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most known terrestrial planets orbit small stars with radii less than 60 per cent of that of the sun1,2. theoretical models predict that these planets are more vulnerable to atmospheric loss than their counterparts orbiting sun-like stars3-6. to determine whether a thick atmosphere has survived on a small planet, one approach is to search for signatures of atmospheric heat redistribution in its thermal phase curve7-10. previous phase curve observations of the super-earth 55 cancri e (1.9 earth radii) showed that its peak brightness is offset from the substellar point (latitude and longitude of 0 degrees)—possibly indicative of atmospheric circulation11. here we report a phase curve measurement for the smaller, cooler exoplanet lhs 3844b, a 1.3-earth-radii world in an 11-hour orbit around the small nearby star lhs 3844. the observed phase variation is symmetric and has a large amplitude, implying a dayside brightness temperature of 1,040 ± 40 kelvin and a nightside temperature consistent with zero kelvin (at one standard deviation). thick atmospheres with surface pressures above 10 bar are ruled out by the data (at three standard deviations), and less-massive atmospheres are susceptible to erosion by stellar wind. the data are well fitted by a bare-rock model with a low bond albedo (lower than 0.2 at two standard deviations). these results support theoretical predictions that hot terrestrial planets orbiting small stars may not retain substantial atmospheres. | absence of a thick atmosphere on the terrestrial exoplanet lhs 3844b |
the first deep-field observations of the jwst have immediately yielded a surprisingly large number of very high redshift candidates, pushing the frontier of observability well beyond z ≳ 10. we here present a detailed sed-fitting analysis of the 10 gravitationally lensed z ~ 9-16 galaxy candidates detected behind the galaxy cluster smacs j0723.3-7327 in a previous paper using the beagle tool. our analysis makes use of dynamical considerations to place limits on the ages of these galaxies and of all three published sl models of the cluster to account for lensing systematics. we find the majority of these galaxies to have relatively low stellar masses $m_{\star }\sim 10^7-10^8\, \mathrm{m}_{\odot }$ and young ages tage ~ 10-100 myr but with a few higher mass exceptions ($m_{\star }\sim 10^9\rm{-}10^{10}\, \mathrm{m}_{\odot }$) due to balmer-break detections at z ~ 9-10. because of their very blue uv-slopes, down to β ~ -3, all of the galaxies in our sample have extremely low dust attenuations av ≲ 0.02. placing the measured parameters into relation, we find a very shallow m⋆ - muv-slope and high ssfrs above the main sequence of star formation with no significant redshift-evolution in either relation. this is in agreement with the bright uv luminosities measured for these objects and indicates that we are naturally selecting uv-bright galaxies that are undergoing intense star formation at the time they are observed. finally, we discuss the robustness of our high-redshift galaxy sample regarding low-redshift interlopers and conclude that low-redshift solutions can safely be ruled out for roughly half of the sample, including the highest redshift galaxies at z ~ 12-16. these objects represent compelling targets for spectroscopic follow-up observations with jwst and alma. | constraining the physical properties of the first lensed z 9 - 16 galaxy candidates with jwst |
cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the x-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. cyclotron features are thought to be due to resonant scattering of photons by electrons in the strong magnetic fields. the main content of this contribution focusses on electron cyclotron lines as found in accreting x-ray binary pulsars (xrbp) with magnetic fields on the order of several 1012 gauss. also, possible proton cyclotron lines from single neutron stars with even stronger magnetic fields are briefly discussed. with regard to electron cyclotron lines, we present an updated list of xrbps that show evidence of such absorption lines. the first such line was discovered in a 1976 balloon observation of the accreting binary pulsar hercules x-1, it is considered to be the first direct measurement of the magnetic field of a neutron star. as of today (end 2018), we list 35 xrbps showing evidence of one ore more electron cyclotron absorption line(s). a few have been measured only once and must be confirmed (several more objects are listed as candidates). in addition to the tables of objects, we summarize the evidence of variability of the cyclotron line as a function of various parameters (especially pulse phase, luminosity and time), and add a discussion of the different observed phenomena and associated attempts of theoretical modeling. we also discuss our understanding of the underlying physics of accretion onto highly magnetized neutron stars. for proton cyclotron lines, we present tables with seven neutron stars and discuss their nature and the physics in these objects. | cyclotron lines in highly magnetized neutron stars |
according to the current understanding of cosmic structure formation, the precursors of the most massive structures in the universe began to form shortly after the big bang, in regions corresponding to the largest fluctuations in the cosmic density field. observing these structures during their period of active growth and assembly—the first few hundred million years of the universe—is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. as a result, very few such objects have been detected so far. here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 million years after the big bang) that was discovered in a wide-field survey. high-resolution imaging shows it to be a pair of extremely massive star-forming galaxies. the larger is forming stars at a rate of 2,900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. its rapid star formation is probably triggered by its companion galaxy at a projected separation of 8 kiloparsecs. this merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbour and physical conditions akin to those observed in lower-metallicity galaxies in the nearby universe. these objects suggest the presence of a dark-matter halo with a mass of more than 100 billion solar masses, making it among the rarest dark-matter haloes that should exist in the universe at this epoch. | galaxy growth in a massive halo in the first billion years of cosmic history |
merging binaries consisting of two neutron stars (nss) or an ns and a stellar-mass black hole typically form a massive accretion torus around the remnant black hole or long-lived ns. outflows from these neutrino-cooled accretion disks represent an important site for r-process nucleosynthesis and the generation of kilonovae. we present the first three-dimensional, general-relativistic magnetohydrodynamic (grmhd) simulations including weak interactions and a realistic equation of state of such accretion disks over viscous timescales (380 ms). we witness the emergence of steady-state mhd turbulence, a magnetic dynamo with an ∼20 ms cycle, and the generation of a “hot” disk corona that launches powerful thermal outflows aided by the energy released as free nucleons recombine into α-particles. we identify a self-regulation mechanism that keeps the midplane electron fraction low (y e ∼ 0.1) over viscous timescales. this neutron-rich reservoir, in turn, feeds outflows that retain a sufficiently low value of y e ≈ 0.2 to robustly synthesize third-peak r-process elements. the quasi-spherical outflows are projected to unbind 40% of the initial disk mass with typical asymptotic escape velocities of 0.1c and may thus represent the dominant mass ejection mechanism in ns-ns mergers. including neutrino absorption, our findings agree with previous hydrodynamical α-disk simulations that the entire range of r-process nuclei from the first to the third r-process peak can be synthesized in the outflows, in good agreement with observed solar system abundances. the asymptotic escape velocities and quantity of ejecta, when extrapolated to moderately higher disk masses, are consistent with those needed to explain the red kilonova emission following the ns merger gw170817. | three-dimensional grmhd simulations of neutrino-cooled accretion disks from neutron star mergers |
in this paper we study a key phase in the formation of massive galaxies: the transition of star-forming galaxies into massive (mstars ∼ 1011m⊙), compact (re ∼ 1 kpc) quiescent galaxies, which takes place from z ∼ 3 to z ∼ 1.5. we use hst grism redshifts and extensive photometry in all five 3d-hst/candels fields, more than doubling the area used previously for such studies, and combine these data with keck mosfire and nirspec spectroscopy. we first confirm that a population of massive, compact, star-forming galaxies exists at z ≳ 2, using k-band spectroscopy of 25 of these objects at 2.0 < z < 2.5. they have a median [n ii]/hα ratio of 0.6, are highly obscured with sfr(tot)/sfr(hα) ∼10, and have a large range of observed line widths. we infer from the kinematics and spatial distribution of hα that the galaxies have rotating disks of ionized gas that are a factor of ∼2 more extended than the stellar distribution. by combining measurements of individual galaxies, we find that the kinematics are consistent with a nearly keplerian fall-off from vrot ∼ 500 km s-1 at 1 kpc to vrot ∼ 250 km s-1 at 7 kpc, and that the total mass out to this radius is dominated by the dense stellar component. next, we study the size and mass evolution of the progenitors of compact massive galaxies. even though individual galaxies may have had complex histories with periods of compaction and mergers, we show that the population of progenitors likely followed a simple inside-out growth track in the size-mass plane of {{δ }}{log}{r}{{e}}∼ 0.3{{δ }}{log}{m}{{stars}}. this mode of growth gradually increases the stellar mass within a fixed physical radius, and galaxies quench when they reach a stellar density or velocity dispersion threshold. as shown in other studies, the mode of growth changes after quenching, as dry mergers take the galaxies on a relatively steep track in the size-mass plane. | forming compact massive galaxies |
we introduce a new self-consistent model of galaxy evolution and reionization, astraeus (seminumerical radiative transfer coupling of galaxy formation and reionization in n-body dark matter simulations), which couples a state-of-the-art n-body simulation with the semi-analytical galaxy evolution delphi and the seminumerical reionization scheme cigog. astraeus includes all the key processes of galaxy formation and evolution (including accretion, mergers, supernova, and radiative feedback) and follows the time and spatial evolution of the ionized regions in the intergalactic medium (igm). importantly, it explores different radiative feedback models that cover the physically plausible parameter space, ranging from a weak and delayed to a strong and immediate reduction of gas mass available for star formation. from our simulation suite that covers the different radiative feedback prescriptions and ionization topologies, we find that radiative feedback continuously reduces star formation in galaxies with $m_\mathrm{ h}\lesssim 10^{9.5}\, {\rm \rm m_\odot }$ upon local reionization; larger mass haloes are unaffected even for the strongest and immediate radiative feedback cases during reionization. for this reason, the ionization topologies of different radiative feedback scenarios differ only on scales smaller than 1-2 comoving mpc, and significant deviations are found only when physical parameters (e.g. the escape fraction of ionizing photons) are altered based on galactic properties. finally, we find that observables (the ultraviolet luminosity function, stellar mass function, reionization histories and ionization topologies) are hardly affected by the choice of the used stellar population synthesis models that model either single stars or binaries. | astraeus i: the interplay between galaxy formation and reionization |
using observations from the mosfire deep evolution field survey, we investigate the physical conditions of star-forming regions in z ∼ 2.3 galaxies, specifically the electron density and ionization state. from measurements of the [o ii]λλ3726,3729 and [s ii]λλ6716,6731 doublets, we find a median electron density of ∼250 cm-3 at z ∼ 2.3, an increase of an order of magnitude compared to measurements of galaxies at z ∼ 0. while z ∼ 2.3 galaxies are offset toward significantly higher o32 values relative to local galaxies at fixed stellar mass, we find that the high-redshift sample follows a similar distribution to the low-metallicity tail of the local distribution in the o32 versus r23 and o3n2 diagrams. based on these results, we propose that z ∼ 2.3 star-forming galaxies have the same ionization parameter as local galaxies at fixed metallicity. in combination with simple photoionization models, the position of local and z ∼ 2.3 galaxies in excitation diagrams suggests that there is no significant change in the hardness of the ionizing spectrum at fixed metallicity from z ∼ 0 to z ∼ 2.3. we find that z ∼ 2.3 galaxies show no offset compared to low-metallicity local galaxies in emission line ratio diagrams involving only lines of hydrogen, oxygen, and sulfur, but show a systematic offset in diagrams involving [n ii]λ6584. we conclude that the offset of z ∼ 2.3 galaxies from the local star-forming sequence in the [n ii] bpt diagram is primarily driven by elevated n/o at fixed o/h compared to local galaxies. these results suggest that the local gas-phase and stellar metallicity sets the ionization state of star-forming regions at z ∼ 0 and z ∼ 2. based on data obtained at the w.m. keck observatory, which is operated as a scientific partnership among the california institute of technology, the university of california, and nasa, and was made possible by the generous financial support of the w.m. keck foundation. | the mosdef survey: electron density and ionization parameter at z ~ 2.3 |
we reproduce the galaxy clustering catalogue from the sdss-iii baryon oscillation spectroscopic survey final data release (boss dr11&dr12) with high fidelity on all relevant scales in order to allow a robust analysis of baryon acoustic oscillations and redshift space distortions. we have generated (6000) 12 288 multidark patchy boss (dr11) dr12 light cones corresponding to an effective volume of ∼192 000 [h-1 gpc]3 (the largest ever simulated volume), including cosmic evolution in the redshift range from 0.15 to 0.75. the mocks have been calibrated using a reference galaxy catalogue based on the halo abundance matching modelling of the boss dr11&dr12 galaxy clustering data and on the data themselves. the production follows three steps. first, we apply the patchy code to generate a dark matter field and an object distribution including non-linear stochastic galaxy bias. secondly, we run the halo/stellar distribution reconstruction hadron code to assign masses to the various objects. this step uses the mass distribution as a function of local density and non-local indicators (i.e. tidal field tensor eigenvalues and relative halo exclusion separation for massive objects) from the reference simulation applied to the corresponding patchy dark matter and galaxy distribution. finally, we apply the sugar code to build the light cones. the resulting multidarkpatchy mock light cones reproduce the number density, selection function, survey geometry, and in general within 1σ, for arbitrary stellar mass bins, the power spectrum up to k = 0.3 h mpc-1, the two-point correlation functions down to a few mpc scales, and the three-point statistics of the boss dr11&dr12 galaxy samples. | the clustering of galaxies in the sdss-iii baryon oscillation spectroscopic survey: mock galaxy catalogues for the boss final data release |
in the past two decades, high-amplitude electromagnetic outbursts have been detected from dormant galaxies and often attributed to the tidal disruption of a star by the central black hole1,2. x-ray emission from the seyfert 2 galaxy gsn 069 (2masx j01190869-3411305) at a redshift of z = 0.018 was first detected in july 2010 and implies an x-ray brightening by a factor of more than 240 over rosat observations performed 16 years earlier3,4. the emission has smoothly decayed over time since 2010, possibly indicating a long-lived tidal disruption event5. the x-ray spectrum is ultra-soft and can be described by accretion disk emission with luminosity proportional to the fourth power of the disk temperature during long-term evolution. here we report observations of quasi-periodic x-ray eruptions from the nucleus of gsn 069 over the course of 54 days, from december 2018 onwards. during these eruptions, the x-ray count rate increases by up to two orders of magnitude with an event duration of just over an hour and a recurrence time of about nine hours. these eruptions are associated with fast spectral transitions between a cold and a warm phase in the accretion flow around a low-mass black hole (of approximately 4 × 105 solar masses) with peak x-ray luminosity of about 5 × 1042 erg per second. the warm phase has kt (where t is the temperature and k is the boltzmann constant) of about 120 electronvolts, reminiscent of the typical soft-x-ray excess, an almost universal thermal-like feature in the x-ray spectra of luminous active nuclei6-8. if the observed properties are not unique to gsn 069, and assuming standard scaling of timescales with black hole mass and accretion properties, typical active galactic nuclei with higher-mass black holes can be expected to exhibit high-amplitude optical to x-ray variability on timescales as short as months or years9. | nine-hour x-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus |
we present results of an all-sky search for continuous gravitational waves which can be produced by spinning neutron stars with an asymmetry around their rotation axis, using data from the third observing run of the advanced ligo and advanced virgo detectors. four different analysis methods are used to search in a gravitational-wave frequency band from 10 to 2048 hz and a first frequency derivative from -10-8 to 10-9 hz /s . no statistically significant periodic gravitational-wave signal is observed by any of the four searches. as a result, upper limits on the gravitational-wave strain amplitude h0 are calculated. the best upper limits are obtained in the frequency range of 100 to 200 hz and they are ∼1.1 ×10-25 at 95% confidence level. the minimum upper limit of 1.10 ×10-25 is achieved at a frequency 111.5 hz. we also place constraints on the rates and abundances of nearby planetary- and asteroid-mass primordial black holes that could give rise to continuous gravitational-wave signals. | all-sky search for continuous gravitational waves from isolated neutron stars using advanced ligo and advanced virgo o3 data |
it has been a half-decade since the first direct detection of gravitational waves, which signifies the coming of the era of the gravitational-wave astronomy and gravitational-wave cosmology. the increasing number of the detected gravitational-wave events has revealed the promising capability of constraining various aspects of cosmology, astronomy, and gravity. due to the limited space in this review article, we will briefly summarize the recent progress over the past five years, but with a special focus on some of our own work for the key project "physics associated with the gravitational waves" supported by the national natural science foundation of china. in particular, (1) we have presented the mechanism of the gravitational-wave production during some physical processes of the early universe, such as inflation, preheating and phase transition, and the cosmological implications of gravitational-wave measurements; (2) we have put constraints on the neutron star maximum mass according to gw170817 observations; (3) we have developed a numerical relativity algorithm based on the finite element method and a waveform model for the binary black hole coalescence along an eccentric orbit. | the gravitational-wave physics ii: progress |
recent measurements of rotation periods ( ${p}_{\mathrm{rot}}$ ) in the benchmark open clusters praesepe (670 myr), ngc 6811 (1 gyr), and ngc 752 (1.4 gyr) demonstrate that, after converging onto a tight sequence of slowly rotating stars in mass-period space, stars temporarily stop spinning down. these data also show that the duration of this epoch of stalled spin-down increases toward lower masses. to determine when stalled stars resume spinning down, we use data from the k2 mission and the palomar transient factory to measure ${p}_{\mathrm{rot}}$ for 58 dwarf members of the 2.7 gyr old cluster ruprecht 147, 39 of which satisfy our criteria designed to remove short-period or near-equal-mass binaries. combined with the kepler ${p}_{\mathrm{rot}}$ data for the approximately coeval cluster ngc 6819 (30 stars with m⋆ > 0.85 ${m}_{\odot }$ ), our new measurements more than double the number of ≈2.5 gyr benchmark rotators and extend this sample down to ≈0.55 ${m}_{\odot }$ . the slowly rotating sequence for this joint sample appears relatively flat (22 ± 2 days) compared to sequences for younger clusters. this sequence also intersects the kepler intermediate-period gap, demonstrating that this gap was not created by a lull in star formation. we calculate the time at which stars resume spinning down and find that 0.55 ${m}_{\odot }$ stars remain stalled for at least 1.3 gyr. to accurately age-date low-mass stars in the field, gyrochronology formulae must be modified to account for this stalling timescale. empirically tuning a core-envelope coupling model with open cluster data can account for most of the apparent stalling effect. however, alternative explanations, e.g., a temporary reduction in the magnetic braking torque, cannot yet be ruled out. | when do stalled stars resume spinning down? advancing gyrochronology with ruprecht 147 |
turbulence is a crucial factor in many models of planet formation, but it has only been directly constrained among a small number of planet-forming disks. building on the upper limits on turbulence placed in disks around hd 163296 and tw hya, we present alma co j = 2-1 line observations at ∼0"3 (20-50 au) resolution and 80 ms-1 channel spacing of the disks around dm tau, mwc 480, and v4046 sgr. using parametric models of disk structure, we robustly detect nonthermal gas motions around dm tau of between 0.25cs and 0.33cs, with the range dominated by systematic effects, making this one of the only systems with directly measured nonzero turbulence. using the same methodology, we place stringent upper limits on the nonthermal gas motion around mwc 480 (<0.08cs) and v4046 sgr (<0.12cs). the preponderance of upper limits in this small sample and the modest turbulence levels consistent with dust studies suggest that weak turbulence (α ≲ 10-3) may be a common, albeit not universal, feature of planet-forming disks. we explore the particular physical conditions around dm tau that could lead this system to be more turbulent than the others. | measuring turbulent motion in planet-forming disks with alma: a detection around dm tau and nondetections around mwc 480 and v4046 sgr |
stellar heating causes atmospheres of close-in exoplanets to expand and escape. these extended atmospheres are difficult to observe because their main spectral signature—neutral hydrogen at ultraviolet wavelengths—is strongly absorbed by interstellar medium. we report the detection of the near-infrared triplet of neutral helium in the transiting warm neptune-mass exoplanet hat-p-11b by using ground-based, high-resolution observations. the helium feature is repeatable over two independent transits, with an average absorption depth of 1.08 ± 0.05%. interpreting absorption spectra with three-dimensional simulations of the planet’s upper atmosphere suggests that it extends beyond 5 planetary radii, with a large-scale height and a helium mass loss rate of ≲3 × 105 grams per second. a net blue-shift of the absorption might be explained by high-altitude winds flowing at 3 kilometers per second from day to night-side. | spectrally resolved helium absorption from the extended atmosphere of a warm neptune-mass exoplanet |
because of gravitational interactions with their companions, the rotational dynamics of planets and stars involve periodic perturbations of their shape, the direction of their rotational vector, and their rotation rate. these perturbations correspond in planetary terms to tides, precession, and longitudinal libration. we review here the flows driven by those mechanical forcings on rotating spheres and ellipsoids. special focus is placed on the associated instabilities and on the various routes toward turbulence recently studied. the key point is that mechanical forcings do not provide the energy to the excited flows: they convey part of the available rotational energy and generate intense fluid motions through the excitation of localized jets, shear layers, and resonant inertial modes. hence, even very small forcings may have large-scale consequences. mechanically driven flows thus play a fundamental role in planets and stars, significantly influencing their shape, their rotational dynamics, and their magnetic field. | flows driven by libration, precession, and tides |
we study the dust content of galaxies from z = 0 to z = 9 in semi-analytic models of galaxy formation that include new recipes to track the production and destruction of dust. we include condensation of dust in stellar ejecta, the growth of dust in the interstellar medium (ism), the destruction of dust by supernovae and in the hot halo, and dusty winds and inflows. the rate of dust growth in the ism depends on the metallicity and density of molecular clouds. our fiducial model reproduces the relation between dust mass and stellar mass from z = 0 to z = 7, the number density of galaxies with dust masses less than 108.3 m⊙ and the cosmic density of dust at z = 0. the model accounts for the double power-law trend between dust-to-gas (dtg) ratio and gas-phase metallicity of local galaxies and the relation between dtg ratio and stellar mass. the dominant mode of dust formation is dust growth in the ism, except for galaxies with m* < 107 m⊙, where condensation of dust in supernova ejecta dominates. the dust-to-metal ratio of galaxies depends on the gas-phase metallicity, unlike what is typically assumed in cosmological simulations. model variants, including higher condensation efficiencies, a fixed time-scale for dust growth in the ism, or no growth at all reproduce some of the observed constraints, but fail to simultaneously reproduce the shape of dust scaling relations and the dust mass of high-redshift galaxies. | the dust content of galaxies from z = 0 to z = 9 |
background: the chart of the nuclides is limited by particle drip lines beyond which nuclear stability to proton or neutron emission is lost. predicting the range of particle-bound isotopes poses an appreciable challenge for nuclear theory as it involves extreme extrapolations of nuclear masses well beyond the regions where experimental information is available. still, quantified extrapolations are crucial for a wide variety of applications, including the modeling of stellar nucleosynthesis. purpose: we use microscopic nuclear global mass models, current mass data, and bayesian methodology to provide quantified predictions of proton and neutron separation energies as well as bayesian probabilities of existence throughout the nuclear landscape all the way to the particle drip lines. methods: we apply nuclear density-functional theory with several energy density functionals. we also consider two global mass models often used in astrophysical nucleosynthesis simulations. to account for uncertainties, bayesian gaussian processes are trained on the separation-energy residuals for each individual model, and the resulting predictions are combined via bayesian model averaging. this framework allows to account for systematic and statistical uncertainties and propagate them to extrapolative predictions. results: we establish and characterize the drip-line regions where the probability that the nucleus is particle bound decreases from 1 to 0. in these regions, we provide quantified predictions for one- and two-nucleon separation energies. according to our bayesian model averaging analysis, 7759 nuclei with z ≤119 have a probability of existence ≥0.5 . conclusions: the extrapolation results obtained in this study will be put through stringent tests when new experimental information on existence and masses of exotic nuclei becomes available. in this respect, the quantified landscape of nuclear existence obtained in this study should be viewed as a dynamical prediction that will be fine-tuned when new experimental information and improved global mass models become available. | quantified limits of the nuclear landscape |
accurate numerical solutions of the equations of hydrodynamics play an ever more important role in many fields of astrophysics. in this work, we reinvestigate the accuracy of the moving-mesh code arepo and show how its convergence order can be improved for general problems. in particular, we clarify that for certain problems arepo only reaches first-order convergence for its original formulation. this can be rectified by simple modifications we propose to the time integration scheme and the spatial gradient estimates of the code, both improving the accuracy of the code. we demonstrate that the new implementation is indeed second-order accurate under the l1 norm, and in particular substantially improves conservation of angular momentum. interestingly, whereas these improvements can significantly change the results of smooth test problems, we also find that cosmological simulations of galaxy formation are unaffected, demonstrating that the numerical errors eliminated by the new formulation do not impact these simulations. in contrast, simulations of binary stars followed over a large number of orbital times are strongly affected, as here it is particularly crucial to avoid a long-term build up of errors in angular momentum conservation. | improving the convergence properties of the moving-mesh code arepo |
using ultraviolet absorption lines, we analyze the systematic properties of the warm ionized phase of starburst-driven winds in a sample of 39 low-redshift objects that spans broad ranges in starburst and galaxy properties. total column densities for the outflows are ∼1021 cm-2. the outflow velocity (vout) correlates only weakly with the galaxy stellar mass ({m}*), or circular velocity (vcir), but strongly with both sfr and sfr/area. the normalized outflow velocity ({v}{out}/{v}{cir}) correlates well with both sfr/area and sfr/{m}*. the estimated outflow rates of warm ionized gas (\dot{m}) are ∼1-4 times the sfr, and the ratio \dot{m}/{sfr} does not correlate with vout. we show that a model of a population of clouds accelerated by the combined forces of gravity and the momentum flux from the starburst matches the data. we find a threshold value for the ratio of the momentum flux supplied by the starburst to the critical momentum flux needed for the wind to overcome gravity acting on the clouds (rcrit). for {r}{crit} \gt 10 (strong-outflows) the outflow’s momentum flux is similar to the total momentum flux from the starburst and the outflow velocity exceeds the galaxy escape velocity. neither of these is the case for the weak outflows ({r}{crit} \lt 10). for the weak-outflows, the data severely disagree with many prescriptions in numerical simulations or semi-analytic models of galaxy evolution. the agreement is better for the strong outflows, and we advocate the use of rcrit to guide future prescriptions. | the systematic properties of the warm phase of starburst-driven galactic winds |
satellite galaxies are predicted to generate gravitational density wakes as they orbit within the dark matter (dm) halos of their hosts, causing their orbits to decay over time. the recent infall of the milky way’s (mw) most massive satellite galaxy, the large magellanic cloud (lmc), affords us the unique opportunity to study this process in action. in this work, we present high-resolution (m dm = 4 × 104 m ⊙) n-body simulations of the mw-lmc interaction over the past 2 gyr. we quantify the impact of the lmc’s passage on the density and kinematics of the mw’s dm halo and the observability of these structures in the mw’s stellar halo. the lmc is found to generate a pronounced wake, which we decompose in transient and collective responses, in both the dm and stellar halos. the wake leads to overdensities and distinct kinematic patterns that should be observable with ongoing and future surveys. specifically, the collective response will result in redshifted radial velocities of stars in the north and blueshifts in the south, at distances >45 kpc. the transient response traces the orbital path of the lmc through the halo (50-200 kpc), resulting in a stellar overdensity with a distinct, tangential kinematic pattern that persists to the present day. the detection of the mw’s halo response will constrain the infall mass of the lmc, its orbital trajectory, and the mass of the mw, and it may inform us about the nature of the dm particle itself. | hunting for the dark matter wake induced by the large magellanic cloud |
we study the expected spin misalignments of merging binary black holes formed in isolation by combining state-of-the-art population-synthesis models with efficient post-newtonian evolutions, thus tracking sources from stellar formation to gravitational-wave detection. we present extensive predictions of the properties of sources detectable by both current and future interferometers. we account for the fact that detectors are more sensitive to spinning black-hole binaries with suitable spin orientations and find that this significantly impacts the population of sources detectable by ligo, while this is not the case for third-generation detectors. we find that three formation pathways, differentiated by the order of core collapse and common-envelope phases, dominate the observed population, and that their relative importance critically depends on the recoils imparted to black holes at birth. our models suggest that measurements of the "effective-spin" parameter χeff will allow for powerful constraints. for instance, we find that the role of spin magnitudes and spin directions in χeff can be largely disentangled, and that the symmetry of the effective-spin distribution is a robust indicator of the binary's formation history. our predictions for individual spin directions and their precessional morphologies confirm and extend early toy models, while exploring substantially more realistic and broader sets of initial conditions. our main conclusion is that specific subpopulations of black-hole binaries will exhibit distinctive precessional dynamics: these classes include (but are not limited to) sources where stellar tidal interactions act on sufficiently short timescales, and massive binaries produced in pulsational pair-instability supernovae. measurements of black-hole spin orientations have enormous potential to constrain specific evolutionary processes in the lives of massive binary stars. | spin orientations of merging black holes formed from the evolution of stellar binaries |
we infer the mass distribution of neutron stars in binary systems using a flexible gaussian mixture model and use bayesian model selection to explore evidence for multimodality and a sharp cut-off in the mass distribution. we find overwhelming evidence for a bimodal distribution, in agreement with previous literature, and report for the first time positive evidence for a sharp cut-off at a maximum neutron star mass. we measure the maximum mass to be 2.0 m⊙ < mmax < 2.2 m⊙ (68 per cent), 2.0 m⊙ < mmax < 2.6 m⊙ (90 per cent), and evidence for a cut-off is robust against the choice of model for the mass distribution and to removing the most extreme (highest mass) neutron stars from the data set. if this sharp cut-off is interpreted as the maximum stable neutron star mass allowed by the equation of state of dense matter, our measurement puts constraints on the equation of state. for a set of realistic equations of state that support >2 m⊙ neutron stars, our inference of mmax is able to distinguish between models at odds ratios of up to 12:1, whilst under a flexible piecewise polytropic equation-of-state model our maximum mass measurement improves constraints on the pressure at 3-7× the nuclear saturation density by ∼ 30-50 per cent compared to simply requiring mmax > 2 m⊙. we obtain a lower bound on the maximum sound speed attained inside the neutron star of c_ s^max > 0.63c (99.8 per cent), ruling out c_ s^max < c/√{3} at high significance. our constraints on the maximum neutron star mass strengthen the case for neutron star-neutron star mergers as the primary source of short gamma-ray bursts. | evidence for a maximum mass cut-off in the neutron star mass distribution and constraints on the equation of state |
the experiment to detect the global epoch of reionization signature (edges) recently reported a strong 21-cm absorption signal relative to the cosmic microwave background at z ∼ 18. while its anomalous amplitude may indicate new physics, in this work we focus on the timing of the signal, as it alone provides an important constraint on galaxy formation models. although rest-frame ultraviolet luminosity functions (uvlfs) over a broad range of redshifts are well fit by simple models in which galaxy star formation histories track the assembly of dark matter haloes, we find that these same models, with reasonable assumptions about x-ray production in star-forming galaxies, cannot generate a narrow absorption trough at z ∼ 18. if verified, the edges signal therefore requires the fundamental inputs of galaxy formation models to evolve rapidly at z ≳ 10. unless extremely faint sources residing in haloes below the atomic cooling threshold are responsible for the edges signal, star formation in {∼ } 10^8-10^{10} m_{⊙ } haloes must be more efficient than expected, implying that the faint end of the uvlf at muv ≲ -12 must steepen at the highest redshifts. this steepening provides a concrete test for future galaxy surveys with the james webb space telescope and ongoing efforts in lensed fields, and is required regardless of whether the amplitude of the edges signal is due to new cooling channels or a strong radio background in the early universe. however, the radio background solution requires that galaxies at z > 15 emit 1-2 ghz photons with an efficiency ≳ 102 times greater than local star-forming galaxies, posing a challenge for models of low-frequency photon production in the early universe. | what does the first highly redshifted 21-cm detection tell us about early galaxies? |
the milky way is a barred spiral galaxy, with physical properties inferred from various tracers informed by the extrapolation of structures seen in other galaxies. however, the distances of these tracers are measured indirectly and are model-dependent. we constructed a map of the milky way in three dimensions, based on the positions and distances of thousands of classical cepheid variable stars. this map shows the structure of our galaxy’s young stellar population and allows us to constrain the warped shape of the milky way’s disk. a simple model of star formation in the spiral arms reproduces the observed distribution of cepheids. | a three-dimensional map of the milky way using classical cepheid variable stars |
we study the nature of phase transitions between dilute and dense axion stars interpreted as self-gravitating bose-einstein condensates. we develop a newtonian model based on the gross-pitaevskii-poisson equations for a complex scalar field with a self-interaction potential v (|ψ |2) involving an attractive |ψ |4 term and a repulsive |ψ |6 term. using a gaussian ansatz for the wave function, we analytically obtain the mass-radius relation of dilute and dense axion stars for arbitrary values of the self-interaction parameter λ ≤0 . we show the existence of a critical point |λ |c∼(m /mp)2, where m is the axion mass and mp is the planck mass, above which a first-order phase transition takes place. we qualitatively estimate general relativistic corrections on the mass-radius relation of axion stars. for weak self-interactions |λ |<|λ |c, a system of self-gravitating axions forms a stable dilute axion star below a general relativistic maximum mass mmax,gr dilute ∼mp2/m and collapses into a black hole above that mass. for strong self-interactions |λ |>|λ |c, a system of self-gravitating axions forms a stable dilute axion star below a newtonian maximum mass mmax,ndilute=5.073 mp/√{|λ | } [phys. rev. d 84, 043531 (2011), 10.1103/physrevd.84.043531], collapses into a dense axion star above that mass, and collapses into a black hole above a general relativistic maximum mass mmax,grdense∼√{|λ | }mp3/m2. dense axion stars explode below a newtonian minimum mass mmin,ndense=98.9 m /√{|λ | } and form dilute axion stars of large size or disperse away. we determine the phase diagram of self-gravitating axions and show the existence of a triple point (|λ |*,m*/(mp2/m )) separating dilute axion stars, dense axion stars, and black holes. we make numerical applications for qcd axions and ultralight axions. our approximate analytical results are in good agreement with the exact numerical results of braaten et al. [phys. rev. lett. 117, 121801 (2016), 10.1103/physrevlett.117.121801] for newtonian dense axion stars. they are also qualitatively similar to those obtained by helfer et al. [j. cosmol. astropart. phys. 03 (2017) 055, 10.1088/1475-7516/2017/03/055] for general relativistic axion stars, but they differ quantitatively for weak self-interactions presumably due to the use of a different self-interaction potential v (|ψ |2). we point out analogies between the evolution of self-gravitating axions (bosons) at zero temperature evolving from dilute axion stars to dense axion stars and black holes and the evolution of compact degenerate (fermion) stars at zero temperature evolving from white dwarfs to neutron stars and black holes. we also discuss some analogies between the phase transitions of newtonian axion stars at zero temperature and the phase transitions of newtonian self-gravitating fermions at nonzero temperature. finally, we suggest that a dense axionic nucleus may form at the center of dark matter halos through the collapse of a dilute axionic core (soliton) passing above the maximum mass mmax,ndilute. it would have a mass 1.11 ×109(f /m )m⊙, a radius 0.949 /(m f1 /3) pc , a density 2.10 ×10-8(m2f2) g /m3, a pulsation period 8.24 /(m f1 /3) yr , and an energy -5.59 ×1062(f /m ) erg , where the axion mass m is measured in units of 10-22 ev /c2 and the axion decay constant f is measured in units of 1 015 gev . this dense axionic nucleus could be the remnant of a bosenova associated with the emission of a characteristic radiation [phys. rev. lett. 118, 011301 (2017), 10.1103/physrevlett.118.011301]. | phase transitions between dilute and dense axion stars |
in this paper, we investigate anisotropic static spherically symmetric solutions in the framework of f(g) gravity through gravitational decoupling approach. for this purpose, we consider krori and barua (known solution) isotropic interior solution for static spherically symmetric self-gravitating system and extend it to two types of anisotropic solutions. we examine the physical viability of our models through energy conditions, squared speed of sound and anisotropy parameter. it is found that the first solution is physically viable as it fulfills the energy bounds as well as stability criteria while the second solution satisfies all energy bounds but is unstable at the core of the compact star. | gravitational decoupled anisotropic solutions in f(g) gravity |
we report the detection of 5 new candidate binary black hole (bbh) merger signals in the publicly released data from the second half of the third observing run (o3b) of advanced ligo and advanced virgo. the ligo-virgo-kagra (lvk) collaboration reported 35 compact binary coalescences (cbcs) in their analysis of the o3b data [1], with 30 bbh mergers having coincidence in the hanford and livingston detectors. we confirm 17 of these for a total of 22 detections in our analysis of the hanford-livingston coincident o3b data. we identify candidates using a search pipeline employing aligned-spin quadrupole-only waveforms. our pipeline is similar to the one used in our o3a coincident analysis [2], except for a few improvements in the veto procedure and the ranking statistic, and we continue to use an astrophysical probability of one half as our detection threshold, following the approach of the lvk catalogs. most of the new candidates reported in this work are placed in the upper and lower-mass gap of the black hole (bh) mass distribution. one bbh event also shows a sign of spin-orbit precession with negatively aligned spins. we also identify a possible neutron star-black hole (nsbh) merger. we expect these events to help inform the black hole mass and spin distributions inferred in a full population analysis. | new binary black hole mergers in the ligo-virgo o3b data |
the recently-discovered stellar system ursa major iii/unions 1 (uma3/u1) is the faintest known milky way satellite to date. with a stellar mass of $16^{+6}_{-5}\,\rm m_\odot$ and a half-light radius of $3\pm1$ pc, it is either the darkest galaxy ever discovered or the faintest self-gravitating star cluster known to orbit the galaxy. its line-of-sight velocity dispersion suggests the presence of dark matter, although current measurements are inconclusive because of the unknown contribution to the dispersion of potential binary stars. we use n-body simulations to show that, if self-gravitating, the system could not survive in the milky way tidal field for more than a single orbit (roughly 0.4 gyr), which strongly suggests that the system is stabilized by the presence of large amounts of dark matter. if uma3/u1 formed at the centre of a ~$10^9\rm m_\odot$ cuspy lcdm halo, its velocity dispersion would be predicted to be of order ~1 km/s. this is roughly consistent with the current estimate, which, neglecting binaries, places $\sigma_{\rm los}$ in the range 1 to 4 km/s. because of its dense cusp, such a halo should be able to survive the milky way tidal field, keeping uma3/u1 relatively unscathed until the present time. this implies that uma3/u1 is in all likelihood the faintest and densest dwarf galaxy satellite of the milky way, with important implications for alternative dark matter models, and for the minimum halo mass threshold for luminous galaxy formation in the lcdm cosmology. | ursa major iii/unions 1: the darkest galaxy ever discovered? |
the gaia mission has provided an invaluable wealth of astrometric data for more than a billion stars in our galaxy. the synergy between gaia astrometry, photometry, and spectroscopic surveys gives us comprehensive information about the milky way. using the bayesian isochrone-fitting code starhorse, we derive distances and extinctions for more than 10 million unique stars listed in both gaia data release 3 and public spectroscopic surveys: 557 559 in galah+ dr3, 4 531 028 in lamost dr7 lrs, 347 535 in lamost dr7 mrs, 562 424 in apogee dr17, 471 490 in rave dr6, 249 991 in sdss dr12 (optical spectra from boss and segue), 67 562 in the gaia-eso dr5 survey, and 4 211 087 in the gaia rvs part of the gaia dr3 release. starhorse can increase the precision of distance and extinction measurements where gaia parallaxes alone would be uncertain. we used starhorse for the first time to derive stellar ages for main-sequence turnoff and subgiant branch stars, around 2.5 million stars, with age uncertainties typically around 30%; the uncertainties drop to 15% for subgiant-branch-only stars, depending on the resolution of the survey. with the derived ages in hand, we investigated the chemical-age relations. in particular, the α and neutron-capture element ratios versus age in the solar neighbourhood show trends similar to previous works, validating our ages. we used the chemical abundances from local subgiant samples of galah dr3, apogee dr17, and lamost mrs dr7 to map groups with similar chemical compositions and starhorse ages, using the dimensionality reduction technique t-sne and the clustering algorithm hdbscan. we identify three distinct groups in all three samples, confirmed by their kinematic properties: the genuine chemical thick disk, the thin disk, and a considerable number of young alpha-rich stars (427) that are also a part of the delivered catalogues. we confirm that the genuine thick disk's kinematics and age properties are radically different from those of the thin disk and compatible with high-redshift (z ≈ 2) star-forming disks with high dispersion velocities. we also find a few extra chemical populations in galah dr3 thanks to the availability of neutron-capture element information. data are only available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/673/a155 | starhorse results for spectroscopic surveys and gaia dr3: chrono-chemical populations in the solar vicinity, the genuine thick disk, and young alpha-rich stars |
in the most extreme astrophysical environments, such as core-collapse supernovae (ccsne) and neutron star mergers (nsms), neutrinos can undergo fast flavor conversions (ffcs) on exceedingly short scales. intensive simulations have demonstrated that ffcs can attain equilibrium states in certain models. in this study, we utilize physics-informed neural networks (pinns) to predict the asymptotic outcomes of ffcs, by specifically targeting the first two moments of neutrino angular distributions. this makes our approach suitable for state-of-the-art ccsn and nsm simulations. through effective feature engineering and the incorporation of customized loss functions that penalize discrepancies in the predicted total number of $\nu_e$ and $\bar\nu_e$, our pinns demonstrate remarkable accuracies, with an error margin of $\lesssim3\%$. our study represents a substantial leap forward in the potential incorporation of ffcs into simulations of ccsne and nsms, thereby enhancing our understanding of these extraordinary astrophysical events. | physics-informed neural networks for predicting the asymptotic outcome of fast neutrino flavor conversions |
providing an accurate modeling of neutrino physics in dense astrophysical environments such as binary neutron star mergers presents a challenge for hydrodynamic simulations. nevertheless, understanding how flavor transformation can occur and affect the dynamics, the mass ejection, and the nucleosynthesis will need to be achieved in the future. we introduce a study of fast flavor oscillations based on a linear stability analysis using the first angular moments of the neutrino distributions, which are the quantities frequently evolved in computationally expensive, large-scale simulations. such a method requires generalizing the classical closure relations that appropriately truncate the hierarchy of moment equations to treat quantum flavor coherence. after showing the efficiency of this method on a well-understood test situation, we perform a systematic search of the occurrence of fast flavor instabilities in a neutron star merger simulation. we discuss the successes and shortcomings of moment linear stability analysis, as this framework provides a time-efficient way to design and study better closure prescriptions in the future. | neutrino fast flavor oscillations with moments: linear stability analysis and application to neutron star mergers |
matrix sensing has many real-world applications in science and engineering, such as system control, distance embedding, and computer vision. the goal of matrix sensing is to recover a matrix $a_\star \in \mathbb{r}^{n \times n}$, based on a sequence of measurements $(u_i,b_i) \in \mathbb{r}^{n} \times \mathbb{r}$ such that $u_i^\top a_\star u_i = b_i$. previous work [zjd15] focused on the scenario where matrix $a_{\star}$ has a small rank, e.g. rank-$k$. their analysis heavily relies on the rip assumption, making it unclear how to generalize to high-rank matrices. in this paper, we relax that rank-$k$ assumption and solve a much more general matrix sensing problem. given an accuracy parameter $\delta \in (0,1)$, we can compute $a \in \mathbb{r}^{n \times n}$ in $\widetilde{o}(m^{3/2} n^2 \delta^{-1} )$, such that $ |u_i^\top a u_i - b_i| \leq \delta$ for all $i \in [m]$. we design an efficient algorithm with provable convergence guarantees using stochastic gradient descent for this problem. | a general algorithm for solving rank-one matrix sensing |
recent observations with the jwst are yielding tantalizing hints of an early population of massive, bright galaxies at z > 10, with atacama large millimeter/submillimeter array (alma) observations indicating significant dust masses as early as z ~ 7. to understand the implications of these observations, we use the delphi semi-analytic model that jointly tracks the assembly of dark matter haloes and their baryons, including the key processes of dust enrichment. our model employs only two redshift- and mass-independent free parameters (the maximum star formation efficiency and the fraction of supernova energy that couples to gas) that are tuned against all available galaxy data at z ~ 5-9 before it is used to make predictions up to z ~ 20. our key results are: (i) the model underpredicts the observed ultraviolet luminosity function (uv lf) at z > 12, observations at z > 16 lie close to, or even above, a 'maximal' model where all available gas is turned into stars; (ii) uv selection would miss 34 per cent of the star formation rate density at z ~ 5, decreasing to 17 per cent by z ~ 10 for bright galaxies with ${m_{\rm uv}} \lt {-}19$; (iii) the dust mass (md) evolves with the stellar mass (m*) and redshift as log (md) = 1.194 log (m*) + 0.0975z - 5.433; (iv) the dust temperature increases with stellar mass, ranging between 30 and 33 k for m* ~ 109-11 m⊙ galaxies at z ~ 7. finally, we predict the far-infrared lf at z ~ 5-20, testable with alma observations, and caution that spectroscopic redshifts and dust masses must be pinned down before invoking unphysical extrema in galaxy formation models. | the dust enrichment of early galaxies in the jwst and alma era |
the capability of the event horizon telescope (eht) to image the nearest supermassive black hole candidates at horizon-scale resolutions offers a novel means to study gravity in its strongest regimes and to test different models for these objects. here, we study the observational appearance at 230 ghz of a surfaceless black hole mimicker, namely a non-rotating boson star, in a scenario consistent with the properties of the accretion flow on to sgr a*. to this end, we perform general relativistic magnetohydrodynamic simulations followed by general relativistic radiative transfer calculations in the boson star space-time. synthetic reconstructed images considering realistic astronomical observing conditions show that, despite qualitative similarities, the differences in the appearance of a black hole - either rotating or not - and a boson star of the type considered here are large enough to be detectable. these differences arise from dynamical effects directly related to the absence of an event horizon, in particular, the accumulation of matter in the form of a small torus or a spheroidal cloud in the interior of the boson star, and the absence of an evacuated high-magnetization funnel in the polar regions. the mechanism behind these effects is general enough to apply to other horizonless and surfaceless black hole mimickers, strengthening confidence in the ability of the eht to identify such objects via radio observations. | how to tell an accreting boson star from a black hole |
we present the spectroscopic time-resolving observatory for broadband energy x-rays (strobe-x), a probe-class mission concept selected for study by nasa. it combines huge collecting area, high throughput, broad energy coverage, and excellent spectral and temporal resolution in a single facility. strobe-x offers an enormous increase in sensitivity for x-ray spectral timing, extending these techniques to extragalactic targets for the first time. it is also an agile mission capable of rapid response to transient events, making it an essential x-ray partner facility in the era of time-domain, multi-wavelength, and multi-messenger astronomy. optimized for study of the most extreme conditions found in the universe, its key science objectives include: (1) robustly measuring mass and spin and mapping inner accretion flows across the black hole mass spectrum, from compact stars to intermediate-mass objects to active galactic nuclei. (2) mapping out the full mass-radius relation of neutron stars using an ensemble of nearly two dozen rotation-powered pulsars and accreting neutron stars, and hence measuring the equation of state for ultradense matter over a much wider range of densities than explored by nicer. (3) identifying and studying x-ray counterparts (in the post-swift era) for multiwavelength and multi-messenger transients in the dynamic sky through cross-correlation with gravitational wave interferometers, neutrino observatories, and high-cadence time-domain surveys in other electromagnetic bands. (4) continuously surveying the dynamic x-ray sky with a large duty cycle and high time resolution to characterize the behavior of x-ray sources over an unprecedentedly vast range of time scales. strobe-x's formidable capabilities will also enable a broad portfolio of additional science. | strobe-x: x-ray timing and spectroscopy on dynamical timescales from microseconds to years |
we present observations with the cosmic origins spectrograph onboard the hubble space telescope of nine low-mass star-forming galaxies at redshifts, z, in the range 0.3179-0.4524, with stellar masses $m_\star \, \lt $ 108 m⊙ and very high specific star-formation rates ssfr ~150-630 gyr-1, aiming to study the dependence of leaking lyman continuum (lyc) emission on stellar mass and some other characteristics of the galaxy. we detect lyc emission in four out of nine galaxies with escape fractions, fesc(lyc), in the range of 11-35 per cent, and establish upper limits for fesc(lyc) in the remaining five galaxies. we observe a narrow ly α emission line with two peaks in seven galaxies and likely more complex ly α profiles in the two remaining galaxies. the velocity separation between the peaks vsep varies in the range from ~229 to ~512 km s-1. our additional data on low-mass galaxies confirm and strengthen the tight anticorrelation between fesc(lyc) and vsep found for previous low-redshift galaxy samples with higher stellar masses. vsep remains the best indirect indicator of lyc leakage. it is better than o32 on which fesc(lyc) depends weakly, with a large scatter. finally, contrary to expectations, we find no increase of fesc(lyc) with decreasing galaxy stellar mass m⋆. | lyman continuum leakage from low-mass galaxies with m⋆ < 108 m⊙ |
we present the discovery of the type ii supernova sn 2023ixf in m101 and follow-up photometric and spectroscopic observations, respectively, in the first month and week of its evolution. our discovery was made within a day of estimated first light, and the following light curve is characterized by a rapid rise (≈5 days) to a luminous peak (mv≈ - 18.2 mag) and plateau (mv≈ - 17.6 mag) extending to 30 days with a fast decline rate of ≈0.03 mag day-1. during the rising phase, u - v color shows blueward evolution, followed by redward evolution in the plateau phase. prominent flash features of hydrogen, helium, carbon, and nitrogen dominate the spectra up to ≈5 days after first light, with a transition to a higher ionization state in the first ≈2 days. both the u-v color and flash ionization states suggest a rise in the temperature, indicative of a delayed shock breakout inside dense circumstellar material (csm). from the timescales of csm interaction, we estimate its compact radial extent of ~(3-7) × 1014 cm. we then construct numerical light-curve models based on both continuous and eruptive mass-loss scenarios shortly before explosion. for the continuous mass-loss scenario, we infer a range of mass-loss history with 0.1-1.0 m ⊙ yr-1 in the final 2-1 yr before explosion, with a potentially decreasing mass loss of 0.01-0.1 m ⊙ yr-1 in ~0.7-0.4 yr toward the explosion. for the eruptive mass-loss scenario, we favor eruptions releasing 0.3-1 m ⊙ of the envelope at about a year before explosion, which result in csm with mass and extent similar to the continuous scenario. we discuss the implications of the available multiwavelength constraints obtained thus far on the progenitor candidate and sn 2023ixf to our variable csm models. | from discovery to the first month of the type ii supernova 2023ixf: high and variable mass loss in the final year before explosion |
we present a simple, analytic and straightforward method to elucidate the effects produced by polytropic fluids on any other gravitational source, no matter its nature, for static and spherically symmetric spacetimes. as a direct application, we study the interaction between polytropes and perfect fluids coexisting inside a self-gravitating stellar object. | energy exchange between relativistic fluids: the polytropic case |
we introduce gwfast, a novel fisher-matrix code for gravitational-wave studies, tuned toward third-generation gravitational-wave detectors such as einstein telescope (et) and cosmic explorer (ce). we use it to perform a comprehensive study of the capabilities of et alone, and of a network made by et and two ce detectors, as well as to provide forecasts for the forthcoming o4 run of the ligo-virgo-kagra (lvk) collaboration. we consider binary neutron stars, binary black holes, and neutron star-black hole binaries, and compute basic metrics such as the distribution of signal-to-noise ratio (s/n), the accuracy in the reconstruction of various parameters (including distance, sky localization, masses, spins, and, for neutron stars, tidal deformabilities), and the redshift distribution of the detections for different thresholds in s/n and different levels of accuracy in localization and distance measurement. we examine the expected distribution and properties of golden events, with especially large values of the s/n. we also pay special attention to the dependence of the results on astrophysical uncertainties and on various technical details (such as choice of waveforms, or the threshold in s/n), and we compare with other fisher codes in the literature. in the companion paper iacovelli et al., we discuss the technical aspects of the code. together with this paper, we publicly release the code gwfast, (https://github.com/cosmostatgw/gwfast) and the library wf4py (https://github.com/cosmostatgw/wf4py) implementing state-of-the-art gravitational-wave waveforms in pure python. | forecasting the detection capabilities of third-generation gravitational-wave detectors using gwfast |
we present the first james webb space telescope/nircam-led determination of 7 < z < 9 galaxy properties based on broadband imaging from 0.8 to 5 μm as part of the glass-jwst early release science program. this is the deepest data set acquired at these wavelengths to date, with an angular resolution ≲0.″14. we robustly identify 13 galaxies with signal-to-noise ratio ≳ 8 in f444w from 8 arcmin2 of data at m ab ≤ 28 from a combination of dropout and photometric redshift selection. from simulated data modeling, we estimate the dropout sample purity to be ≳90%. we find that the number density of these f444w-selected sources is broadly consistent with expectations from the uv luminosity function determined from hubble space telescope data. we characterize galaxy physical properties using a bayesian spectral energy distribution fitting method, finding a median stellar mass of 108.5 m ⊙ and age 140 myr, indicating they started ionizing their surroundings at redshift z > 9.5. their star formation main sequence is consistent with predictions from simulations. lastly, we introduce an analytical framework to constrain main-sequence evolution at z > 7 based on galaxy ages and basic assumptions, through which we find results consistent with expectations from cosmological simulations. while this work only gives a glimpse of the properties of typical galaxies that are thought to drive the reionization of the universe, it clearly shows the potential of jwst to unveil unprecedented details of galaxy formation in the first billion years. | early results from glass-jwst. x. rest-frame uv-optical properties of galaxies at 7 < z < 9 |
spectroscopic detection of narrow emission lines traces the presence of circumstellar mass distributions around massive stars exploding as core-collapse supernovae. transient emission lines disappearing shortly after the supernova explosion suggest that the material spatial extent is compact and implies an increased mass loss shortly prior to explosion. here, we present a systematic survey for such transient emission lines (flash spectroscopy) among type ii supernovae detected in the first year of the zwicky transient facility survey. we find that at least six out of ten events for which a spectrum was obtained within two days of the estimated explosion time show evidence for such transient flash lines. our measured flash event fraction (>30% at 95% confidence level) indicates that elevated mass loss is a common process occurring in massive stars that are about to explode as supernovae. | a large fraction of hydrogen-rich supernova progenitors experience elevated mass loss shortly prior to explosion |
finding the emergence of the first generation of metals in the early universe, and identifying their origin, are some of the most important goals of modern astrophysics. we present deep jwst/nirspec spectroscopy of gs-z12, a galaxy at z=12.5, in which we report the detection of c iii]${\lambda}{\lambda}$1907,1909 nebular emission. this is the most distant detection of a metal transition and the most distant redshift determination via emission lines. in addition, we report tentative detections of [o ii]${\lambda}{\lambda}$3726,3729 and [ne iii]${\lambda}$3869, and possibly o iii]${\lambda}{\lambda}$1661,1666. by using the accurate redshift from c iii], we can model the ly${\alpha}$ drop to reliably measure an absorbing column density of hydrogen of $n_{hi} \approx 10^{22}$ cm$^{-2}$ - too high for an igm origin and implying abundant ism in gs-z12 or cgm around it. we infer a lower limit for the neutral gas mass of about $10^7$ msun which, compared with a stellar mass of $\approx4 \times 10^7$ msun inferred from the continuum fitting, implies a gas fraction higher than about 0.1-0.5. we derive a solar or even super-solar carbon-to-oxygen ratio, tentatively [c/o]>0.15. this is higher than the c/o measured in galaxies discovered by jwst at z=6-9, and higher than the c/o arising from type-ii supernovae enrichment, while agb stars cannot contribute to carbon enrichment at these early epochs and low metallicities. such a high c/o in a galaxy observed 350 myr after the big bang may be explained by the yields of extremely metal poor stars, and may even be the heritage of the first generation of supernovae from population iii progenitors. | jades: carbon enrichment 350 myr after the big bang in a gas-rich galaxy |
the availability of reliable bolometric corrections and reddening estimates, rather than the quality of parallaxes, will be one of the main limiting factors in determining the luminosities of a large fraction of gaia stars. with this goal in mind, we provide gaiagbp, g, and grp synthetic photometry for the entire marcs grid and test the performance of our synthetic colours and bolometric corrections against space-borne absolute spectrophotometry. we find indication of a magnitude-dependent offset in gaia dr2 g magnitudes, which must be taken into account in high-accuracy investigations. our interpolation routines are easily used to derive bolometric corrections at desired stellar parameters and to explore the dependence of gaia photometry on teff, log g, {[fe/h]}, [α /{fe}], and e(b - v). gaia colours for the sun and vega, and teff-dependent extinction coefficients are also provided. | on the use of gaia magnitudes and new tables of bolometric corrections |
we describe the next generation transit survey (ngts), which is a ground-based project searching for transiting exoplanets orbiting bright stars. ngts builds on the legacy of previous surveys, most notably wasp, and is designed to achieve higher photometric precision and hence find smaller planets than have previously been detected from the ground. it also operates in red light, maximizing sensitivity to late k and early m dwarf stars. the survey specifications call for photometric precision of 0.1 per cent in red light over an instantaneous field of view of 100 deg2, enabling the detection of neptune-sized exoplanets around sun-like stars and super-earths around m dwarfs. the survey is carried out with a purpose-built facility at cerro paranal, chile, which is the premier site of the european southern observatory (eso). an array of twelve 20 cm f/2.8 telescopes fitted with back-illuminated deep-depletion ccd cameras is used to survey fields intensively at intermediate galactic latitudes. the instrument is also ideally suited to ground-based photometric follow-up of exoplanet candidates from space telescopes such as tess, gaia and plato. we present observations that combine precise autoguiding and the superb observing conditions at paranal to provide routine photometric precision of 0.1 per cent in 1 h for stars with i-band magnitudes brighter than 13. we describe the instrument and data analysis methods as well as the status of the survey, which achieved first light in 2015 and began full-survey operations in 2016. ngts data will be made publicly available through the eso archive. | the next generation transit survey (ngts) |
we present euv solar observations showing evidence for omnipresent jetting activity driven by small-scale magnetic reconnection at the base of the solar corona. we argue that the physical mechanism that heats and drives the solar wind at its source is ubiquitous magnetic reconnection in the form of small-scale jetting activity (a.k.a. jetlets). this jetting activity, like the solar wind and the heating of the coronal plasma, is ubiquitous regardless of the solar cycle phase. each event arises from small-scale reconnection of opposite-polarity magnetic fields producing a short-lived jet of hot plasma and alfvén waves into the corona. the discrete nature of these jetlet events leads to intermittent outflows from the corona, which homogenize as they propagate away from the sun and form the solar wind. this discovery establishes the importance of small-scale magnetic reconnection in solar and stellar atmospheres in understanding ubiquitous phenomena such as coronal heating and solar wind acceleration. based on previous analyses linking the switchbacks to the magnetic network, we also argue that these new observations might provide the link between the magnetic activity at the base of the corona and the switchback solar wind phenomenon. these new observations need to be put in the bigger picture of the role of magnetic reconnection and the diverse form of jetting in the solar atmosphere. | magnetic reconnection as the driver of the solar wind |
we present a new study of late-type eclipsing binary stars in the small magellanic cloud (smc) undertaken with the aim of improving the distance determination to this important galaxy. a sample of 10 new detached, double-lined eclipsing binaries identified from the ogle variable star catalogs and consisting of f- and g-type giant components has been analyzed. the absolute physical parameters of the individual components have been measured with a typical accuracy of better than 3%. all but one of the systems consist of young and intermediate population stars with masses in the range of 1.4 to 3.8 m⊙. this new sample has been combined with five smc eclipsing binaries previously published by our team. distances to the binary systems were calculated using a surface brightness—color calibration. the targets form an elongated structure, highly inclined to the plane of the sky. the distance difference between the nearest and most-distant system amounts to 10 kpc with the line-of-sight depth reaching 7 kpc. we find tentative evidence of the existence of a spherical stellar substructure (core) in the smc coinciding with its stellar center, containing about 40% of the young and intermediate age stars in the galaxy. the radial extension of this substructure is ∼1.5 kpc. we derive a distance to the smc center of dsmc = 62.44 ± 0.47 (stat.) ± 0.81 (syst.) kpc corresponding to a distance modulus (m - m)smc = 18.977 ± 0.016 ± 0.028 mag, representing an accuracy of better than 2%. | a distance determination to the small magellanic cloud with an accuracy of better than two percent based on late-type eclipsing binary stars |
context. the carmenes exoplanet survey of m dwarfs has obtained more than 18 000 spectra of 329 nearby m dwarfs over the past five years as part of its guaranteed time observations (gto) program.aims: we determine planet occurrence rates with the 71 stars from the gto program for which we have more than 50 observations.methods: we use injection-and-retrieval experiments on the radial-velocity time series to measure detection probabilities. we include 27 planets in 21 planetary systems in our analysis.results: we find 0.06−0.03+0.04 giant planets (100 m⊕ < mpl sin i < 1000 m⊕) per star in periods of up to 1000 d, but due to a selection bias this number could be up to a factor of five lower in the whole 329-star sample. the upper limit for hot jupiters (orbital period of less than 10 d) is 0.03 planets per star, while the occurrence rate of planets with intermediate masses (10 m⊕ < mpl sin i < 100 m⊕) is 0.18−0.05+0.07 planets per star. less massive planets with 1 m⊕ < mpl sin i < 10 m⊕ are very abundant, with an estimated rate of 1.32−0.31+0.33 planets per star for periods of up to 100 d. when considering only late m dwarfs with masses m⋆ < 0.34 m⊙, planets more massive than 10 m⊕ become rare. instead, low-mass planets with periods shorter than 10 d are significantly overabundant.conclusions: for orbital periods shorter than 100 d, our results confirm the known stellar mass dependences from the kepler survey: m dwarfs host fewer giant planets and at least two times more planets with mpl sin i < 10 m⊕ than g-type stars. in contrast to previous results, planets around our sample of very low-mass stars have a higher occurrence rate in short-period orbits of less than 10 d. our results demonstrate the need to take into account host star masses in planet formation models. | the carmenes search for exoplanets around m dwarfs. planet occurrence rates from a subsample of 71 stars |
compose (compstar online supernovae equations of state) is an online repository of equations of state (eos) for use in nuclear physics and astrophysics, e.g., in the description of compact stars or the simulation of core-collapse supernovae and neutron-star mergers, see https://compose.obspm.fr. the main services, offered via the website, are: a collection of data tables in a flexible and easily extendable data format for different eos types and related physical quantities with extensive documentation and referencing; software for download to extract and to interpolate these data and to calculate additional quantities; webtools to generate eos tables that are customized to the needs of the users and to illustrate dependencies of various eos quantities in graphical form. this manual is an update of previous versions that are available on the compose website, at arxiv:1307.5715 [astro-ph.sr], and that was originally published in the journal "physics of particles and nuclei" with doi:10.1134/s1063779615040061. it contains a detailed description of the service, containing a general introduction as well as instructions for potential contributors and for users. short versions of the manual for eos users and providers will also be available as separate publications. | compose reference manual |
photometric stellar surveys now cover a large fraction of the sky, probe to fainter magnitudes than large-scale spectroscopic studies, and are relatively free from the target-selection biases often associated with such studies. photometric-metallicity estimates that include narrow/medium-band filters can achieve comparable accuracy and precision to existing low- and medium-resolution spectroscopic surveys such as sdss/segue and lamost, with metallicities as low as [fe/h] $\sim -3.5$ to $-4.0$. here we report on an effort to identify likely members of the galactic disk system among the very metal-poor (vmp; [fe/h] $\leq$ -2) and extremely metal-poor (emp; [fe/h] $\leq$ -3) stars. our analysis is based on a sample of some 11.5 million stars with full space motions selected from the skymapper southern survey (smss) and stellar abundance and galactic evolution survey (sages). after applying a number of quality cuts, designed to obtain the best available metallicity and dynamical estimates, we analyze a total of about 7.74 million stars in the combined smss/sages sample. we employ two techniques which, depending on the method, identify between 5,878 and 7,600 vmp stars (19% to 25% of all vmp stars) and between 345 and 399 emp stars (35% to 40% of all emp stars) that appear to be members of the galactic disk system on highly prograde orbits (v$_{\phi} > 150$ kms$^{-1}$), the majority of which have low orbital eccentricities (ecc $\le 0.4$). the large fractions of vmp/emp stars that are associated with the mw disk system strongly suggests the presence of an early forming ``primordial" disk. | candidate members of the vmp/emp disk system of the galaxy from the skymapper and sages surveys |
we present the second data release of the muse hubble ultra-deep field surveys, which includes the deepest spectroscopic survey ever performed. the muse data, with their 3d content, amazing depth, wide spectral range, and excellent spatial and medium spectral resolution, are rich in information. their location in the hubble ultra-deep field area, which benefits from an exquisite collection of ancillary panchromatic information, is a major asset. this update of the first release incorporates a new 141-h adaptive-optics-assisted muse extremely deep field (mxdf; 1 arcmin diameter field of view) in addition to the reprocessed 10-h mosaic (3 × 3 arcmin2) and the single 31-h deep field (1 × 1 arcmin2). all three data sets were processed and analyzed homogeneously using advanced data reduction and analysis methods. the 3σ point-source flux limit of an unresolved emission line reaches 3.1 × 10−19 and 6.3 × 10−20 erg s−1 cm−2 at 10- and 141-h depths, respectively. we have securely identified and measured the redshift of 2221 sources, an increase of 41% compared to the first release. with the exception of eight stars, the collected sample consists of 25 nearby galaxies (z < 0.25), 677 [o ii] emitters (z = 0.25 − 1.5), 201 galaxies in the muse redshift desert range (z = 1.5 − 2.8), and 1308 lyα emitters (z = 2.8 − 6.7). this represents an order of magnitude more redshifts than the collection of all spectroscopic redshifts obtained before muse in the hubble ultra-deep field area (i.e., 2221 versus 292). at high redshift (z > 3), the difference is even more striking, with a factor of 65 increase (1308 versus 20). we compared the measured redshifts against three published photometric redshift catalogs and find the photo-z accuracy to be lower than the constraints provided by photo-z fitting codes. eighty percent of the galaxies in our final catalog have an hst counterpart. these galaxies are on average faint, with a median ab f775w magnitude of 25.7 and 28.7 for the [o ii] and lyα emitters, respectively. fits of their spectral energy distribution show that these galaxies tend to be low-mass star-forming galaxies, with a median stellar mass of 6.2 × 108 m⊙ and a median star-formation rate of 0.4 m⊙ yr−1. we measured the completeness of our catalog with respect to hst and found that, in the deepest 141-h area, 50% completeness is achieved for an ab magnitude of 27.6 and 28.7 (f775w) at z = 0.8 − 1.6 and z = 3.2 − 4.5, respectively. twenty percent of our catalog, or 424 galaxies, have no hst counterpart. the vast majority of these new sources are high equivalent-width z > 2.8 lyα emitters that are detected by muse thanks to their bright and asymmetric broad lyα line. we release advanced data products, specific software, and a web interface to select and download data sets. catalogs are only available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/670/a4 based on observations made with eso telescopes at the la silla paranal observatory under the programs 094.a-0289(b), 095.a-0010(a), 096.a-0045(a), 096.a-0045(b) and 1101.a-0127. | the muse hubble ultra deep field surveys: data release ii |
we review the role of stellar flybys and encounters in shaping planet-forming discs around young stars, based on the published literature on this topic in the last 30 years. since most stars ≤2 myr old harbour protoplanetary discs, tidal perturbations affect planet formation. first, we examine the probability of experiencing flybys or encounters: more than 50% of stars with planet-forming discs in a typical star-forming environment should experience a close stellar encounter or flyby within 1000 au. second, we detail the dynamical effects of flybys on planet-forming discs. prograde, parabolic, disc-penetrating flybys are the most destructive. grazing and penetrating flybys in particular lead to the capture of disc material by the secondary to form a highly misaligned circumsecondary disc with respect to the disc around the primary. one or both discs may undergo extreme accretion and outburst events, similar to the ones observed in fu orionis-type stars. warps and broken discs are distinct signatures of retrograde flybys. third, we review some recently observed stellar systems with discs where a stellar flyby or an encounter is suspected—including ux tau, rw aur, as 205, z cma, and fu ori. finally, we discuss the implications of stellar flybys for planet formation and exoplanet demographics, including possible imprints of a flyby in the solar system in the orbits of trans-neptunian objects and the sun's obliquity. | close encounters: how stellar flybys shape planet-forming discs |
we present timing models for 20 millisecond pulsars in the parkes pulsar timing array. the precision of the parameter measurements in these models has been improved over earlier results by using longer data sets and modelling the non-stationary noise. we describe a new noise modelling procedure and demonstrate its effectiveness using simulated data. our methodology includes the addition of annual dispersion measure (dm) variations to the timing models of some pulsars. we present the first significant parallax measurements for psrs j1024-0719, j1045-4509, j1600-3053, j1603-7202, and j1730-2304, as well as the first significant measurements of some post-keplerian orbital parameters in six binary pulsars, caused by kinematic effects. improved shapiro delay measurements have resulted in much improved pulsar mass measurements, particularly for psrs j0437-4715 and j1909-3744 with mp = 1.44 ± 0.07 and 1.47 ± 0.03 m⊙, respectively. the improved orbital period-derivative measurement for psr j0437-4715 results in a derived distance measurement at the 0.16 per cent level of precision, d = 156.79 ± 0.25 pc, one of the most fractionally precise distance measurements of any star to date. | timing analysis for 20 millisecond pulsars in the parkes pulsar timing array |
gravitational-wave (gw) and electromagnetic (em) signals from the merger of a neutron star (ns) and a black hole (bh) are a highly anticipated discovery. we present a simple formula, validated with 75 simulations, that distinguishes between potential merger outcomes and predicts the baryon mass left outside of the bh after merger. our formula describes critical unexplored regimes: comparable masses with nonspinning bhs, and higher bh spins, and is essential in assessing whether events such as gw170817 could be ns-bh systems instead of ns-ns mergers. | remnant baryon mass in neutron star-black hole mergers: predictions for binary neutron star mimickers and rapidly spinning black holes |
the source of the gravitational-wave (gw) signal gw170817, very likely a binary neutron star merger, was also observed electromagnetically, providing the first multi-messenger observations of this type. the two-week-long electromagnetic (em) counterpart had a signature indicative of an r-process-induced optical transient known as a kilonova. this letter examines how the mass of the dynamical ejecta can be estimated without a direct electromagnetic observation of the kilonova, using gw measurements and a phenomenological model calibrated to numerical simulations of mergers with dynamical ejecta. specifically, we apply the model to the binary masses inferred from the gw measurements, and use the resulting mass of the dynamical ejecta to estimate its contribution (without the effects of wind ejecta) to the corresponding kilonova light curves from various models. the distributions of dynamical ejecta mass range between {m}{ej}={10}-3-{10}-2 {m}⊙for various equations of state, assuming that the neutron stars are rotating slowly. in addition, we use our estimates of the dynamical ejecta mass and the neutron star merger rates inferred from gw170817 to constrain the contribution of events like this to the r-process element abundance in the galaxy when ejecta mass from post-merger winds is neglected. we find that if ≳10% of the matter dynamically ejected from binary neutron star (bns) mergers is converted to r-process elements, gw170817-like bns mergers could fully account for the amount of r-process material observed in the milky way. | estimating the contribution of dynamical ejecta in the kilonova associated with gw170817 |
the observation of binary neutron star merger gw170817, along with its optical counterpart, provided the first constraint on the hubble constant h0 using gravitational wave standard sirens. when no counterpart is identified, a galaxy catalog can be used to provide the necessary redshift information. however, the true host might not be contained in a catalog which is not complete out to the limit of gravitational-wave detectability. these electromagnetic and gravitational-wave selection effects must be accounted for. we describe and implement a method to estimate h0 using both the counterpart and the galaxy catalog standard siren methods. we perform a series of mock data analyses using binary neutron star mergers to confirm our ability to recover an unbiased estimate of h0. our simulations used a simplified universe with no redshift uncertainties or galaxy clustering, but with different magnitude-limited catalogs and assumed host galaxy properties, to test our treatment of both selection effects. we explore how the incompleteness of catalogs affects the final measurement of h0, as well as the effect of weighting each galaxy's likelihood of being a host by its luminosity. in our most realistic simulation, where the simulated catalog is about three times denser than the density of galaxies in the local universe, we find that a 4.4% measurement precision can be reached using galaxy catalogs with 50% completeness and ∼250 binary neutron star detections with sensitivity similar to that of advanced ligo's second observing run. | cosmological inference using gravitational wave standard sirens: a mock data analysis |
we prove that einstein's equations coupled to equations of the israel-stewart-type, describing the dynamics of a relativistic fluid with bulk viscosity and nonzero baryon charge (without shear viscosity or baryon diffusion) dynamically coupled to gravity, are causal in the full nonlinear regime. we also show that these equations can be written as a first-order symmetric hyperbolic system, implying local existence and uniqueness of solutions to the equations of motion. we use an arbitrary equation of state and do not make any simplifying symmetry or near-equilibrium assumption, requiring only physically natural conditions on the fields. these results pave the way for the inclusion of bulk viscosity effects in simulations of gravitational-wave signals coming from neutron star mergers. | causality of the einstein-israel-stewart theory with bulk viscosity |
the possibility that nucleosynthesis in neutron star mergers may reach fissioning nuclei introduces significant uncertainties in predicting the relative abundances of r-process material from such events. we evaluate the impact of using sets of fission yields given by the 2016 gef code for spontaneous (sf), neutron-induced ((n, f)), and β-delayed (βdf) fission processes which take into account the approximate initial excitation energy of the fissioning compound nucleus. we further explore energy-dependent fission dynamics in the r process by considering the sensitivity of our results to the treatment of the energy sharing and de-excitation of the fission fragments using the freya code. we show that the asymmetric-to-symmetric yield trends predicted by gef 2016 can reproduce the high-mass edge of the second r-process peak seen in solar data and examine the sensitivity of this result to the mass model and astrophysical conditions applied. we consider the effect of fission yields and barrier heights on the nuclear heating rates used to predict kilonova light curves. we find that fission barriers influence the contribution of 254cf spontaneous fission to the heating at ∼100 d, such that a light curve observation consistent with such late-time heating would both confirm that actinides were produced in the event and imply the fission barriers are relatively high along the 254cf β-feeding path. we lastly determine the key nuclei responsible for setting the r-process abundance pattern by averaging over thirty trajectories from a 1.2-1.4 m⊙ neutron star merger simulation. we show it is largely the odd-n nuclei undergoing (z, n)(n, f) and (z, n)βdf that control the relative abundances near the second peak. we find the 'hot spots' for β-delayed and neutron-induced fission given all mass models considered and show most of these nuclei lie between the predicted n = 184 shell closure and the location of currently available experimental decay data. | using excitation-energy dependent fission yields to identify key fissioning nuclei in r-process nucleosynthesis |
we present a comparison of parallaxes and radii from asteroseismology and gaia dr1 (tgas) for 2200 kepler stars spanning from the main sequence to the red-giant branch. we show that previously identified offsets between tgas parallaxes and distances derived from asteroseismology and eclipsing binaries have likely been overestimated for parallaxes ≲ 5{--}10 mas (≈90%-98% of the tgas sample). the observed differences in our sample can furthermore be partially compensated by adopting a hotter {t}{eff} scale (such as the infrared flux method) instead of spectroscopic temperatures for dwarfs and subgiants. residual systematic differences are at the ≈2% level in parallax across three orders of magnitude. we use tgas parallaxes to empirically demonstrate that asteroseismic radii are accurate to ≈5% or better for stars between ≈ 0.8{--}8 {r}⊙ . we find no significant offset for main-sequence (≲ 1.5 {r}⊙ ) and low-luminosity rgb stars (≈3-8 {r}⊙ ), but seismic radii appear to be systematically underestimated by ≈5% for subgiants (≈1.5-3 {r}⊙ ). we find no systematic errors as a function of metallicity between [{fe}/{{h}}]≈ -0.8 to +0.4 dex, and show tentative evidence that corrections to the scaling relation for the large frequency separation ({{δ }}ν ) improve the agreement with tgas for rgb stars. finally, we demonstrate that beyond ≈ 3 {kpc} asteroseismology will provide more precise distances than end-of-mission gaia data, highlighting the synergy and complementary nature of gaia and asteroseismology for studying galactic stellar populations. | asteroseismology and gaia: testing scaling relations using 2200 keplerstars with tgas parallaxes |
we report the detection of extended lyα haloes around 145 individual star-forming galaxies at redshifts 3 ≤ z ≤ 6 in the hubble ultra deep field observed with the multi-unit spectroscopic explorer (muse) at eso-vlt. our sample consists of continuum-faint (- 15 ≥ muv ≥ -22) lyα emitters (laes). using a 2d, two-component (continuum-like and halo) decomposition of lyα emission assuming circular exponential distributions, we measure scale lengths and luminosities of lyα haloes. we find that 80% of our objects having reliable lyα halo measurements show lyα emission that is significantly more extended than the uv continuum detected by hst (by a factor ≈4 to >20). the median exponential scale length of the lyα haloes in our sample is ≈4.5 kpc with a few haloes exceeding 10 kpc. by comparing the maximal detected extent of the lyα emission with the predicted dark matter halo virial radii of simulated galaxies, we show that the detected lyα emission of our selected sample of lyα emitters probes a significant portion of the cold circum-galactic medium of these galaxies (>50% in average). this result therefore shows that there must be significant hi reservoirs in the circum-galactic medium and reinforces the idea that lyα haloes are ubiquitous around high-redshift lyα emitting galaxies. our characterization of the lyα haloes indicates that the majority of the lyα flux comes from the halo (≈65%) and that their scale lengths seem to be linked to the uv properties of the galaxies (sizes and magnitudes). we do not observe a significant lyα halo size evolution with redshift, although our sample for z> 5 is very small. we also explore the diversity of the lyα line profiles in our sample and we find that the lyα lines cover a large range of full width at half maximum (fwhm) from 118 to 512 km s-1. while the fwhm does not seem to be correlated to the lyα scale length, most compact lyα haloes and those that are not detected with high significance tend to have narrower lyα profiles (<350 km s-1). finally, we investigate the origin of the extended lyα emission but we conclude that our data do not allow us to disentangle the possible processes, i.e. scattering from star-forming regions, fluorescence, cooling radiation from cold gas accretion, and emission from satellite galaxies. muse ultra deep field lyα haloes catalog (table b.1) is also available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/608/a8 | the muse hubble ultra deep field survey. viii. extended lyman-α haloes around high-z star-forming galaxies |
the javalambre photometric local universe survey (j-plus ) is an ongoing 12-band photometric optical survey, observing thousands of square degrees of the northern hemisphere from the dedicated jast/t80 telescope at the observatorio astrofísico de javalambre (oaj). the t80cam is a camera with a field of view of 2 deg2 mounted on a telescope with a diameter of 83 cm, and is equipped with a unique system of filters spanning the entire optical range (3500-10 000 å). this filter system is a combination of broad-, medium-, and narrow-band filters, optimally designed to extract the rest-frame spectral features (the 3700-4000 å balmer break region, hδ, ca h+k, the g band, and the mg b and ca triplets) that are key to characterizing stellar types and delivering a low-resolution photospectrum for each pixel of the observed sky. with a typical depth of ab ∼21.25 mag per band, this filter set thus allows for an unbiased and accurate characterization of the stellar population in our galaxy, it provides an unprecedented 2d photospectral information for all resolved galaxies in the local universe, as well as accurate photo-z estimates (at the δ z/(1 + z)∼0.005-0.03 precision level) for moderately bright (up to r ∼ 20 mag) extragalactic sources. while some narrow-band filters are designed for the study of particular emission features ([o ii]/λ3727, hα/λ6563) up to z < 0.017, they also provide well-defined windows for the analysis of other emission lines at higher redshifts. as a result, j-plus has the potential to contribute to a wide range of fields in astrophysics, both in the nearby universe (milky way structure, globular clusters, 2d ifu-like studies, stellar populations of nearby and moderate-redshift galaxies, clusters of galaxies) and at high redshifts (emission-line galaxies at z ≈ 0.77, 2.2, and 4.4, quasi-stellar objects, etc.). with this paper, we release the first ∼1000 deg2 of j-plus data, containing about 4.3 million stars and 3.0 million galaxies at r < 21 mag. with a goal of 8500 deg2 for the total j-plus footprint, these numbers are expected to rise to about 35 million stars and 24 million galaxies by the end of the survey. | j-plus: the javalambre photometric local universe survey |
einstein's gravity minimally coupled to free, massive, classical fundamental fields admits particle-like solutions. these are asymptotically flat, everywhere non-singular configurations that realise wheeler's concept of a geon: a localised lump of self-gravitating energy whose existence is anchored on the non-linearities of general relativity, trivialising in the flat spacetime limit. in [1] the key properties for the existence of these solutions (also referred to as stars or self-gravitating solitons) were discussed - which include a harmonic time dependence in the matter field -, and a comparative analysis of the stars arising in the einstein-klein-gordon, einstein-dirac and einstein-proca models was performed, for the particular case of static, spherically symmetric spacetimes. in the present work we generalise this analysis for spinning solutions. in particular, the spinning einstein-dirac stars are reported here for the first time. our analysis shows that the high degree of universality observed in the spherical case remains when angular momentum is allowed. thus, as classical field theory solutions, these self-gravitating solitons are rather insensitive to the fundamental fermionic or bosonic nature of the corresponding field, displaying similar features. we describe some physical properties and, in particular, we observe that the angular momentum of the spinning stars satisfies the quantisation condition j = mn, for all models, where n is the particle number and m is an integer for the bosonic fields and a half-integer for the dirac field. the way in which this quantisation condition arises, however, is more subtle for the non-zero spin fields. | asymptotically flat spinning scalar, dirac and proca stars |
we discuss stiffening of matter in quark-hadron continuity. we introduce a model that relates quark wave functions in a baryon and the occupation probability of states for baryons and quarks in dense matter. in a dilute regime, the confined quarks contribute to the energy density through the masses of baryons but do not directly contribute to the pressure; hence, the equations of state are very soft. this dilute regime continues until the low momentum states for quarks get saturated; this may happen even before baryons fully overlap, possibly at density slightly above the nuclear saturation density. after the saturation, the pressure grows rapidly while changes in energy density are modest, producing a peak in the speed of sound. if we use baryonic descriptions for quark distributions near the fermi surface, we reach a description similar to the quarkyonic matter model of mclerran and reddy. with a simple adjustment of quark interactions to get the nucleon mass, our model becomes consistent with the constraints from 1.4-solar mass neutron stars, but the high density part is too soft to account for two-solar mass neutron stars. we delineate the relation between the saturation effects and short range interactions of quarks, suggesting interactions that leave low density equations of state unchanged but stiffen the high density part. | stiffening of matter in quark-hadron continuity |
the fast radio burst frb 121102 has repeated multiple times, enabling the identification of its host galaxy and of a spatially coincident, compact, steady (“persistent”) radio synchrotron source. it was proposed that frb 121102 is powered by a young flaring magnetar, embedded within a decades-old supernova remnant. using a time-dependent one-zone model, we show that a single expanding magnetized electron-ion nebula (created by the same outbursts likely responsible for the fast radio bursts) can explain all of the basic properties of the persistent source (size, flux, self-absorption constraints) and the large but decreasing rotation measure (rm) of the bursts. the persistent emission is powered by relativistic thermal electrons heated at the termination shock of the magnetar wind, while the rm originates from non-relativistic electrons injected earlier in the nebula’s evolution and cooled through expansion and radiative losses. the model contains few free parameters, which are tightly constrained by observations: the total energy injected into the nebula over its history, ∼1050-1051 erg, agrees with the magnetic energy of a millisecond magnetar; the baryon loading of the magnetar outflow (driven by intermittent flares) is close to the neutron star escape speed; the predicted source age ∼10-40 yr is consistent with other constraints on the nebula size. for an energy input rate \dot{e}\propto {t}-αfollowing the onset of magnetar activity, we predict secular decay of the rm and persistent source flux, which approximately follow rm ∝ t -(6+α)/2 and {f}ν \propto {t}-({α 2+7α -2)/4}, respectively. | a concordance picture of frb 121102 as a flaring magnetar embedded in a magnetized ion-electron wind nebula |
high-resolution doppler-resolved spectroscopy has opened up a new window into the atmospheres of both transiting and non-transiting exoplanets. here, we present vlt/uves observations of a transit of wasp-121b, an `ultra-hot' jupiter previously found to exhibit a temperature inversion and detections of multiple species at optical wavelengths. we present initial results using the blue arm of uves (≈3700-5000 å), recovering a clear signal of neutral fe in the planet's atmosphere at >8 σ, which could contribute to (or even fully explain) the temperature inversion in the stratosphere. however, using standard cross-correlation methods, it is difficult to extract physical parameters such as temperature and abundances. recent pioneering efforts have sought to develop likelihood `mappings' that can be used to directly fit models to high-resolution data sets. we introduce a new framework that directly computes the likelihood of the model fit to the data, and can be used to explore the posterior distribution of parametrised model atmospheres via mcmc techniques. our method also recovers the physical extent of the atmosphere, as well as account for time- and wavelength-dependent uncertainties. we measure a temperature of 3710^{+490}_{-510} k, indicating a higher temperature in the upper atmosphere when compared to low-resolution observations. we also show that the fe i signal is physically separated from the exospheric fe ii. however, the temperature measurements are highly degenerate with aerosol properties; detection of additional species, using more sophisticated atmospheric models, or combining these methods with low-resolution spectra should help break these degeneracies. | detection of fe i in the atmosphere of the ultra-hot jupiter wasp-121b, and a new likelihood-based approach for doppler-resolved spectroscopy |
we present cosmos-drift and shift (dash), a hubble space telescope (hst) wide field camera 3 (wfc3) imaging survey of the cosmos field in the h 160 filter. the survey comprises 456 individual wfc3 pointings corresponding to an area of 0.49 deg2 (0.66 deg2 when including archival data) and reaches a 5σ point-source limit of h 160 = 25.1 (0.″3 aperture). cosmos-dash is the widest hst/wfc3 imaging survey in the h 160 filter, tripling the extragalactic survey area in the near-infrared at hst resolution. we make the reduced h 160 mosaic available to the community. we use this data set to measure the sizes of 169 galaxies with {log}({m}\star /{m}⊙ )> 11.3 at 1.5 < z < 3.0 and augment this sample with 749 galaxies at 0.1 < z < 1.5 using archival acs imaging. we find that the median size of galaxies in this mass range changes with redshift as < {r}eff}> ={(13.4+/- 0.5)× (1+z)}(-0.95+/- 0.05) kpc. separating the galaxies into star-forming and quiescent galaxies using their rest-frame u - v and v - j colors, we find no statistical difference between the median sizes of the most massive star-forming and quiescent galaxies at < z> =2.5: they are 4.9 ± 0.9 kpc and 4.3 ± 0.3 kpc, respectively. however, we do find a significant difference in the sèrsic index between the two samples, such that massive quiescent galaxies have higher central densities than star-forming galaxies. we extend the size-mass analysis to lower masses by combining it with the 3d-hst/candels sample of van der wel et al. and derive empirical relations between size, mass, and redshift. fitting a relation of the form {r}eff}=a× {m}\star α , with {m}\star ={m}\star /5× {10}10 {m}⊙and r eff in kpc, we find log a = -0.25 log(1 + z) + 0.80 and α = -0.13 log(1 + z) + 0.27. we also provide relations for the subsamples of star-forming and quiescent galaxies. our results confirm previous studies that were based on smaller samples or ground-based imaging. | cosmos-dash: the evolution of the galaxy size-mass relation since z ∼ 3 from new wide-field wfc3 imaging combined with candels/3d-hst |
we report the discovery of a milky way satellite in the constellation of antlia. the antlia 2 dwarf galaxy is located behind the galactic disc at a latitude of b ∼ 11° and spans 1.26°, which corresponds to ∼2.9 kpc at its distance of 130 kpc. while similar in spatial extent to the large magellanic cloud, antlia 2 is orders of magnitude fainter at mv = -9 mag, making it by far the lowest surface brightness system known (at ∼31.9 mag arcsec-2), ∼100 times more diffuse than the so-called ultra diffuse galaxies. the satellite was identified using a combination of astrometry, photometry, and variability data from gaia data release 2, and its nature confirmed with deep archival decam imaging, which revealed a conspicuous bhb signal. we have also obtained follow-up spectroscopy using aaomega on the aat, identifying 159 member stars, and we used them to measure the dwarf's systemic velocity, 290.9 ± 0.5 km s-1, its velocity dispersion, 5.7 ± 1.1 km s-1, and mean metallicity, [fe/h] = -1.4. from these properties we conclude that antlia 2 inhabits one of the least dense dark matter (dm) haloes probed to date. dynamical modelling and tidal-disruption simulations suggest that a combination of a cored dm profile and strong tidal stripping may explain the observed properties of this satellite. the origin of this core may be consistent with aggressive feedback, or may even require alternatives to cold dark matter (such as ultra-light bosons). | the hidden giant: discovery of an enormous galactic dwarf satellite in gaia dr2 |
massive stars have strong stellar winds that direct their evolution through the upper hertzsprung-russell diagram and determine the black hole mass function. furthermore, wind strength dictates the atmospheric structure that sets the ionizing flux. finally, the wind directly intervenes with the stellar envelope structure, which is decisive for both single-star and binary evolution, affecting predictions for gravitational wave events. key findings of current hot star research include: the traditional line-driven wind theory is being updated with monte carlo and comoving frame computations, revealing a rich multivariate behavior of the mass-loss rate in terms of m, l, eddington γ, teff, and chemical composition z. concerning the latter, is shown to depend on the iron (fe) opacity, making wolf-rayet populations, and gravitational wave events dependent on host galaxy z. on top of smooth mass-loss behavior, there are several transitions in the hertzsprung-russell diagram, involving bistability jumps around fe recombination temperatures, leading to quasi-stationary episodic, and not necessarily eruptive, luminous blue variable and pre-sn mass loss. furthermore, there are kinks. at 100 a high γ mass-loss transition implies that hydrogen-rich, very massive stars have higher mass-loss rates than commonly considered. at the other end of the mass spectrum, low-mass stripped helium stars no longer appear as wolf-rayet stars but as optically thin stars. these stripped stars, in addition to very massive stars, are two newly identified sources of ionizing radiation that could play a key role in local star formation as well as at high redshift. | theory and diagnostics of hot star mass loss |
if a phase transition is allowed to take place in the core of a compact star, a new stable branch of equilibrium configurations can appear, providing solutions with the same mass as the purely hadronic branch and hence giving rise to "twin-star" configurations. we perform an extensive analysis of the features of the phase transition leading to twin-star configurations and, at the same time, fulfilling the constraints coming from the maximum mass of 2 m⊙ and the information following gravitational-wave event gw170817. in particular, we use a general equation of state for the neutron-star matter that parametrizes the hadron-quark phase transition between the model describing the hadronic phase and a constant speed of sound for the quark phase. we find that the largest number of twin-star solutions has masses in the neutron-star branch that are in the range 1 - 2 m⊙ and maximum masses ≳2 m⊙ in the twin-star branch. the analysis of the masses, radii, and tidal deformabilities also reveals that when twin stars appear, the tidal deformability shows two distinct branches with the same mass, thus differing considerably from the behavior expected for normal neutron stars. in addition, we find that the data from gw170817 is compatible with the existence of hybrid stars and could also be interpreted as being produced by the merger of a binary system of hybrid stars or of a hybrid star with a neutron star. indeed, with the use of a well-established hadronic equation of state, the presence of a hybrid star in the inspiral phase could be revealed if future gravitational-wave detections measure chirp masses m ≲1.2 m⊙ and tidal deformabilities of λ1.4≲400 for 1.4 m⊙ stars. finally, combining all observational information available so far, we set constraints on the parameters that characterize the phase transition, the maximum masses, and the radii of 1.4 m⊙ stars described by equations of state leading to twin-star configurations. | constraining twin stars with gw170817 |
a long (110 cmpc h-1) and deep absorption trough in the ly α forest has been observed extending down to redshift 5.5 in the spectrum of ulas j0148+0600. although no ly α transmission is detected, ly β spikes are present which has led to claims that the gas along this trough must be ionized. using high-resolution cosmological radiative transfer simulations in large volumes, we show that in a scenario where reionization ends late (z ∼ 5.2), our simulations can reproduce troughs as long as observed. in this model, we find that the troughs are caused by islands of neutral hydrogen. small ionized holes within the neutral islands allow for the transmission of ly β. we have also modelled the ly α emitter population around the simulated troughs, and show that there is a deficit of ly α emitters close to the trough as is observed. | long troughs in the lyman-α forest below redshift 6 due to islands of neutral hydrogen |
at the end of its life, a very massive star is expected to collapse into a black hole (bh). the recent detection of an 85 m⊙ bh from the gravitational wave event gw 190521 appears to present a fundamental problem as to how such heavy bhs exist above the approximately 50 m⊙ pair-instability (pi) limit where stars are expected to be blown to pieces with no remnant left. using mesa, we show that for stellar models with non-extreme assumptions, 90-100 m⊙ stars at reduced metallicity ($z/\mbox{ $\mathrm{z}_{\odot }$}\le 0.1$) can produce blue supergiant progenitors with core masses sufficiently small to remain below the fundamental pi limit, yet at the same time lose an amount of mass via stellar winds that is small enough to end up in the range of an 'impossible' 85 m⊙ bh. the two key points are the proper consideration of core overshooting and stellar wind physics with an improved scaling of mass-loss with iron (fe) contents characteristic for the host galaxy metallicity. our modelling provides a robust scenario that not only doubles the maximum bh mass set by pi, but also allows us to probe the maximum stellar bh mass as a function of metallicity and cosmic time in a physically sound framework. | maximum black hole mass across cosmic time |
the hot and dense core formed in the collapse of a massive star is a powerful source of hypothetical feebly interacting particles such as sterile neutrinos, dark photons, axionlike particles (alps), and others. radiative decays such as a →2 γ deposit this energy in the surrounding material if the mean free path is less than the radius of the progenitor star. for the first time, we use a supernova (sn) population with particularly low explosion energies as the most sensitive calorimeters to constrain this possibility. these sne are observationally identified as low-luminosity events with low ejecta velocities and low masses of ejected 56ni. their low energies limit the energy deposition from particle decays to less than about 0.1 b, where 1 b (bethe)=1051 erg . for 1-500 mev-mass alps, this generic argument excludes alp-photon couplings ga γ γ in the 10-10−10-8 gev-1 range. | low-energy supernovae severely constrain radiative particle decays |
kerr black holes (bhs) with scalar hair are solutions of the einstein-klein-gordon field equations describing regular (on and outside an event horizon), asymptotically flat bhs with scalar hair (herdeiro and radu 2014 phys. rev. lett. 112 221101). these bhs interpolate continuously between the kerr solution and rotating boson stars in d = 4 spacetime dimensions. here we provide details on their construction, discussing properties of the ansatz, the field equations, the boundary conditions and the numerical strategy. then, we present an overview of the parameter space of the solutions, and describe in detail the space-time structure of the bh's exterior geometry and of the scalar field for a sample of reference solutions. phenomenological properties of potential astrophysical interest are also discussed, and the stability properties and possible generalizations are commented on. as supplementary material to this paper we make available numerical data files for the sample of reference solutions discussed, for public use (see stacks.iop.org/cqg/32/144001/mmedia). | construction and physical properties of kerr black holes with scalar hair |
with the advent of new wide-field, high-cadence optical transient surveys, our understanding of the diversity of core-collapse supernovae has grown tremendously in the last decade. however, the pre-supernova evolution of massive stars, which sets the physical backdrop to these violent events, is theoretically not well understood and difficult to probe observationally. here we report the discovery of the supernova iptf 13dqy = sn 2013fs a mere ~3 h after explosion. our rapid follow-up observations, which include multiwavelength photometry and extremely early (beginning at ~6 h post-explosion) spectra, map the distribution of material in the immediate environment (<~1015 cm) of the exploding star and establish that it was surrounded by circumstellar material (csm) that was ejected during the final ~1 yr prior to explosion at a high rate, around 10-3 solar masses per year. the complete disappearance of flash-ionized emission lines within the first several days requires that the dense csm be confined to within <~1015 cm, consistent with radio non-detections at 70-100 days. the observations indicate that iptf 13dqy was a regular type ii supernova; thus, the finding that the probable red supergiant progenitor of this common explosion ejected material at a highly elevated rate just prior to its demise suggests that pre-supernova instabilities may be common among exploding massive stars. | confined dense circumstellar material surrounding a regular type ii supernova |
we introduce the cluster-eagle (c-eagle) simulation project, a set of cosmological hydrodynamical zoom simulations of the formation of 30 galaxy clusters in the mass range of 1014 < m200/m⊙ < 1015.4 that incorporates the hydrangea sample of bahé et al. (2017). the simulations adopt the state-of-the-art eagle galaxy formation model, with a gas particle mass of 1.8 × 106 m⊙ and physical softening length of 0.7 kpc. in this paper, we introduce the sample and present the low-redshift global properties of the clusters. we calculate the x-ray properties in a manner consistent with observational techniques, demonstrating the bias and scatter introduced by using estimated masses. we find the total stellar content and black hole masses of the clusters to be in good agreement with the observed relations. however, the clusters are too gas rich, suggesting that the active galactic nucleus (agn) feedback model is not efficient enough at expelling gas from the high-redshift progenitors of the clusters. the x-ray properties, such as the spectroscopic temperature and the soft-band luminosity, and the sunyaev-zel'dovich properties are in reasonable agreement with the observed relations. however, the clusters have too high central temperatures and larger-than-observed entropy cores, which is likely driven by the agn feedback after the cluster core has formed. the total metal content and its distribution throughout the intracluster medium are a good match to the observations. | the cluster-eagle project: global properties of simulated clusters with resolved galaxies |
ultralight bosons and axion-like particles appear naturally in different scenarios and could solve some long-standing puzzles. their detection is challenging, and all direct methods hinge on unknown couplings to the standard model of particle physics. however, the universal coupling to gravity provides model-independent signatures for these fields. we explore here the superradiant instability of spinning black holes triggered in the presence of such fields. the instability taps angular momentum from and limits the maximum spin of astrophysical black holes. we compute, for the first time, the spectrum of the most unstable modes of a massive vector (proca) field for generic black-hole spin and proca mass. the observed stability of the inner disk of stellar-mass black holes can be used to derive direct constraints on the mass of dark photons in the mass range 10-13 evlesssim mv lesssim 3× 10-12 ev. by including also higher azimuthal modes, similar constraints apply to axion-like particles in the mass range 6×10-13 evlesssim malp lesssim 10-11 ev. likewise, mass and spin distributions of supermassive bhs—as measured through continuum fitting, kα iron line, or with the future space-based gravitational-wave detector lisa - imply indirect bounds in the mass range approximately 10-19 evlesssim mv, malp lesssim 10-13 ev, for both axion-like particles and dark photons. overall, superradiance allows to explore a region of approximately 8 orders of magnitude in the mass of ultralight bosons. | constraining the mass of dark photons and axion-like particles through black-hole superradiance |
the kepler survey provides a statistical census of planetary systems out to the habitable zone. because most planets are non-transiting, orbital architectures are best estimated using simulated observations of ensemble populations. here, we introduce epos, the exoplanet population observation simulator, to estimate the prevalence and orbital architectures of multi-planet systems based on the latest kepler data release, dr25. we estimate that at least 42% of sun-like stars have nearly coplanar planetary systems with seven or more exoplanets. the fraction of stars with at least one planet within 1 au could be as high as 100% depending on assumptions about the distribution of single transiting planets. we estimate an occurrence rate of planets in the habitable zone around sun-like stars of η ⊕ = 36 ± 14%. the innermost planets in multi-planet systems are clustered around an orbital period of 10 days (0.1 au), reminiscent of the protoplanetary disk inner edge, or which could be explained by a planet trap at that location. only a small fraction of planetary systems have the innermost planet at long orbital periods, with fewer than ≈8% and ≈3% having no planet interior to the orbit of mercury and venus, respectively. these results reinforce the view that the solar system is not a typical planetary system, but an outlier among the distribution of known exoplanetary systems. we predict that at least half of the habitable zone exoplanets are accompanied by (non-transiting) planets at shorter orbital periods, hence knowledge of a close-in exoplanet could be used as a way to optimize the search for earth-size planets in the habitable zone with future direct imaging missions. | the exoplanet population observation simulator. i. the inner edges of planetary systems |
we study the rest-frame ultraviolet (uv) continuum slopes (β) of galaxies at redshifts 8 < z < 16 (⟨z⟩ = 10), using a combination of jwst ero and ers nircam imaging and ground-based near-infrared imaging of the cosmos field. the combination of jwst and ground-based imaging provides a wide baseline in both redshift and absolute uv magnitude (-22.6 < muv < -17.9), sufficient to allow a meaningful comparison to previous results at lower redshift. using a power-law fitting technique, we find that our full sample (median muv = -19.3 ± 1.3) returns an inverse-variance weighted mean value of ⟨β⟩ = -2.10 ± 0.05, with a corresponding median value of β = -2.29 ± 0.09. these values imply that the uv colours of galaxies at z > 8 are, on average, no bluer than the bluest galaxies in the local universe (e.g. ngc 1705; β = -2.46). we find evidence for a β - muv relation, such that brighter uv galaxies display redder uv slopes ($\rm {d}\beta / \rm {d} m_{\rm uv} = -0.17 \pm 0.05$). comparing to results at lower redshift, we find that the slope of our β - muv relation is consistent with the slope observed at z ≃ 5 and that, at a given muv, our 8 < z < 16 galaxies are bluer than their z ≃ 5 counterparts, with an inverse-variance weighted mean offset of ⟨δβ⟩ = -0.38 ± 0.09. we do not find strong evidence that any objects in our sample display ultra-blue uv continuum slopes (i.e. β ≲ -3) that would require their uv emission to be dominated by ultra-young, dust-free stellar populations with high lyman-continuum escape fractions. comparing our results to the predictions of theoretical galaxy formation models, we find that the galaxies in our sample are consistent with the young, metal-poor, and moderately dust-reddened galaxies expected at z > 8. | the ultraviolet continuum slopes (β) of galaxies at z ≃ 8-16 from jwst and ground-based near-infrared imaging |
there is a long-standing debate regarding the origin of the terrestrial planets' water as well as the hydrated c-type asteroids. here we show that the inner solar system's water is a simple byproduct of the giant planets' formation. giant planet cores accrete gas slowly until the conditions are met for a rapid phase of runaway growth. as a gas giant's mass rapidly increases, the orbits of nearby planetesimals are destabilized and gravitationally scattered in all directions. under the action of aerodynamic gas drag, a fraction of scattered planetesimals are deposited onto stable orbits interior to jupiter's. this process is effective in populating the outer main belt with c-type asteroids that originated from a broad (5-20 au-wide) region of the disk. as the disk starts to dissipate, scattered planetesimals reach sufficiently eccentric orbits to cross the terrestrial planet region and deliver water to the growing earth. this mechanism does not depend strongly on the giant planets' orbital migration history and is generic: whenever a giant planet forms it invariably pollutes its inner planetary system with water-rich bodies. | origin of water in the inner solar system: planetesimals scattered inward during jupiter and saturn's rapid gas accretion |
distant star-forming galaxies show a correlation between their star formation rates (sfrs) and stellar masses, and this has deep implications for galaxy formation. here, we present a study on the evolution of the slope and scatter of the sfr-stellar mass relation for galaxies at 3.5 <= z <= 6.5 using multi-wavelength photometry in goods-s from the cosmic assembly near-infrared deep extragalactic legacy survey (candels) and spitzer extended deep survey. we describe an updated, bayesian spectral-energy distribution fitting method that incorporates effects of nebular line emission, star formation histories that are constant or rising with time, and different dust-attenuation prescriptions (starburst and small magellanic cloud). from z = 6.5 to z = 3.5 star-forming galaxies in candels follow a nearly unevolving correlation between stellar mass and sfr that follows sfr ~ m_\star ^a with a =0.54 ± 0.16 at z ~ 6 and 0.70 ± 0.21 at z ~ 4. this evolution requires a star formation history that increases with decreasing redshift (on average, the sfrs of individual galaxies rise with time). the observed scatter in the sfr-stellar mass relation is tight, σ(log sfr/m ⊙ yr-1) < 0.3-0.4 dex, for galaxies with log m sstarf/m ⊙ > 9 dex. assuming that the sfr is tied to the net gas inflow rate (sfr ~ \dot{m}gas), then the scatter in the gas inflow rate is also smaller than 0.3-0.4 dex for star-forming galaxies in these stellar mass and redshift ranges, at least when averaged over the timescale of star formation. we further show that the implied star formation history of objects selected on the basis of their co-moving number densities is consistent with the evolution in the sfr-stellar mass relation. | the relation between star formation rate and stellar mass for galaxies at 3.5 <= z <= 6.5 in candels |
context. the astrometric discovery of sub-stellar mass companions orbiting stars is exceedingly hard due to the required sub-milliarcsecond precision, limiting the application of this technique to only a few instruments on a target-per-target basis and to the global astrometry space missions hipparcos and gaia. the third gaia data release (gaia dr3) includes the first gaia astrometric orbital solutions whose sensitivity in terms of estimated companion mass extends down to the planetary-mass regime.aims: we present the contribution of the exoplanet pipeline to the gaia dr3 sample of astrometric orbital solutions by describing the methods used for fitting the orbits, the identification of significant solutions, and their validation. we then present an overview of the statistical properties of the solution parameters.methods: using both a markov chain monte carlo and a genetic algorithm, we fitted the 34 months of gaia dr3 astrometric time series with a single keplerian astrometric-orbit model that had 12 free parameters and an additional jitter term, and retained the solutions with the lowest χ2. verification and validation steps were taken using significance tests, internal consistency checks using the gaia radial velocity measurements (when available), as well as literature radial velocity and astrometric data, leading to a subset of candidates that were labelled "validated".results: we determined astrometric-orbit solutions for 1162 sources, and 198 solutions were assigned the "validated" label. precise companion-mass estimates require external information and are presented elsewhere. to broadly categorise the different mass regimes in this paper, we use the pseudo-companion mass m̃c assuming a solar-mass host and define three solution groups: 17 (9 validated) solutions with companions in the planetary-mass regime (m̃c < 20 mj), 52 (29 validated) in the brown dwarf regime (20 mj ≤ m̃c ≤ 120 mj), and 1093 (160 validated) in the low-mass stellar companion regime (m̃c > 120 mj). from internal and external verification and validation, we estimate the level of spurious and incorrect solutions in our sample to be ∼5% and ∼10% in the `orbitalalternative' and `orbitaltargetedsearch' candidate sample, respectively.conclusions: we demonstrate that gaia is able to confirm and sometimes refine the orbits of known orbital companions and to identify new candidates, providing us with a positive outlook for the expected harvest from the full mission data in future data releases. tables refsols.dat, bd-18113.dat, 46_10046.dat, gj812a.dat, gj9732.dat, hd26596.dat, hd40503.dat, hd68638.dat, hd89010.dat, hd134237.dat, hd183162.dat, hip9095.dat, and toi-288.dat are only available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/674/a10 | gaia data release 3. astrometric orbit determination with markov chain monte carlo and genetic algorithms: systems with stellar, sub-stellar, and planetary mass companions |
high dust density in the midplane of protoplanetary disks is favorable for efficient grain growth and can allow fast formation of planetesimals and planets, before disks dissipate. vertical settling and dust trapping in pressure maxima are two mechanisms allowing dust to concentrate in geometrically thin and high-density regions. in this work, we aim to study these mechanisms in the highly inclined protoplanetary disk sstc2d j163131.2-242627 (oph 163131, i ~ 84°). we present new high-angular-resolution continuum and 12co alma observations of oph 163131. the gas emission appears significantly more extended in the vertical and radial direction compared to the dust emission, consistent with vertical settling and possibly radial drift. in addition, the new continuum observations reveal two clear rings. the outer ring, located at ~100 au, is well-resolved in the observations, allowing us to put stringent constraints on the vertical extent of millimeter dust particles. we model the disk using radiative transfer and find that the scale height of millimeter-sized grains is 0.5 au or less at 100 au from the central star. this value is about one order of magnitude smaller than the scale height of smaller micron-sized dust grains constrained by previous modeling, which implies that efficient settling of the large grains is occurring in the disk. when adopting a parametric dust settling prescription, we find that the observations are consistent with a turbulent viscosity coefficient of about α ≲ 10-5 at 100 au. finally, we find that the thin dust scale height measured in oph 163131 is favorable for planetary growth by pebble accretion: a 10 m e planet may grow within less than 10 myr, even in orbits exceeding 50 au. | a highly settled disk around oph163131 |
we constrain the intrinsic architecture of kepler planetary systems by modeling the observed multiplicities of the transiting planets (tranets) and their transit timing variations (ttvs). we robustly determine that the fraction of sun-like stars with kepler-like planets, η kepler, is 30 ± 3%. here, kepler-like planets are planets that have radii r p ≳ r ⊕ and orbital periods p < 400 days. our result thus significantly revises previous claims that more than 50% of sun-like stars have such planets. combined with the average number of kepler planets per star (∼0.9), we obtain that on average each planetary system has 3.0 ± 0.3 planets within 400 days. we also find that the dispersion in orbital inclinations of planets within a given planetary system, σi,k , is a steep function of its number of planets, k. this can be parameterized as {σ }i,k\propto {k}αand we find that -4 < α < -2 at the 2σ level. such a distribution well describes the observed multiplicities of both transits and ttvs with no excess of single-tranet systems. therefore we do not find evidence supporting the so-called “kepler dichotomy.” together with a previous study on orbital eccentricities, we now have a consistent picture: the fewer planets in a system, the hotter it is dynamically. we discuss briefly possible scenarios that lead to such a trend. despite our solar system not belonging to the kepler club, it is interesting to notice that the solar system also has three planets within 400 days and that the inclination dispersion is similar to kepler systems of the same multiplicity. | about 30% of sun-like stars have kepler-like planetary systems: a study of their intrinsic architecture |
context. gaia data and stellar surveys open the way to the construction of detailed 3d maps of the galactic interstellar (is) dust based on the synthesis of star distances and extinctions. dust maps are tools of broad use, also for gaia-related milky way studies.aims: reliable extinction measurements require very accurate photometric calibrations. we show the first step of an iterative process linking 3d dust maps and photometric calibrations, and improving them simultaneously.methods: our previous 3d map of nearby is dust was used to select low-reddening sdss/apogee-dr14 red giants, and this database served for an empirical effective temperature- and metallicity-dependent photometric calibration in the gaia g and 2mass ks bands. this calibration has been combined with gaia g-band empirical extinction coefficients recently published, g, j, and ks photometry and apogee atmospheric parameters to derive the extinction of a large fraction of the survey targets. distances were estimated independently using isochrones and the magnitude-independent extinction kj-ks. this new dataset has been merged with the one used for the earlier version of dust map. a new bayesian inversion of distance-extinction pairs has been performed to produce an updated 3d map.results: we present several properties of the new map. a comparison with 2d dust emission reveals that all large dust shells seen in emission at middle and high latitudes are closer than 300 pc. the updated distribution constrains the well-debated, x-ray bright north polar spur to originate beyond 800 pc. we use the orion region to illustrate additional details and distant clouds. on the large scale the map reveals a complex structure of the local arm. chains of clouds of 2-3 kpc in length appear in planes tilted by ≃15° with respect to the galactic plane. a series of cavities oriented along a l ≃ 60-240° axis crosses the arm.conclusions: the results illustrate the ongoing synergy between 3d mapping of is dust and stellar calibrations in the context of gaia. dust maps provide prior foregrounds for future calibrations appropriate to different target characteristics or ranges of extinction, allowing us in turn to increase extinction data and produce more detailed and extended maps. | three-dimensional maps of interstellar dust in the local arm: using gaia, 2mass, and apogee-dr14 |
nuclear matter and finite nuclei exhibit the property of superfluidity by forming cooper pairs. we review the microscopic theories and methods that are being employed to understand the basic properties of superfluid nuclear systems, with emphasis on the spatially extended matter encountered in neutron stars, supernova envelopes, and nuclear collisions. our survey of quantum many-body methods includes techniques that employ green functions, correlated basis functions, and monte carlo sampling of quantum states. with respect to empirical realizations of nucleonic and hadronic superfluids, this review is focused on progress that has been made toward quantitative understanding of their properties at the level of microscopic theories of pairing, with emphasis on the condensates that exist under conditions prevailing in neutron-star interiors. these include singlet s-wave pairing of neutrons in the inner crust, and, in the quantum fluid interior, singlet- s proton pairing and triplet coupled p- f-wave neutron pairing. additionally, calculations of weak-interaction rates in neutron-star superfluids within the green function formalism are examined in detail. we close with a discussion of quantum vortex states in nuclear systems and their dynamics in neutron-star superfluid interiors. | superfluidity in nuclear systems and neutron stars |
the density structure surrounding the iron core of a massive star when it dies is known to have a major effect on whether or not the star explodes. here we repeat previous surveys of presupernova evolution with some important corrections to code physics and four to 10 times better mass resolution in each star. the number of presupernova masses considered is also much larger. over 4000 models are calculated in the range from 12 to 60 m ⊙ with varying mass loss rates. the core structure is not greatly affected by the increased spatial resolution. the qualitative patterns of compactness measures and their extrema are the same, but with the increased number of models, the scatter seen in previous studies is replaced by several localized branches. more physics-based analyses by ertl et al. and müller et al. show these branches with less scatter than the single-parameter characterization of o’connor & ott. these branches are particularly apparent for stars in the mass ranges 14-19 and 22-24 m ⊙. the multivalued solutions are a consequence of interference between several carbon- and oxygen-burning shells during the late stages of evolution. for a relevant range of masses, whether a star explodes or not may reflect the small, almost random differences in its late evolution more than its initial mass. the large number of models allows statistically meaningful statements about the radius, luminosity, and effective temperatures of presupernova stars, their core structures, and their remnant mass distributions. | a high-resolution study of presupernova core structure |
radio observations of tidal disruption events (tdes) probe material ejected by the disruption of stars by supermassive black holes (smbhs), uniquely tracing the formation and evolution of jets and outflows, revealing details of the disruption hydrodynamics, and illuminating the environments around previously-dormant smbhs. to date, observations reveal a surprisingly diverse population. a small fraction of tdes (at most a few percent) have been observed to produce radio-luminous mildly relativistic jets. the remainder of the population are radio quiet, producing less luminous jets, non-relativistic outflows or, possibly, no radio emission at all. here, we review the radio observations that have been made of tdes to date and discuss possible explanations for their properties, focusing on detected sources and, in particular, on the two best-studied events: sw j1644+57 and asassn-14li. we also discuss what we have learned about the host galaxies of tdes from radio observations and review constraints on the rates of bright and faint radio outflows in tdes. upcoming x-ray, optical, near-ir, and radio surveys will greatly expand the sample of tdes, and technological advances open the exciting possibility of discovering a sample of tdes in the radio band unbiased by host galaxy extinction. | radio properties of tidal disruption events |
mapping nearby galaxies at apache point observatory (manga), one of three core programs in the sloan digital sky survey-iv, is an integral-field spectroscopic survey of roughly 10,000 nearby galaxies. it employs dithered observations using 17 hexagonal bundles of 2″ fibers to obtain resolved spectroscopy over a wide wavelength range of 3600-10300 å. to map the internal variations within each galaxy, we need to perform accurate spectral surface photometry, which is to calibrate the specific intensity at every spatial location sampled by each individual aperture element of the integral field unit. the calibration must correct only for the flux loss due to atmospheric throughput and the instrument response, but not for losses due to the finite geometry of the fiber aperture. this requires the use of standard star measurements to strictly separate these two flux loss factors (throughput versus geometry), a difficult challenge with standard single-fiber spectroscopy techniques due to various practical limitations. therefore, we developed a technique for spectral surface photometry using multiple small fiber-bundles targeting standard stars simultaneously with galaxy observations. we discuss the principles of our approach and how they compare to previous efforts, and we demonstrate the precision and accuracy achieved. manga's relative calibration between the wavelengths of hα and hβ has an rms of 1.7%, while that between [n ii] λ6583 and [o ii] λ3727 has an rms of 4.7%. using extinction-corrected star formation rates and gas-phase metallicities as an illustration, this level of precision guarantees that flux calibration errors will be sub-dominant when estimating these quantities. the absolute calibration is better than 5% for more than 89% of manga's wavelength range. | sdss-iv/manga: spectrophotometric calibration technique |
we have entered a new era where integral-field spectroscopic surveys of galaxies are sufficiently large to adequately sample large-scale structure over a cosmologically significant volume. this was the primary design goal of the sami galaxy survey. here, in data release 3, we release data for the full sample of 3068 unique galaxies observed. this includes the sami cluster sample of 888 unique galaxies for the first time. for each galaxy, there are two primary spectral cubes covering the blue (370-570 nm) and red (630-740 nm) optical wavelength ranges at spectral resolving power of r = 1808 and 4304, respectively. for each primary cube, we also provide three spatially binned spectral cubes and a set of standardized aperture spectra. for each galaxy, we include complete 2d maps from parametrized fitting to the emission-line and absorption-line spectral data. these maps provide information on the gas ionization and kinematics, stellar kinematics and populations, and more. all data are available online through australian astronomical optics data central. | the sami galaxy survey: the third and final data release |
outflows from accreting, rotating, and magnetized systems are ubiquitous. protostellar outflows can be observed from radio to x-ray wavelengths in the continuum and a multitude of spectral lines that probe a wide range of physical conditions, chemical phases, radial velocities, and proper motions. wide-field visual and near-ir data, mid-ir observations from space, and aperture synthesis with centimeter- and millimeterwave interferometers are revolutionizing outflow studies. many outflows originate in multiple systems and clusters. although most flows are bipolar and some contain highly collimated jets, others are wide-angle winds, and a few are nearly isotropic and exhibit explosive behavior. morphologies and velocity fields indicate variations in ejection velocity, mass-loss rate, and in some cases, flow orientation and degree of collimation. these trends indicate that stellar accretion is episodic and often occurs in a complex dynamical environment. outflow power increases with source luminosity but decreases with evolutionary stage. the youngest outflows are small and best traced by molecules such as co, sio, h2o, and h2. older outflows can grow to parsec scales and are best traced by shock-excited atoms and ions such as hydrogen-recombination lines, [sii], and [oii]. outflows inject momentum and energy into their surroundings and provide an important mechanism in the self-regulation of star formation. however, momentum injection rates remain uncertain with estimates providing lower bounds. | protostellar outflows |
some of the heavy elements, such as gold and europium (eu), are almost exclusively formed by the rapid neutron capture process (r-process). however, it is still unclear which astrophysical site between core-collapse supernovae and neutron star-neutron star (ns-ns) mergers produced most of the r-process elements in the universe. galactic chemical evolution (gce) models can test these scenarios by quantifying the frequency and yields required to reproduce the amount of europium (eu) observed in galaxies. although ns-ns mergers have become popular candidates, their required frequency (or rate) needs to be consistent with that obtained from gravitational wave measurements. here, we address the first ns-ns merger detected by ligo/virgo (gw170817) and its associated gamma-ray burst and analyze their implication for the origin of r-process elements. the range of ns-ns merger rate densities of 320-4740 gpc-3 yr-1 provided by ligo/virgo is remarkably consistent with the range required by gce to explain the eu abundances in the milky way with ns-ns mergers, assuming the solar r-process abundance pattern for the ejecta. under the same assumption, this event has produced about 1-5 earth masses of eu, and 3-13 earth masses of gold. when using theoretical calculations to derive eu yields, constraining the role of ns-ns mergers becomes more challenging because of nuclear astrophysics uncertainties. this is the first study that directly combines nuclear physics uncertainties with gce calculations. if gw170817 is a representative event, ns-ns mergers can produce eu in sufficient amounts and are likely to be the main r-process site. | the origin of r-process elements in the milky way |
since more than 70 years ago, the colours of galaxies derived from flux measurements at different wavelengths have been used to estimate their cosmological distances. such distance measurements, called photometric redshifts, are necessary for many scientific projects, ranging from investigations of the formation and evolution of galaxies and active galactic nuclei to precision cosmology. the primary benefit of photometric redshifts is that distance estimates can be obtained relatively cheaply for all sources detected in photometric images. the drawback is that these cheap estimates have low precision compared with resource-expensive spectroscopic ones. the methodology for estimating redshifts has been through several revolutions in recent decades, triggered by increasingly stringent requirements on the photometric redshift accuracy. here, we review the various techniques for obtaining photometric redshifts, from template-fitting to machine learning and hybrid schemes. we also describe state-of-the-art results on current extragalactic samples and explain how survey strategy choices affect redshift accuracy. we close with a description of the photometric redshift efforts planned for upcoming wide-field surveys, which will collect data on billions of galaxies, aiming to investigate, among other matters, the stellar mass assembly and the nature of dark energy. | the many flavours of photometric redshifts |
the detailed observations of gw170817 proved for the first time directly that neutron star mergers are a major production site of heavy elements. the observations could be fit by a number of simulations that qualitatively agree, but can quantitatively differ (e.g., in total r-process mass) by an order of magnitude. we categorize kilonova ejecta into several typical morphologies motivated by numerical simulations, and apply a radiative transfer monte carlo code to study how the geometric distribution of the ejecta shapes the emitted radiation. we find major impacts on both spectra and light curves. the peak bolometric luminosity can vary by two orders of magnitude and the timing of its peak by a factor of five. these findings provide the crucial implication that the ejecta masses inferred from observations around the peak brightness are uncertain by at least an order of magnitude. mixed two-component models with lanthanide-rich ejecta are particularly sensitive to geometric distribution. a subset of mixed models shows very strong viewing angle dependence due to lanthanide "curtaining," which persists even if the relative mass of lanthanide-rich component is small. the angular dependence is weak in the rest of our models, but different geometric combinations of the two components lead to a highly diverse set of light curves. we identify geometry-dependent p cygni features in late spectra that directly map out strong lines in the simulated opacity of neodymium, which can help to constrain the ejecta geometry and to directly probe the r-process abundances. | axisymmetric radiative transfer models of kilonovae |
six gravitational wave detections have been reported so far, providing crucial insights on the merger rate of double compact objects. we investigate the cosmic merger rate of double neutron stars (dnss), neutron star black hole binaries (nsbhs), and black hole binaries (bhbs) by means of population-synthesis simulations coupled with the illustris cosmological simulation. we have performed six different simulations, considering different assumptions for the efficiency of common envelope (ce) ejection and exploring two distributions for the supernova (sn) kicks. the current bhb merger rate derived from our simulations spans from ∼150 to ∼240 gpc-3 yr-1 and is only mildly dependent on ce efficiency. in contrast, the current merger rates of dnss (ranging from ∼20 to ∼600 gpc-3 yr-1) and nsbhs (ranging from ∼10 to ∼100 gpc-3 yr-1) strongly depend on the assumptions on ce and natal kicks. the merger rate of dnss is consistent with the one inferred from the detection of gw170817 only if a high efficiency of ce ejection and low-sn kicks (drawn from a maxwellian distribution with one-dimensional root mean square σ = 15 km s-1) are assumed. | the cosmic merger rate of neutron stars and black holes |
motivated by the recent discovery of a compact object with mass in the range 2.5-2.67 m⊙ in the binary merger gw190814, we revisit the question of the maximum mass of neutron stars (nss). we use a markov chain monte carlo approach to generate about two million phenomenological equations of state with and without first-order phase transitions. we fix the crust equation of state and only assume causality at higher densities. we show how a strict upper bound on the maximum ns mass can be inferred from upcoming observation of ns radii and masses. the derived upper bounds depend only on relativity and causality, so it is not affected by nuclear physics uncertainties. we show how a lower limit on the maximum mass of nss, in combination with upcoming measurements of ns radii by ligo/virgo and nicer, would constrain the equation of state of dense matter. finally, we discuss the implications for gw190814. | on the maximum mass of neutron stars and gw190814 |
context. reliable predictions of mass-loss rates are important for massive-star evolution computations.aims: we aim to provide predictions for mass-loss rates and wind-momentum rates of o-type stars, while carefully studying the behaviour of these winds as functions of stellar parameters, such as luminosity and metallicity.methods: we used newly developed steady-state models of radiation-driven winds to compute the global properties of a grid of o-stars. the self-consistent models were calculated by means of an iterative solution to the equation of motion using full non-local thermodynamic equilibrium radiative transfer in the co-moving frame to compute the radiative acceleration. in order to study winds in different galactic environments, the grid covers main-sequence stars, giants, and supergiants in the galaxy and both magellanic clouds.results: we find a strong dependence of mass-loss on both luminosity and metallicity. mean values across the grid are ṁ~l*2.2 and ṁ~l*0.95; however, we also find a somewhat stronger dependence on metallicity for lower luminosities. similarly, the mass loss-luminosity relation is somewhat steeper for the small magellanic cloud (smc) than for the galaxy. in addition, the computed rates are systematically lower (by a factor 2 and more) than those commonly used in stellar-evolution calculations. overall, our results are in good agreement with observations in the galaxy that properly account for wind-clumping, with empirical ṁ versus z* scaling relations and with observations of o-dwarfs in the smc.conclusions: our results provide simple fit relations for mass-loss rates and wind momenta of massive o-stars stars as functions of luminosity and metallicity, which are valid in the range teff = 28 000-45 000 k. due to the systematically lower values for ṁ, our new models suggest that new rates might be needed in evolution simulations of massive stars. | new predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars. ii. a grid of o-type stars in the galaxy and the magellanic clouds |
kilonova spectra imprint valuable information about the elements synthesized in neutron star mergers. in at2017gfo, the kilonova associated with gw170817, the spectroscopic feature centered around 8000 angstroms has been interpreted as the p-cygni profile arising from singly ionized strontium. recently, perego et al. (2022) suggested that helium 10833 line can be an alternative explanation of the feature. here, we study the line features under non-local thermodynamic equilibrium. we find that the ionization of ejecta by the stopping of radioactive decay product can significantly enhance the ionization states around the line forming region. we compute the kilonova spectrum under the assumption of spherical symmetry and uniform elemental fraction in the line-forming region. we find that 0.2\% (in mass) of helium in the ejecta can reproduce the p-cygni feature in the observed spectrum at $1.43$ -- $4.40$ days. strontium with a mass fraction of $1\%$ is also able to make the absorption feature at $\sim 1.5\,$days, but it gets weaker with time due to ionization by radioactive decay products. the strength of the he line signature depends sensitively on uv strength for the first two epochs. further modeling of uv line blanketing by $r$-process elements and the optical properties of light $r$-process elements would be crucial to distinguish between helium and strontium features. the mass fraction of he is a good indicator for ejecta entropy that allows us to probe the mass ejection mechanism. | non-lte analysis for helium and strontium lines in the kilonova at2017gfo |
clear windows onto emergent hadron mass (ehm) and modulations thereof by higgs boson interactions are provided by observable measures of pion and kaon structure, many of which are accessible via generalised parton distributions (gpds). beginning with algebraic gpd ansätze, constrained entirely by hadron-scale $\pi$ and k valence-parton distribution functions (dfs), in whose forms both ehm and higgs boson influences are manifest, numerous illustrations are provided. they include the properties of electromagnetic form factors, impact parameter space gpds, gravitational form factors and associated pressure profiles, and the character and consequences of all-orders evolution. the analyses predict that mass-squared gravitational form factors are stiffer than electromagnetic form factors; reveal that k pressure profiles are tighter than $\pi$ profiles, with both mesons sustaining near-core pressures at magnitudes similar to that expected at the core of neutron stars; deliver parameter-free predictions for $\pi$ and k valence, glue, and sea gpds at the resolving scale $\zeta=2\,$ gev; and predict that at this scale the fraction of meson mass-squared carried by glue and sea combined matches that lodged with the valence degrees-of-freedom, with a similar statement holding for mass-squared radii. *supported by national natural science foundation of china (12135007, 11805097); jiangsu provincial natural science foundation of china (bk20180323); spanish ministry of science and innovation (micinn) (pid2019-107844gb-c22); junta de andalucía (p18-fr-5057, uhu-1264517); and university of huelva (epit-2019) | revealing pion and kaon structure via generalised parton distributions |
we apply novel, recently developed plasma ray-tracing techniques to model the propagation of radio photons produced by axion dark matter in neutron star magnetospheres and combine this with both archival and new data for the galactic center magnetar psr j1745-2900. the emission direction to the observer and the magnetic orientation are not constrained for this object leading to parametric uncertainty. our analysis reveals that ray-tracing greatly reduces the signal sensitivity to this uncertainty, contrary to previous calculations where there was no emission at all in some directions. based on a goldreich-julian (gj) model for the magnetosphere and a navarro-frenk-white model for axion density in the galactic center, we obtain the most robust limits on the axion-photon coupling, to date. these are comparable to those from the cast solar axion experiment in the mass range ∼4.2 - 60 μ ev . if the dark matter density is larger, as might predicted by a "spike" model, the limits could be much stronger. for a fixed gj magnetosphere model, we conclude that of the two principle uncertainties considered in this work—observing angle and dark matter density—the latter is the larger of the two in our present calculations. | towards robust constraints on axion dark matter using psr j1745-2900 |
we present a much improved equation of state for neutron star matter, qhc19, with a smooth crossover from the hadronic regime at lower densities to the quark regime at higher densities. we now use the togashi et al. equation of state, a generalization of the akmal-pandharipande-ravenhall equation of state of uniform nuclear matter, in the entire hadronic regime; the togashi equation of state consistently describes nonuniform as well as uniform matter, and matter at beta equilibrium without the need for an interpolation between pure neutron and symmetric nuclear matter. we describe the quark matter regime at higher densities with the nambu-jona-lasinio model, now identifying tight constraints on the phenomenological universal vector repulsion between quarks and the pairing interaction between quarks arising from the requirements of thermodynamic stability and causal propagation of sound. the resultant neutron star properties agree very well with the inferences of the ligo/virgo collaboration, from gw170817, of the pressure versus baryon density, neutron star radii, and tidal deformabilities. the maximum neutron star mass allowed by qhc19 is 2.35 m ⊙, consistent with all neutron star mass determinations. | new neutron star equation of state with quark-hadron crossover |
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