observations and data products available in the cosmos field. the design of cosmos-web is motivated by three primary science goals: (1) to discover thousands of galaxies in the epoch of reionization (6 ≲ z ≲ 11) and map reionization's spatial distribution, environments, and drivers on scales sufficiently large to mitigate cosmic variance, (2) to identify hundreds of rare quiescent galaxies at z > 4 and place constraints on the formation of the universe's most-massive galaxies (m ⋆ > 1010 m ⊙), and (3) directly measure the evolution of the stellar-mass-to-halo-mass relation using weak gravitational lensing out to z ~ 2.5 and measure its variance with galaxies' star formation histories and morphologies. in addition, we anticipate cosmos-web's legacy value to reach far beyond these scientific goals, touching many other areas of astrophysics, such as the identification of the first direct collapse black hole candidates, ultracool subdwarf stars in the galactic halo, and possibly the identification of z > 10 pair-instability supernovae. in this paper we provide an overview of the survey's key measurements, specifications, goals, and prospects for new discovery. | cosmos-web: an overview of the jwst cosmic origins survey |
exoplanets smaller than neptune are common around red dwarf stars (m dwarfs), with those that transit their host star constituting the bulk of known temperate worlds amenable for atmospheric characterization. we analyze the masses and radii of all known small transiting planets around m dwarfs, identifying three populations: rocky, water-rich, and gas-rich. our results are inconsistent with the previously known bimodal radius distribution arising from atmospheric loss of a hydrogen/helium envelope. instead, we propose that a density gap separates rocky from water-rich exoplanets. formation models that include orbital migration can explain the observations: rocky planets form within the snow line, whereas water-rich worlds form outside it and later migrate inward. | density, not radius, separates rocky and water-rich small planets orbiting m dwarf stars |
what is the size of the atomic nucleus? this deceivably simple question is difficult to answer. although the electric charge distributions in atomic nuclei were measured accurately already half a century ago, our knowledge of the distribution of neutrons is still deficient. in addition to constraining the size of atomic nuclei, the neutron distribution also impacts the number of nuclei that can exist and the size of neutron stars. we present an ab initio calculation of the neutron distribution of the neutron-rich nucleus 48ca. we show that the neutron skin (difference between the radii of the neutron and proton distributions) is significantly smaller than previously thought. we also make predictions for the electric dipole polarizability and the weak form factor; both quantities that are at present targeted by precision measurements. based on ab initio results for 48ca, we provide a constraint on the size of a neutron star. | neutron and weak-charge distributions of the 48ca nucleus |
fast radio bursts are millisecond-duration, extragalactic radio flashes of unknown physical origin. the only known repeating fast radio burst source—frb 121102—has been localized to a star-forming region in a dwarf galaxy at redshift 0.193 and is spatially coincident with a compact, persistent radio source. the origin of the bursts, the nature of the persistent source and the properties of the local environment are still unclear. here we report observations of frb 121102 that show almost 100 per cent linearly polarized emission at a very high and variable faraday rotation measure in the source frame (varying from +1.46 × 105 radians per square metre to +1.33 × 105 radians per square metre at epochs separated by seven months) and narrow (below 30 microseconds) temporal structure. the large and variable rotation measure demonstrates that frb 121102 is in an extreme and dynamic magneto-ionic environment, and the short durations of the bursts suggest a neutron star origin. such large rotation measures have hitherto been observed only in the vicinities of massive black holes (larger than about 10,000 solar masses). indeed, the properties of the persistent radio source are compatible with those of a low-luminosity, accreting massive black hole. the bursts may therefore come from a neutron star in such an environment or could be explained by other models, such as a highly magnetized wind nebula or supernova remnant surrounding a young neutron star. | an extreme magneto-ionic environment associated with the fast radio burst source frb 121102 |
on april 1st, 2019, the advanced laser interferometer gravitational-wave observatory (aligo), joined by the advanced virgo detector, began the third observing run, a year-long dedicated search for gravitational radiation. the ligo detectors have achieved a higher duty cycle and greater sensitivity to gravitational waves than ever before, with ligo hanford achieving angle-averaged sensitivity to binary neutron star coalescences to a distance of 111 mpc, and ligo livingston to 134 mpc with duty factors of 74.6% and 77.0% respectively. the improvement in sensitivity and stability is a result of several upgrades to the detectors, including doubled intracavity power, the addition of an in-vacuum optical parametric oscillator for squeezed-light injection, replacement of core optics and end reaction masses, and installation of acoustic mode dampers. this paper explores the purposes behind these upgrades, and explains to the best of our knowledge the noise currently limiting the sensitivity of each detector. | sensitivity and performance of the advanced ligo detectors in the third observing run |
the reionization era bright emission line survey (rebels) is a cycle-7 alma large program (lp) that is identifying and performing a first characterization of many of the most luminous star-forming galaxies known in the z > 6.5 universe. rebels is providing this probe by systematically scanning 40 of the brightest uv-selected galaxies identified over a 7 deg2 area for bright [c ii]158 μm and [o iii]88 μm lines and dust-continuum emission. selection of the 40 rebels targets was done by combining our own and other photometric selections, each of which is subject to extensive vetting using three completely independent sets of photometry and template-fitting codes. building on the observational strategy deployed in two pilot programs, we are increasing the number of massive interstellar medium (ism) reservoirs known at z > 6.5 by ~4-5× to >30. in this manuscript, we motivate the observational strategy deployed in the rebels program and present initial results. based on the first-year observations, 18 highly significant ≥ 7σ [c ii]158 μm lines have already been discovered, the bulk of which (13/18) also show ≥3.3σ dust-continuum emission. these newly discovered lines more than triple the number of bright ism-cooling lines known in the z > 6.5 universe, such that the number of alma-derived redshifts at z > 6.5 rival lyα discoveries. an analysis of the completeness of our search results versus star formation rate (sfr) suggests an ~79% efficiency in scanning for [c ii]158 μm when the sfruv+ir is >28 m ⊙ yr-1. these new lp results further demonstrate alma's efficiency as a "redshift machine," particularly in the epoch of reionization. | reionization era bright emission line survey: selection and characterization of luminous interstellar medium reservoirs in the z > 6.5 universe |
intense, millisecond-duration bursts of radio waves (named fast radio bursts) have been detected from beyond the milky way1. their dispersion measures—which are greater than would be expected if they had propagated only through the interstellar medium of the milky way—indicate extragalactic origins and imply contributions from the intergalactic medium and perhaps from other galaxies2. although several theories exist regarding the sources of these fast radio bursts, their intensities, durations and temporal structures suggest coherent emission from highly magnetized plasma3,4. two of these bursts have been observed to repeat5,6, and one repeater (frb 121102) has been localized to the largest star-forming region of a dwarf galaxy at a cosmological redshift of 0.19 (refs. 7-9). however, the host galaxies and distances of the hitherto non-repeating fast radio bursts are yet to be identified. unlike repeating sources, these events must be observed with an interferometer that has sufficient spatial resolution for arcsecond localization at the time of discovery. here we report the localization of a fast radio burst (frb 190523) to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66. this galaxy is different from the host of frb 121102, as it is a thousand times more massive, with a specific star-formation rate (the star-formation rate divided by the mass) a hundred times smaller. | a fast radio burst localized to a massive galaxy |
we identify an observable imprint of a first-order hadron-quark phase transition at supranuclear densities on the gravitational-wave (gw) emission of neutron-star mergers. specifically, we show that the dominant postmerger gw frequency fpeak may exhibit a significant deviation from an empirical relation between fpeak and the tidal deformability if a strong first-order phase transition leads to the formation of a gravitationally stable extended quark matter core in the postmerger remnant. a comparison of the gw signatures from a large, representative sample of microphysical, purely hadronic equations of state indicates that this imprint is only observed in those systems which undergo a strong first-order phase transition. such a shift of the dominant postmerger gw frequency can be revealed by future gw observations, which would provide evidence for the existence of a strong first-order phase transition in the interior of neutron-stars. | identifying a first-order phase transition in neutron-star mergers through gravitational waves |
nonparametric star formation histories (sfhs) have long promised to be the “gold standard” for galaxy spectral energy distribution (sed) modeling as they are flexible enough to describe the full diversity of sfh shapes, whereas parametric models rule out a significant fraction of these shapes a priori. however, this flexibility is not fully constrained even with high-quality observations, making it critical to choose a well-motivated prior. here, we use the sed-fitting code prospector to explore the effect of different nonparametric priors by fitting sfhs to mock uv-ir photometry generated from a diverse set of input sfhs. first, we confirm that nonparametric sfhs recover input sfhs with less bias and return more accurate errors than do parametric sfhs. we further find that, while nonparametric sfhs robustly recover the overall shape of the input sfh, the primary determinant of the size and shape of the posterior star formation rate as a function of time (sfr(t)) is the choice of prior, rather than the photometric noise. as a practical demonstration, we fit the uv-ir photometry of ∼6000 galaxies from the galaxy and mass assembly survey and measure scatters between priors to be 0.1 dex in mass, 0.8 dex in sfr100 myr, and 0.2 dex in mass-weighted ages, with the bluest star-forming galaxies showing the most sensitivity. an important distinguishing characteristic for nonparametric models is the characteristic timescale for changes in sfr(t). this difference controls whether galaxies are assembled in bursts or in steady-state star formation, corresponding respectively to (feedback-dominated/accretion-dominated) models of galaxy formation and to (larger/smaller) confidence intervals derived from sed fitting. high-quality spectroscopy has the potential to further distinguish between these proposed models of sfr(t). | how to measure galaxy star formation histories. ii. nonparametric models |
previous analyses of various standard candles observed by the gaia satellite have reported statistically significant systematics in the parallaxes that have improved from ∼250 μas in the first data release (dr1) to 50-80 μas in the second data release (dr2). here we examine the parallaxes newly reported in the gaia early third data release (edr3) using the same sample of benchmark eclipsing binaries (ebs) we used to assess the dr1 and dr2 parallaxes. we find a mean offset of -37 ± 20 μas (gaia - eb), which decreases to -15 ± 18 μas after applying the corrections recommended by the gaia mission team; global systematics in the gaia parallaxes have clearly improved and are no longer statistically significant for the eb sample, which spans 5 ≲ g ≲ 12 in brightness and 0.03-3 kpc in distance. we also find that the renormalized unit weight error (ruwe) goodness-of-fit statistic reported in gaia dr3 is highly sensitive to unresolved companions (tertiaries in the case of our eb sample) as well as to photocenter motion of the binaries themselves. ruwe is nearly perfectly correlated (r2 = 0.82) with photocenter motions down to ≲0.1 mas, and surprisingly this correlation exists entirely within the nominal "good" ruwe range of 1.0-1.4. this suggests that ruwe values even slightly greater than 1.0 may signify unresolved binaries in gaia, and that the ruwe value can serve as a quantitative predictor of the photocenter motion. | parallax systematics and photocenter motions of benchmark eclipsing binaries in gaia edr3 |
fast radio bursts (frbs) can arise from synchrotron maser emission at ultrarelativistic magnetized shocks, such as produced by flare ejecta from young magnetars. we combine particle-in-cell simulation results for the maser emission with the dynamics of self-similar shock deceleration, as commonly applied to gamma-ray bursts (grbs), to explore the implications for frbs. the upstream environment is a mildly relativistic baryon-loaded shell released following a previous flare, motivated by the high electron-ion injection rate \dot{m} ∼ 10^{19}-10^{21} g s-1 needed to power the persistent radio nebula coincident with the repeating burster frb 121102 and its high rotation measure. the radio fluence peaks once the optical depth ahead of the shock to induced compton scattering τc ≲ 3. given intervals between major ion ejection events δt ∼ 105 s similar to the occurrence rate of the most powerful bursts from frb 121102, we demonstrate the production of ∼0.1-10 ghz frbs with isotropic radiated energies ∼1037-1040 erg and durations ∼0.1-10 ms for flare energies e ∼ 1043-1045 erg. deceleration of the blast wave, and increasing transparency of the upstream medium, generates temporal decay of the peak frequency, similar to the observed downward frequency drift seen in frb 121102 and frb 180814.j0422+73. the delay δt ≳ 105 s between major ion-injection events needed to clear sufficiently low densities around the engine for frb emission could explain prolonged `dark periods' and clustered burst arrival times. thermal electrons heated at the shock generate a short-lived ≲1 ms (1 s) synchrotron transient at gamma-ray (x-ray) energies, analogous to a scaled-down grb afterglow. | fast radio bursts as synchrotron maser emission from decelerating relativistic blast waves |
to constrain the equation of state of cold dense matter, astrophysical measurements are essential. these are mostly based on observations of neutron stars in the x-ray band, and, more recently, also on gravitational wave observations. of particular interest are observations of unusually heavy or light neutron stars which extend the range of central densities probed by observations and thus permit the testing of nuclear-physics predictions over a wider parameter space. here we report on the analysis of such a star, a central compact object within the supernova remnant hess j1731-347. we estimate the mass and radius of the neutron star to be m =0.7 7−0.17+0.20m⊙ and r =10 .4−0.78+0.86 km, respectively, based on modelling of the x-ray spectrum and a robust distance estimate from gaia observations. our estimate implies that this object is either the lightest neutron star known, or a `strange star' with a more exotic equation of state. adopting a standard neutron star matter hypothesis allows the corresponding equations of state to be constrained. | a strangely light neutron star within a supernova remnant |
fast radio bursts are mysterious millisecond-duration transients prevalent in the radio sky. rapid accumulation of data in recent years has facilitated an understanding of the underlying physical mechanisms of these events. knowledge gained from the neighbouring fields of gamma-ray bursts and radio pulsars has also offered insights. here i review developments in this fast-moving field. two generic categories of radiation model invoking either magnetospheres of compact objects (neutron stars or black holes) or relativistic shocks launched from such objects have been much debated. the recent detection of a galactic fast radio burst in association with a soft gamma-ray repeater suggests that magnetar engines can produce at least some, and probably all, fast radio bursts. other engines that could produce fast radio bursts are not required, but are also not impossible. | the physical mechanisms of fast radio bursts |
we report the transport properties of kagome superconductor csv3 sb5 single crystals at magnetic field up to 32 t. the shubnikov-de haas oscillations emerge at low temperature and four frequencies of fα=27 t , fβ=73 t , fε=727 t , and fη=786 t with relatively small cyclotron masses are observed. for fβ and fε, the berry phases are close to π , providing clear evidence of nontrivial topological band structures of csv3 sb5 . furthermore, the consistence between theoretical calculations and experimental results implies that these frequencies can be assigned to the fermi surfaces locating near the boundary of brillouin zone and confirms that the structure with an inverse star of david distortion could be the most stable structure at charge density wave state. these results will shed light on the nature of correlated topological physics in kagome material csv3 sb5 . | quantum transport evidence of topological band structures of kagome superconductor csv3 sb5 |
current interferometric gravitational-wave detectors are limited by quantum noise over a wide range of their measurement bandwidth. one method to overcome the quantum limit is the injection of squeezed vacuum states of light into the interferometer's dark port. here, we report on the successful application of this quantum technology to improve the shot noise limited sensitivity of the advanced virgo gravitational-wave detector. a sensitivity enhancement of up to 3.2 ±0.1 db beyond the shot noise limit is achieved. this nonclassical improvement corresponds to a 5%-8% increase of the binary neutron star horizon. the squeezing injection was fully automated and over the first 5 months of the third joint ligo-virgo observation run o3 squeezing was applied for more than 99% of the science time. during this period several gravitational-wave candidates have been recorded. | increasing the astrophysical reach of the advanced virgo detector via the application of squeezed vacuum states of light |
the disk substructures at high angular resolution project (dsharp) provides a large sample of protoplanetary disks with substructures that could be induced by young forming planets. to explore the properties of planets that may be responsible for these substructures, we systematically carry out a grid of 2d hydrodynamical simulations, including both gas and dust components. we present the resulting gas structures, including the relationship between the planet mass, as well as (1) the gaseous gap depth/width and (2) the sub/super-keplerian motion across the gap. we then compute dust continuum intensity maps at the frequency of the dsharp observations. we provide the relationship between the planet mass, as well as (1) the depth/width of the gaps at millimeter intensity maps, (2) the gap edge ellipticity and asymmetry, and (3) the position of secondary gaps induced by the planet. with these relationships, we lay out the procedure to constrain the planet mass using gap properties, and study the potential planets in the dsharp disks. we highlight the excellent agreement between observations and simulations for as 209 and the detectability of the young solar system analog. finally, under the assumption that the detected gaps are induced by young planets, we characterize the young planet population in the planet mass-semimajor axis diagram. we find that the occurrence rate for >5 m j planets beyond 5-10 au is consistent with direct imaging constraints. disk substructures allow us to probe a wide-orbit planet population (neptune to jupiter mass planets beyond 10 au) that is not accessible to other planet searching techniques. | the disk substructures at high angular resolution project (dsharp). vii. the planet-disk interactions interpretation |
we introduce xcold gass, a legacy survey providing a census of molecular gas in the local universe. building on the original cold gass survey, we present here the full sample of 532 galaxies with co (1-0) measurements from the iram 30 m telescope. the sample is mass-selected in the redshift interval 0.01< z< 0.05 from the sloan digital sky survey (sdss) and therefore representative of the local galaxy population with {m}*> {10}9 {m}⊙ . the co (1-0) flux measurements are complemented by observations of the co (2-1) line with both the iram 30 m and apex telescopes, h i observations from arecibo, and photometry from sdss, wise, and galex. combining the iram and apex data, we find that the ratio of co (2-1) to co (1-0) luminosity for integrated measurements is {r}21=0.79+/- 0.03, with no systematic variations across the sample. the co (1-0) luminosity function is constructed and best fit with a schechter function with parameters {l}{co}* =(7.77+/- 2.11)× {10}9 {{k}} {km} {{{s}}}-1 {{pc}}2, {φ }* =(9.84+/- 5.41)× {10}-4 {{mpc}}-3, and α =-1.19+/- 0.05. with the sample now complete down to stellar masses of 109 {m}⊙ , we are able to extend our study of gas scaling relations and confirm that both molecular gas fractions ({f}{{{h}}2}) and depletion timescale ({t}{dep}({{{h}}}2)) vary with specific star formation rate (or offset from the star formation main sequence) much more strongly than they depend on stellar mass. comparing the xcold gass results with outputs from hydrodynamic and semianalytic models, we highlight the constraining power of cold gas scaling relations on models of galaxy formation. | xcold gass: the complete iram 30 m legacy survey of molecular gas for galaxy evolution studies |
the nuclear symmetry energy characterizes the variation of the binding energy as the neutron to proton ratio of a nuclear system is varied. this is one of the most important features of nuclear physics in general, since it is just related to the two component nature of the nuclear systems. as such it is one of the most relevant physical parameters that affect the physics of many phenomena and nuclear processes. this review paper presents a survey of the role and relevance of the nuclear symmetry energy in different fields of research and of the accuracy of its determination from the phenomenology and from the microscopic many-body theory. in recent years, a great interest was devoted not only to the nuclear matter symmetry energy at saturation density but also to its whole density dependence, which is an essential ingredient for our understanding of many phenomena. we analyze the nuclear symmetry energy in different realms of nuclear physics and astrophysics. in particular we consider the nuclear symmetry energy in relation to nuclear structure, astrophysics of neutron stars and supernovae, and heavy ion collision experiments, trying to elucidate the connections of these different fields on the basis of the symmetry energy peculiarities. the interplay between experimental and observational data and theoretical developments is stressed. the expected future developments and improvements are schematically addressed, together with most demanded experimental and theoretical advances for the next few years. | the nuclear symmetry energy |
hot jupiters were the first exoplanets to be discovered around main sequence stars and astonished us with their close-in orbits. they are a prime example of how exoplanets have challenged our textbook, solar-system inspired story of how planetary systems form and evolve. more than twenty years after the discovery of the first hot jupiter, there is no consensus on their predominant origin channel. three classes of hot jupiter creation hypotheses have been proposed: in situ formation, disk migration, and high-eccentricity tidal migration. although no origin channel alone satisfactorily explains all the evidence, two major origin channels together plausibly account for properties of hot jupiters themselves and their connections to other exoplanet populations. | origins of hot jupiters |
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