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gravity is a new instrument to coherently combine the light of the european southern observatory very large telescope interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m2. the instrument comprises fiber fed integrated optics beam combination, high resolution spectroscopy, built-in beam analysis and control, near-infrared wavefront sensing, phase-tracking, dual-beam operation, and laser metrology. gravity opens up to optical/infrared interferometry the techniques of phase referenced imaging and narrow angle astrometry, in many aspects following the concepts of radio interferometry. this article gives an overview of gravity and reports on the performance and the first astronomical observations during commissioning in 2015/16. we demonstrate phase-tracking on stars as faint as mk ≈ 10 mag, phase-referenced interferometry of objects fainter than mk ≈ 15 mag with a limiting magnitude of mk ≈ 17 mag, minute long coherent integrations, a visibility accuracy of better than 0.25%, and spectro-differential phase and closure phase accuracy better than 0.5°, corresponding to a differential astrometric precision of better than ten microarcseconds (μas). the dual-beam astrometry, measuring the phase difference of two objects with laser metrology, is still under commissioning. first observations show residuals as low as 50 μas when following objects over several months. we illustrate the instrument performance with the observations of archetypical objects for the different instrument modes. examples include the galactic center supermassive black hole and its fast orbiting star s2 for phase referenced dual-beam observations and infrared wavefront sensing, the high mass x-ray binary bp cru and the active galactic nucleus of pds 456 for a few μas spectro-differential astrometry, the t tauri star s cra for a spectro-differential visibility analysis, ξ tel and 24 cap for high accuracy visibility observations, and η car for interferometric imaging with gravity. | first light for gravity: phase referencing optical interferometry for the very large telescope interferometer |
continued timing observations of the double pulsar psr j0737-3039a/b, which consists of two active radio pulsars (a and b) that orbit each other with a period of 2.45 h in a mildly eccentric (e =0.088 ) binary system, have led to large improvements in the measurement of relativistic effects in this system. with a 16-yr data span, the results enable precision tests of theories of gravity for strongly self-gravitating bodies and also reveal new relativistic effects that have been expected but are now observed for the first time. these include effects of light propagation in strong gravitational fields which are currently not testable by any other method. in particular, we observe the effects of retardation and aberrational light bending that allow determination of the spin direction of the pulsar. in total, we detect seven post-keplerian parameters in this system, more than for any other known binary pulsar. for some of these effects, the measurement precision is now so high that for the first time we have to take higher-order contributions into account. these include the contribution of the a pulsar's effective mass loss (due to spin-down) to the observed orbital period decay, a relativistic deformation of the orbit, and the effects of the equation of state of superdense matter on the observed post-keplerian parameters via relativistic spin-orbit coupling. we discuss the implications of our findings, including those for the moment of inertia of neutron stars, and present the currently most precise test of general relativity's quadrupolar description of gravitational waves, validating the prediction of general relativity at a level of 1.3 ×10-4 with 95% confidence. we demonstrate the utility of the double pulsar for tests of alternative theories of gravity by focusing on two specific examples and also discuss some implications of the observations for studies of the interstellar medium and models for the formation of the double pulsar system. finally, we provide context to other types of related experiments and prospects for the future. | strong-field gravity tests with the double pulsar |
over the last 15 years, the supernova community has endeavoured to directly identify progenitor stars for core-collapse supernovae discovered in nearby galaxies. these precursors are often visible as resolved stars in high-resolution images from space-and ground-based telescopes. the discovery rate of progenitor stars is limited by the local supernova rate and the availability and depth of archive images of galaxies, with 18 detections of precursor objects and 27 upper limits. this review compiles these results (from 1999 to 2013) in a distance-limited sample and discusses the implications of the findings. the vast majority of the detections of progenitor stars are of type ii-p, ii-l, or iib with one type ib progenitor system detected and many more upper limits for progenitors of ibc supernovae (14 in all). the data for these 45 supernovae progenitors illustrate a remarkable deficit of high-luminosity stars above an apparent limit of logl/l⊙ ≃ 5.1 dex. for a typical salpeter initial mass function, one would expect to have found 13 high-luminosity and high-mass progenitors by now. there is, possibly, only one object in this time- and volume-limited sample that is unambiguously high-mass (the progenitor of sn2009ip) although the nature of that supernovae is still debated. the possible biases due to the influence of circumstellar dust, the luminosity analysis, and sample selection methods are reviewed. it does not appear likely that these can explain the missing high-mass progenitor stars. this review concludes that the community's work to date shows that the observed populations of supernovae in the local universe are not, on the whole, produced by high-mass (m ≳ 18 m⊙) stars. theoretical explosions of model stars also predict that black hole formation and failed supernovae tend to occur above an initial mass of m ≃ 18 m⊙. the models also suggest there is no simple single mass division for neutron star or black-hole formation and that there are islands of explodability for stars in the 8-120 m⊙ range.the observational constraints are quite consistent with the bulk of stars above m ≳ 18 m⊙ collapsing to form black holes with no visible supernovae. | observational constraints on the progenitors of core-collapse supernovae: the case for missing high-mass stars |
axion stars are hypothetical objects formed of axions, obtained as localized and coherently oscillating solutions to their classical equation of motion. depending on the value of the field amplitude at the core |θ0 | ≡ | θ (r = 0) |, the equilibrium of the system arises from the balance of the kinetic pressure and either self-gravity or axion self-interactions. starting from a general relativistic framework, we obtain the set of equations describing the configuration of the axion star, which we solve as a function of |θ0 |. for small |θ0 | ≲ 1, we reproduce results previously obtained in the literature, and we provide arguments for the stability of such configurations in terms of first principles. we compare qualitative analytical results with a numerical calculation. for large amplitudes |θ0 | ≳ 1, the axion field probes the full non-harmonic qcd chiral potential and the axion star enters the dense branch. our numerical solutions show that in this latter regime the axions are relativistic, and that one should not use a single frequency approximation, as previously applied in the literature. we employ a multi-harmonic expansion to solve the relativistic equation for the axion field in the star, and demonstrate that higher modes cannot be neglected in the dense regime. we interpret the solutions in the dense regime as pseudo-breathers, and show that the life-time of such configurations is much smaller than any cosmological time scale. | dilute and dense axion stars |
since september 2018, lamost starts a new 5-year medium-resolution spectroscopic survey (mrs) using bright/gray nights. we present the scientific goals of lamost-mrs and propose a near optimistic strategy of the survey. a complete footprint is also provided. not only the regular medium-resolution survey, but also a time-domain spectroscopic survey is being conducted since 2018 and will be end in 2023. according to the detailed survey plan, we expect that lamost-mrs can observe about 2 million stellar spectra with ~7500 and limiting magnitude of around g=15 mag. moreover, it will also provide about 200 thousand stars with averagely 60-epoch observations and limiting magnitude of g~14 mag. these high quality spectra will give around 20 elemental abundances, rotational velocities, emission line profiles as well as precise radial velocity with uncertainty less than 1 km/s. with these data, we expect that lamost can effectively leverage sciences on stellar physics, e.g. exotic binary stars, detailed observation of many types of variable stars etc., planet host stars, emission nebulae, open clusters, young pre-main-sequence stars etc. | lamost medium-resolution spectroscopic survey (lamost-mrs): scientific goals and survey plan |
we present the first generalization of navier-stokes theory to relativity that satisfies all of the following properties: (a) the system coupled to einstein's equations is causal and strongly hyperbolic; (b) equilibrium states are stable; (c) all leading dissipative contributions are present, i.e., shear viscosity, bulk viscosity, and thermal conductivity; (d) nonzero baryon number is included; (e) entropy production is non-negative in the regime of validity of the theory; (f) all of the above hold in the nonlinear regime without any simplifying symmetry assumptions. these properties are accomplished using a generalization of eckart's theory containing only the hydrodynamic variables, so that no new extended degrees of freedom are needed as in müller-israel-stewart theories. property (b), in particular, follows from a more general result that we also establish, namely, sufficient conditions that when added to stability in the fluid's rest frame imply stability in any reference frame obtained via a lorentz transformation all of our results are mathematically rigorously established. the framework presented here provides the starting point for systematic investigations of general-relativistic viscous phenomena in neutron star mergers. | first-order general-relativistic viscous fluid dynamics |
astrophysical plasmas have the remarkable ability to preserve magnetic topology, which inevitably gives rise to the accumulation of magnetic energy within stressed regions including current sheets. this stored energy is often released explosively through the process of magnetic reconnection, which produces a reconfiguration of the magnetic field, along with high-speed flows, thermal heating and nonthermal particle acceleration. either collisional or kinetic dissipation mechanisms are required to overcome the topological constraints, both of which have been predicted by theory and validated with in situ spacecraft observations or laboratory experiments. however, major challenges remain in understanding magnetic reconnection in large systems, such as the solar corona, where the collisionality is weak and the kinetic scales are vanishingly small in comparison with macroscopic scales. the plasmoid instability or formation of multiple plasmoids in long, reconnecting current sheets is one possible multiscale solution for bridging this vast range of scales, and new laboratory experiments are poised to study these regimes. in conjunction with these efforts, we anticipate that the coming era of exascale computing, together with the next generation of observational capabilities, will enable new progress on a range of challenging problems, including the energy build-up and onset of reconnection, partially ionized regimes, the influence of magnetic turbulence and particle acceleration. | magnetic reconnection in the era of exascale computing and multiscale experiments |
as china's first x-ray astronomical satellite, the hard x-ray modulation telescope (hxmt), which was dubbed as insight-hxmt after the launch on june 15, 2017, is a wide-band (1-250 kev) slat-collimator-based x-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 mev. it was designed to perform pointing, scanning and gamma-ray burst (grb) observations and, based on the direct demodulation method (ddm), the image of the scanned sky region can be reconstructed. here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results. | overview to the hard x-ray modulation telescope (insight-hxmt) satellite |
we measure the stellar mass function (smf) and stellar mass density of galaxies in the cosmos field up to z ~ 6. we select them in the near-ir bands of the cosmos2015 catalogue, which includes ultra-deep photometry from ultravista-dr2, splash, and subaru/hyper suprime-cam. at z> 2.5 we use new precise photometric redshifts with error σz = 0.03(1 + z) and an outlier fraction of 12%, estimated by means of the unique spectroscopic sample of cosmos (~100 000 spectroscopic measurements in total, more than one thousand having robust zspec> 2.5). the increased exposure time in the dr2, along with our panchromatic detection strategy, allow us to improve the completeness at high z with respect to previous ultravista catalogues (e.g. our sample is >75% complete at 1010 ℳ⊙ and z = 5). we also identify passive galaxies through a robust colour-colour selection, extending their smf estimate up to z = 4. our work provides a comprehensive view of galaxy-stellar-mass assembly between z = 0.1 and 6, for the first time using consistent estimates across the entire redshift range. we fit these measurements with a schechter function, correcting for eddington bias. we compare the smf fit with the halo mass function predicted from λcdm simulations, finding that at z> 3 both functions decline with a similar slope in thehigh-mass end. this feature could be explained assuming that mechanisms quenching star formation in massive haloes become less effective at high redshifts; however further work needs to be done to confirm this scenario. concerning the smf low-mass end, it shows a progressive steepening as it moves towards higher redshifts, with α decreasing from -1.47+0.02-0.02 at z ≃ 0.1 to -2.11+0.30-0.13<!-- inline-formula><alternatives><![cdata[-2.11-0.13+0.30]]><inline-graphic mime-subtype="png" mimetype="image" xlink:href="aa30419-17-eq20.png"/>-2.11-0.13+0.30</alternatives> at z ≃ 5. this slope depends on the characterisation of the observational uncertainties, which is crucial to properly remove the eddington bias. we show that there is currently no consensus on the method to quantify such errors: different error models result in different best-fit schechter parameters. based on data products from observations made with eso telescopes at the la silla paranal observatory under eso programme id 179.a-2005 and on data products produced by terapix and the cambridge astronomy survey unit on behalf of the ultravista consortium (http://ultravista.org/). based on data produced by the splash team from observations made with the spitzer space telescope (http://splash.caltech.edu). | the cosmos2015 galaxy stellar mass function . thirteen billion years of stellar mass assembly in ten snapshots |
the dense matter equation of state (eos) determines neutron star (ns) structure but can be calculated reliably only up to one to two times the nuclear saturation density, using accurate many-body methods that employ nuclear interactions from chiral effective field theory constrained by scattering data. in this work, we use physically motivated ansatzes for the speed of sound csat high density to extend microscopic calculations of neutron-rich matter to the highest densities encountered in stable ns cores. we show how existing and expected astrophysical constraints on ns masses and radii from x-ray observations can constrain the speed of sound in the ns core. we confirm earlier expectations that csis likely to violate the conformal limit of {c}s2≤slant {c}2/3, possibly reaching values closer to the speed of light c at a few times the nuclear saturation density, independent of the nuclear hamiltonian. if qcd obeys the conformal limit, we conclude that the rapid increase of csrequired to accommodate a 2 m ⊙ ns suggests a form of strongly interacting matter where a description in terms of nucleons will be unwieldy, even between one and two times the nuclear saturation density. for typical nss with masses in the range of 1.2-1.4 m ⊙, we find radii between 10 and 14 km, and the smallest possible radius of a 1.4 m ⊙ ns consistent with constraints from nuclear physics and observations is 8.4 km. we also discuss how future observations could constrain the eos and guide theoretical developments in nuclear physics. | constraining the speed of sound inside neutron stars with chiral effective field theory interactions and observations |
stars orbiting the compact radio source sgr a* in the galactic center serve as precision probes of the gravitational field around the closest massive black hole. in addition to adaptive optics-assisted astrometry (with naco/vlt) and spectroscopy (with sinfoni/vlt, nirc2/keck and gnirs/gemini) over three decades, we have obtained 30-100 μas astrometry since 2017 with the four-telescope interferometric beam combiner gravity/vlti, capable of reaching a sensitivity of mk = 20 when combining data from one night. we present the simultaneous detection of several stars within the diffraction limit of a single telescope, illustrating the power of interferometry in the field. the new data for the stars s2, s29, s38, and s55 yield significant accelerations between march and july 2021, as these stars pass the pericenters of their orbits between 2018 and 2023. this allows for a high-precision determination of the gravitational potential around sgr a*. our data are in excellent agreement with general relativity orbits around a single central point mass, m• = 4.30 × 106 m⊙, with a precision of about ±0.25%. we improve the significance of our detection of the schwarzschild precession in the s2 orbit to 7σ. assuming plausible density profiles, the extended mass component inside the s2 apocenter (≈0.23″ or 2.4 × 104 rs) must be ≲3000 m⊙ (1σ), or ≲0.1% of m•. adding the enclosed mass determinations from 13 stars orbiting sgr a* at larger radii, the innermost radius at which the excess mass beyond sgr a* is tentatively seen is r ≈ 2.5″ ≥ 10× the apocenter of s2. this is in full harmony with the stellar mass distribution (including stellar-mass black holes) obtained from the spatially resolved luminosity function. | mass distribution in the galactic center based on interferometric astrometry of multiple stellar orbits |
we have generated synthetic images of ∼27 000 galaxies from the illustristng and the original illustris hydrodynamic cosmological simulations, designed to match pan-starrs observations of log10(m*/m⊙) ≈ 9.8-11.3 galaxies at z ≈ 0.05. most of our synthetic images were created with the skirt radiative transfer code, including the effects of dust attenuation and scattering, and performing the radiative transfer directly on the voronoi mesh used by the simulations themselves. we have analysed both our synthetic and real pan-starrs images with the newly developed statmorph code, which calculates non-parametric morphological diagnostics - including the gini-m20 and concentration-asymmetry-smoothness statistics - and performs 2d sérsic fits. overall, we find that the optical morphologies of illustristng galaxies are in good agreement with observations, and represent a substantial improvement compared to the original illustris simulation. in particular, the locus of the gini-m20 diagram is consistent with that inferred from observations, while the median trends with stellar mass of all the morphological, size and shape parameters considered in this work lie within the ∼1σ scatter of the observational trends. however, the illustristng model has some difficulty with more stringent tests, such as producing a strong morphology-colour relation. this results in a somewhat higher fraction of red discs and blue spheroids compared to observations. similarly, the morphology-size relation is problematic: while observations show that discs tend to be larger than spheroids at a fixed stellar mass, such a trend is not present in illustristng. | the optical morphologies of galaxies in the illustristng simulation: a comparison to pan-starrs observations |
we complement the parsec data base of stellar evolutionary tracks with new models of massive stars, from the pre-main-sequence phase to the central carbon ignition. we consider a broad range of metallicities, 0.0001 ≤ z ≤ 0.04 and initial masses up to mini = 350 m⊙. the main difference with respect to our previous models of massive stars is the adoption of a recent formalizm accounting for the mass-loss enhancement when the ratio of the stellar to the eddington luminosity, γe, approaches unity. with this new formalizm, the models are able to reproduce the humphreys-davidson limit observed in the galactic and large magellanic cloud colour-magnitude diagrams, without an ad hoc mass-loss enhancement. we also follow the predictions of recent wind models indicating that the metallicity dependence of the mass-loss rates becomes shallower when γe approaches unity. we thus find that the more massive stars may suffer from substantial mass-loss even at low metallicity. we also predict that the humphreys-davidson limit should become brighter at decreasing metallicity. we supplement the evolutionary tracks with new tables of theoretical bolometric corrections, useful to compare tracks and isochrones with the observations. for this purpose, we homogenize existing stellar atmosphere libraries of hot and cool stars (potsdam wolf-rayet, atlas9 and phoenix) and we add, where needed, new atmosphere models computed with wm-basic. the mass, age and metallicity grids are fully adequate to perform detailed investigations of the properties of very young stellar systems, both in local and distant galaxies. the new tracks supersede the previous old padova models of massive stars. | parsec evolutionary tracks of massive stars up to 350 m⊙ at metallicities 0.0001 ≤ z ≤ 0.04 |
the evolution of massive stars is influenced by the mass lost to stellar winds over their lifetimes. these winds limit the masses of the stellar remnants (such as black holes) that the stars ultimately produce. we used radio astrometry to refine the distance to the black hole x-ray binary cygnus x-1, which we found to be 2.22−0.17+0.18 kiloparsecs. when combined with archival optical data, this implies a black hole mass of 21.2 ± 2.2 solar masses, which is higher than previous measurements. the formation of such a high-mass black hole in a high-metallicity system (within the milky way) constrains wind mass loss from massive stars. | cygnus x-1 contains a 21-solar mass black hole—implications for massive star winds |
over the next 5 yr, the dark energy spectroscopic instrument (desi) will use 10 spectrographs with 5000 fibers on the 4 m mayall telescope at kitt peak national observatory to conduct the first stage iv dark energy galaxy survey. at z < 0.6, the desi bright galaxy survey (bgs) will produce the most detailed map of the universe during the dark-energy-dominated epoch with redshifts of >10 million galaxies spanning 14,000 deg2. in this work, we present and validate the final bgs target selection and survey design. from the legacy surveys, bgs will target an r < 19.5 mag limited sample (bgs bright), a fainter 19.5 < r < 20.175 color-selected sample (bgs faint), and a smaller low-z quasar sample. bgs will observe these targets using exposure times scaled to achieve homogeneous completeness and cover the footprint three times. we use observations from the survey validation programs conducted prior to the main survey along with simulations to show that bgs can complete its strategy and make optimal use of "bright" time. bgs targets have stellar contamination <1%, and their densities do not depend strongly on imaging properties. bgs bright will achieve >80% fiber assignment efficiency. finally, bgs bright and bgs faint will achieve >95% redshift success over any observing condition. bgs meets the requirements for an extensive range of scientific applications. bgs will yield the most precise baryon acoustic oscillation and redshift-space distortion measurements at z < 0.4. it presents opportunities for new methods that require highly complete and dense samples (e.g., n-point statistics, multitracers). bgs further provides a powerful tool to study galaxy populations and the relations between galaxies and dark matter. | the desi bright galaxy survey: final target selection, design, and validation |
the characterising exoplanet satellite (cheops) was selected on october 19, 2012, as the first small mission (s-mission) in the esa science programme and successfully launched on december 18, 2019, as a secondary passenger on a soyuz-fregat rocket from kourou, french guiana. cheops is a partnership between esa and switzerland with important contributions by ten additional esa member states. cheops is the first mission dedicated to search for transits of exoplanets using ultrahigh precision photometry on bright stars already known to host planets. as a follow-up mission, cheops is mainly dedicated to improving, whenever possible, existing radii measurements or provide first accurate measurements for a subset of those planets for which the mass has already been estimated from ground-based spectroscopic surveys. the expected photometric precision will also allow cheops to go beyond measuring only transits and to follow phase curves or to search for exo-moons, for example. finally, by unveiling transiting exoplanets with high potential for in-depth characterisation, cheops will also provide prime targets for future instruments suited to the spectroscopic characterisation of exoplanetary atmospheres. to reach its science objectives, requirements on the photometric precision and stability have been derived for stars with magnitudes ranging from 6 to 12 in the v band. in particular, cheops shall be able to detect earth-size planets transiting g5 dwarf stars (stellar radius of 0.9r⊙) in the magnitude range 6 ≤ v ≤ 9 by achieving a photometric precision of 20 ppm in 6 hours of integration time. in the case of k-type stars (stellar radius of 0.7r⊙) of magnitude in the range 9 ≤ v ≤ 12, cheops shall be able to detect transiting neptune-size planets achieving a photometric precision of 85 ppm in 3 hours of integration time. this precision has to be maintained over continuous periods of observation for up to 48 hours. this precision and stability will be achieved by using a single, frame-transfer, back-illuminated ccd detector at the focal plane assembly of a 33.5 cm diameter, on-axis ritchey-chrétien telescope. the nearly 275 kg spacecraft is nadir-locked, with a pointing accuracy of about 1 arcsec rms, and will allow for at least 1 gbit/day downlink. the sun-synchronous dusk-dawn orbit at 700 km altitude enables having the sun permanently on the backside of the spacecraft thus minimising earth stray light. a mission duration of 3.5 years in orbit is foreseen to enable the execution of the science programme. during this period, 20% of the observing time is available to the wider community through yearly esa call for proposals, as well as through discretionary time approved by esa's director of science. at the time of this writing, cheops commissioning has been completed and cheops has been shown to fulfill all its requirements. the mission has now started the execution of its science programme. | the cheops mission |
globular clusters (gcs) formed when the milky way experienced a phase of rapid assembly. we use the wealth of information contained in the galactic gc population to quantify the properties of the satellite galaxies from which the milky way assembled. to achieve this, we train an artificial neural network on the e-mosaics cosmological simulations of the co-formation and co-evolution of gcs and their host galaxies. the network uses the ages, metallicities, and orbital properties of gcs that formed in the same progenitor galaxies to predict the stellar masses and accretion redshifts of these progenitors. we apply the network to galactic gcs associated with five progenitors: gaia-enceladus, the helmi streams, sequoia, sagittarius, and the recently discovered 'low-energy' gcs, which provide an excellent match to the predicted properties of the enigmatic galaxy 'kraken'. the five galaxies cover a narrow stellar mass range [m⋆ = (0.6-4.6) × 108 m⊙], but have widely different accretion redshifts ( $\mbox{$z_{\rm acc}$}=0.57\!-\!2.65$ ). all accretion events represent minor mergers, but kraken likely represents the most major merger ever experienced by the milky way, with stellar and virial mass ratios of $\mbox{$r_{m_\star }$}=1$ : $31^{+34}_{-16}$ and $\mbox{$r_{m_{\rm h}}$}=1$ : $7^{+4}_{-2}$ , respectively. the progenitors match the z = 0 relation between gc number and halo virial mass, but have elevated specific frequencies, suggesting an evolution with redshift. even though these progenitors likely were the milky way's most massive accretion events, they contributed a total mass of only log (m⋆, tot/m⊙) = 9.0 ± 0.1, similar to the stellar halo. this implies that the milky way grew its stellar mass mostly by in-situ star formation. we conclude by organizing these accretion events into the most detailed reconstruction to date of the milky way's merger tree. | kraken reveals itself - the merger history of the milky way reconstructed with the e-mosaics simulations |
we report the detection of ten new binary black hole (bbh) mergers in the publicly released data from the first half of the third observing run (o3a) of advanced ligo and advanced virgo. we identify candidates using an updated version of the search pipeline described in venumadhav et al. [phys. rev. d 100, 023011 (2019), 10.1103/physrevd.100.023011] (the "ias pipeline" [t. venumadhav et al., phys. rev. d 101, 083030 (2020)., 10.1103/physrevd.101.083030]) and compile a catalog of signals that pass a significance threshold of astrophysical probability greater than 0.5 (following the gwtc-2.1 [r. abbott et al. (<collab>the ligo scientific collaboration, the virgo collaboration</collab>), arxiv:2108.01045</pub-id>.] and 3-ogc [a. h. nitz et al., astrophys. j. 922, 76 (2021)., 10.3847/1538-4357/ac1c03] catalogs). the updated ias pipeline is sensitive to a larger region of parameter space, applies a template prior that accounts for different search volume as a function of intrinsic parameters, and uses an improved coherent detection statistic that optimally combines the data from the hanford and livingston detectors. among the ten new events, we observe interesting astrophysical scenarios including sources with confidently large effective spin parameters in both the positive and negative directions, high-mass black holes that are difficult to form in stellar collapse models due to (pulsational) pair instability, and low-mass mergers that bridge the gap between neutron stars and the lightest observed black holes. we infer source parameters in the upper and lower black hole mass gaps with both extreme and near-unity mass ratios, and one of the possible neutron star-black hole (nsbh) mergers is well localized for electromagnetic (em) counterpart searches. we detect all of the gwtc-2.1 bbh mergers with coincident data in hanford and livingston except for three loud events that get vetoed, which is compatible with the false-positive rate of our veto procedure, and three that fall below the detection threshold. we also return to significance the event gw190909_114149, which was reduced to a subthreshold trigger after its initial appearance in gwtc-2 [r. abbott et al., phys. rev. x 11, 021053 (2021).<pub-id pub-id-type="doi" specific-use="suppress-display">10.1103/physrevx.11.021053]. this amounts to a total of 42 bbh mergers detected by our pipeline's search of the coincident hanford-livingston o3a data. | new binary black hole mergers in the ligo-virgo o3a data |
in galaxy and mass assembly data release 4 (gama dr4), we make available our full spectroscopic redshift sample. this includes 248 682 galaxy spectra, and, in combination with earlier surveys, results in 330 542 redshifts across five sky regions covering ~250 deg2. the redshift density, is the highest available over such a sustained area, has exceptionally high completeness (95 per cent to rkids = 19.65 mag), and is well-suited for the study of galaxy mergers, galaxy groups, and the low redshift (z < 0.25) galaxy population. dr4 includes 32 value-added tables or data management units (dmus) that provide a number of measured and derived data products including galex, eso kids, eso viking, wise, and herschelspace observatory imaging. within this release, we provide visual morphologies for 15 330 galaxies to z < 0.08, photometric redshift estimates for all 18 million objects to rkids ~ 25 mag, and stellar velocity dispersions for 111 830 galaxies. we conclude by deriving the total galaxy stellar mass function (gsmf) and its sub-division by morphological class (elliptical, compact-bulge and disc, diffuse-bulge and disc, and disc only). this extends our previous measurement of the total gsmf down to 106.75 m$_{\odot } \, h_{70}^{-2}$ and we find a total stellar mass density of ρ* = (2.97 ± 0.04) × 108 m$_{\odot } \, h_{70}$ mpc-3 or $\omega _*=(2.17 \pm 0.03) \times 10^{-3} \, h_{70}^{-1}$. we conclude that at z < 0.1, the universe has converted 4.9 ± 0.1 per cent of the baryonic mass implied by big bang nucleosynthesis into stars that are gravitationally bound within the galaxy population. | galaxy and mass assembly (gama): data release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions |
the gaia mission has opened a new window into the internal kinematics of young star clusters at the sub-km s-1 level, with implications for our understanding of how star clusters form and evolve. we use a sample of 28 clusters and associations with ages from ∼1-5 myr, where lists of members are available from previous x-ray, optical, and infrared studies. proper motions from gaia dr2 reveal that at least 75% of these systems are expanding; however, rotation is only detected in one system. typical expansion velocities are on the order of ∼0.5 km s-1, and in several systems, there is a positive radial gradient in expansion velocity. systems that are still embedded in molecular clouds are less likely to be expanding than those that are partially or fully revealed. one-dimensional velocity dispersions, which range from {σ }1{{d}}=1 to 3 km s-1, imply that most of the stellar systems in our sample are supervirial and that some are unbound. in star-forming regions that contain multiple clusters or subclusters, we find no evidence that these groups are coalescing, implying that hierarchical cluster assembly, if it occurs, must happen rapidly during the embedded stage. | kinematics in young star clusters and associations with gaia dr2 |
we use high-precision photometry of red-giant-branch (rgb) stars in 57 galactic globular clusters (gcs), mostly from the `hubble space telescope (hst) uv legacy survey of galactic gcs', to identify and characterize their multiple stellar populations. for each cluster the pseudo-two-colour diagram (or `chromosome map') is presented, built with a suitable combination of stellar magnitudes in the f275w, f336w, f438w, and f814w filters that maximizes the separation between multiple populations. in the chromosome map of most gcs (type-i clusters), stars separate in two distinct groups that we identify with the first (1g) and the second generation (2g). this identification is further supported by noticing that 1g stars have primordial (oxygen-rich, sodium-poor) chemical composition, whereas 2g stars are enhanced in sodium and depleted in oxygen. this 1g-2g separation is not possible for a few gcs where the two sequences have apparently merged into an extended, continuous sequence. in some gcs (type-ii clusters) the 1g and/or the 2g sequences appear to be split, hence displaying more complex chromosome maps. these clusters exhibit multiple subgiant branches (sgbs) also in purely optical colour-magnitude diagrams, with the fainter sgb joining into a red rgb which is populated by stars with enhanced heavy-element abundance. we measure the rgb width by using appropriate colours and pseudo-colours. when the metallicity dependence is removed, the rgb width correlates with the cluster mass. the fraction of 1g stars ranges from ∼8 per cent to ∼67 per cent and anticorrelates with the cluster mass, indicating that incidence and complexity of the multiple population phenomenon both increase with cluster mass. | the hubble space telescope uv legacy survey of galactic globular clusters - ix. the atlas of multiple stellar populations |
exoplanetary science is on the verge of an unprecedented revolution. the thousands of exoplanets discovered over the past decade have most recently been supplemented by discoveries of potentially habitable planets around nearby low-mass stars. currently, the field is rapidly progressing toward detailed spectroscopic observations to characterize the atmospheres of these planets. various surveys from space and the ground are expected to detect numerous more exoplanets orbiting nearby stars that make the planets conducive for atmospheric characterization. the current state of this frontier of exoplanetary atmospheres may be summarized as follows. we have entered the era of comparative exoplanetology thanks to high-fidelity atmospheric observations now available for tens of exoplanets. recent studies reveal a rich diversity of chemical compositions and atmospheric processes hitherto unseen in the solar system. elemental abundances of exoplanetary atmospheres place important constraints on exoplanetary formation and migration histories. upcoming observational facilities promise to revolutionize exoplanetary spectroscopy down to rocky exoplanets. the detection of a biosignature in an exoplanetary atmosphere is conceivable over the next decade. in the present review, we discuss the modern and future landscape of this frontier area of exoplanetary atmospheres. we start with a brief review of the area, emphasising the key insights gained from different observationalmethods and theoretical studies. this is followed by an in-depth discussion of the state of the art, challenges, and future prospects in three forefront branches of the area. | exoplanetary atmospheres: key insights, challenges, and prospects |
the disk mass is among the most important input parameter for every planet formation model to determine the number and masses of the planets that can form. we present an alma 887 μm survey of the disk population around objects from ∼2 to 0.03 m ⊙ in the nearby ∼2 myr old chamaeleon i star-forming region. we detect thermal dust emission from 66 out of 93 disks, spatially resolve 34 of them, and identify two disks with large dust cavities of about 45 au in radius. assuming isothermal and optically thin emission, we convert the 887 μm flux densities into dust disk masses, hereafter m dust. we find that the {m}{dust}{--}{m}*relation is steeper than linear and of the form m dust ∝ (m *)1.3-1.9, where the range in the power-law index reflects two extremes of the possible relation between the average dust temperature and stellar luminosity. by reanalyzing all millimeter data available for nearby regions in a self-consistent way, we show that the 1-3 myr old regions of taurus, lupus, and chamaeleon i share the same {m}{dust}{--}{m}*relation, while the 10 myr old upper sco association has a steeper relation. theoretical models of grain growth, drift, and fragmentation reproduce this trend and suggest that disks are in the fragmentation-limited regime. in this regime millimeter grains will be located closer in around lower-mass stars, a prediction that can be tested with deeper and higher spatial resolution alma observations. | a steeper than linear disk mass-stellar mass scaling relation |
we present the kmos3d survey, a new integral field survey of over 600 galaxies at 0.7 < z < 2.7 using kmos at the very large telescope. the kmos3d survey utilizes synergies with multi-wavelength ground- and space-based surveys to trace the evolution of spatially resolved kinematics and star formation from a homogeneous sample over 5 gyr of cosmic history. targets, drawn from a mass-selected parent sample from the 3d-hst survey, cover the star formation-stellar mass (m *) and rest-frame (u - v) - m * planes uniformly. we describe the selection of targets, the observations, and the data reduction. in the first-year of data we detect hα emission in 191 m * = 3 × 109-7 × 1011 m ⊙ galaxies at z = 0.7-1.1 and z = 1.9-2.7. in the current sample 83% of the resolved galaxies are rotation dominated, determined from a continuous velocity gradient and v rot/σ0 > 1, implying that the star-forming "main sequence" is primarily composed of rotating galaxies at both redshift regimes. when considering additional stricter criteria, the hα kinematic maps indicate that at least ~70% of the resolved galaxies are disk-like systems. our high-quality kmos data confirm the elevated velocity dispersions reported in previous integral field spectroscopy studies at z >~ 0.7. for rotation-dominated disks, the average intrinsic velocity dispersion decreases by a factor of two from 50 km s-1at z ~ 2.3 to 25 km s-1at z ~ 0.9. combined with existing results spanning z ~ 0-3, we show that disk velocity dispersions follow an evolution that is consistent with the dependence of velocity dispersion on gas fractions predicted by marginally stable disk theory. based on observations obtained at the very large telescope (vlt) of the european southern observatory (eso), paranal, chile (eso program ids 092a-0091, 093.a-0079). | the kmos3d survey: design, first results, and the evolution of galaxy kinematics from 0.7 <= z <= 2.7 |
the alma-alpine [cii] survey is aimed at characterizing the properties of a sample of normal star-forming galaxies (sfgs). the alma large program to investigate (alpine) features 118 galaxies observed in the [cii]-158 μm line and far infrared (fir) continuum emission during the period of rapid mass assembly, right after the end of the hi reionization, at redshifts of 4 < z < 6. we present the survey science goals, the observational strategy, and the sample selection of the 118 galaxies observed with alma, with an average beam minor axis of about 0.85″, or ∼5 kpc at the median redshift of the survey. the properties of the sample are described, including spectroscopic redshifts derived from the uv-rest frame, stellar masses, and star-formation rates obtained from a spectral energy distribution (sed) fitting. the observed properties derived from the alma data are presented and discussed in terms of the overall detection rate in [cii] and fir continuum, with the observed signal-to-noise distribution. the sample is representative of the sfg population in the main sequence at these redshifts. the overall detection rate in [cii] is 64% for a signal-to-noise ratio (s/n) threshold larger than 3.5 corresponding to a 95% purity (40% detection rate for s/n > 5). based on a visual inspection of the [cii] data cubes together with the large wealth of ancillary data, we find a surprisingly wide range of galaxy types, including 40% that are mergers, 20% extended and dispersion-dominated, 13% compact, and 11% rotating discs, with the remaining 16% too faint to be classified. this diversity indicates that a wide array of physical processes must be at work at this epoch, first and foremost, those of galaxy mergers. this paper sets a reference sample for the gas distribution in normal sfgs at 4 < z < 6, a key epoch in galaxy assembly, which is ideally suited for studies with future facilities, such as the james webb space telescope (jwst) and the extremely large telescopes (elts). | the alpine-alma [cii] survey. survey strategy, observations, and sample properties of 118 star-forming galaxies at 4 < z < 6 |
local galaxies are broadly divided into two main classes, star-forming (gas-rich) and quiescent (passive and gas-poor). the primary mechanism responsible for quenching star formation in galaxies and transforming them into quiescent and passive systems is still unclear. sudden removal of gas through outflows or stripping is one of the mechanisms often proposed. an alternative mechanism is so-called ``strangulation'', in which the supply of cold gas to the galaxy is halted. here we report an analysis of the stellar metallicity (the fraction of elements heavier than helium in stellar atmospheres) in local galaxies, from 26,000 spectra, that clearly reveals that strangulation is the primary mechanism responsible for quenching star formation, with a typical timescale of four billion years, at least for local galaxies with a stellar mass less than 1011 solar masses. this result is further supported independently by the stellar age difference between quiescent and star-forming galaxies, which indicates that quiescent galaxies of less than 1011 solar masses are on average observed four billion years after quenching due to strangulation. | strangulation as the primary mechanism for shutting down star formation in galaxies |
the evolution of the large-scale distribution of matter is sensitive to a variety of fundamental parameters that characterize the dark matter, dark energy, and other aspects of our cosmological framework. since the majority of the mass density is in the form of dark matter that cannot be directly observed, to do cosmology with large-scale structure, one must use observable (baryonic) quantities that trace the underlying matter distribution in a (hopefully) predictable way. however, recent numerical studies have demonstrated that the mapping between observable and total mass, as well as the total mass itself, are sensitive to unresolved feedback processes associated with galaxy formation, motivating explicit calibration of the feedback efficiencies. here, we construct a new suite of large-volume cosmological hydrodynamical simulations (called bahamas, for baryons and haloes of massive systems), where subgrid models of stellar and active galactic nucleus feedback have been calibrated to reproduce the present-day galaxy stellar mass function and the hot gas mass fractions of groups and clusters in order to ensure the effects of feedback on the overall matter distribution are broadly correct. we show that the calibrated simulations reproduce an unprecedentedly wide range of properties of massive systems, including the various observed mappings between galaxies, hot gas, total mass, and black holes, and represent a significant advance in our ability to mitigate the primary systematic uncertainty in most present large-scale structure tests. | the bahamas project: calibrated hydrodynamical simulations for large-scale structure cosmology |
astrometric surveys such as gaia and lsst will measure parallaxes for hundreds of millions of stars. yet they will not measure a single distance. rather, a distance must be estimated from a parallax. in this didactic article, i show that doing this is not trivial once the fractional parallax error is larger than about 20%, which will be the case for about 80% of stars in the gaia catalogue. estimating distances is an inference problem in which the use of prior assumptions is unavoidable. i investigate the properties and performance of various priors and examine their implications. a supposed uninformative uniform prior in distance is shown to give very poor distance estimates (large bias and variance). any prior with a sharp cut-off at some distance has similar problems. the choice of prior depends on the information one has available - and is willing to use - concerning, for example, the survey and the galaxy. i demonstrate that a simple prior which decreases asymptotically to zero at infinite distance has good performance, accommodates non-positive parallaxes, and does not require a bias correction. | estimating distances from parallaxes |
the milestone of gw 170817-grb 170817a-at 2017gfo has shown that gravitational wave (gw) is produced during the merger of neutron star-neutron star/black hole and that in electromagnetic (em) wave a gamma-ray burst (grb) and a kilonovae (kn) are generated in sequence after the merger. observationally, however, em property during a merger is still unclear. here we report a peculiar precursor in a kn-associated long grb 211211a. the duration of the precursor is $\sim$ 0.2 s, and the waiting time between the precursor and the main emission (me) of the burst is $\sim$ 1 s, which is about the same as the time interval between gw 170817 and grb 170817a. quasi-periodic oscillations (qpo) with frequency $\sim$22 hz (at $>5\sigma$ significance) are found throughout the precursor, the first detection of periodic signals from any {\it bona fide} grbs. this indicates most likely that a magnetar participated in the merger, and the precursor might be produced due to a catastrophic flare accompanying with torsional or crustal oscillations of the magnetar. the strong seed magnetic field of $\sim 10^{14-15}$ g at the surface of the magnetar may also account for the prolonged duration of grb 211211a. however, it is a challenge to reconcile the rather short lifetime of a magnetar \cite{kaspi2017magnetars} with the rather long spiraling time of a binary neutron star system only by gravitational wave radiation before merger. | the quasi-periodically oscillating precursor of a long gamma-ray burst from a binary neutron star merger |
we combine deep imaging data from the ceers early release jwst survey and hst imaging from candels to examine the size-mass relation of star-forming galaxies and the morphology-quenching relation at stellar masses $\textrm{m}_{\star} \geq 10^{9.5} \ \textrm{m}_{\odot}$ over the redshift range $0.5 < z < 5.5$. in this study with a sample of 2,450 galaxies, we separate star-forming and quiescent galaxies based on their star-formation activity and confirm that star-forming and quiescent galaxies have different morphologies out to $z=5.5$, extending the results of earlier studies out to higher redshifts. we find that star-forming and quiescent galaxies have typical sérsic indices of $n\sim1.3$ and $n\sim4.3$, respectively. focusing on star-forming galaxies, we find that the slope of the size-mass relation is nearly constant with redshift, as was found previously, but shows a modest increase at $z \sim 4.2$. the intercept in the size-mass relation declines out to $z=5.5$ at rates that are similar to what earlier studies found. the intrinsic scatter in the size-mass relation is relatively constant out to $z=5.5$. | evolution of the size-mass relation of star-forming galaxies since $z=5.5$ revealed by ceers |
multi-messenger astrophysics has produced a wealth of data with much more to come in the future. this enormous data set will reveal new insights into the physics of core collapse supernovae, neutron star mergers, and many other objects where it is actually possible, if not probable, that new physics is in operation. to tease out different possibilities, we will need to analyze signals from photons, neutrinos, gravitational waves, and chemical elements. this task is made all the more difficult when it is necessary to evolve the neutrino component of the radiation field and associated quantum-mechanical property of flavor in order to model the astrophysical system of interest -- a numerical challenge that has not been addressed to this day. in this work, we take a step in this direction by adopting the technique of angular-integrated moments with a truncated tower of dynamical equations and a closure, convolving the flavor-transformation with spatial transport to evolve the neutrino radiation quantum field. we show that moments capture the dynamical features of fast flavor instabilities in a variety of systems, although our technique is by no means a universal blueprint for solving fast flavor transformation. to evaluate the effectiveness of our moment results, we compare to a more precise particle-in-cell method. based on our results, we propose areas for improvement and application to complementary techniques in the future. | two-moment neutrino flavor transformation with applications to the fast flavor instability in neutron star mergers |
we determine the adiabatic tidal contributions to the radiation reacted momentum impulse $\delta p_i^\mu$ and scattering angle $\theta$ between two scattered massive bodies (neutron stars) at next-to-next-to-leading post-minkowskian (pm) order. the state-of-the-art three-loop (4pm) worldline quantum field theory toolkit using dimensional regularization is employed to establish the classical observables. we encounter divergent terms in the gravito-electric and gravito-magnetic quadrupolar sectors necessitating the addition of post-adiabatic counterterms in this classical theory. this leads us to include also the leading post-adiabatic tidal contributions to the observables. the resulting renormalization group flow of the associated post-adiabatic love numbers is established and shown to agree with a recent gravito-electric third post-newtonian analysis in the non-relativistic limit. | tidal effects and renormalization at fourth post-minkowskian order |
with the aim of exploring the evidence for or against phase transitions in cold and dense baryonic matter, the inference of the sound speed and equation of state for dense matter in neutron stars is extended in view of recent new observational data. the impact of the heavy (2.35 m⊙) black-widow pulsar psr j0952-0607 and the unusually light supernova remnant hess j1731-347 is inspected. in addition, a detailed reanalysis is performed of the low-density constraint based on chiral effective field theory and of the perturbative qcd constraint at asymptotically high densities, in order to clarify the influence of these constraints on the inference procedure. the trace anomaly measure, δ =1 /3 -p /ϵ , is also computed and discussed. a systematic bayes factor assessment quantifies the evidence (or nonevidence) of low averaged sound speeds (cs2≤0.1 ), a prerequisite for a phase transition, within the range of densities realized in the core of neutron stars. one of the consequences of including psr j0952-0607 in the database is a further stiffening of the equation of state, resulting for a 2.1 solar-mass neutron star in a reduced central density of less than 5 times the equilibrium density of normal nuclear matter at the 68% level. the evidence against small sound speeds in neutron star cores is further strengthened. within the inferred 68% posterior credible bands, only a weak first-order phase transition with a coexistence density interval δ n /n ≲0.2 would be compatible with the observed data. | evidence against a strong first-order phase transition in neutron star cores: impact of new data |
hydrodynamical cosmological simulations are increasing their level of realism by considering more physical processes and having greater resolution or larger statistics. however, usually either the statistical power of such simulations or the resolution reached within galaxies are sacrificed. here, we introduce the newhorizon project in which we simulate at high resolution a zoom-in region of ∼(16 mpc)3 that is larger than a standard zoom-in region around a single halo and is embedded in a larger box. a resolution of up to 34 pc, which is typical of individual zoom-in, up-to-date resimulated halos, is reached within galaxies; this allows the simulation to capture the multi-phase nature of the interstellar medium and the clumpy nature of the star formation process in galaxies. in this introductory paper, we present several key fundamental properties of galaxies and their black holes, including the galaxy mass function, cosmic star formation rate, galactic metallicities, the kennicutt-schmidt relation, the stellar-to-halo mass relation, galaxy sizes, stellar kinematics and morphology, gas content within galaxies and its kinematics, and the black hole mass and spin properties over time. the various scaling relations are broadly reproduced by newhorizon with some differences with the standard observables. owing to its exquisite spatial resolution, newhorizon captures the inefficient process of star formation in galaxies, which evolve over time from being more turbulent, gas rich, and star bursting at high redshift. these high-redshift galaxies are also more compact, and they are more elliptical and clumpier until the level of internal gas turbulence decays enough to allow for the formation of discs. the newhorizon simulation gives access to a broad range of galaxy formation and evolution physics at low-to-intermediate stellar masses, which is a regime that will become accessible in the near future through surveys such as the lsst. | introducing the newhorizon simulation: galaxy properties with resolved internal dynamics across cosmic time |
the stern-gerlach effect, discovered a century ago, has become a paradigm of quantum mechanics. surprisingly there has been little evidence that the original scheme with freely propagating atoms exposed to gradients from macroscopic magnets is a fully coherent quantum process. specifically, no full-loop stern-gerlach interferometer has been realized with the scheme as envisioned decades ago. furthermore, several theoretical studies have explained why such an interferometer is a formidable challenge. here we provide a detailed account of the first full-loop stern-gerlach interferometer realization, based on highly accurate magnetic fields, originating from an atom chip, that ensure coherent operation within strict constraints described by previous theoretical analyses. achieving this high level of control over magnetic gradients is expected to facilitate technological as well as fundamental applications, such as probing the interface of quantum mechanics and gravity. while the experimental realization described here is for a single atom, future challenges would benefit from utilizing macroscopic objects doped with a single spin. specifically, we show that such an experiment is in principle feasible, opening the door to a new era of fundamental probes. | realization of a complete stern-gerlach interferometer: toward a test of quantum gravity |
we present the results of a systematic study of the rest-frame optical morphology of quiescent galaxies at $z \geq 3$ using the near-infrared camera (nircam) onboard $jwst$. based on a sample selected by $uvj$ color or $nuvuvj$ color, we focus on 26 quiescent galaxies with $9.8<\log{(m_\star/m_\odot)}<11.4$ at $2.8<z_{\rm phot}<4.6$ with publicly available $jwst$ data. their sizes are constrained by fitting the sérsic profile to all available nircam images. we see a negative correlation between the observed wavelength and the size in our sample and derive their size at the rest-frame $0.5\, {\rm \mu m}$ taking into account this trend. our quiescent galaxies show a significant correlation between the rest-frame $0.5\, {\rm \mu m}$ size and the stellar mass at $z\geq3$. the analytical fit for them at $\log{(m_\star/m_\odot)}>10.3$ implies that our size - stellar mass relations are below those at lower redshifts, with the amplitude of $\sim0.6\, {\rm kpc}$ at $m_\star = 5\times 10^{10}\, m_\odot$. this value agrees with the extrapolation from the size evolution of quiescent galaxies at $z<3$ in the literature, implying that the size of quiescent galaxies increases monotonically from $z\sim3-5$. our sample is mainly composed of galaxies with bulge-like structures according to their median sérsic index and axis ratio of $n\sim3-4$ and $q\sim0.6-0.8$, respectively. on the other hand, there is a trend of increasing fraction of galaxies with low sérsic index, suggesting $3<z<5$ might be the epoch of onset of morphological transformation with a fraction of very notable disky quenched galaxies. | size - stellar mass relation and morphology of quiescent galaxies at $z\\geq3$ in public $jwst$ fields |
we present preexplosion optical and infrared (ir) imaging at the site of the type ii supernova (sn ii) 2023ixf in messier 101 at 6.9 mpc. we astrometrically registered a ground-based image of sn 2023ixf to archival hubble space telescope (hst), spitzer space telescope (spitzer), and ground-based near-ir images. a single point source is detected at a position consistent with the sn at wavelengths ranging from hst r band to spitzer 4.5 μm. fitting with blackbody and red supergiant (rsg) spectral energy distributions (seds), we find that the source is anomalously cool with a significant mid-ir excess. we interpret this sed as reprocessed emission in a 8600 r ⊙ circumstellar shell of dusty material with a mass ~5 × 10-5 m ⊙ surrounding a $\mathrm{log}(l/{l}_{\odot })=4.74\pm 0.07$ and ${t}_{\mathrm{eff}}={3920}_{-160}^{+200}$ k rsg. this luminosity is consistent with rsg models of initial mass 11 m ⊙, depending on assumptions of rotation and overshooting. in addition, the counterpart was significantly variable in preexplosion spitzer 3.6 and 4.5 μm imaging, exhibiting ~70% variability in both bands correlated across 9 yr and 29 epochs of imaging. the variations appear to have a timescale of 2.8 yr, which is consistent with κ-mechanism pulsations observed in rsgs, albeit with a much larger amplitude than rsgs such as α orionis (betelgeuse). | sn 2023ixf in messier 101: a variable red supergiant as the progenitor candidate to a type ii supernova |
we reprise the analysis of stassun & torres, comparing the parallaxes of the eclipsing binaries reported in that paper to the parallaxes newly reported in the gaia second data release (dr2). we find evidence for a systematic offset of -82 ± 33 μas, in the sense of the gaia parallaxes being too small, for brightnesses (g ≲ 12) and for distances (0.03-3 kpc) in the ranges spanned by the eclipsing binary sample. the offset does not appear to depend strongly on distance within this range, though there is marginal evidence that the offset increases (becomes slightly more negative) for distances ≳1 kpc, up to the 3 kpc distances probed by the test sample. the offset reported here is consistent with the expectation that global systematics in the gaia dr2 parallaxes are below 100 μas. | evidence for a systematic offset of -80 μas in the gaia dr2 parallaxes |
while most of the compact-binary mergers detected by ligo and virgo are expected to consist of first-generation black holes formed from the collapse of stars, others might instead be of second (or higher) generation, containing the remnants of previous black-hole mergers. we review theoretical findings, astrophysical modelling and current gravitational-wave evidence of hierarchical stellar-mass black-hole mergers. such a subpopulation of hierarchically assembled black holes presents distinctive gravitational-wave signatures, namely higher masses, possibly within the pair-instability mass gap, and dimensionless spins clustered at the characteristic value of ~0.7. to produce hierarchical mergers, astrophysical environments need to overcome the relativistic recoils imparted to black-hole merger remnants, a condition that prefers hosts with escape speeds of ≳100 km s−1. promising locations for efficient production of hierarchical mergers include nuclear star clusters and accretion disks surrounding active galactic nuclei, though environments that are less efficient at retaining merger products such as globular clusters may still contribute significantly to the detectable population of repeated mergers. while gw190521 is the single most promising hierarchical-merger candidate to date, constraints from large population analyses are becoming increasingly more powerful. | hierarchical mergers of stellar-mass black holes and their gravitational-wave signatures |
we measure host galaxy stellar masses for a sample of five luminous quasars at $z\sim5-7$. using jwst/nircam medium-band images of nearby psf reference stars, we carefully subtract the contribution from the quasar light to place upper and lower limits on the flux of each host galaxy. we find that the members of our sample of quasar host galaxies have masses of $10^{9.7} - 10^{10.8} m_{\odot}$, significantly less than expected from their smbh masses and the local \magorrian relation. we additionally obtain jwst/nirspec ifu spectra of three of our quasars to calculate black hole masses, which we find are consistent with those in the literature, and to search for the presence of a bright but compact galaxy via a balmer break, which we do not find evidence for. we discuss the potential effects of dust extinction on our measured fluxes and the impact of selection effects on high-redshift quasar samples. we conclude that the masses of the smbhs relative to the host galaxy stellar masses have a much larger scatter than locally, large enough that these selection effects cannot be responsible. the result is reinforced by other studies. finally, we explore the potential implications of these results on the picture of smbh-galaxy coeval growth in the early universe. | undermassive host galaxies of five z~6 luminous quasars detected with jwst |
we use the cosmic archaeology tool (cat) semi-analytical model to explore the contribution of population (pop) iii/ii stars and active galactic nuclei (agns) to the galaxy uv luminosity function (lf) evolution at $4 \leq z \leq 20$. we compare in particular with recent jwst data in order to explore the apparent tension between observations and theoretical models in the number density of bright galaxies at $z \gtrsim 10$. the model predicts a star formation history dominated by uv faint ($m_{\rm uv} > - 18$) galaxies, with a pop iii contribution of $\lesssim 10\%$ ($\lesssim 0.5\%$) at $z \simeq 20$ ($z \simeq 10$). stars are the primary sources of cosmic reionization, with $5 - 10 \%$ of ionizing photons escaping into the intergalatic medium at $5 \leq z \leq 10$, while the contribution of unobscured agns becomes dominant only at $z \lesssim 5$. the predicted stellar and agn uv lfs reproduce the observational data at $5 \lesssim z \lesssim 9 - 10$. at higher redshift, cat predicts a steeper evolution in the faint-end slope ($m_{\rm uv} > - 18$), and a number density of bright galaxies ($m_{\rm uv} \simeq -20$) consistent with data at $z \sim 10 - 11$, but smaller by 0.8 dex at $z \sim 12 - 13$, and 1.2 dex at $z \sim 14 - 16$, when compared to the values estimated by recent studies. including the agn emission does not affect the above findings, as agns contribute at most to $\lesssim 10 \%$ of the total uv luminosity at $m_{\rm uv} < - 19$ and $z \gtrsim 10$. interestingly, considering a gradual transition in the stellar imf, modulated by metallicity and redshift as suggested by recent simulations, the model agrees with jwst data at $z \sim 12 - 13$, and the disagreement at $z \sim 14 - 16$ is reduced to 0.5 dex. | exploring the nature of uv-bright $z \\gtrsim 10$ galaxies detected by jwst: star formation, black hole accretion, or a non-universal imf? |
in this paper we describe a new uv-initiative hubble space telescope project (go-13297) that will complement the existing f606w and f814w database of the advanced camera for surveys globular cluster (gc) treasury by imaging most of its clusters through uv/blue wfc3/uvis filters f275w, f336w, and f438w. this “magic trio” of filters has shown an uncanny ability to disentangle and characterize multiple population (mp) patterns in gcs in a way that is exquisitely sensitive to c, n, and o abundance variations. combination of these passbands with those in the optical also gives the best leverage for measuring helium enrichment. the dozen clusters that had previously been observed in these bands exhibit a bewildering variety of mp patterns, and the new survey will map the full variance of the phenomenon. the ubiquity of multiple stellar generations in gcs has made the formation of these cornerstone objects more intriguing than ever; gc formation and the origin of their mps have now become one and the same problem. in this paper we will describe the database and our data reduction strategy, as well as the uses we intend to make of the final photometry, astrometry, and pms. we will also present preliminary color-magnitude diagrams from the data so far collected. these diagrams also draw on data from go-12605 and go-12311, which served as a pilot project for the present go-13297. based on observations with the nasa/esa hubble space telescope, obtained at the space telescope science institute, which is operated by aura, inc., under nasa contract nas 5-26555. | the hubble space telescope uv legacy survey of galactic globular clusters. i. overview of the project and detection of multiple stellar populations |
we report on the high-precision timing of 42 radio millisecond pulsars (msps) observed by the european pulsar timing array (epta). this epta data release 1.0 extends up to mid-2014 and baselines range from 7-18 yr. it forms the basis for the stochastic gravitational-wave background, anisotropic background, and continuous-wave limits recently presented by the epta elsewhere. the bayesian timing analysis performed with temponest yields the detection of several new parameters: seven parallaxes, nine proper motions and, in the case of six binary pulsars, an apparent change of the semimajor axis. we find the ne2001 galactic electron density model to be a better match to our parallax distances (after correction from the lutz-kelker bias) than the m2 and m3 models by schnitzeler. however, we measure an average uncertainty of 80 per cent (fractional) for ne2001, three times larger than what is typically assumed in the literature. we revisit the transverse velocity distribution for a set of 19 isolated and 57 binary msps and find no statistical difference between these two populations. we detect shapiro delay in the timing residuals of psrs j1600-3053 and j1918-0642, implying pulsar and companion masses m_p=1.22_{-0.35}^{+0.5} m_{⊙}, m_c = 0.21_{-0.04}^{+0.06} m_{⊙} and m_p=1.25_{-0.4}^{+0.6} m_{⊙}, m_c = 0.23_{-0.05}^{+0.07} m_{⊙}, respectively. finally, we use the measurement of the orbital period derivative to set a stringent constraint on the distance to psrs j1012+5307 and j1909-3744, and set limits on the longitude of ascending node through the search of the annual-orbital parallax for psrs j1600-3053 and j1909-3744. | high-precision timing of 42 millisecond pulsars with the european pulsar timing array |
combining the precise parallaxes and optical photometry delivered by gaia's second data release with the photometric catalogues of pan-starrs1, 2mass, and allwise, we derived bayesian stellar parameters, distances, and extinctions for 265 million of the 285 million objects brighter than g = 18. because of the wide wavelength range used, our results substantially improve the accuracy and precision of previous extinction and effective temperature estimates. after cleaning our results for both unreliable input and output data, we retain 137 million stars, for which we achieve a median precision of 5% in distance, 0.20 mag in v-band extinction, and 245 k in effective temperature for g ≤ 14, degrading towards fainter magnitudes (12%, 0.20 mag, and 245 k at g = 16; 16%, 0.23 mag, and 260 k at g = 17, respectively). we find a very good agreement with the asteroseismic surface gravities and distances of 7000 stars in the kepler, k2-c3, and k2-c6 fields, with stellar parameters from the apogee survey, and with distances to star clusters. our results are available through the adql query interface of the gaia mirror at the leibniz-institut für astrophysik potsdam (gaia.aip.de) and as binary tables at data.aip.de. as a first application, we provide distance- and extinction-corrected colour-magnitude diagrams, extinction maps as a function of distance, and extensive density maps. these demonstrate the potential of our value-added dataset for mapping the three-dimensional structure of our galaxy. in particular, we see a clear manifestation of the galactic bar in the stellar density distributions, an observation that can almost be considered direct imaging of the galactic bar. | photo-astrometric distances, extinctions, and astrophysical parameters for gaia dr2 stars brighter than g = 18 |
in this paper, we describe the international pulsar timing array second data release, which includes recent pulsar timing data obtained by three regional consortia: the european pulsar timing array, the north american nanohertz observatory for gravitational waves, and the parkes pulsar timing array. we analyse and where possible combine high-precision timing data for 65 millisecond pulsars which are regularly observed by these groups. a basic noise analysis, including the processes which are both correlated and uncorrelated in time, provides noise models and timing ephemerides for the pulsars. we find that the timing precisions of pulsars are generally improved compared to the previous data release, mainly due to the addition of new data in the combination. the main purpose of this work is to create the most up-to-date ipta data release. these data are publicly available for searches for low-frequency gravitational waves and other pulsar science. | the international pulsar timing array: second data release |
as part of an on-going effort to identify, understand and correct for astrophysics biases in the standardization of type ia supernovae (sn ia) for cosmology, we have statistically classified a large sample of nearby sne ia into those that are located in predominantly younger or older environments. this classification is based on the specific star formation rate measured within a projected distance of 1 kpc from each sn location (lssfr). this is an important refinement compared to using the local star formation rate directly, as it provides a normalization for relative numbers of available sn progenitors and is more robust against extinction by dust. we find that the sne ia in predominantly younger environments are δy = 0.163 ± 0.029 mag (5.7σ) fainter than those in predominantly older environments after conventional light-curve standardization. this is the strongest standardized sn ia brightness systematic connected to the host-galaxy environment measured to date. the well-established step in standardized brightnesses between sne ia in hosts with lower or higher total stellar masses is smaller, at δm = 0.119 ± 0.032 mag (4.5σ), for the same set of sne ia. when fit simultaneously, the environment-age offset remains very significant, with δy = 0.129 ± 0.032 mag (4.0σ), while the global stellar mass step is reduced to δm = 0.064 ± 0.029 mag (2.2σ). thus, approximately 70% of the variance from the stellar mass step is due to an underlying dependence on environment-based progenitor age. also, we verify that using the local star formation rate alone is not as powerful as lssfr at sorting sne ia into brighter and fainter subsets. standardization that only uses the sne ia in younger environments reduces the total dispersion from 0.142 ± 0.008 mag to 0.120 ± 0.010 mag. we show that as environment-ages evolve with redshift, a strong bias, especially on the measurement of the derivative of the dark energy equation of state, can develop. fortunately, data that measure and correct for this effect using our local specific star formation rate indicator, are likely to be available for many next-generation sn ia cosmology experiments. full tables 1 and 2 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/644/a176 | strong dependence of type ia supernova standardization on the local specific star formation rate |
as they evolve, white dwarfs undergo major changes in surface composition, a phenomenon known as spectral evolution. in particular, some stars enter the cooling sequence with helium atmospheres (type do) but eventually develop hydrogen atmospheres (type da), most likely through the upward diffusion of residual hydrogen. our empirical knowledge of this process remains scarce: the fractions of white dwarfs that are born helium rich and that experience the do-to-da transformation are poorly constrained. we tackle this issue by performing a detailed model-atmosphere investigation of 1806 hot ( ${t}_{\mathrm{eff}}$ ≥ 30,000 k) white dwarfs observed spectroscopically by the sloan digital sky survey. we first introduce our new generations of model atmospheres and theoretical cooling tracks, both appropriate for hot white dwarfs. we then present our spectroscopic analysis, from which we determine the atmospheric and stellar parameters of our sample objects. we find that ∼24% of white dwarfs begin their degenerate life as do stars, among which ∼2/3 later become da stars. we also infer that the do-to-da transition occurs at substantially different temperatures (75,000 k > ${t}_{\mathrm{eff}}$ > 30,000 k) for different objects, implying a broad range of hydrogen content within the do population. furthermore, we identify 127 hybrid white dwarfs, including 31 showing evidence of chemical stratification, and we discuss how these stars fit in our understanding of the spectral evolution. finally, we uncover significant problems in the spectroscopic mass scale of very hot ( ${t}_{\mathrm{eff}}$ > 60,000 k) white dwarfs. | on the spectral evolution of hot white dwarf stars. i. a detailed model atmosphere analysis of hot white dwarfs from sdss dr12 |
we use cosmological simulations from the fire (feedback in realistic environments) project to study the baryon cycle and galaxy mass assembly for central galaxies in the halo mass range mhalo ∼ 1010-1013 m⊙. by tracing cosmic inflows, galactic outflows, gas recycling and merger histories, we quantify the contribution of physically distinct sources of material to galaxy growth. we show that in situ star formation fuelled by fresh accretion dominates the early growth of galaxies of all masses, while the re-accretion of gas previously ejected in galactic winds often dominates the gas supply for a large portion of every galaxy's evolution. externally processed material contributes increasingly to the growth of central galaxies at lower redshifts. this includes stars formed ex situ and gas delivered by mergers, as well as smooth intergalactic transfer of gas from other galaxies, an important but previously underappreciated growth mode. by z = 0, wind transfer, i.e. the exchange of gas between galaxies via winds, can dominate gas accretion on to ∼l* galaxies over fresh accretion and standard wind recycling. galaxies of all masses re-accrete ≳50 per cent of the gas ejected in winds and recurrent recycling is common. the total mass deposited in the intergalactic medium per unit stellar mass formed increases in lower mass galaxies. re-accretion of wind ejecta occurs over a broad range of time-scales, with median recycling times (∼100-350 myr) shorter than previously found. wind recycling typically occurs at the scale radius of the halo, independent of halo mass and redshift, suggesting a characteristic recycling zone around galaxies that scales with the size of the inner halo and the galaxy's stellar component. | the cosmic baryon cycle and galaxy mass assembly in the fire simulations |
we present an updated version of the hmcode augmented halo model that can be used to make accurate predictions of the non-linear matter power spectrum over a wide range of cosmologies. major improvements include modelling of baryon-acoustic oscillation (bao) damping in the power spectrum and an updated treatment of massive neutrinos. we fit our model to simulated power spectra and show that we can match the results with an root mean square (rms) error of 2.5 per cent across a range of cosmologies, scales $k \lt 10\, h\, \mathrm{mpc}^{-1}$, and redshifts z < 2. the error rarely exceeds 5 per cent and never exceeds 16 per cent. the worst-case errors occur at z ≃ 2, or for cosmologies with unusual dark energy equations of state. this represents a significant improvement over previous versions of hmcode, and over other popular fitting functions, particularly for massive-neutrino cosmologies with high neutrino mass. we also present a simple halo model that can be used to model the impact of baryonic feedback on the power spectrum. this six-parameter physical model includes gas expulsion by active galactic nuclei (agn) feedback and encapsulates star formation. by comparing this model to data from hydrodynamical simulations, we demonstrate that the power spectrum response to feedback is matched at the <1 per cent level for z < 1 and $k\lt 20\, h\, \mathrm{mpc}^{-1}$. we also present a single-parameter variant of this model, parametrized in terms of feedback strength, which is only slightly less accurate. we make code available for our non-linear and baryon models at https://github.com/alexander-mead/hmcode and it is also available within camb and soon within class. | hmcode-2020: improved modelling of non-linear cosmological power spectra with baryonic feedback |
we introduce a new technique to search for gravitational wave events from compact binary mergers that produce a clear signal only in a single gravitational wave detector, and marginal signals in other detectors. such a situation can arise when the detectors in a network have different sensitivities, or when sources have unfavorable sky locations or orientations. we start with a short list of loud single-detector triggers from regions of parameter space that are empirically unaffected by glitches (after applying signal-quality vetoes). for each of these triggers, we compute evidence for astrophysical origin from the rest of the detector network by coherently combining the likelihoods from all detectors and marginalizing over extrinsic geometric parameters. we report the discovery of two new binary black hole (bbh) mergers in the second observing run of advanced ligo and virgo (o2), in addition to the ones that were reported in [b. p. abbott et al. (ligo scientific and virgo collaborations), phys. rev. x 9, 031040 (2019), 10.1103/physrevx.9.031040 and [t. venumadhav et al., phys. rev. d 101, 083030 (2020), 10.1103/physrevd.101.083030]. we estimate that the two events have false alarm rates of one in 19 years (60 o2) and one in 11 years (36 o2). one of the events, gw170817a, has primary and secondary masses m1src=5 6-10+16 m⊙ and m2src=4 0-11+10 m⊙ in the source frame. the existence of gw170817a should be very informative about the theoretically predicted upper mass gap for stellar mass black holes. its effective spin parameter is measured to be χeff=0.5 ±0.2 , which is consistent with the tendency of the heavier detected bbh systems to have large and positive effective spin parameters. the other event, gwc170402, will be discussed thoroughly in future work. | detecting gravitational waves with disparate detector responses: two new binary black hole mergers |
context. the explosion of observational data on exoplanets gives many constraints on theoretical models of planet formation and evolution. observational data probe very large areas of the parameter space and many different planet properties.aims: comparing theoretical models with observations allows one to take a key step forward towards understanding planetary systems. it however requires a model able to (i) predict all the necessary observable quantities (not only masses and orbits, but also radii, luminosities, magnitudes, or evaporation rates) and (ii) address the large range in relevant planetary masses (from mars mass to super-jupiters) and distances (from stellar-grazing to wide orbits).methods: we have developed a combined global end-to-end planetary formation and evolution model, the generation iii bern model, based on the core accretion paradigm. this model solves as directly as possible the underlying differential equations for the structure and evolution of the gas disc, the dynamical state of the planetesimals, the internal structure of the planets yielding their planetesimal and gas accretion rates, disc-driven orbital migration, and the gravitational interaction of concurrently forming planets via a full n-body calculation. importantly, the model also follows the long-term evolution of the planets on gigayear timescales after formation including the effects of cooling and contraction, atmospheric escape, bloating, and stellar tides.results: to test the model, we compared it with classical scenarios of solar system formation. for the terrestrial planets, we find that we obtain a giant impact phase of protoplanet-protoplanet collisions provided enough embryos (~100) are initially emplaced in the disc. for the giant planets, we find that jupiter-mass planets must accrete their core shortly before the dispersal of the gas disc to prevent strong inward migration that would bring them to the inner edge of the disc. regarding the emergence of entire planetary systems, many aspects can be understood with the comparison of the timescales of growth and migration, the capture into resonances, and the consequences of large-scale dynamical instabilities caused by the gravitational interactions of protoplanets, including the situation when a second core starts runaway gas accretion.conclusions: the generation iii bern model provides one of the most comprehensive global end-to-end models of planetary system formation and evolution developed so far, linking a multitude of crucial physical processes self-consistently. the model can form planetary systems with a wide range of properties. we find that systems with only terrestrial planets are often well-ordered (in period, mass, and radius), while giant-planet bearing systems show no such similarity. in a series of papers, the model will be used to perform extensive planetary population syntheses, putting the current theoretical understanding of planet formation and evolution to the observational test. | the new generation planetary population synthesis (ngpps). i. bern global model of planet formation and evolution, model tests, and emerging planetary systems |
we present the first part of our disks around t tauri stars with sphere (dartts-s) survey: observations of eight t tauri stars that were selected based on their strong (sub)millimeter excesses using sphere/irdis polarimetric differential imaging in the j and h bands. all observations successfully detect the disks, which appear vastly different in size, from ≈80 au in scattered light to >400 au, and display total polarized disk fluxes between 0.06% and 0.89% of the stellar flux. for five of these disks, we are able to determine the three-dimensional structure and the flaring of the disk surface, which appears to be relatively consistent across the different disks, with flaring exponents α between ≈1.1 and ≈1.6. we also confirm literature results with regard to the inclination and position angle of several of our disks and are able to determine which side is the near side of the disk in most cases. while there is a clear trend of disk mass with stellar ages (≈1 to >10 myr), no correlations of disk structures with age were found. there are also no correlations with either stellar mass or submillimeter flux. we do not detect significant differences between the j and h bands. however, we note that while a high fraction (7/8) of the disks in our sample show ring-shaped substructures, none of them display spirals, in contrast to the disks around more massive herbig ae/be stars, where spiral features are common. based on observations collected at the european organisation for astronomical research in the southern hemisphere, chile, under program 096.c-0523(a). | disks around t tauri stars with sphere (dartts-s). i. sphere/irdis polarimetric imaging of eight prominent t tauri disks |
we use cosmological simulations to study a characteristic evolution pattern of high-redshift galaxies. early, stream-fed, highly perturbed, gas-rich discs undergo phases of dissipative contraction into compact, star-forming systems (`blue' nuggets) at z ∼ 4-2. the peak of gas compaction marks the onset of central gas depletion and inside-out quenching into compact ellipticals (red nuggets) by z ∼ 2. these are sometimes surrounded by gas rings or grow extended dry stellar envelopes. the compaction occurs at a roughly constant specific star formation rate (sfr), and the quenching occurs at a constant stellar surface density within the inner kpc (σ1). massive galaxies quench earlier, faster, and at a higher σ1 than lower mass galaxies, which compactify and attempt to quench more than once. this evolution pattern is consistent with the way galaxies populate the sfr-size-mass space, and with gradients and scatter across the main sequence. the compaction is triggered by an intense inflow episode, involving (mostly minor) mergers, counter-rotating streams or recycled gas, and is commonly associated with violent disc instability. the contraction is dissipative, with the inflow rate >sfr, and the maximum σ1 anticorrelated with the initial spin parameter. the central quenching is triggered by the high sfr and stellar/supernova feedback (maybe also active galactic nucleus feedback) due to the high central gas density, while the central inflow weakens as the disc vanishes. suppression of fresh gas supply by a hot halo allows the long-term maintenance of quenching once above a threshold halo mass, inducing the quenching downsizing. | compaction and quenching of high-z galaxies in cosmological simulations: blue and red nuggets |
an accurate and precise kepler stellar properties catalog is essential for the interpretation of the kepler exoplanet survey results. previous kepler stellar properties catalogs have focused on reporting the best-available parameters for each star, but this has required combining data from a variety of heterogeneous sources. we present the gaia-kepler stellar properties catalog, a set of stellar properties of 186,301 kepler stars, homogeneously derived from isochrones and broadband photometry, gaia data release 2 parallaxes, and spectroscopic metallicities, where available. our photometric effective temperatures, derived from $g\,\mathrm{to}\,{k}_{s}$ colors, are calibrated on stars with interferometric angular diameters. median catalog uncertainties are 112 k for ${t}_{\mathrm{eff}}$ , 0.05 dex for $\mathrm{log}\,g$ , 4% for ${r}_{\star }$ , 7% for ${m}_{\star }$ , 13% for ${\rho }_{\star }$ , 10% for ${l}_{\star }$ , and 56% for stellar age. these precise constraints on stellar properties for this sample of stars will allow unprecedented investigations into trends in stellar and exoplanet properties as a function of stellar mass and age. in addition, our homogeneous parameter determinations will permit more accurate calculations of planet occurrence and trends with stellar properties. | the gaia-kepler stellar properties catalog. i. homogeneous fundamental properties for 186,301 kepler stars |
we report a new analysis of the hubble frontier fields clusters abell 2744 and macs 0416 using wavelet decomposition to remove the cluster light, enabling the detection of highly magnified (>50×) galaxies a factor of 10× fainter in luminosity than previous studies. we find 167 galaxies at z≳ 6, and with this sample we are able to characterize the uv luminosity function to {m}{uv}=-12.5 at z∼ 6, -14 at z∼ 7, and -15 at z∼ 8. we find a steep faint-end slope (α < -2), and with our improved statistics at the faint end we reduce the fractional uncertainty on α to < 2 % at z∼ 6{--}7 and 4% at z∼ 8. we also investigate the systematic uncertainty due to the lens modeling by using every available lens model individually and comparing the results; this systematic fractional uncertainty on α is < 4 % at all redshifts. we now directly observe galaxies in the luminosity regime where some simulations predict a change in the faint-end slope of the luminosity function, yet our results provide statistically very strong evidence against any turnover in the luminosity range probed, more consistent with simulations in which stars form in lower-mass halos. thus, we find strong support for the extension of the steep luminosity function to {m}{uv}=-13 at z> 6, consistent with the number of faint galaxies needed to reionize the universe under standard assumptions. | directly observing the galaxies likely responsible for reionization |
the discovery of a fast radio burst (frb) in our galaxy associated with a magnetar (neutron star with strong magnetic field) has provided a critical piece of information to help us finally understand these enigmatic transients. we show that the volumetric rate of galactic-frb like events is consistent with the faint end of the cosmological frb rate, and hence they most likely belong to the same class of transients. the galactic frb had an accompanying x-ray burst, but many x-ray bursts from the same object had no radio counterpart. their relative rates suggest that for every frb there are roughly 102-103 x-ray bursts. the radio light curve of the galactic frb had two spikes, separated by 30 ms in the 400-800 mhz frequency band. this is an important clue and highly constraining of the class of models where the radio emission is produced outside the light cylinder of the magnetar. we suggest that magnetic disturbances close to the magnetar surface propagate to a distance of a few tens of neutron star radii where they damp and produce radio emission. the coincident hard x-ray spikes associated with the two frb pulses seen in this burst and the flux ratio between the two frequency bands can be understood in this scenario. this model provides a unified picture for faint bursts like the galactic frb as well as the bright events seen at cosmological distances. | a unified picture of galactic and cosmological fast radio bursts |
characterizing the relationship between stars, gas, and metals in galaxies is a critical component of understanding the cosmic baryon cycle. we compile contemporary censuses of the baryons in collapsed structures and their chemical makeup and dust content. we show the following: the [formula: see text] mass density of the universe is well determined to redshifts [formula: see text] and shows minor evolution with time. new observations of molecular hydrogen reveal its evolution mirrors that of the global star-formation rate density, implying a universal cosmic molecular gas depletion timescale. the low-redshift decline of the star-formation history is thus driven by the lack of molecular gas supply due to a drop in net accretion rate related to the decreased growth of dark matter halos. the metal mass density in cold gas ([formula: see text] k) contains virtually all the metals produced by stars for [formula: see text]. at lower redshifts, the contributors to the total amount of metals are more diverse; at [formula: see text], most of the observed metals are bound in stars. overall, there is little evidence for a "missing metals problem" in modern censuses. we characterize the dust content of neutral gas over cosmic time, finding the dust-to-gas and dust-to-metals ratios fall with decreasing metallicity. we calculate the cosmological dust mass density in the neutral gas up to [formula: see text]. there is good agreement between multiple tracers of the dust content of the universe. | the cosmic baryon and metal cycles |
we present a first-look analysis of the jwst ero data in the smacs j0723.3-7327 cluster field. we begin by reporting 10 new spectroscopic redshifts from λobs = 1.8-5.2 μm nirspec medium-resolution (r = λ/δλ = 1000) data. these are determined via multiple high-snr emission line detections with five objects at 1 < z < 3 displaying multiple rest-frame near-infrared hydrogen paschen lines, and five objects at 5 < z < 9 displaying rest-frame optical oxygen and hydrogen balmer lines. for the five higher-redshift galaxies we extract fluxes in six nircam bands spanning λobs = 0.8-5 μm and perform spectral energy distribution fitting in combination with existing hst photometry. the 7 < z < 9 objects exhibit a u-shaped pattern across the f277w, f356w, and f444w bands, indicating a balmer break seen in emission (balmer jump) and high-equivalent-width [o iii] emission. this indicates an extremely young stellar population with the bulk of the current mass having formed within the past 10 myr. we report robust stellar masses and mean stellar ages from our spectral fitting with the four z > 6 galaxies exhibiting low-stellar masses from log10 (m*/m⊙) = 7.1-8.2, and correspondingly young mean stellar ages of only a few myr. this work highlights the critical importance of combining large upcoming nircam surveys with nirspec follow-up to measure the spectroscopic redshifts necessary to robustly constrain physical parameters. | a first look at the smacs0723 jwst ero: spectroscopic redshifts, stellar masses, and star-formation histories |
context. many of the open clusters listed in modern catalogues were initially reported by visual astronomers as apparent overdensities of bright stars. as observational techniques and analysis methods continue to improve, some of them have been shown to be chance alignments of stars and not true clusters. recent publications making use of gaia dr2 data have provided membership lists for over a thousand clusters, however, many nearby objects listed in the literature have so far evaded detection.aims: we aim to update the gaia dr2 cluster census by performing membership determinations for known clusters that had been missed by previous studies and for recently-discovered clusters. we investigate a sub-set of non-detected clusters that, according to their literature parameters, should be easily visible in gaia. confirming or disproving the existence of old, inner-disc, high-altitude clusters is especially important as their survival or disruption is linked to the dynamical processes that drive the evolution of the milky way.methods: we employed the gaia dr2 catalogue and a membership assignment procedure, as well as visual inspections of spatial, proper motion, and parallax distributions. we used membership lists provided by other authors when available.results: we derived membership lists for 150 objects, including ten that were already known prior to gaia. we compiled a final list of members for 1481 clusters. among the objects that we are still unable to identify with the gaia data, we argue that many (mostly putatively old, relatively nearby, high-altitude objects) are not true clusters.conclusions: at present, the only confirmed cluster located further than 500 pc away from the galactic plane within the solar circle is ngc 6791. it is likely that the objects discussed in this study only represent a fraction of the non-physical groupings erroneously listed in the catalogues as genuine open clusters and that those lists need further cleaning. full table 1 and the list of individual members are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/633/a99 | clusters and mirages: cataloguing stellar aggregates in the milky way |
the extremely rapid assembly of the earliest galaxies during the first billion years of cosmic history is a major challenge for our understanding of galaxy formation physics1-5. the advent of the james webb space telescope (jwst) has exacerbated this issue by confirming the existence of galaxies in substantial numbers as early as the first few hundred million years6-8. perhaps even more surprisingly, in some galaxies, this initial highly efficient star formation rapidly shuts down, or quenches, giving rise to massive quiescent galaxies as little as 1.5 billion years after the big bang9,10. however, due to their faintness and red colour, it has proven extremely challenging to learn about these extreme quiescent galaxies, or to confirm whether any existed at earlier times. here we report the spectroscopic confirmation of a massive quiescent galaxy, gs-9209, at redshift, z = 4.658, just 1.25 billion years after the big bang, using the jwst near-infrared spectrograph (nirspec). from these data we infer a stellar mass of m* = 3.8 ± 0.2 × 1010 m⊙, which formed over a roughly 200 myr period before this galaxy quenched its star-formation activity at z =6.5-0.5+0.2 , when the universe was approximately 800 myr old. this galaxy is both a likely descendent of the highest-redshift submillimetre galaxies and quasars, and a likely progenitor for the dense, ancient cores of the most massive local galaxies. | a massive quiescent galaxy at redshift 4.658 |
several lines of evidence suggest that the milky way underwent a major merger at z ~ 2 with the gaia-sausage-enceladus (gse) galaxy. here we use h3 survey data to argue that gse entered the galaxy on a retrograde orbit based on a population of highly retrograde stars with chemistry similar to the largely radial gse debris. we present the first tailored n-body simulations of the merger. from a grid of ≈500 simulations we find that a gse with m ⋆ = 5 × 108 m ⊙, m dm = 2 × 1011 m ⊙ best matches the h3 data. this simulation shows that the retrograde stars are stripped from gse's outer disk early in the merger. despite being selected purely on angular momenta and radial distributions, this simulation reproduces and explains the following phenomena: (i) the triaxial shape of the inner halo, whose major axis is at ≈35° to the plane and connects gse's apocenters; (ii) the hercules-aquila cloud and the virgo overdensity, which arise due to apocenter pileup; and (iii) the 2 gyr lag between the quenching of gse and the truncation of the age distribution of the in situ halo, which tracks the lag between the first and final gse pericenters. we make the following predictions: (i) the inner halo has a "double-break" density profile with breaks at both ≈15-18 kpc and 30 kpc, coincident with the gse apocenters; and (ii) the outer halo has retrograde streams awaiting discovery at >30 kpc that contain ≈10% of gse's stars. the retrograde (radial) gse debris originates from its outer (inner) disk-exploiting this trend, we reconstruct the stellar metallicity gradient of gse (-0.04 ± 0.01 dex ${r}_{50}^{-1}$ ). these simulations imply that gse delivered ≈20% of the milky way's present-day dark matter and ≈50% of its stellar halo. | reconstructing the last major merger of the milky way with the h3 survey |
studies of galaxy surveys in the context of the cold dark matter paradigm have shown that the mass of the dark matter halo and the total stellar mass are coupled through a function that varies smoothly with mass. their average ratio mhalo/mstars has a minimum of about 30 for galaxies with stellar masses near that of the milky way (approximately 5 × 1010 solar masses) and increases both towards lower masses and towards higher masses. the scatter in this relation is not well known; it is generally thought to be less than a factor of two for massive galaxies but much larger for dwarf galaxies. here we report the radial velocities of ten luminous globular-cluster-like objects in the ultra-diffuse galaxy ngc1052-df2, which has a stellar mass of approximately 2 × 108 solar masses. we infer that its velocity dispersion is less than 10.5 kilometres per second with 90 per cent confidence, and we determine from this that its total mass within a radius of 7.6 kiloparsecs is less than 3.4 × 108 solar masses. this implies that the ratio mhalo/mstars is of order unity (and consistent with zero), a factor of at least 400 lower than expected. ngc1052-df2 demonstrates that dark matter is not always coupled with baryonic matter on galactic scales. | a galaxy lacking dark matter |
a fundamental quest of modern astronomy is to locate the earliest galaxies and study how they influenced the intergalactic medium a few hundred million years after the big bang1-3. the abundance of star-forming galaxies is known to decline4,5 from redshifts of about 6 to 10, but a key question is the extent of star formation at even earlier times, corresponding to the period when the first galaxies might have emerged. here we report spectroscopic observations of macs1149-jd16, a gravitationally lensed galaxy observed when the universe was less than four per cent of its present age. we detect an emission line of doubly ionized oxygen at a redshift of 9.1096 ± 0.0006, with an uncertainty of one standard deviation. this precisely determined redshift indicates that the red rest-frame optical colour arises from a dominant stellar component that formed about 250 million years after the big bang, corresponding to a redshift of about 15. our results indicate that it may be possible to detect such early episodes of star formation in similar galaxies with future telescopes. | the onset of star formation 250 million years after the big bang |
it is generally believed that long-duration gamma-ray bursts (grbs) are associated with massive star core collapse1, whereas short-duration grbs are associated with mergers of compact star binaries2. however, growing observations3-6 have suggested that oddball grbs do exist, and several criteria (prompt emission properties, supernova/kilonova associations and host galaxy properties) rather than burst duration only are needed to classify grbs physically7. a previously reported long-duration burst, grb 060614 (ref. 3), could be viewed as a short grb with extended emission if it were observed at a larger distance8 and was associated with a kilonova-like feature9. as a result, it belongs to the type i (compact star merger) grb category and is probably of binary neutron star (ns) merger origin. here we report a peculiar long-duration burst, grb 211211a, whose prompt emission properties in many aspects differ from all known type i grbs, yet its multiband observations suggest a non-massive-star origin. in particular, substantial excess emission in both optical and near-infrared wavelengths has been discovered (see also ref. 10), which resembles kilonova emission, as observed in some type i grbs. these observations point towards a new progenitor type of grbs. a scenario invoking a white dwarf (wd)-ns merger with a post-merger magnetar engine provides a self-consistent interpretation for all the observations, including prompt gamma rays, early x-ray afterglow, as well as the engine-fed11,12 kilonova emission. | a long-duration gamma-ray burst with a peculiar origin |
variable accretion in young stellar objects reveals itself photometrically and spectroscopically over a continuum of timescales and amplitudes. most dramatic are the large outbursts (e.g., fu ori, v1647 ori, and ex lup type events), but more frequent are the less coherent, smaller burst-like variations in accretion rate. improving our understanding of time-variable accretion directly addresses the fundamental question of how stars gain their masses. we review variability phenomena, as characterized from observations across the wavelength spectrum, and how those observations probe underlying physical conditions. the diversity of observed lightcurves and spectra at optical and infrared wavelengths defies a simple classification of outbursts and bursts into well-defined categories. mid-infrared and submillimeter wavelengths are sensitive to lower-temperature phenomena and more embedded, younger sources, and it is currently unclear if observed flux variations probe similar or distinct physics relative to the shorter wavelengths. we highlight unresolved issues and emphasize the value of spectroscopy, multiwavelength studies, and ultimately patience in using variable accretion to understand stellar mass assembly. | accretion variability as a guide to stellar mass assembly |
context. the carmenes survey is a high-precision radial velocity (rv) programme that aims to detect earth-like planets orbiting low-mass stars.aims: we develop least-squares fitting algorithms to derive the rvs and additional spectral diagnostics implemented in the spectrum radial velocity analyser (serval), a publicly available python code.methods: we measured the rvs using high signal-to-noise templates created by coadding all available spectra of each star. we define the chromatic index as the rv gradient as a function of wavelength with the rvs measured in the echelle orders. additionally, we computed the differential line width by correlating the fit residuals with the second derivative of the template to track variations in the stellar line width.results: using harps data, our serval code achieves a rv precision at the level of 1 m/s. applying the chromatic index to carmenes data of the active star yz cmi, we identify apparent rv variations induced by stellar activity. the differential line width is found to be an alternative indicator to the commonly used full width half maximum.conclusions: we find that at the red optical wavelengths (700-900 nm) obtained by the visual channel of carmenes, the chromatic index is an excellent tool to investigate stellar active regions and to identify and perhaps even correct for activity-induced rv variations. | spectrum radial velocity analyser (serval). high-precision radial velocities and two alternative spectral indicators |
we present a self-consistent, absolute isochronal age scale for young ( ≲ 200 myr), nearby ( ≲ 100 pc) moving groups in the solar neighbourhood based on homogeneous fitting of semi-empirical pre-main-sequence model isochrones using the τ2 maximum-likelihood fitting statistic of naylor & jeffries in the mv, v - j colour-magnitude diagram. the final adopted ages for the groups are as follows: 149^{+51}_{-19} {myr} for the ab dor moving group, 24 ± 3 myr for the β pic moving group (bpmg), 45^{+11}_{-7} {myr} for the carina association, 42^{+6}_{-4} {myr} for the columba association, 11 ± 3 myr for the η cha cluster, 45 ± 4 myr for the tucana-horologium moving group (tuc-hor), 10 ± 3 myr for the tw hya association and 22^{+4}_{-3} {myr} for the 32 ori group. at this stage we are uncomfortable assigning a final, unambiguous age to the argus association as our membership list for the association appears to suffer from a high level of contamination, and therefore it remains unclear whether these stars represent a single population of coeval stars. our isochronal ages for both the bpmg and tuc-hor are consistent with recent lithium depletion boundary (ldb) ages, which unlike isochronal ages, are relatively insensitive to the choice of low-mass evolutionary models. this consistency between the isochronal and ldb ages instils confidence that our self-consistent, absolute age scale for young, nearby moving groups is robust, and hence we suggest that these ages be adopted for future studies of these groups. software implementing the methods described in this study is available from http://www.astro.ex.ac.uk/people/timn/tau-squared/. | a self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood |
we describe the dark energy survey (des) photometric data set assembled from the first three years of science operations to support des year 3 cosmologic analyses, and provide usage notes aimed at the broad astrophysics community. y3 gold improves on previous releases from des, y1 gold, and data release 1 (des dr1), presenting an expanded and curated data set that incorporates algorithmic developments in image detrending and processing, photometric calibration, and object classification. y3 gold comprises nearly 5000 deg2 of grizy imaging in the south galactic cap, including nearly 390 million objects, with depth reaching a signal-to-noise ratio ∼10 for extended objects up to iab ∼ 23.0, and top-of-the-atmosphere photometric uniformity <3 mmag. compared to dr1, photometric residuals with respect to gaia are reduced by 50%, and per-object chromatic corrections are introduced. y3 gold augments des dr1 with simultaneous fits to multi-epoch photometry for more robust galactic color measurements and corresponding photometric redshift estimates. y3 gold features improved morphological star-galaxy classification with efficiency >98% and purity >99% for galaxies with 19 < iab < 22.5. additionally, it includes per-object quality information, and accompanying maps of the footprint coverage, masked regions, imaging depth, survey conditions, and astrophysical foregrounds that are used to select the cosmologic analysis samples. | dark energy survey year 3 results: photometric data set for cosmology |
we investigate the impact of uncertainty in the metallicity-specific star formation rate over cosmic time on predictions of the rates and masses of double compact object mergers observable through gravitational waves. we find that this uncertainty can change the predicted detectable merger rate by more than an order of magnitude, comparable to contributions from uncertain physical assumptions regarding binary evolution, such as mass transfer efficiency or supernova kicks. we statistically compare the results produced by the compas population synthesis suite against a catalogue of gravitational-wave detections from the first two advanced ligo and virgo observing runs. we find that the rate and chirp mass of observed binary black hole mergers can be well matched under our default evolutionary model with a star formation metallicity spread of 0.39 dex around a mean metallicity <z> that scales with redshift z as <z> = 0.035 × 10-0.23z, assuming a star formation rate of 0.01 × (1+z)^{2.77} / (1+((1+z)/2.9)^{4.7}) m_⊙ mpc-3 yr-1. intriguingly, this default model predicts that 80 per cent of the approximately one binary black hole merger per day that will be detectable at design sensitivity will have formed through isolated binary evolution with only dynamically stable mass transfer, i.e. without experiencing a common-envelope event. | the effect of the metallicity-specific star formation history on double compact object mergers |
we discuss the mass-radius diagram for static neutron star models obtained by the numerical solution of modified tolman-oppenheimer-volkoff equations in f (r ) gravity where the lagrangians f (r )=r +α r2(1 +γ r ) and f (r )=r1 +ɛ are adopted. unlike the case of the perturbative approach previously reported, the solutions are constrained by the presence of an extra degree of freedom, coming from the trace of the field equations. in particular, the stiffness of the equation of state determines an upper limit on the central density ρc above which the positivity condition of energy-matter tensor trace tm=ρ -3 p holds. in the case of quadratic f (r ) gravity, we find higher masses and radii at lower central densities with an inversion of the behavior around a pivoting ρc which depends on the choice of the equation of state. when considering the cubic corrections, we find solutions converging to the required asymptotic behavior of the flat metric only for γ <0 . a similar analysis is performed for f (r )=r1 +ɛ considering ɛ as the leading parameter. we work strictly in the jordan frame in order to consider matter minimally coupled with respect to geometry. this fact allows us to avoid ambiguities that could emerge in adopting the einstein frame. | mass-radius relation for neutron stars in f (r ) gravity |
we present a series of high-resolution echelle spectra of sn 2023ixf in m101, obtained nightly during the first week or so after discovery using pepsi on the large binocular telescope. na i d absorption in these spectra indicates a host reddening of e(b - v) = 0.031 mag and a systemic velocity of +7 km s-1 relative to the average redshift of m101. dramatic changes are seen in the strength and shape of strong emission lines emitted by circumstellar material (csm), including he ii λ4686, c iv λλ5801,5811, hα, and n iv λλ7109,7123. in general, these narrow lines broaden to become intermediate-width lines before disappearing from the spectrum within a few days, indicating a limited extent to the dense csm of around 20-30 au (or ≲1014.7 cm). hα persists in the spectrum for about a week as an intermediate-width emission line with p cyg absorption at 700-1300 km s-1 arising in the post-shock shell of swept-up csm. early narrow emission lines are blueshifted and indicate an expansion speed in the pre-shock csm of about 115 km s-1, but with even broader emission in higher-ionization lines. this is faster than the normal winds of red supergiants, suggesting some mode of eruptive mass loss from the progenitor or radiative acceleration of the csm. a lack of narrow blueshifted absorption suggests that most of the csm is not along our line of sight. this and several other clues indicate that the csm of sn 2023ixf is significantly aspherical. we find that csm lines disappear after a few days because the asymmetric csm is engulfed by the supernova photosphere. | high-resolution spectroscopy of sn 2023ixf's first week: engulfing the asymmetric circumstellar material |
the angular momentum (am) evolution of stellar interiors, along with the resulting rotation rates of stellar remnants, remains poorly understood. asteroseismic measurements of red giant stars reveal that their cores rotate much faster than their surfaces, but much slower than theoretically predicted, indicating an unidentified source of am transport operates in their radiative cores. motivated by this, we investigate the magnetic tayler instability and argue that it saturates when turbulent dissipation of the perturbed magnetic field energy is equal to magnetic energy generation via winding. this leads to larger magnetic field amplitudes, more efficient am transport, and smaller shears than predicted by the classic tayler-spruit dynamo. we provide prescriptions for the effective am diffusivity and incorporate them into numerical stellar models, finding they largely reproduce (1) the nearly rigid rotation of the sun and main sequence stars, (2) the core rotation rates of low-mass red giants during hydrogen shell and helium burning, and (3) the rotation rates of white dwarfs. we discuss implications for stellar rotational evolution, internal rotation profiles, rotational mixing, and the spins of compact objects. | slowing the spins of stellar cores |
the vertical structure and dynamics of stars in our local galactic neighbourhood contains much information about the local distribution of visible and dark matter and of perturbations to the milky way disc. we use data on the positions and velocities of stars in the solar neighbourhood from gaia data release 2 (dr2) and large spectroscopic surveys to investigate the vertical number counts and mean velocity trend as a function of distance from the local galactic mid-plane. we perform a detailed measurement of the wave-like north-south asymmetry in the vertical number counts, which reveals a number of deficits at heights ≈0.4, ≈0.9, and {≈ } 1.5 kpc, and peaks at ≈0.2, ≈0.7, and {≈ } 1.1 kpc. we find that the asymmetry pattern is independent of colour. the mean vertical velocity is almost constant to < 1 km s^{-1} within a few 100 pc from the mid-plane and then displays a north-south symmetric dip at {≈ }0.5 kpc with an amplitude of {≈ } 2 km s^{-1} that is a plausible velocity counterpart to the main number count dip at a similar height. thus, with gaia dr2 we confirm at high fidelity that the local galactic disc is undergoing a wave-like oscillation and a dynamically consistent observational picture of the perturbed local vertical structure emerges for the first time. we also present the most precise and accurate determination of the sun's height above the local galactic mid-plane, correcting for any asymmetry in the vertical density: z_{⊙} = 20.8 ± 0.3 pc. | vertical waves in the solar neighbourhood in gaia dr2 |
we use accurate estimates of aluminium abundance from the apogee data release 17 and gaia early data release 3 astrometry to select a highly pure sample of stars with metallicity -1.5 ≲ [fe/h] ≲ 0.5 born in-situ in the milky way proper. the low-metallicity ([fe/h] ≲ -1.3) in-situ component we dub aurora is kinematically hot with an approximately isotropic velocity ellipsoid and a modest net rotation. aurora stars exhibit large scatter in metallicity and in many element abundance ratios. the median tangential velocity of the in-situ stars increases sharply with metallicity between [fe/h] = -1.3 and -0.9, the transition that we call the spin-up. the observed and theoretically expected age-metallicity correlations imply that this increase reflects a rapid formation of the mw disc over ≈1-2 gyr. the transformation of the stellar kinematics as a function of [fe/h] is accompanied by a qualitative change in chemical abundances: the scatter drops sharply once the galaxy builds up a disc during later epochs corresponding to [fe/h] > -0.9. results of galaxy formation models presented in this and other recent studies strongly indicate that the trends observed in the mw reflect generic processes during the early evolution of progenitors of mw-sized galaxies: a period of chaotic pre-disc evolution, when gas is accreted along cold narrow filaments and when stars are born in irregular configurations, and subsequent rapid disc formation. the latter signals formation of a stable hot gaseous halo around the mw progenitor, which changes the mode of gas accretion and allows development of coherently rotating disc. | from dawn till disc: milky way's turbulent youth revealed by the apogee+gaia data |
we examine in greater detail the recent proposal of using superconductors for detecting dark matter as light as the warm dark matter limit of o (kev). detection of suc light dark matter is possible if the entire kinetic energy of the dark matter is extracted in the scattering, and if the experiment is sensitive to o (mev) energy depositions. this is the case for fermi-degenerate materials in which the fermi velocity exceeds the dark matter velocity dispersion in the milky way of ∼ 10-3. we focus on a concrete experimental proposal using a superconducting target with a transition edge sensor in order to detect the small energy deposits from the dark matter scatterings. considering a wide variety of constraints, from dark matter self-interactions to the cosmic microwave background, we show that models consistent with cosmological/astrophysical and terrestrial constraints are observable with such detectors. a wider range of viable models with dark matter mass below an mev is available if dark matter or mediator properties (such as couplings or masses) differ at bbn epoch or in stellar interiors from those in superconductors. we also show that metal targets pay a strong in-medium suppression for kinetically mixed mediators; this suppression is alleviated with insulating targets. | detecting superlight dark matter with fermi-degenerate materials |
we analyse the physical properties of a large, homogeneously selected sample of alma-located sub-millimetre galaxies (smgs). this survey, as2uds, identified 707 smgs across the ∼1 deg2 field, including ∼17 per cent, which are undetected at k ≳ 25.7 mag. we interpret their ultraviolet-to-radio data using magphys and determine a median redshift of z = 2.61 ± 0.08 (1σ range of z = 1.8-3.4) with just ∼6 per cent at z > 4. our survey provides a sample of massive dusty galaxies at z ≳ 1, with median dust and stellar masses of md = (6.8 ± 0.3) × 108 m⊙ (thus, gas masses of ∼1011 m⊙) and m* = (1.26 ± 0.05) × 1011 m⊙. we find no evolution in dust temperature at a constant far-infrared luminosity across z ∼ 1.5-4. the gas mass function of our sample increases to z ∼ 2-3 and then declines at z > 3. the space density and masses of smgs suggest that almost all galaxies with m* ≳ 3 × 1011 m⊙ have passed through an smg-like phase. the redshift distribution is well fit by a model combining evolution of the gas fraction in haloes with the growth of halo mass past a critical threshold of mh ∼ 6 × 1012 m⊙, thus smgs may represent the highly efficient collapse of gas-rich massive haloes. we show that smgs are broadly consistent with simple homologous systems in the far-infrared, consistent with a centrally illuminated starburst. our study provides strong support for an evolutionary link between the active, gas-rich smg population at z > 1 and the formation of massive, bulge-dominated galaxies across the history of the universe. | an alma survey of the scuba-2 cls uds field: physical properties of 707 sub-millimetre galaxies |
six gravitational wave events have been reported by the ligo-virgo collaboration (lvc), five of them associated with black hole binary (bhb) mergers and one with a double neutron star (dns) merger, while the coalescence of a black hole-neutron star (bhns) binary is still missing. we investigate the progenitors of double compact object binaries with our population-synthesis code mobse. mobse includes advanced prescriptions for mass loss by stellar winds (depending on metallicity and on the eddington ratio) and a formalism for core-collapse, electron-capture and (pulsational) pair instability supernovae. we investigate the impact of progenitor's metallicity, of the common-envelope parameter α and of the natal kicks on the properties of dnss, bhnss and bhbs. we find that neutron-star (ns) masses in dnss span from 1.1 to 2.0 m⊙, with a preference for light nss, while nss in merging bhnss have mostly large masses (1.3-2.0m⊙). bhs in merging bhnss are preferentially of low mass (5-15m⊙). bh masses in merging bhbs strongly depend on the progenitor's metallicity and span from ∼5 to ∼45 m⊙. the local merger rate density of both bhnss and bhbs derived from our simulations is consistent with the values reported by the lvc in all our simulations. in contrast, the local merger rate density of dnss matches the value inferred from the lvc only if low natal kicks are assumed. this result adds another piece to the intricate puzzle of natal kicks and dns formation. | the progenitors of compact-object binaries: impact of metallicity, common envelope and natal kicks |
the direct detection of gravitational waves (gws) is an invaluable new tool to probe gravity and the nature of cosmic acceleration. a large class of scalar-tensor theories predicts that gws propagate with velocity different than the speed of light, a difference that can be o (1 ) for many models of dark energy. we determine the conditions behind the anomalous gw speed, namely, that the scalar field spontaneously breaks lorentz invariance and couples to the metric perturbations via the weyl tensor. if these conditions are realized in nature, the delay between gw and electromagnetic signals from distant events will run beyond human time scales, making it impossible to measure the speed of gws using neutron star mergers or other violent events. we present a robust strategy to exclude or confirm an anomalous speed of gws using eclipsing binary systems, the electromagnetic phase of which can be exquisitely determined. the white dwarf binary j 0651 +2844 is a known example of such a system that can be used to probe deviations in the gw speed as small as cg/c -1 ≳2 ×10-12 when lisa comes online. this test will either eliminate many contender models for cosmic acceleration or wreck a fundamental pillar of general relativity. | speed of gravitational waves and the fate of scalar-tensor gravity |
the age of gravitational-wave astronomy has begun, and black hole (bh) mergers detected by the laser interferometer gravitational-wave observatory (ligo) are providing novel constraints on massive star evolution. a major uncertainty in stellar theory is the angular momentum (am) transport within the star that determines its core rotation rate and the resulting bh’s spin. internal rotation rates of low-mass stars measured from asteroseismology prove that am transport is efficient, suggesting that massive stellar cores may rotate slower than prior expectations. we investigate am transport via the magnetic tayler instability, which can largely explain the rotation rates of low-mass stars and white dwarfs. implementing an updated am transport prescription into models of high-mass stars, we compute the spins of their bh remnants. we predict that bhs born from single stars rotate very slowly, with a ∼ 10-2, regardless of initial rotation rate, possibly explaining the low χ eff of most bh binaries detected by ligo thus far. a limited set of binary models suggests slow rotation for many binary scenarios as well, although homogeneous evolution and tidal spin-up of post-common-envelope helium stars can create moderate or high bh spins. we make predictions for the values of χ eff in future ligo events, and we discuss implications for engine-powered transients. | most black holes are born very slowly rotating |
the interplay between cosmic gas accretion on to galaxies and galaxy mergers drives the observed morphological diversity of galaxies. by comparing the state-of-the-art hydrodynamical cosmological simulations horizon-agn and horizon-noagn, we unambiguously identify the critical role of active galactic nuclei (agn) in setting up the correct galaxy morphology for the massive end of the population. with agn feedback, typical kinematic and morpho-metric properties of galaxy populations as well as the galaxy-halo mass relation are in much better agreement with observations. only agn feedback allows massive galaxies at the centre of groups and clusters to become ellipticals, while without agn feedback those galaxies reform discs. it is the merger-enhanced agn activity that is able to freeze the morphological type of the post-merger remnant by durably quenching its quiescent star formation. hence morphology is shown to be driven not only by mass but also by the nature of cosmic accretion: at constant galaxy mass, ellipticals are galaxies that are mainly assembled through mergers, while discs are preferentially built from the in situ star formation fed by smooth cosmic gas infall. | the horizon-agn simulation: morphological diversity of galaxies promoted by agn feedback |
extending prior work by pankow et al, we introduce rift, an algorithm to perform rapid parameter inference on gravitational wave sources via iterative fitting. we demonstrate this approach can correctly recover the parameters of coalescing compact binary systems, using detailed comparisons of rift to the well-tested lalinference software library. we provide several examples where the unique speed and flexibility of rift enables otherwise intractable or awkward parameter inference analyses, including (a) adopting either costly and novel models for outgoing gravitational waves; and (b) mixed approximations, each suitable to different parts of the compact binary parameter space. we demonstrate how \rift{} can be applied to binary neutron stars, both for parameter inference and direct constraints on the nuclear equation of state. | rapid and accurate parameter inference for coalescing, precessing compact binaries |
the combined detection of a binary neutron star merger in both gravitational waves (gws) and electromagnetic (em) radiation spanning the entire spectrum - gw170817/at2017gfo/grb170817a - marks a breakthrough in the field of multimessenger astronomy. between the plethora of modelling and observations, the rich synergy that exists among the available data sets creates a unique opportunity to constrain the binary parameters, the equation of state of supranuclear density matter, and the physical processes at work during the kilonova and gamma-ray burst. we report, for the first time, bayesian parameter estimation combining information from gw170817, at2017gfo, and grb170817 to obtain truly multimessenger constraints on the tidal deformability \tilde{λ } \in [302,860], total binary mass m ∈ [2.722, 2.751] m⊙, the radius of a 1.4 solar mass neutron star r \in [11.3,13.5] km (with additional 0.2 km systematic uncertainty), and an upper bound on the mass ratio of q ≤ 1.27, all at 90 per cent confidence. our joint novel analysis uses new phenomenological descriptions of the dynamical ejecta, debris disc mass, and remnant black hole properties, all derived from a large suite of numerical relativity simulations. | multimessenger bayesian parameter inference of a binary neutron star merger |
we present the ultraviolet luminosity function and an estimate of the cosmic star formation rate density at 8 < z < 13 derived from deep nircam observations taken in parallel with the miri deep survey of the hubble ultra deep field (hudf), nircam covering the parallel field 2. our deep (40 hr) nircam observations reach an f277w magnitude of 30.8 (5σ), more than 2 mag deeper than jwst public data sets already analyzed to find high-redshift galaxies. we select a sample of 44 z > 8 galaxy candidates based on their dropout nature in the f115w and/or f150w filters, a high probability for their photometric redshifts, estimated with three different codes, being at z > 8, good fits based on χ 2 calculations, and predominant solutions compared to z < 8 alternatives. we find mild evolution in the luminosity function from z ~ 13 to z ~ 8, i.e., only a small increase in the average number density of ~0.2 dex, while the faint-end slope and absolute magnitude of the knee remain approximately constant, with values α = - 2.2 ± 0.1, and m * = - 20.8 ± 0.2 mag. comparing our results with the predictions of state-of-the-art galaxy evolution models, we find two main results: (1) a slower increase with time in the cosmic star formation rate density compared to a steeper rise predicted by models; (2) nearly a factor of 10 higher star formation activity concentrated in scales around 2 kpc in galaxies with stellar masses ~108 m ⊙ during the first 350 myr of the universe, z ~ 12, with models matching better the luminosity density observational estimations ~150 myr later, by z ~ 9. | life beyond 30: probing the -20 < m uv < -17 luminosity function at 8 < z < 13 with the nircam parallel field of the miri deep survey |
one bottleneck for the exploitation of data from the kepler mission for stellar astrophysics and exoplanet research has been the lack of precise radii and evolutionary states for most of the observed stars. we report revised radii of 177,911 kepler stars derived by combining parallaxes from the gaia data release 2 with the dr25 kepler stellar properties catalog. the median radius precision is ≈8%, a typical improvement by a factor of 4-5 over previous estimates for typical kepler stars. we find that ≈67% (≈120,000) of all kepler targets are main-sequence stars, ≈21% (≈37,000) are subgiants, and ≈12% (≈21,000) are red giants, demonstrating that subgiant contamination is less severe than some previous estimates and that kepler targets are mostly main-sequence stars. using the revised stellar radii, we recalculate the radii for 2123 confirmed and 1922 candidate exoplanets. we confirm the presence of a gap in the radius distribution of small, close-in planets, but find that the gap is mostly limited to incident fluxes >200 {f}\oplus , and its location may be at a slightly larger radius (closer to ≈2 r ⊕) when compared to previous results. furthermore, we find several confirmed exoplanets occupying a previously described “hot super-earth desert” at high irradiance, show the relation between a gas-giant planet’s radius and its incident flux, and establish a bona fide sample of eight confirmed planets and 30 planet candidates with {r}{{p}} < 2 r ⊕ in circumstellar “habitable zones” (incident fluxes between 0.25 and 1.50 {f}\oplus ). the results presented here demonstrate the potential for transformative characterization of stellar and exoplanet populations using gaia data. | revised radii of kepler stars and planets using gaia data release 2 |
in this work, we study the prospect of detecting the stochastic gravitational-wave background with the tianqin observatory. we consider sources of both astrophysical and cosmological origin, including stellar-mass binary black holes, binary neutron stars, galactic white dwarves, inflation, first-order phase transitions, and cosmic defects. for the detector configurations, we consider tianqin, tianqin i +ii , and tianqin +lisa . we study the detectability of stochastic gravitational-wave backgrounds with both the cross correlation and null channel methods, and present the corresponding power-law integrated sensitivity curves. we introduce the definition of the "joint foreground" with a network of detectors. with the joint foreground, the number of resolved double white dwarves in the galaxy will be increased by 5-22% compared with a simple combination of individual detectors. the astrophysical background is expected to be detectable with a signal-to-noise ratio of 100 after 5 years of operation and dominated by the extragalactic double white dwarves. on the other hand, due to the uncertain nature of underlying models, we can only estimate the detection capability of the cosmological background for specific cases. | science with the tianqin observatory: preliminary results on stochastic gravitational-wave background |
in this study, we follow up our recent paper (monteiro et al. 2020) and present a homogeneous sample of fundamental parameters of open clusters in our galaxy, entirely based on gaia dr2 data. we used published membership probability of the stars derived from gaia dr2 data and applied our isochrone fitting code, updated as in monteiro et al. (2020), to gbp and grpgaia dr2 data for member stars. in doing this, we take into account the nominal errors in the data and derive distance, age, and extinction of each cluster. this work therefore provides parameters for 1743 open clusters and, as a by-product, a list of likely not physical or dubious open clusters is provided as well for future investigations. furthermore, it was possible to estimate the mean radial velocity of 831 clusters (198 of which are new and unpublished so far), using stellar radial velocities from gaia dr2 catalogue. by comparing the open cluster distances obtained from isochrone fitting with those obtained from a maximum likelihood estimate of individual member parallaxes, we found a systematic offset of (-0.05 ± 0.04) mas. | updated parameters of 1743 open clusters based on gaia dr2 |
we review the impact of nuclear forces on matter at neutron-rich extremes. recent results have shown that neutron-rich nuclei become increasingly sensitive to three-nucleon forces, which are at the forefront of theoretical developments based on effective field theories of quantum chromodynamics. these developments include the formation of shell structure, the spectroscopy of exotic nuclei, and the location of the neutron drip line. nuclear forces also constrain the properties of neutron-rich matter, including the neutron skin, the symmetry energy, and the structure of neutron stars. first, we review our understanding of three-nucleon forces and show how chiral effective field theory makes unique predictions for many-body forces. then, we survey results with three-nucleon forces in neutron-rich oxygen and calcium isotopes and neutron-rich matter, which have been explored with a range of many-body methods. three-nucleon forces therefore provide an exciting link between theoretical, experimental, and observational nuclear physics frontiers. | nuclear forces and their impact on neutron-rich nuclei and neutron-rich matter |
results from the kepler mission indicate that the occurrence rate of small planets (<3 r ⊕) in the habitable zone of nearby low-mass stars may be as high as 80%. despite this abundance, probing the conditions and atmospheric properties on any habitable-zone planet is extremely difficult and has remained elusive to date. here, we report the detection of water vapor and the likely presence of liquid and icy water clouds in the atmosphere of the 2.6 r ⊕ habitable-zone planet k2-18b. the simultaneous detection of water vapor and clouds in the mid-atmosphere of k2-18b is particularly intriguing because k2-18b receives virtually the same amount of total insolation from its host star ({1368}-107+114 w m-2) as the earth receives from the sun (1361 w m-2), resulting in the right conditions for water vapor to condense and explain the detected clouds. in this study we observed nine transits of k2-18b using hubble space telescope/wfc3 in order to achieve the necessary sensitivity to detect the water vapor, and we supplement this data set with spitzer and k2 observations to obtain a broader wavelength coverage. while the thick hydrogen-dominated envelope we detect on k2-18b means that the planet is not a true earth analog, our observations demonstrate that low-mass habitable-zone planets with the right conditions for liquid water are accessible with state-of-the-art telescopes. | water vapor and clouds on the habitable-zone sub-neptune exoplanet k2-18b |
we report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (bh). we used the hubble space telescope (hst) to carry out precise astrometry of the source star of the long-duration (t e ≃ 270 days), high-magnification microlensing event moa-2011-blg-191/ogle-2011-blg-0462 (hereafter designated as moa-11-191/ogle-11-462), in the direction of the galactic bulge. hst imaging, conducted at eight epochs over an interval of 6 yr, reveals a clear relativistic astrometric deflection of the background star's apparent position. ground-based photometry of moa-11-191/ogle-11-462 shows a parallactic signature of the effect of earth's motion on the microlensing light curve. combining the hst astrometry with the ground-based light curve and the derived parallax, we obtain a lens mass of 7.1 ± 1.3 m ⊙ and a distance of 1.58 ± 0.18 kpc. we show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its bh nature. our analysis also provides an absolute proper motion for the bh. the proper motion is offset from the mean motion of galactic disk stars at similar distances by an amount corresponding to a transverse space velocity of ~45 km s-1, suggesting that the bh received a "natal kick" from its supernova explosion. previous mass determinations for stellar-mass bhs have come from radial velocity measurements of galactic x-ray binaries and from gravitational radiation emitted by merging bhs in binary systems in external galaxies. our mass measurement is the first for an isolated stellar-mass bh using any technique. *this research is based in part on observations made with the nasa/esa hubble space telescope, obtained from the space telescope science institute, which is operated by the association of universities for research in astronomy, inc., under nasa contract nas 5-26555. | an isolated stellar-mass black hole detected through astrometric microlensing |
how black holes consume and eject matter has been the subject of intense studies for more than 60 years. the luminosity of these systems are often compared to the eddington limit, the border at which the spherical accretion is inhibited by the radiation pressure of photons it produces. the discovery of ultraluminous x-ray sources (ulxs) showed that accretion can proceed even when the apparent luminosity exceeds the eddington limit (kaaret et al. 2017). high apparent luminosity might be produced by the beaming of the incident radiation by a thick collimated outflow or by a truly super-eddington accretion flow. however, possibilities to study these outflows in detail are limited, as ulxs are typically found in distant galaxies. using the imaging x-ray polarimetry explorer (ixpe, weisskopf et al. 2022), we made the first measurement of x-ray polarization in galactic x-ray binary cyg x-3. the detection of high, $\approx$25\%, nearly energy-independent linear polarization, orthogonal to the direction of the radio ejections, unambiguously indicates the primary source is obscured and the observer on earth only sees reflected and scattered light. modelling shows there is an optically thick envelope with a narrow funnel around the primary x-ray source in the system. we derive an upper limit on the opening angle of the funnel that implies a lower limit on the beamed luminosity exceeding the eddington value. we show that cyg x-3 is viewed as a ulx to an extragalactic observer located along the axis of the funnel. our findings reveal this unique persistent source as an ideal laboratory for the study of the inner workings of ulx central engines. | astronomical puzzle cyg x-3 is a hidden galactic ultraluminous x-ray source |
the millisecond-duration radio flashes known as fast radio bursts (frbs) represent an enigmatic astrophysical phenomenon. recently, the sub-arcsecond localization (∼100 mas precision) of frb 121102 using the very large array has led to its unambiguous association with persistent radio and optical counterparts, and to the identification of its host galaxy. however, an even more precise localization is needed in order to probe the direct physical relationship between the millisecond bursts themselves and the associated persistent emission. here, we report very-long-baseline radio interferometric observations using the european vlbi network and the 305 m arecibo telescope, which simultaneously detect both the bursts and the persistent radio emission at milliarcsecond angular scales and show that they are co-located to within a projected linear separation of ≲40 pc (≲12 mas angular separation, at 95% confidence). we detect consistent angular broadening of the bursts and persistent radio source (∼2-4 mas at 1.7 ghz), which are both similar to the expected milky way scattering contribution. the persistent radio source has a projected size constrained to be ≲ 0.7 pc (≲0.2 mas angular extent at 5.0 ghz) and a lower limit for the brightness temperature of {t}b≳ 5× {10}7 {{k}}. together, these observations provide strong evidence for a direct physical link between frb 121102 and the compact persistent radio source. we argue that a burst source associated with a low-luminosity active galactic nucleus or a young neutron star energizing a supernova remnant are the two scenarios for frb 121102 that best match the observed data. | the repeating fast radio burst frb 121102 as seen on milliarcsecond angular scales |
clusters of galaxies are the most massive gravitationally bound objects in the universe and are still forming. they are thus important probes of cosmological parameters and many astrophysical processes. however, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. x-rays from the core of the perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. the active galactic nucleus of the central galaxy ngc 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. these bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling—a process known as active galactic nucleus feedback. here we report x-ray observations of the core of the perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 ± 10 kilometres per second in the region 30-60 kiloparsecs from the central nucleus. a gradient in the line-of-sight velocity of 150 ± 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. we infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure. | the quiescent intracluster medium in the core of the perseus cluster |
we conduct a systematic tidal disruption event (tde) demographics analysis using the largest sample of optically selected tdes. a flux-limited, spectroscopically complete sample of 33 tdes is constructed using the zwicky transient facility over 3 yr (from 2018 october to 2021 september). we infer the black hole (bh) mass (m bh) with host galaxy scaling relations, showing that the sample m bh ranges from 105.1 m ⊙ to 108.2 m ⊙. we developed a survey efficiency corrected maximum volume method to infer the rates. the rest-frame g-band luminosity function can be well described by a broken power law of $\phi ({l}_{g})\propto {\left[{\left({l}_{g}/{l}_{\mathrm{bk}}\right)}^{0.3}+{\left({l}_{g}/{l}_{\mathrm{bk}}\right)}^{2.6}\right]}^{-1}$ , with l bk = 1043.1 erg s-1. in the bh mass regime of 105.3 ≲ (m bh/m ⊙) ≲ 107.3, the tde mass function follows $\phi ({m}_{\mathrm{bh}})\propto {m}_{\mathrm{bh}}^{-0.25}$ , which favors a flat local bh mass function ( ${{dn}}_{\mathrm{bh}}/d\mathrm{log}{m}_{\mathrm{bh}}\approx \mathrm{constant}$ ). we confirm the significant rate suppression at the high-mass end (m bh ≳ 107.5 m ⊙), which is consistent with theoretical predictions considering direct capture of hydrogen-burning stars by the event horizon. at a host galaxy mass of m gal ~ 1010 m ⊙, the average optical tde rate is ≈3.2 × 10-5 galaxy-1 yr-1. we constrain the optical tde rate to be [3.7, 7.4, and 1.6] × 10-5 galaxy-1 yr-1 in galaxies with red, green, and blue colors. | tidal disruption event demographics with the zwicky transient facility: volumetric rates, luminosity function, and implications for the local black hole mass function |
we present ias15, a 15th-order integrator to simulate gravitational dynamics. the integrator is based on a gauß-radau quadrature and can handle conservative as well as non-conservative forces. we develop a step-size control that can automatically choose an optimal timestep. the algorithm can handle close encounters and high-eccentricity orbits. the systematic errors are kept well below machine precision, and long-term orbit integrations over 109 orbits show that ias15 is optimal in the sense that it follows brouwer's law, i.e. the energy error behaves like a random walk. our tests show that ias15 is superior to a mixed-variable symplectic integrator and other popular integrators, including high-order ones, in both speed and accuracy. in fact, ias15 preserves the symplecticity of hamiltonian systems better than the commonly used nominally symplectic integrators to which we compared it. we provide an open-source implementation of ias15. the package comes with several easy-to-extend examples involving resonant planetary systems, kozai-lidov cycles, close encounters, radiation pressure, quadrupole moment and generic damping functions that can, among other things, be used to simulate planet-disc interactions. other non-conservative forces can be added easily. | ias15: a fast, adaptive, high-order integrator for gravitational dynamics, accurate to machine precision over a billion orbits |
a transient gravitational-wave signal, gw150914, was identified in the twin advanced ligo detectors on 2015 september 2015 at 09:50:45 utc. to assess the implications of this discovery, the detectors remained in operation with unchanged configurations over a period of 39 days around the time of the signal. at the detection statistic threshold corresponding to that observed for gw150914, our search of the 16 days of simultaneous two-detector observational data is estimated to have a false-alarm rate (far) of \lt 4.9× {10}-6 {{yr}}-1, yielding a p-value for gw150914 of \lt 2× {10}-7. parameter estimation follow-up on this trigger identifies its source as a binary black hole (bbh) merger with component masses ({m}1,{m}2)=({36}-4+5,{29}-4+4) {m}⊙at redshift z={0.09}-0.04+0.03 (median and 90% credible range). here, we report on the constraints these observations place on the rate of bbh coalescences. considering only gw150914, assuming that all bbhs in the universe have the same masses and spins as this event, imposing a search far threshold of 1 per 100 years, and assuming that the bbh merger rate is constant in the comoving frame, we infer a 90% credible range of merger rates between 2{--}53 {{gpc}}-3 {{yr}}-1 (comoving frame). incorporating all search triggers that pass a much lower threshold while accounting for the uncertainty in the astrophysical origin of each trigger, we estimate a higher rate, ranging from 13{--}600 {{gpc}}-3 {{yr}}-1 depending on assumptions about the bbh mass distribution. all together, our various rate estimates fall in the conservative range 2{--}600 {{gpc}}-3 {{yr}}-1. | the rate of binary black hole mergers inferred from advanced ligo observations surrounding gw150914 |
we assemble a catalogue of candidate sagittarius stream members with 5d and 6d phase-space information, using astrometric data from gaia dr2, distances estimated from rr lyrae stars, and line-of-sight velocities from various spectroscopic surveys. we find a clear misalignment between the stream track and the direction of the reflex-corrected proper motions in the leading arm of the stream, which we interpret as a signature of a time-dependent perturbation of the gravitational potential. a likely cause of this perturbation is the recent passage of the most massive milky way satellite - the large magellanic cloud (lmc). we develop novel methods for simulating the sagittarius stream in the presence of the lmc, using specially tailored n-body simulations and a flexible parametrization of the milky way halo density profile. we find that while models without the lmc can fit most stream features rather well, they fail to reproduce the misalignment and overestimate the distance to the leading arm apocentre. on the other hand, models with an lmc mass in the range $(1.3\pm 0.3)\times 10^{11}\, \mathrm{m}_\odot$ rectify these deficiencies. we demonstrate that the stream can not be modelled adequately in a static milky way. instead, our galaxy is required to lurch toward the massive in-falling cloud, giving the sgr stream its peculiar shape and kinematics. by exploring the parameter space of milky way potentials, we determine the enclosed mass within 100 kpc to be $(5.6\pm 0.4)\times 10^{11}\, \mathrm{m}_\odot$ , and the virial mass to be $(9.0\pm 1.3)\times 10^{11}\, \mathrm{m}_\odot$ , and find tentative evidence for a radially-varying shape and orientation of the galactic halo. | tango for three: sagittarius, lmc, and the milky way |
we summarize the determination of some neutrino properties from the global analysis of solar, atmospheric, reactor, and accelerator neutrino data in the framework of three-neutrino mixing as well as in some extended scenarios such as the mixing with ev-scale sterile neutrinos invoked for the interpretation of the short baseline anomalies, and the presence of non-standard neutrino interactions. | global analyses of neutrino oscillation experiments |
context. gaia has been in operations since 2014, and two full data releases (dr) have been delivered so far: dr1 in 2016 and dr2 in 2018. the third gaia data release expands from the early data release (edr3) in 2020, which contained the five-parameter astrometric solution and mean photometry for 1.8 billion sources by providing 34 months of multi-epoch observations that allowed us to systematically probe, characterise, and classify variable celestial phenomena.aims: we present a summary of the variability processing and analysis of the photometric and spectroscopic time series of 1.8 billion sources carried out for gaia dr3.methods: we used statistical and machine learning methods to characterise and classify the variable sources. training sets were built from a global revision of major published variable star catalogues. for a subset of classes, specific detailed studies were conducted to confirm their class membership and to derive parameters that are adapted to the peculiarity of the considered class.results: in total, 10.5 million objects are identified as variable in gaia dr3 and have associated time series in g, gbp, and grp and, in some cases, radial velocity time series. the dr3 variable sources subdivide into 9.5 million variable stars and 1 million active galactic nuclei or `quasars'. in addition, supervised classification identified 2.5 million galaxies thanks to spurious variability induced by the extent of these objects. the variability analysis output in the dr3 archive amounts to 17 tables, containing a total of 365 parameters. we publish 35 types and subtypes of variable objects. for 11 variable types, additional specific object parameters are published. here, we provide an overview of the estimated completeness and contamination of most variability classes.conclusions: thanks to gaia, we present the largest whole-sky variability analysis based on coherent photometric, astrometric, and spectroscopic data. future gaia data releases will more than double the span of time series and the number of observations, allowing the publication of an even richer catalogue. | gaia data release 3. summary of the variability processing and analysis |
we report the discovery of 47 low surface brightness objects in deep images of a 3° × 3° field centered on the coma cluster, obtained with the dragonfly telephoto array. the objects have central surface brightness μ(g, 0) ranging from 24-26 mag arcsec-2 and effective radii r eff = 3''-10'', as measured from archival canada-france-hawaii telescope images. from their spatial distribution we infer that most or all of the objects are galaxies in the coma cluster. this relatively large distance is surprising as it implies that the galaxies are very large: with r eff = 1.5-4.6 kpc their sizes are similar to those of l * galaxies even though their median stellar mass is only ~6 × 107 m ⊙. the galaxies are relatively red and round, with langg - irang = 0.8 and langb/arang = 0.74. one of the 47 galaxies is fortuitously covered by a deep hubble space telescope advanced camera for surveys (acs) observation. the acs imaging shows a large spheroidal object with a central surface brightness μ475 = 25.8 mag arcsec-2, a sérsic index n = 0.6, and an effective radius of 7'', corresponding to 3.4 kpc at the distance of coma. the galaxy is not resolved into stars, consistent with expectations for a coma cluster object. we speculate that these "ultra-diffuse galaxies" may have lost their gas supply at early times, possibly resulting in very high dark matter fractions. | forty-seven milky way-sized, extremely diffuse galaxies in the coma cluster |
the neutrino fast flavor instability (ffi) can change neutrino flavor on time scales of nanoseconds and length scales of centimeters. it is expected to be ubiquitous in core-collapse supernovae and neutron star mergers, potentially modifying the neutrino signal we see, how matter is ejected from these explosions, and the types of heavy elements that form in the ejecta and enrich the universe. there has been a great deal of recent interest in understanding the role the ffi plays in supernovae and mergers, but the short length and time scales and the strong nonlinearity have prevented the ffi from being included consistently in these models. we review the theoretical nature of the ffi starting with the quantum kinetic equations, where the instability exists in neutron star mergers and supernovae, and how the instability behaves after saturation in simplified simulations. we review the proposed methods to test for instability in moment-based calculations where the full distribution is not available and describe the numerical methods used to simulate the instability directly. finally, we close by outlining the trajectory toward realistic, self-consistent models that will allow a more complete understanding of the impact of the ffi in supernovae and mergers. | fast flavor transformations |
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