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we present a combined analysis of rest-frame far-uv (fuv; 1000-2000 å) and rest-frame optical (3600-7000 å) composite spectra formed from very deep keck/lris and keck/mosfire observations of a sample of 30 star-forming galaxies with z=2.40+/- 0.11, selected to be broadly representative of the full kbss-mosfire spectroscopic survey. since the same massive stars are responsible for the observed fuv continuum and for the excitation of the observed nebular emission, a self-consistent stellar population synthesis model should simultaneously match the details of the fuv stellar+nebular continuum and—when inserted as the excitation source in photoionization models—predict all observed nebular emission line ratios. we find that only models including massive star binaries, having low stellar metallicity ({z}* /{z}⊙ ≃ 0.1) but relatively high nebular (ionized gas-phase) abundances ({z}{{neb}}/{z}⊙ ≃ 0.5), can successfully match all of the observational constraints. we show that this apparent discrepancy is naturally explained by highly super-solar o/fe (≃ 4{--}5 {({{o}}/{fe})}⊙ ), expected for a gas whose enrichment is dominated by the products of core-collapse supernovae. while o dominates the physics of the ionized gas (and thus the nebular emission lines), fe dominates the extreme-uv (euv) and fuv opacity and controls the mass-loss rate from massive stars, resulting in particularly dramatic effects for massive stars in binary systems. this high nebular excitation—caused by the hard euv spectra of fe-poor massive stars—is much more common at high redshift (z≳ 2) than low redshift due to systematic differences in the star formation history of typical galaxies. 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. | reconciling the stellar and nebular spectra of high-redshift galaxies |
ultrahot giant exoplanets receive thousands of times earth's insolation1,2. their high-temperature atmospheres (greater than 2,000 kelvin) are ideal laboratories for studying extreme planetary climates and chemistry3-5. daysides are predicted to be cloud-free, dominated by atomic species6 and much hotter than nightsides5,7,8. atoms are expected to recombine into molecules over the nightside9, resulting in different day and night chemistries. although metallic elements and a large temperature contrast have been observed10-14, no chemical gradient has been measured across the surface of such an exoplanet. different atmospheric chemistry between the day-to-night (`evening') and night-to-day (`morning') terminators could, however, be revealed as an asymmetric absorption signature during transit4,7,15. here we report the detection of an asymmetric atmospheric signature in the ultrahot exoplanet wasp-76b. we spectrally and temporally resolve this signature using a combination of high-dispersion spectroscopy with a large photon-collecting area. the absorption signal, attributed to neutral iron, is blueshifted by -11 ± 0.7 kilometres per second on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside16. in contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. we conclude that iron must therefore condense during its journey across the nightside. | nightside condensation of iron in an ultrahot giant exoplanet |
pds 70 is a unique system in which two protoplanets, pds 70 b and c, have been discovered within the dust-depleted cavity of their disk, at ~22 and 34 au, respectively, by direct imaging at infrared wavelengths. subsequent detection of the planets in the hα line indicates that they are still accreting material through circumplanetary disks. in this letter, we present new atacama large millimeter/submillimeter array (alma) observations of the dust continuum emission at 855 μm at high angular resolution (~20 mas, 2.3 au) that aim to resolve the circumplanetary disks and constrain their dust masses. our observations confirm the presence of a compact source of emission co-located with pds 70 c, spatially separated from the circumstellar disk and less extended than ~1.2 au in radius, a value close to the expected truncation radius of the circumplanetary disk at a third of the hill radius. the emission around pds 70 c has a peak intensity of ~86 ± 16 μjy beam-1, which corresponds to a dust mass of ~0.031 m⊕ or ~0.007 m⊕, assuming that it is only constituted of 1 μm or 1 mm sized grains, respectively. we also detect extended, low surface brightness continuum emission within the cavity near pds 70 b. we observe an optically thin inner disk within 18 au of the star with an emission that could result from small micron-sized grains transported from the outer disk through the orbits of b and c. in addition, we find that the outer disk resolves into a narrow and bright ring with a faint inner shoulder. | a circumplanetary disk around pds70c |
we present new alma observations and physical properties of a lyman break galaxy at z = 7.15. our target, b14-65666, has a bright ultra-violet (uv) absolute magnitude, muv ≈ -22.4, and has been spectroscopically identified in lyα with a small rest-frame equivalent width of ≈4 å. a previous hubble space telescope (hst) image has shown that the target is composed of two spatially separated clumps in the rest-frame uv. with alma, we have newly detected spatially resolved [o iii] 88 μm, [c ii] 158 μm, and their underlying dust continuum emission. in the whole system of b14-65666, the [o iii] and [c ii] lines have consistent redshifts of 7.1520 ± 0.0003, and the [o iii] luminosity, (34.4 ± 4.1) × 108 l⊙, is about three times higher than the [c ii] luminosity, (11.0 ± 1.4) × 108 l⊙. with our two continuum flux densities, the dust temperature is constrained to be td ≈ 50-60 k under the assumption of a dust emissivity index of βd = 2.0-1.5, leading to a large total infrared luminosity of ltir ≈ 1 × 1012 l⊙. owing to our high spatial resolution data, we show that the [o iii] and [c ii] emission can be spatially decomposed into two clumps associated with the two rest-frame uv clumps whose spectra are kinematically separated by ≈200 km s-1. we also find these two clumps have comparable uv, infrared, [o iii], and [c ii] luminosities. based on these results, we argue that b14-65666 is a starburst galaxy induced by a major merger. the merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), ssfr = 260^{+119}_{-57}gyr-1, inferred from our sed fitting. probably, a strong uv radiation field caused by intense star formation contributes to its high dust temperature and the [o iii]-to-[c ii] luminosity ratio. | big three dragons: a z = 7.15 lyman-break galaxy detected in [o iii] 88 μm, [c ii] 158 μm, and dust continuum with alma |
extreme climatic events have recently impacted marine ecosystems around the world, including foundation species such as corals and kelps. here, we describe the rapid climate-driven catastrophic shift in 2014 from a previously robust kelp forest to unproductive large scale urchin barrens in northern california. bull kelp canopy was reduced by >90% along more than 350 km of coastline. twenty years of kelp ecosystem surveys reveal the timing and magnitude of events, including mass mortalities of sea stars (2013-), intense ocean warming (2014-2017), and sea urchin barrens (2015-). multiple stressors led to the unprecedented and long-lasting decline of the kelp forest. kelp deforestation triggered mass (80%) abalone mortality (2017) resulting in the closure in 2018 of the recreational abalone fishery worth an estimated 44 m and the collapse of the north coast commercial red sea urchin fishery (2015-) worth 3 m. key questions remain such as the relative roles of ocean warming and sea star disease in the massive purple sea urchin population increase. science and policy will need to partner to better understand drivers, build climate-resilient fisheries and kelp forest recovery strategies in order to restore essential kelp forest ecosystem services. | marine heat wave and multiple stressors tip bull kelp forest to sea urchin barrens |
we present the extended galex arecibo sdss survey (xgass), a gas fraction-limited census of the atomic hydrogen (h i) gas content of 1179 galaxies selected only by stellar mass (m⋆ = 109-1011.5 m⊙) and redshift (0.01 < z < 0.05). this includes new arecibo observations of 208 galaxies, for which we release catalogues and h i spectra. in addition to extending the gass h i scaling relations by one decade in stellar mass, we quantify total (atomic+molecular) cold gas fractions and molecular-to-atomic gas mass ratios, rmol, for the subset of 477 galaxies observed with the iram 30 m telescope. we find that atomic gas fractions keep increasing with decreasing stellar mass, with no sign of a plateau down to log m⋆/m⊙ = 9. total gas reservoirs remain h i-dominated across our full stellar mass range, hence total gas fraction scaling relations closely resemble atomic ones, but with a scatter that strongly correlates with rmol, especially at fixed specific star formation rate. on average, rmol weakly increases with stellar mass and stellar surface density μ⋆, but individual values vary by almost two orders of magnitude at fixed m⋆ or μ⋆. we show that, for galaxies on the star-forming sequence, variations of rmol are mostly driven by changes of the h i reservoirs, with a clear dependence on μ⋆. establishing if galaxy mass or structure plays the most important role in regulating the cold gas content of galaxies requires an accurate separation of bulge and disc components for the study of gas scaling relations. | xgass: total cold gas scaling relations and molecular-to-atomic gas ratios of galaxies in the local universe |
we use sedz* -- a code designed to chart star formation histories (sfhs) of 6<z<12 galaxies -- to analyze the seds of 894 galaxies with deep jwst/nircam imaging by jades in the goods-s field. we show how sedz* matches observed seds using stellar-population templates, graphing the contribution of each epoch-by-epoch to confirm the robustness of the technique. very good sed fits for most sfhs demonstrates the compatibility of the templates with stars in the first galaxies -- as expected, because their light is primarily from main-sequence a-stars, free of post-main-sequence complexity and insensitive to heavy-element compositions. we confirm earlier results from dressler(2023): (1) four types of star formation histories: sfh1 -- burst; sfh2 -- stochastic; sfh3 -- `contiguous' (3-epochs); and sfh4 -- `continuous' (4-6 epochs); (2) starbursts -- both single and multiple -- are predominate (~70%) in this critical period of cosmic history, although longer sfhs (0.5-1.0 gyr) contribute one-third of the accumulated stellar mass. these 894 sfhs contribute log m/msun = 11.14, 11.09, 11.00, and 10.60 for sfh1-4, respectively, adding up to 4x10^11 msun by z=6 for this field. we suggest that the absence of rising sfhs could be explained as an intense dust-enshrouded phase of star formation lasting tens of myr that preceded each of the sfhs we measure. we find no strong dependencies of sfh type with the large-scale environment, however, the discovery of a compact group of 30 galaxies, 11 of which had first star formation at z=11-12, suggests that long sfhs could dominate in rare, dense environments. | building the first galaxies -- chapter 2. starbursts dominate the star formation histories of 6 < z <12 galaxies |
context. after years of scientific progress, the origin of stellar binary black holes is still a great mystery. several formation channels for merging black holes have been proposed in the literature. as more merger detections are expected with future gravitational-wave observations, population synthesis studies can help to distinguish between them.aims: we study the formation of coalescing binary black holes via the evolution of isolated field binaries that go through the common envelope phase in order to obtain the combined distributions of observables such as black-hole spins, masses and cosmological redshifts of mergers.methods: to achieve this aim, we used a hybrid technique that combines the parametric binary population synthesis code compas with detailed binary evolution simulations performed with the mesa code. we then convolved our binary evolution calculations with the redshift- and metallicity-dependent star-formation rate and the selection effects of gravitational-wave detectors to obtain predictions of observable properties.results: by assuming efficient angular momentum transport, we are able to present a model that is capable of simultaneously predicting the following three main gravitational-wave observables: the effective inspiral spin parameter χeff, the chirp mass mchirp and the cosmological redshift of merger zmerger. we find an excellent agreement between our model and the ten events from the first two advanced detector observing runs. we make predictions for the third observing run o3 and for advanced ligo design sensitivity. we expect approximately 80% of events with χeff < 0.1, while the remaining 20% of events with χeff ≥ 0.1 are split into ∼10% with mchirp < 15 m⊙ and ∼10% with mchirp ≥ 15 m⊙. moreover, we find that mchirp and χeff distributions are very weakly dependent on the detector sensitivity.conclusions: the favorable comparison of the existing ligo/virgo observations with our model predictions gives support to the idea that the majority, if not all of the observed mergers, originate from the evolution of isolated binaries. the first-born black hole has negligible spin because it lost its envelope after it expanded to become a giant star, while the spin of the second-born black hole is determined by the tidal spin up of its naked helium star progenitor by the first-born black hole companion after the binary finished the common-envelope phase. | the origin of spin in binary black holes. predicting the distributions of the main observables of advanced ligo |
we describe the sample design for the sdss-iv manga survey and present the final properties of the main samples along with important considerations for using these samples for science. our target selection criteria were developed while simultaneously optimizing the size distribution of the manga integral field units (ifus), the ifu allocation strategy, and the target density to produce a survey defined in terms of maximizing signal-to-noise ratio, spatial resolution, and sample size. our selection strategy makes use of redshift limits that only depend on i-band absolute magnitude (mi ), or, for a small subset of our sample, miand color (nuv - i). such a strategy ensures that all galaxies span the same range in angular size irrespective of luminosity and are therefore covered evenly by the adopted range of ifu sizes. we define three samples: the primary and secondary samples are selected to have a flat number density with respect to miand are targeted to have spectroscopic coverage to 1.5 and 2.5 effective radii (re ), respectively. the color-enhanced supplement increases the number of galaxies in the low-density regions of color-magnitude space by extending the redshift limits of the primary sample in the appropriate color bins. the samples cover the stellar mass range 5× {10}8≤slant {m}* ≤slant 3× {10}11 {m}⊙{h}-2 and are sampled at median physical resolutions of 1.37 and 2.5 kpc for the primary and secondary samples, respectively. we provide weights that will statistically correct for our luminosity and color-dependent selection function and ifu allocation strategy, thus correcting the observed sample to a volume-limited sample. | the sdss-iv manga sample: design, optimization, and usage considerations |
we analyze pre-explosion near- and mid-infrared (ir) imaging of the site of sn 2023ixf in the nearby spiral galaxy m101 and characterize the candidate progenitor star. the star displays compelling evidence of variability with a possible period of ≈1000 days and an amplitude of δm ≈ 0.6 mag in extensive monitoring with the spitzer space telescope since 2004, likely indicative of radial pulsations. variability consistent with this period is also seen in the near-ir j and ksbands between 2010 and 2023, up to just 10 days before the explosion. beyond the periodic variability, we do not find evidence for any ir-bright pre-supernova outbursts in this time period. the ir brightness ( ${m}_{{k}_{s}}=-10.7$ mag) and color (j - ks= 1.6 mag) of the star suggest a luminous and dusty red supergiant. modeling of the phase-averaged spectral energy distribution (sed) yields constraints on the stellar temperature ( ${t}_{\mathrm{eff}}={3500}_{-1400}^{+800}$ k) and luminosity ( $\mathrm{log}l/{l}_{\odot }=5.1\pm 0.2$ ). this places the candidate among the most luminous type ii supernova progenitors with direct imaging constraints, with the caveat that many of these rely only on optical measurements. comparison with stellar evolution models gives an initial mass of m init = 17 ± 4 m ⊙. we estimate the pre-supernova mass-loss rate of the star between 3 and 19 yr before explosion from the sed modeling at $\dot{m}\approx 3\times {10}^{-5}$ to 3 × 10-4 m ⊙ yr-1 for an assumed wind velocity of vw= 10 km s-1, perhaps pointing to enhanced mass loss in a pulsation-driven wind. | a luminous red supergiant and dusty long-period variable progenitor for sn 2023ixf |
in this white paper, we present an experimental road map for spectroscopic experiments beyond desi. desi will be a transformative cosmological survey in the 2020s, mapping 40 million galaxies and quasars and capturing a significant fraction of the available linear modes up to z=1.2. desi-ii will pilot observations of galaxies both at much higher densities and extending to higher redshifts. a stage-5 experiment would build out those high-density and high-redshift observations, mapping hundreds of millions of stars and galaxies in three dimensions, to address the problems of inflation, dark energy, light relativistic species, and dark matter. these spectroscopic data will also complement the next generation of weak lensing, line intensity mapping and cmb experiments and allow them to reach their full potential. | a spectroscopic road map for cosmic frontier: desi, desi-ii, stage-5 |
we present astrophysical false positive probability calculations for every kepler object of interest (koi)—the first large-scale demonstration of a fully automated transiting planet validation procedure. out of 7056 kois, we determine that 1935 have probabilities <1% of being astrophysical false positives, and thus may be considered validated planets. of these, 1284 have not yet been validated or confirmed by other methods. in addition, we identify 428 kois that are likely to be false positives, but have not yet been identified as such, though some of these may be a result of unidentified transit timing variations. a side product of these calculations is full stellar property posterior samplings for every host star, modeled as single, binary, and triple systems. these calculations use vespa, a publicly available python package that is able to be easily applied to any transiting exoplanet candidate. | false positive probabilities for all kepler objects of interest: 1284 newly validated planets and 428 likely false positives |
we have conducted a survey of 328 protostars in the orion molecular clouds with the atacama large millimeter/submillimeter array at 0.87 mm at a resolution of ∼0"1 (40 au), including observations with the very large array at 9 mm toward 148 protostars at a resolution of ∼0"08 (32 au). this is the largest multiwavelength survey of protostars at this resolution by an order of magnitude. we use the dust continuum emission at 0.87 and 9 mm to measure the dust disk radii and masses toward the class 0, class i, and flat-spectrum protostars, characterizing the evolution of these disk properties in the protostellar phase. the mean dust disk radii for the class 0, class i, and flat-spectrum protostars are ${44.9}_{-3.4}^{+5.8}$ , ${37.0}_{-3.0}^{+4.9}$ , and ${28.5}_{-2.3}^{+3.7}$ au, respectively, and the mean protostellar dust disk masses are 25.9 ${}_{-4.0}^{+7.7}$ , ${14.9}_{-2.2}^{+3.8}$ , ${11.6}_{-1.9}^{+3.5}$ ${m}_{\oplus }$ , respectively. the decrease in dust disk masses is expected from disk evolution and accretion, but the decrease in disk radii may point to the initial conditions of star formation not leading to the systematic growth of disk radii or that radial drift is keeping the dust disk sizes small. at least 146 protostellar disks (35% of 379 detected 0.87 mm continuum sources plus 42 nondetections) have disk radii greater than 50 au in our sample. these properties are not found to vary significantly between different regions within orion. the protostellar dust disk mass distributions are systematically larger than those of class ii disks by a factor of >4, providing evidence that the cores of giant planets may need to at least begin their formation during the protostellar phase. | the vla/alma nascent disk and multiplicity (vandam) survey of orion protostars. ii. a statistical characterization of class 0 and class i protostellar disks |
we report discovery of a bright, nearby ($g = 13.8;\, \, d = 480\, \rm pc$) sun-like star orbiting a dark object. we identified the system as a black hole candidate via its astrometric orbital solution from the gaia mission. radial velocities validated and refined the gaia solution, and spectroscopy ruled out significant light contributions from another star. joint modelling of radial velocities and astrometry constrains the companion mass of $m_2 = 9.62\pm 0.18\, \mathrm{m}_{\odot }$. the spectroscopic orbit alone sets a minimum companion mass of $m_2\gt 5\, \mathrm{m}_{\odot }$; if the companion were a $5\, \mathrm{m}_{\odot }$ star, it would be 500 times more luminous than the entire system. these constraints are insensitive to the mass of the luminous star, which appears as a slowly rotating g dwarf ($t_{\rm eff}=5850\, \rm k$, log g = 4.5, $m=0.93\, \mathrm{m}_{\odot }$), with near-solar metallicity ($\rm [fe/h] = -0.2$) and an unremarkable abundance pattern. we find no plausible astrophysical scenario that can explain the orbit and does not involve a black hole. the orbital period, porb = 185.6 d, is longer than that of any known stellar-mass black hole binary. the system's modest eccentricity (e = 0.45), high metallicity, and thin-disc galactic orbit suggest that it was born in the milky way disc with at most a weak natal kick. how the system formed is uncertain. common envelope evolution can only produce the system's wide orbit under extreme and likely unphysical assumptions. formation models involving triples or dynamical assembly in an open cluster may be more promising. this is the nearest known black hole by a factor of 3, and its discovery suggests the existence of a sizable population of dormant black holes in binaries. future gaia releases will likely facilitate the discovery of dozens more. | a sun-like star orbiting a black hole |
we calculate the potential contributions of the motion of binary mass systems in gravity to the fifth post-newtonian order ab initio using coupling and velocity expansions within an effective field theory approach based on feynman amplitudes starting with harmonic coordinates and using dimensional regularization. furthermore, the singular and logarithmic tail contributions are calculated. we also consider the non-local tail contributions. further steps towards the complete calculation are discussed. we calculate all but the rational o (ν2) contributions to the bound state energy for circular motion and periastron advance k (e ˆ , j). comparisons are given to results in the literature. | the fifth-order post-newtonian hamiltonian dynamics of two-body systems from an effective field theory approach: potential contributions |
the mass-luminosity relation for late-type stars has long been a critical tool for estimating stellar masses. however, there is growing need for both a higher-precision relation and a better understanding of systematic effects (e.g., metallicity). here we present an empirical relationship between {m}{ks} and m * spanning 0.075 m ⊙ < m * < 0.70 m ⊙. the relation is derived from 62 nearby binaries, whose orbits we determine using a combination of keck/nirc2 imaging, archival adaptive optics data, and literature astrometry. from their orbital parameters, we determine the total mass of each system, with a precision better than 1% in the best cases. we use these total masses, in combination with resolved ksmagnitudes and system parallaxes, to calibrate the {m}{ks}-m * relation. the resulting posteriors can be used to determine masses of single stars with a precision of 2%-3%, which we confirm by testing the relation on stars with individual dynamical masses from the literature. the precision is limited by scatter around the best-fit relation beyond measured m * uncertainties, perhaps driven by intrinsic variation in the {m}{ks}-m * relation or underestimated uncertainties in the input parallaxes. we find that the effect of [fe/h] on the {m}{ks}-m * relation is likely negligible for metallicities in the solar neighborhood (0.0% ± 2.2% change in mass per dex change in [fe/h]). this weak effect is consistent with predictions from the dartmouth stellar evolution database, but inconsistent with those from mesa isochrones and stellar tracks (at 5σ). a sample of binaries with a wider range of abundances will be required to discern the importance of metallicity in extreme populations (e.g., in the galactic halo or thick disk). | how to constrain your m dwarf. ii. the mass-luminosity-metallicity relation from 0.075 to 0.70 solar masses |
we report the discovery of the unusually bright long-duration gamma-ray burst (grb), grb 221009a, as observed by the neil gehrels swift observatory (swift), monitor of all-sky x-ray image, and neutron star interior composition explorer mission. this energetic grb was located relatively nearby (z = 0.151), allowing for sustained observations of the afterglow. the large x-ray luminosity and low galactic latitude (b = 4.°3) make grb 221009a a powerful probe of dust in the milky way. using echo tomography, we map the line-of-sight dust distribution and find evidence for significant column densities at large distances (≳10 kpc). we present analysis of the light curves and spectra at x-ray and uv-optical wavelengths, and find that the x-ray afterglow of grb 221009a is more than an order of magnitude brighter at t 0 + 4.5 ks than that from any previous grb observed by swift. in its rest frame, grb 221009a is at the high end of the afterglow luminosity distribution, but not uniquely so. in a simulation of randomly generated bursts, only 1 in 104 long grbs were as energetic as grb 221009a; such a large eγ,iso implies a narrow jet structure, but the afterglow light curve is inconsistent with simple top-hat jet models. using the sample of swift grbs with redshifts, we estimate that grbs as energetic and nearby as grb 221009a occur at a rate of ≲1 per 1000 yr-making this a truly remarkable opportunity unlikely to be repeated in our lifetime. | grb 221009a: discovery of an exceptionally rare nearby and energetic gamma-ray burst |
the atacama large millimetre/submillimetre array (alma) is currently in the process of transforming our view of star-forming galaxies in the distant (z ≳1 ) universe. before alma, most of what we knew about dust-obscured star formation in distant galaxies was limited to the brightest submillimetre sources—the so-called submillimetre galaxies (smgs)—and even the information on those sources was sparse, with resolved (i.e. sub-galactic) observations of the obscured star formation and gas reservoirs typically restricted to the most extreme and/or strongly lensed sources. starting with the beginning of early science operations in 2011, the last 9 years of alma observations have ushered in a new era for studies of high-redshift star formation. with its long baselines, alma has allowed observations of distant dust-obscured star formation with angular resolutions comparable to—or even far surpassing—the best current optical telescopes. with its bandwidth and frequency coverage, it has provided an unprecedented look at the associated molecular and atomic gas in these distant galaxies through targeted follow-up and serendipitous detections/blind line scans. finally, with its leap in sensitivity compared to previous (sub-)millimetre arrays, it has enabled the detection of these powerful dust/gas tracers much further down the luminosity function through both statistical studies of colour/mass-selected galaxy populations and dedicated deep fields. we review the main advances alma has helped bring about in our understanding of the dust and gas properties of high-redshift (z ≳1 ) star-forming galaxies during these first 9 years of its science operations, and we highlight the interesting questions that may be answered by alma in the years to come. | high-redshift star formation in the atacama large millimetre/submillimetre array era |
the transiting exoplanet survey satellite (tess) is a nasa-sponsored explorer mission that will perform a wide-field survey for planets that transit bright host stars. here, we predict the properties of the transiting planets that tess will detect along with the eb stars that produce false-positive photometric signals. the predictions are based on monte carlo simulations of the nearby population of stars, occurrence rates of planets derived from kepler, and models for the photometric performance and sky coverage of the tess cameras. we expect that tess will find approximately 1700 transiting planets from 2× {10}5 pre-selected target stars. this includes 556 planets smaller than twice the size of earth, of which 419 are hosted by m dwarf stars and 137 are hosted by fgk dwarfs. approximately 130 of the r< 2 {r}\oplusplanets will have host stars brighter than {k}s=9. approximately 48 of the planets with r< 2 {r}\opluslie within or near the habitable zone (0.2< s/{s}\oplus < 2); between 2 and 7 such planets have host stars brighter than {k}s=9. we also expect approximately 1100 detections of planets with radii 2-4 {r}\oplus , and 67 planets larger than 4 {r}\oplus . additional planets larger than 2 {r}\opluscan be detected around stars that are not among the pre-selected target stars, because tess will also deliver full-frame images at a 30-minute cadence. the planet detections are accompanied by over 1000 astrophysical false positives. we discuss how tess data and ground-based observations can be used to distinguish the false positives from genuine planets. we also discuss the prospects for follow-up observations to measure the masses and atmospheres of the tess planets. | the transiting exoplanet survey satellite: simulations of planet detections and astrophysical false positives |
av3sb5 (a = k, rb, cs) is a novel kagome superconductor coexisting with the charge density wave (cdw) order. identifying the structure of the cdw order is crucial for understanding the exotic normal state and superconductivity in this system. here, we report 51v nuclear magnetic resonance (nmr) and 121/123sb nuclear quadrupole resonance (nqr) studies on kagome-metal csv3sb5. below the cdw transition temperature tcdw ~ 98 k, an abrupt change of spectra was observed, indicating that the transition is of the first order. by further analyzing the spectra, we find that the cdw order is commensurate. and most remarkably, the obtained experimental results suggest that the charge modulation of the cdw order is of star-of-david pattern and accompanied by an additional charge modulation in bulk below t* ~ 40 k. our results revealing the unconventional cdw order provide new insights into av3sb5. | possible star-of-david pattern charge density wave with additional modulation in the kagome superconductor csv3sb5 |
coalescence of neutron stars (nss) gives rise to kilonova, thermal emission powered by radioactive decays of freshly synthesized r-process nuclei. although observational properties are largely affected by bound-bound opacities of r-process elements, available atomic data have been limited. in this paper, we study element-to-element variation of the opacities in the ejecta of ns mergers by performing systematic atomic structure calculations of r-process elements for the first time. we show that the distributions of energy levels tend to be higher as electron occupation increases for each electron shell due to the larger energy spacing caused by larger effects of spin-orbit and electron-electron interactions. as a result, elements with a fewer number of electrons in the outermost shells tend to give larger contributions to the bound-bound opacities. this implies that fe is not representative for the opacities of light r-process elements. the average opacities for the mixture of r-process elements are found to be κ ∼ 20-30 cm2 g-1 for the electron fraction of ye ≤ 0.20, κ ∼ 3-5 cm2 g-1 for ye = 0.25-0.35, and κ ∼ 1 cm2 g-1 for ye = 0.40 at $t = 5000\!-\!10\, 000$ k, and they steeply decrease at lower temperature. we show that, even with the same abundance or ye, the opacity in the ejecta changes with time by one order of magnitude from 1 to 10 d after the merger. our radiative transfer simulations with the new opacity data confirm that ejecta with a high electron fraction (ye ≳ 0.25, with no lanthanide) are needed to explain the early, blue emission in gw170817/at2017gfo while lanthanide-rich ejecta (with a mass fraction of lanthanides ∼5 × 10-3) reproduce the long-lasting near-infrared emission. | systematic opacity calculations for kilonovae |
we report the first detections of the repeating fast radio burst source frb 121102 above 5.2 ghz. observations were performed using the 4-8 ghz receiver of the robert c. byrd green bank telescope with the breakthrough listen digital backend. we present the spectral, temporal, and polarization properties of 21 bursts detected within the first 60 minutes of a total of 6 hr of observations. these observations comprise the highest burst density yet reported in the literature, with 18 bursts being detected in the first 30 minutes. a few bursts clearly show temporal sub-structure with distinct spectral properties. these sub-structures superimpose to provide an enhanced peak signal-to-noise ratio at higher trial dispersion measures. broad features occur in ∼1 ghz wide subbands that typically differ in peak frequency between bursts within the band. finer-scale structures (∼10-50 mhz) within these bursts are consistent with the structure expected from galactic diffractive interstellar scintillation. the bursts exhibit nearly 100% linear polarization, and a large average rotation measure of 9.359 ± 0.012 × 104 rad m-2 (in the observer’s frame). no circular polarization was found for any burst. we measure an approximately constant polarization position angle in the 13 brightest bursts. the peak flux densities of the reported bursts have average values (0.2 ± 0.1 jy) similar to those seen at lower frequencies (<3 ghz), while the average burst widths (0.64 ± 0.46 ms) are relatively narrower. | highest frequency detection of frb 121102 at 4-8 ghz using the breakthrough listen digital backend at the green bank telescope |
due to its ubiquitous presence, turbulence is often invoked to explain the origin of nonthermal particles in astrophysical sources of high-energy emission. with particle-in-cell simulations, we study decaying turbulence in magnetically dominated (or, equivalently, "relativistic") pair plasmas. we find that the generation of a power-law particle energy spectrum is a generic by-product of relativistic turbulence. the power-law slope is harder for higher magnetizations and stronger turbulence levels. in large systems, the slope attains an asymptotic, system-size-independent value, while the high-energy spectral cutoff increases linearly with system size; both the slope and the cutoff do not depend on the dimensionality of our domain. by following a large sample of particles, we show that particle injection happens at reconnecting current sheets; the injected particles are then further accelerated by stochastic interactions with turbulent fluctuations. our results have important implications for the origin of nonthermal particles in high-energy astrophysical sources. | particle acceleration in relativistic plasma turbulence |
we present the results of the first, deep atacama large millimeter array (alma) imaging covering the full ≃4.5 arcmin2 of the hubble ultra deep field (hudf) imaged with wide field camera 3/ir on hst. using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mm image reaching σ1.3 ≃ 35 μjy, at a resolution of ≃0.7 arcsec. from an initial list of ≃50 > 3.5σ peaks, a rigorous analysis confirms 16 sources with s1.3 > 120 μjy. all of these have secure galaxy counterparts with robust redshifts (<z> = 2.15). due to the unparalleled supporting data, the physical properties of the alma sources are well constrained, including their stellar masses (m*) and uv+fir star formation rates (sfr). our results show that stellar mass is the best predictor of sfr in the high-redshift universe; indeed at z ≥ 2 our alma sample contains seven of the nine galaxies in the hudf with m* ≥ 2 × 1010 m⊙, and we detect only one galaxy at z > 3.5, reflecting the rapid drop-off of high-mass galaxies with increasing redshift. the detections, coupled with stacking, allow us to probe the redshift/mass distribution of the 1.3-mm background down to s1.3 ≃ 10 μjy. we find strong evidence for a steep star-forming 'main sequence' at z ≃ 2, with sfr ∝m* and a mean specific sfr ≃ 2.2 gyr-1. moreover, we find that ≃85 per cent of total star formation at z ≃ 2 is enshrouded in dust, with ≃65 per cent of all star formation at this epoch occurring in high-mass galaxies (m* > 2 × 1010 m⊙), for which the average obscured:unobscured sf ratio is ≃200. finally, we revisit the cosmic evolution of sfr density; we find this peaks at z ≃ 2.5, and that the star-forming universe transits from primarily unobscured to primarily obscured at z ≃ 4. | a deep alma image of the hubble ultra deep field |
the sdss-iii/apache point observatory galactic evolution experiment (apogee) survey operated from 2011-2014 using the apogee spectrograph, which collects high-resolution (r ∼ 22,500), near-ir (1.51-1.70 μm) spectra with a multiplexing (300 fiber-fed objects) capability. we describe the survey data products that are publicly available, which include catalogs with radial velocity, stellar parameters, and 15 elemental abundances for over 150,000 stars, as well as the more than 500,000 spectra from which these quantities are derived. calibration relations for the stellar parameters ({t}{eff}, {log} g, [m/h], [α/m]) and abundances (c, n, o, na, mg, al, si, s, k, ca, ti, v, mn, fe, ni) are presented and discussed. the internal scatter of the abundances within clusters indicates that abundance precision is generally between 0.05 and 0.09 dex across a broad temperature range; it is smaller for some elemental abundances within more limited ranges and at high signal-to-noise ratio. we assess the accuracy of the abundances using comparison of mean cluster metallicities with literature values, apogee observations of the solar spectrum and of arcturus, comparison of individual star abundances with other measurements, and consideration of the locus of derived parameters and abundances of the entire sample, and find that it is challenging to determine the absolute abundance scale; external accuracy may be good to 0.1-0.2 dex. uncertainties may be larger at cooler temperatures ({t}{eff} \lt 4000 {{k}}). access to the public data release and data products is described, and some guidance for using the data products is provided. | abundances, stellar parameters, and spectra from the sdss-iii/apogee survey |
fast radio bursts (frbs) are a powerful and mysterious new class of transient that are luminous enough to be detected at cosmological distances. by associating frbs to host galaxies, we can measure intrinsic and environmental properties that test frb origin models, in addition to using them as precise probes of distant cosmic gas. the deep synoptic array (dsa-110) is a radio interferometer built to maximize the rate at which it can simultaneously detect and localize frbs. here, we present the first sample of frbs and host galaxies discovered by the dsa-110. this sample of 11 frbs is the largest, most uniform sample of localized frbs to date, as it is selected based on association to host galaxies identified in optical imaging by pan-starrs1. these frbs have not been observed to repeat and their radio properties (dispersion, temporal scattering, energy) are similar to that of the known non-repeating frb population. most host galaxies have ongoing star formation, as has been identified before for frb hosts. two hosts of the new sample are massive, quiescent galaxies. the distribution of star-formation history across this host-galaxy sample shows that the delay-time distribution is wide, with a powerlaw model that spans from $\sim100$\,myr to $\gtrsim2$\,gyr. this requires the existence of one or more progenitor formation channels associated with old stellar populations, such as the binary evolution of compact objects. | deep synoptic array science: first frb and host galaxy catalog |
in this study, we explore several new characteristics of a static anisotropic hybrid star with strange quark matter (sqm) and ordinary baryonic matter (obm) distribution. here, we use the mit bag model equation of state to connect the density and pressure of sqm inside stars, whereas the linear equation of state pr=α ρ -β connects the radial pressure and matter density caused by baryonic matter. the stellar model was developed under a background of f(q) gravity using the quadratic form of f(q). we utilized the tolman-kuchowicz ansatz (tolman in phys. rev. 55:364-373, 1939; kuchowicz in acta phys pol 33: 541, 1968) to find the solutions to the field equations under modified gravity. we have matched the interior solution to the external schwarzschild spacetime in order to acquire the numerical values of the model parameters. we have selected the star her x-1 to develop various profiles of the model parameters. several significant physical characteristics have been examined analytically and graphically, including matter densities, tangential and radial pressures, energy conditions, anisotropy factor, redshirt, compactness, etc. the main finding is that there is no core singularity present in the formations of the star under investigation. the nature of mass and the bag constant bg have been studied in details through equi-mass and equi-bg contour. the maximum allowable mass and the corresponding radius have been obtained via m -r plots. | physical characteristics and maximum allowable mass of hybrid star in the context of f(q) gravity |
our understanding of the planet formation has been rapidly evolving in recent years. the classical planet formation theory, developed when the only known planetary system was our own solar system, has been revised to account for the observed diversity of the exoplanetary systems. at the same time, the increasing observational capabilities of the young stars and their surrounding disks bring new constraints on the planet formation process. in this chapter, we summarize the new information derived from the exoplanets population and the circumstellar disks observations. we describe the new developments in planet formation theory, from dust evolution to the growth of planetary cores by accretion of planetesimals, pebbles, and gas. we review the state-of-the-art models for the formation of diverse planetary systems, including the population synthesis approach which is necessary to compare theoretical model outcomes to the exoplanet population. we emphasize that the planet formation process may not be spatially uniform in the disk and there are preferential locations for the formation of planetesimals and planets. outside of these locations, a significant fraction of solids is not growing past the pebble-sizes. the reservoir of pebbles plays an important role in the growth of planetary cores in the pebble accretion process. the timescale of the emergence of massive planetary cores is an important aspect of the present models and it is likely that the cores within one disk form at different times. in addition, there is growing evidence that the first planetary cores start forming early, during the circumstellar disk buildup process. | planet formation theory in the era of alma and kepler: from pebbles to exoplanets |
advanced ligo may be the first experiment to detect gravitational waves. through superradiance of stellar black holes, it may also be the first experiment to discover the qcd axion with decay constant above the grand unification scale. when an axion's compton wavelength is comparable to the size of a black hole, the axion binds to the black hole, forming a "gravitational atom." through the superradiance process, the number of axions occupying the bound levels grows exponentially, extracting energy and angular momentum from the black hole. axions transitioning between levels of the gravitational atom and axions annihilating to gravitons can produce observable gravitational wave signals. the signals are long lasting, monochromatic, and can be distinguished from ordinary astrophysical sources. we estimate up to o (1 ) transition events at aligo for an axion between 1 0-11 and 1 0-10 ev and up to 1 04 annihilation events for an axion between 1 0-13 and 1 0-11 ev . in the event of a null search, aligo can constrain the axion mass for a range of rapidly spinning black hole formation rates. axion annihilations are also promising for much lighter masses at future lower-frequency gravitational wave observatories; the rates have large uncertainties, dominated by supermassive black hole spin distributions. our projections for aligo are robust against perturbations from the black hole environment and account for our updated exclusion on the qcd axion of 6 ×1 0-13 ev <μa<2 ×1 0-11 ev suggested by stellar black hole spin measurements. | discovering the qcd axion with black holes and gravitational waves |
one of the key open questions in extragalactic astronomy is what stops star formation in galaxies. while it is clear that the cold gas reservoir, which fuels the formation of new stars, must be affected first, how this happens and what are the dominant physical mechanisms involved is still a matter of debate. at least for satellite galaxies, it is generally accepted that internal processes alone cannot be responsible for fully quenching their star formation, but that environment should play an important, if not dominant, role. in nearby clusters, we see examples of cold gas being removed from the star-forming discs of galaxies moving through the intracluster medium, but whether active stripping is widespread and/or necessary to halt star formation in satellites, or quenching is just a consequence of the inability of these galaxies to replenish their cold gas reservoirs, remains unclear. in this work, we review the current status of environmental studies of cold gas in star-forming satellites in the local universe from an observational perspective, focusing on the evidence for a physical link between cold gas stripping and quenching of the star formation. we find that stripping of cold gas is ubiquitous in satellite galaxies in both group and cluster environments. while hydrodynamical mechanisms such as ram pressure are important, the emerging picture across the full range of dark matter halos and stellar masses is a complex one, where different physical mechanisms may act simultaneously and cannot always be easily separated. most importantly, we show that stripping does not always lead to full quenching, as only a fraction of the cold gas reservoir might be affected at the first pericentre passage. we argue that this is a key point to reconcile apparent tensions between statistical and detailed analyses of satellite galaxies, as well as disagreements between various estimates of quenching timescales. we conclude by highlighting several outstanding questions where we expect to see substantial progress in the coming decades, thanks to the advent of the square kilometre array and its precursors, as well as the next-generation optical and millimeter facilities. | the dawes review 9: the role of cold gas stripping on the star formation quenching of satellite galaxies |
in this paper we present a new scenario where massive primordial black holes (pbhs) are produced from the collapse of large curvature perturbations generated during a mild-waterfall phase of hybrid inflation. we determine the values of the inflaton potential parameters leading to a pbh mass spectrum peaking on planetarylike masses at matter-radiation equality and producing abundances comparable to those of dark matter today, while the matter power spectrum on scales probed by cosmic microwave background (cmb) anisotropies agrees with planck data. these pbhs could have acquired large stellar masses today, via merging, and the model passes both the constraints from cmb distortions and microlensing. this scenario is supported by chandra observations of numerous bh candidates in the central region of andromeda. moreover, the tail of the pbh mass distribution could be responsible for the seeds of supermassive black holes at the center of galaxies, as well as for ultraluminous x-ray sources. we find that our effective hybrid potential can originate e.g. from d-term inflation with a fayet-iliopoulos term of the order of the planck scale but sub-planckian values of the inflaton field. finally, we discuss the implications of quantum diffusion at the instability point of the potential, able to generate a swiss-cheese-like structure of the universe, eventually leading to apparent accelerated cosmic expansion. | massive primordial black holes from hybrid inflation as dark matter and the seeds of galaxies |
the relationships between stellar mass, gas-phase metallicity and star-formation rate (i.e. the mass-metallicity, mzr, and the fundamental metallicity relation, fmr) in the local universe are revisited by fully anchoring the metallicity determination for sdss galaxies on the te abundance scale defined exploiting the strong-line metallicity calibrations presented by curti et al. self-consistent metallicity measurements allow a more unbiased assessment of the scaling relations involving m, z and sfr, which provide powerful constraints for the chemical evolution models. we parametrize the mzr with a new functional form that allows us to better characterize the turnover mass. the slope and saturation metallicity are in good agreement with previous determinations of the mzr based on the te method, while showing significantly lower normalization compared to those based on photoionization models. the z-sfr dependence at fixed stellar mass is also investigated, being particularly evident for highly star-forming galaxies, where the scatter in metallicity is reduced up to a factor of ∼30 per cent. a new parametrization of the fmr is given by explicitly introducing the sfr dependence of the turnover mass into the mzr. the residual scatter in metallicity for the global galaxy population around the new fmr is 0.054 dex. the new fmr presented in this work represents a useful local benchmark to compare theoretical predictions and observational studies (of both local and high-redshift galaxies) whose metallicity measurements are tied to the abundance scale defined by the te method, hence allowing proper assessment of its evolution with cosmic time. | the mass-metallicity and the fundamental metallicity relation revisited on a fully te-based abundance scale for galaxies |
the confirmation of the presence of very massive quiescent galaxies at epochs only 1-2 gyr after the big bang has challenged models of cosmology and galaxy formation. producing sufficient numbers of these requires abundant numbers of the host dark matter halos to have been assembled and sufficient time for star formation to proceed extremely quickly and then cease just as rapidly. ground-based spectroscopy has suggested ages of 200-300 myr at redshifts 3<z<4. the true number and ages of these objects have however been highly uncertain as ground-based spectra has been limited to the brightest of them, at wavelengths ~2{\mu}m, which introduces a significant potential bias towards younger objects. the launch of the james webb space telescope (jwst) enables dramatically more sensitive and constraining spectroscopic observations due to the very low sky background, sharp image quality, and access to wavelengths beyond 2{\mu}m. here we report jwst nirspec (0.6-5.3{\mu}m) observations of 5 new quiescent galaxy candidates that were beyond the limit of previous ground-based spectroscopy. the high signal/noise spectra of galaxies with continuum significantly fainter than earlier confirmations show that they are also at redshifts 3<z<4, and that they have substantial stellar masses of $\sim 0.5-1.0\times10^{11} m_\odot$ comparable to massive galaxies in the nearby universe. one of the galaxies has been quenched for >~ 1 billion years pointing to a presence of substantially older and fainter galaxies than those revealed so far by ground-based spectroscopy. this suggests that some of the massive galaxies have very early formation epochs (during the epoch of reionization, z>~6) pointing to a need for high conversion rates of baryons to stars in the first massive galaxy halos in the early universe. | a population of faint, old, and massive quiescent galaxies at 3 < z < 4 revealed by jwst nirspec spectroscopy |
we present hubble space telescope (hst) photometry of 17 cepheids in open clusters and their cluster mean parallaxes from gaia edr3. these parallaxes are more precise than those from individual cepheids (g < 8 mag) previously used to measure the hubble constant because they are derived from an average of >300 stars per cluster. cluster parallaxes also have smaller systematic uncertainty because their stars lie in the range (g > 13 mag) where the gaia parallax calibration is the most comprehensive. cepheid photometry employed in the period-luminosity relation was measured using the same hst instrument (wfc3) and filters (f555w, f814w, f160w) as extragalactic cepheids in type ia supernova hosts. we find no evidence of residual parallax offset in this magnitude range, zp = -3 ± 4 μas, consistent with the results from lindegren et al. and most studies. the cepheid luminosity (at p = 10 d and solar metallicity) in the hst near-infrared, wesenheit magnitude system derived from the cluster sample is ${m}_{h,1}^{w}=-5.902\pm 0.025$ mag and -5.890 ± 0.018 mag with or without simultaneous determination of a parallax offset, respectively. these results are similar to measurements from field cepheids, confirming the accuracy of the gaia parallaxes over a broad range of magnitudes. the sh0es distance ladder calibrated only from this sample gives h 0 = 72.9 ± 1.3 and h 0 = 73.3 ± 1.1 km s-1 mpc-1 with or without offset marginalization; combined with all other anchors we find h 0 = 73.01 ± 0.99 and 73.15 ± 0.97 km s-1 mpc-1, respectively, a 5% or 7% reduction in the uncertainty in h 0 and a ~5.3σ hubble tension relative to planck+λcdm. it appears increasingly difficult to reconcile two of the best-measured cosmic scales, parallaxes from gaia and the angular size of the acoustic scale of the cosmic microwave background, using the simplest form of λcdm to connect the two. | cluster cepheids with high precision gaia parallaxes, low zero-point uncertainties, and hubble space telescope photometry |
we measure a value for the cosmic expansion of h(z) = 89 ± 23(stat) ± 44(syst) km s-1 mpc-1 at a redshift of z ≃ 0.47 based on the differential age technique. this technique, also known as cosmic chronometers, uses the age difference between two redshifts for a passively evolving population of galaxies to calculate the expansion rate of the universe. our measurement is based on the analysis of high-quality spectra of luminous red galaxies obtained with the southern african large telescope in two narrow redshift ranges of z ≃ 0.40 and 0.55 as part of an initial pilot study. ages were estimated by fitting single stellar population models to the observed spectra. this measurement presents one of the best estimates of h(z) via this method at z ∼ 0.5 to date. | age-dating luminous red galaxies observed with the southern african large telescope |
x-ray pulse profile modeling of psr j 0740 +6620 , the most massive known pulsar, with data from the nicer and xmm-newton observatories recently led to a measurement of its radius. we investigate this measurement's implications for the neutron star equation of state (eos), employing a nonparametric eos model based on gaussian processes and combining information from other x-ray, radio and gravitational-wave observations of neutron stars. our analysis mildly disfavors eoss that support a disconnected hybrid star branch in the mass-radius relation, a proxy for strong phase transitions, with a bayes factor of 6.9. for such eoss, the transition mass from the hadronic to the hybrid branch is constrained to lie outside (1 ,2 ) m⊙ . we also find that the conformal sound-speed bound is violated inside neutron star cores, which implies that the core matter is strongly interacting. the squared sound speed reaches a maximum of 0.7 5-0.24+0.25 c2 at 3.60-1.89+2.25 times nuclear saturation density at 90% credibility. since all but the gravitational-wave observations prefer a relatively stiff eos, psr j 0740 +6620 's central density is only 3.57-1.3+1.3 times nuclear saturation, limiting the density range probed by observations of cold, nonrotating neutron stars in β -equilibrium. | impact of the psr j 0740 +6620 radius constraint on the properties of high-density matter |
"exoplanet" is a toolkit for probabilistic modeling of astronomical time series data, with a focus on observations of exoplanets, using pymc3 (salvatier et al., 2016). pymc3 is a flexible and high-performance model-building language and inference engine that scales well to problems with a large number of parameters. "exoplanet" extends pymc3's modeling language to support many of the custom functions and probability distributions required when fitting exoplanet datasets or other astronomical time series. while it has been used for other applications, such as the study of stellar variability, the primary purpose of "exoplanet" is the characterization of exoplanets or multiple star systems using time-series photometry, astrometry, and/or radial velocity. in particular, the typical use case would be to use one or more of these datasets to place constraints on the physical and orbital parameters of the system, such as planet mass or orbital period, while simultaneously taking into account the effects of stellar variability. | exoplanet: gradient-based probabilistic inference for exoplanet data & other astronomical time series |
we present very large array (vla) and atacama large millimeter/submillimeter array (alma) radio observations of gw170817, the first laser interferometer gravitational-wave observatory (ligo)/virgo gravitational wave (gw) event from a binary neutron star merger and the first gw event with an electromagnetic (em) counterpart. our data include the first observations following the discovery of the optical transient at both the centimeter (13.7 hr post-merger) and millimeter (2.41 days post-merger) bands. we detect faint emission at 6 ghz at 19.47 and 39.23 days after the merger, but not in an earlier observation at 2.46 days. we do not detect cm/mm emission at the position of the optical counterpart at frequencies of 10-97.5 ghz at times ranging from 0.6 to 30 days post-merger, ruling out an on-axis short gamma-ray burst (sgrb) for energies ≳ {10}48 erg. for fiducial sgrb parameters, our limits require an observer viewer angle of ≳20°. the radio and x-ray data can be jointly explained as the afterglow emission from an sgrb with a jet energy of ∼ {10}49{--}{10}50 erg that exploded in a uniform density environment with n∼ {10}-4{--}{10}-2 cm-3, viewed at an angle of ∼20°-40° from the jet axis. using the results of our light curve and spectral modeling, in conjunction with the inference of the circumbinary density, we predict the emergence of late-time radio emission from the deceleration of the kilonova (kn) ejecta on a timescale of ∼5-10 years that will remain detectable for decades with next-generation radio facilities, making gw170817 a compelling target for long-term radio monitoring. | the electromagnetic counterpart of the binary neutron star merger ligo/virgo gw170817. vi. radio constraints on a relativistic jet and predictions for late-time emission from the kilonova ejecta |
we report jwst/nirspec spectra of three distant t-type brown dwarfs identified in the ultradeep nirspec and nircam observations before the epoch of reionization (uncover) survey of the abell 2744 lensing field. one source was previously reported as a candidate t dwarf on the basis of nircam photometry, while two sources were initially identified as candidate active galactic nuclei. low-resolution 1--5 $\mu$m spectra confirm the presence of molecular features consistent with t dwarf atmospheres, and comparison to spectral standards infers classifications of sdt1, t6, and t8--t9. the warmest source, uncover-bd-1, shows evidence of subsolar metallicity, and atmosphere model fits indicates t$_{eff}$ = 1300 k and [m/h] $\sim$ $-$1.0, making this one of the few spectroscopically-confirmed t subdwarfs known. the coldest source, uncover-bd-3, is near the t/y dwarf boundary with t$_{eff}$ = 550 k, and our analysis indicates the presence of ph$_3$ in the 3--5~$\mu$m region, favored over co$_2$ and a possible indicator of subsolar metallicity. we estimate distances of 0.9--4.5 kpc from the galactic midplane, making these the most distant brown dwarfs with spectroscopic confirmation. population simulations indicate high probabilities of membership in the galactic thick disk for two of these brown dwarfs, and potential halo membership for uncover-bd-1. our simulations indicate that there are approximately 5 t dwarfs and 1--2 l dwarfs in the abell 2744 field down to f444w = 30 ab mag, roughly one-third of which are thick disk members. these results highlight the utility of deep jwst/nirspec spectroscopy for identifying and characterizing the oldest metal-poor brown dwarfs in the milky way. | uncover: jwst spectroscopy of three cold brown dwarfs at kiloparsec-scale distances |
subarcsecond localization of the repeating fast radio burst frb 121102 revealed its coincidence with a dwarf host galaxy and a steady (“quiescent”) nonthermal radio source. we show that the properties of the host galaxy are consistent with those of long-duration gamma-ray bursts (lgrb) and hydrogen-poor superluminous supernovae (slsne-i). both lgrbs and slsne-i were previously hypothesized to be powered by the electromagnetic spin-down of newly formed, strongly magnetized neutron stars with millisecond birth rotation periods (“millisecond magnetars”). this motivates considering a scenario whereby the repeated bursts from frb 121102 originate from a young magnetar remnant embedded within a young hydrogen-poor supernova (sn) remnant. requirements on the gigahertz free-free optical depth through the expanding sn ejecta (accounting for photoionization by the rotationally powered magnetar nebula), energetic constraints on the bursts, and constraints on the size of the quiescent source all point to an age of less than a few decades. the quiescent radio source can be attributed to synchrotron emission from the shock interaction between the fast outer layer of the supernova ejecta with the surrounding wind of the progenitor star, or the radio source can from deeper within the magnetar wind nebula as outlined in metzger et al. alternatively, the radio emission could be an orphan afterglow from an initially off-axis lgrb jet, though this might require the source to be too young. the young age of the source can be tested by searching for a time derivative of the dispersion measure and the predicted fading of the quiescent radio source. we propose future tests of the slsne-i/lgrb/frb connection, such as searches for frbs from nearby slsne-i/lgrbs on timescales of decades after their explosions. | millisecond magnetar birth connects frb 121102 to superluminous supernovae and long-duration gamma-ray bursts |
we present a comprehensive search and analysis of high-redshift galaxies in a suite of nine public jwst extragalactic fields taken in cycle 1, covering a total effective search area of $\sim358{\rm arcmin^2}$. through conservative ($8\sigma$) photometric selection, we identify 341 galaxies at $5<z<14$, with 109 having spectroscopic redshift measurements from the literature, including recent jwst nirspec observations. our regression analysis reveals that the rest-frame uv size-stellar mass relation follows $r_{\rm eff}\propto m_*^{0.19\pm0.03}$, similar to that of star-forming galaxies at $z\sim3$, but scaled down in size by $\sim0.7$dex. we find a much slower rate for the average size evolution over the redshift range, $r_{\rm eff}\propto(1+z)^{-0.4\pm0.2}$, than that derived in the literature. a fraction ($\sim13\,\%$) of our sample are marginally resolved even in the nircam imaging ($<100$pc), located at $>1.5\,\sigma$ below the derived size-mass slope. these compact sources exhibit a high star formation surface density $\sigma_{\rm sfr}>10\,m_\odot\,{\rm yr^{-1}\,kpc^{-2}}$, a range in which only $<0.01\,\%$ of the local star-forming galaxy sample is found. for those with available nirspec data, no evidence of ongoing supermassive black hole accretion is observed. a potential explanation for the observed high [oiii]-to-hbeta ratios could be high shock velocities, likely originating within intense star-forming regions characterized by high $\sigma_{\rm sfr}$. lastly, we find that the rest-frame uv and optical sizes of our sample are comparable. our results are consistent with these early galaxies building up their structures inside-out and yet to exhibit the strong color gradient seen at lower redshift. | enhanced sub-kpc scale star-formation: results from a jwst size analysis of 341 galaxies at 5<z<14 |
we use the spectro-photometric information of ~219 million stars from gaia's dr3 to calculate synthetic, narrow-band, metallicity-sensitive cahk magnitudes that mimic the observations of the pristine survey, a survey of photometric metallicities of milky way stars that has been mapping more than 6,500 deg^2 of the northern sky with the cfht since 2015. these synthetic magnitudes are used for an absolute re-calibration of the deeper pristine photometry and, combined with broadband gaia information, synthetic and pristine cahk magnitudes are used to estimate photometric metallicities over the whole sky. the resulting metallicity catalogue is accurate down to [fe/h]~-3.5 and is particularly suited for the exploration of the metal-poor milky way ([fe/h]<-1.0). we make available here the catalogue of synthetic cahk_syn magnitudes for all stars with bp/rp information in gaia dr3, as well as an associated catalogue of more than ~30 million photometric metallicities for high s/n fgk stars. this paper further provides the first public dr of the pristine catalogue in the form of higher quality recalibrated pristine cahk magnitudes and photometric metallicities for all stars in common with the bp/rp information in gaia dr3. we demonstrate that, when available, the much deeper pristine data greatly enhances the quality of the derived metallicities, in particular at the faint end of the catalogue (g_bp>16). combined, both catalogues include more than 2 million metal-poor star candidates as well as more than 200,000 and ~8,000 very and extremely metal-poor candidates. finally, we show that these metallicity catalogues can be used efficiently, among other applications, for galactic archaeology, to hunt for the most metal-poor stars, and to study how the structure of the milky way varies with metallicity, from the flat distribution of disk stars to the spheroid-shaped metal-poor halo. (shortened) | the pristine survey -- xxiii. data release 1 and an all-sky metallicity catalogue based on gaia dr3 bp/rp spectro-photometry |
a review is made of constraints on the nuclear symmetry energy parameters arising from nuclear binding energy measurements, theoretical chiral effective field predictions of neutron matter properties, the unitary gas conjecture, and measurements of neutron skin thicknesses and dipole polarizabilities. while most studies have been confined to the parameters sv and l, the important roles played by, and constraints on ksym, or, equivalently, the neutron matter incompressibility kn, are discussed. strong correlations among sv,l, and kn are found from both nuclear binding energies and neutron matter theory. however, these correlations somewhat differ in the two cases, and those from neutron matter theory have smaller uncertainties. to 68% confidence, it is found from neutron matter theory that sv=32.0±1.1 mev, l=51.9±7.9 mev and kn=152.2±38.1 mev. theoretical predictions for neutron skin thickness and dipole polarizability measurements of the neutron-rich nuclei 48ca, 120sn, and 208pb are compared to recent experimental measurements, most notably the crex and prex neutron skin experiments from jefferson laboratory. by themselves, prex i+ii measurements of 208pb and crex measurement of 48ca suggest l=121±47 mev and l=‑5±40 mev, respectively, to 68% confidence. however, we show that nuclear interactions optimally satisfying both measurements imply l=53±13 mev, nearly the range suggested by either nuclear mass measurements or neutron matter theory, and is also consistent with nuclear dipole polarizability measurements. this small parameter range implies r1.4=11.6±1.0 km and λ1.4=228‑90+148, which are consistent with nicer x-ray and ligo/virgo gravitational wave observations of neutron stars. | constraints on nuclear symmetry energy parameters |
a previous paper~\cite{bern:2022kto} identified a puzzle stemming from the amplitudes-based approach to spinning bodies in general relativity: additional wilson coefficients appear compared to current worldline approaches to conservative dynamics of generic astrophysical objects, including neutron stars. in this paper we clarify the nature of analogous wilson coefficients in the simpler theory of electrodynamics. we analyze the original field-theory construction, identifying definite-spin states some of which have negative norms, and relating the additional wilson coefficients in the classical theory to transitions between different quantum spin states. we produce a new version of the theory which also has additional wilson coefficients, but no negative-norm states. we match, through $\mathcal o(\alpha^2)$ and $\mathcal o(s^2)$, the compton amplitudes of these field theories with those of a modified worldline theory with extra degrees of freedom introduced by releasing the spin supplementary condition. we build an effective two-body hamiltonian that matches the impulse and spin kick of the modified field theory and of the worldline theory, displaying additional wilson coefficients compared to standard worldline approaches. the results are then compactly expressed in terms of an eikonal formula. our key conclusion is that, contrary to standard approaches, while the magnitude of the spin tensor is still conserved, the magnitude of the spin vector can change under conserved hamiltonian dynamics and this change is governed by the additional wilson coefficients. for specific values of wilson coefficients the results are equivalent to those from a definite spin obeying the spin supplementary condition, but for generic values they are physically inequivalent. these results warrant detailed studies of the corresponding issues in general relativity. | quantum field theory, worldline theory, and spin magnitude change in orbital evolution |
the asteroid terrestrial impact last alert system (atlas) system consists of two 0.5 m schmidt telescopes with cameras covering 29 square degrees at plate scale of 1.86 arcsec per pixel. working in tandem, the telescopes routinely survey the whole sky visible from hawaii (above $\delta \gt -50^\circ $ ) every two nights, exposing four times per night, typically reaching $o\lt 19$ magnitude per exposure when the moon is illuminated and $c\lt 19.5$ magnitude per exposure in dark skies. construction is underway of two further units to be sited in chile and south africa which will result in an all-sky daily cadence from 2021. initially designed for detecting potentially hazardous near earth objects, the atlas data enable a range of astrophysical time domain science. to extract transients from the data stream requires a computing system to process the data, assimilate detections in time and space and associate them with known astrophysical sources. here we describe the hardware and software infrastructure to produce a stream of clean, real, astrophysical transients in real time. this involves machine learning and boosted decision tree algorithms to identify extragalactic and galactic transients. typically we detect 10-15 supernova candidates per night which we immediately announce publicly. the atlas discoveries not only enable rapid follow-up of interesting sources but will provide complete statistical samples within the local volume of 100 mpc. a simple comparison of the detected supernova rate within 100 mpc, with no corrections for completeness, is already significantly higher (factor 1.5 to 2) than the current accepted rates. | design and operation of the atlas transient science server |
the mergers of binaries containing neutron stars and stellar-mass black holes are among the most promising sources for direct detection in gravitational waves by the interferometers advanced ligo and virgo over the next few years. the concurrent detection of electromagnetic emission from these events would greatly enhance the scientific return of these discoveries. we review the state of the art in modeling the electromagnetic signal of neutron star binary mergers across different phases of the merger and multiple wavelengths. we focus on those observables that provide the most sensitive diagnostics of the merger physics and the contribution to the synthesis of rapid neutron capture (r-process) elements in the galaxy. we also outline expected future developments on the observational and theoretical sides of this rapidly evolving field. | electromagnetic signatures of neutron star mergers in the advanced ligo era |
we present hubble wfc3/ir slitless grism spectra of a remarkably bright z ≳ 10 galaxy candidate, gn-z11, identified initially from candels/goods-n imaging data. a significant spectroscopic continuum break is detected at λ =1.47+/- 0.01 μ {{m}}. the new grism data, combined with the photometric data, rule out all plausible lower redshift solutions for this source. the only viable solution is that this continuum break is the lyα break redshifted to {z}{grism}={11.09}-0.12+0.08, just ∼400 myr after the big bang. this observation extends the current spectroscopic frontier by 150 myr to well before the planck (instantaneous) cosmic reionization peak at z ∼ 8.8, demonstrating that galaxy build-up was well underway early in the reionization epoch at z > 10. gn-z11 is remarkably, and unexpectedly, luminous for a galaxy at such an early time: its uv luminosity is 3× larger than {l}* measured at z ∼ 6-8. the spitzer irac detections up to 4.5 μm of this galaxy are consistent with a stellar mass of ∼109 m⊙. this spectroscopic redshift measurement suggests that james webb space telescope (jwst) will be able to similarly and easily confirm such sources at z > 10 and characterize their physical properties through detailed spectroscopy. furthermore, wfirst, with its wide-field near-ir imaging, would find large numbers of similar galaxies and contribute greatly to jwst's spectroscopy, if it is launched early enough to overlap with jwst. | a remarkably luminous galaxy at z=11.1 measured with hubble space telescope grism spectroscopy |
massive primordial black holes (mpbh) can be formed after inflation due to broad peaks in the primordial curvature power spectrum that collapse gravitationally during the radiation era, to form clusters of black holes that merge and increase in mass after recombination, generating today a broad mass-spectrum of black holes with masses ranging from 0.01 to 105 m⊙ . these mpbh could act as seeds for galaxies and quick-start structure formation, initiating reionization, forming galaxies at redshift z > 10 and clusters at z > 1. they may also be the seeds on which smbh and imbh form, by accreting gas onto them and forming the centers of galaxies and quasars at high redshift. they form at rest with zero spin and have negligible cross-section with ordinary matter. if there are enough of these mpbh, they could constitute the bulk of the dark matter today. such pbh could be responsible for the observed fluctuations in the cib and x-ray backgrounds. mpbh could be directly detected by the gravitational waves emitted when they merge to form more massive black holes, as recently reported by ligo. their continuous merging since recombination could have generated a stochastic background of gravitational waves that could eventually be detected by lisa and pta. mpbh may actually be responsible for the unidentified point sources seen by fermi, magic and chandra. furthermore, the ejection of stars from shallow potential wells like those of dwarf spheroidals (dsph), via the gravitational slingshot effect, could be due to mpbh, thus alleviating the substructure and too-big-to-fail problems of standard collisionless cdm. their mass distribution peaks at a few tens of m⊙ today, and could therefore be detected also with long-duration microlensing events, as well as by the anomalous motion of stars in the field of gaia. their presence as cdm in the universe could be seen in the time-dilation of strong-lensing images of quasars. the hierarchical large scale structure behaviour of mpbh does not differ from that of ordinary cdm. | massive primordial black holes as dark matter and their detection with gravitational waves |
the transiting exoplanet survey satellite (tess) has a goal of detecting small planets orbiting stars bright enough for mass determination via ground-based radial velocity observations. here, we present estimates of how many exoplanets the tess mission will detect, the physical properties of the detected planets, and the properties of the stars that those planets orbit. this work uses stars drawn from the tess input catalog candidate target list and revises yields from prior studies that were based on galactic models. we modeled the tess observing strategy to select approximately 200,000 stars at 2-minute cadence, while the remaining stars are observed at 30-minute cadence in full-frame image data. we placed zero or more planets in orbit around each star, with physical properties following measured exoplanet occurrence rates, and used the tess noise model to predict the derived properties of the detected exoplanets. in the tess 2-minute cadence mode we estimate that tess will find 1250 ± 70 exoplanets (90% confidence), including 250 smaller than 2 r ⊕. furthermore, we predict that an additional 3100 planets will be found in full-frame image data orbiting bright dwarf stars and more than 10,000 around fainter stars. we predict that tess will find 500 planets orbiting m dwarfs, but the majority of planets will orbit stars larger than the sun. our simulated sample of planets contains hundreds of small planets amenable to radial velocity follow-up, potentially more than tripling the number of planets smaller than 4 r ⊕ with mass measurements. this sample of simulated planets is available for use in planning follow-up observations and analyses. | a revised exoplanet yield from the transiting exoplanet survey satellite (tess) |
in this work we review the role of hyperons on the properties of neutron and proto-neutron stars. in particular, we revise the so-called "hyperon puzzle", go over some of the solutions proposed to tackle it, and discuss the implications that the recent measurements of unusually high neutron star masses have on our present knowledge of hypernuclear physics. we re-examine also the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability. | do hyperons exist in the interior of neutron stars? |
tidal effects have an important impact on the late inspiral of compact binary systems containing neutron stars. most current models of tidal deformations of neutron stars assume that the tidal bulge is directly related to the tidal field generated by the companion, with a constant response coefficient. however, if the orbital motion approaches a resonance with one of the internal modes of the neutron star, this adiabatic description of tidal effects starts to break down, and the tides become dynamical. in this paper, we consider dynamical tides in general relativity due to the quadrupolar fundamental oscillation mode of a neutron star. we devise a description of the effects of the neutron star's finite size on the orbital dynamics based on an effective point-particle action augmented by dynamical quadrupolar degrees of freedom. we analyze the post-newtonian and test-particle approximations of this model and incorporate the results into an effective-one-body hamiltonian. this enables us to extend the description of dynamical tides over the entire inspiral. we demonstrate that dynamical tides give a significant enhancement of matter effects compared to adiabatic tides, at least for neutron stars with large radii and for low mass-ratio systems, and should therefore be included in accurate models for gravitational-wave data analysis. | dynamical tides in general relativity: effective action and effective-one-body hamiltonian |
the formation of our milky way can be split up qualitatively into different phases that resulted in its structurally different stellar populations: the halo and the disk components1-3. revealing a quantitative overall picture of our galaxy's assembly requires a large sample of stars with very precise ages. here we report an analysis of such a sample using subgiant stars. we find that the stellar age-metallicity distribution p(τ, [fe/h]) splits into two almost disjoint parts, separated at age τ ≃ 8 gyr. the younger part reflects a late phase of dynamically quiescent galactic disk formation with manifest evidence for stellar radial orbit migration4-6; the other part reflects the earlier phase, when the stellar halo7 and the old α-process-enhanced (thick) disk8,9 formed. our results indicate that the formation of the galaxy's old (thick) disk started approximately 13 gyr ago, only 0.8 gyr after the big bang, and 2 gyr earlier than the final assembly of the inner galactic halo. most of these stars formed around 11 gyr ago, when the gaia-sausage-enceladus satellite merged with our galaxy10,11. over the next 5-6 gyr, the galaxy experienced continuous chemical element enrichment, ultimately by a factor of 10, while the star-forming gas managed to stay well mixed. | a time-resolved picture of our milky way's early formation history |
the complex nature of the nuclear forces generates a broad range and diversity of observational phenomena. heavy nuclei, though orders of magnitude less massive than neutron stars, are governed by the same underlying physics, which is enshrined in the nuclear equation of state. heavy nuclei are expected to develop a neutron-rich skin where many neutrons collect near the surface. the thickness of this skin is strongly sensitive to the poorly-known density dependence of the symmetry energy near saturation density. an accurate and model-independent determination of the neutron-skin thickness of heavy nuclei would provide a significant first constraint on the density dependence of the nuclear symmetry energy. the determination of the neutron-skin thickness of heavy nuclei has far reaching consequences in many areas of physics as diverse as heavy-ion collisions, polarized electron and proton scattering off nuclei, precision tests of the standard model using atomic parity violation, and nuclear astrophysics. while a systematic and concerted experimental effort has been made to measure the neutron-skin thickness of heavy nuclei, a precise and model-independent determination remains elusive. the measurement of parity-violating asymmetries provides a clean and model-independent determination of the weak form factor of the nucleus which is dominated by the neutron distribution. however, measuring parity-violating asymmetries of the order of a part per million is both challenging and time-consuming. alternative observables sensitive to the symmetry energy have been proposed and measured successfully in recent experimental campaigns. these data are valuable, but interpretations contain implicit model dependence that hinder the clean determination of the neutron-skin thickness. how to move forward at a time when many new facilities are being commissioned and how to strengthen the synergy with other areas of physics are primary goals of this review. | neutron skins of atomic nuclei: per aspera ad astra |
we present the stage ii results from the ongoing satellites around galactic analogs (saga) survey. upon completion, the saga survey will spectroscopically identify satellite galaxies brighter than mr,o = -12.3 around 100 milky way (mw) analogs at z ∼ 0.01. in stage ii, we have more than quadrupled the sample size of stage i, delivering results from 127 satellites around 36 mw analogs with an improved target selection strategy and deep photometric imaging catalogs from the dark energy survey and the legacy surveys. we have obtained 25,372 galaxy redshifts, peaking around z = 0.2. these data significantly increase spectroscopic coverage for very low redshift objects in 17 < ro < 20.75 around saga hosts, creating a unique data set that places the local group in a wider context. the number of confirmed satellites per system ranges from zero to nine and correlates with host galaxy and brightest satellite luminosities. we find that the number and luminosities of mw satellites are consistent with being drawn from the same underlying distribution as saga systems. the majority of confirmed saga satellites are star-forming, and the quenched fraction increases as satellite stellar mass and projected radius from the host galaxy decrease. overall, the satellite quenched fraction among saga systems is lower than that in the local group. we compare the luminosity functions and radial distributions of saga satellites with theoretical predictions based on cold dark matter simulations and an empirical galaxy-halo connection model and find that the results are broadly in agreement. | the saga survey. ii. building a statistical sample of satellite systems around milky way-like galaxies |
pulsar timing array (pta) collaborations in north america, australia, and europe, have been exploiting the exquisite timing precision of millisecond pulsars over decades of observations to search for correlated timing deviations induced by gravitational waves (gws). ptas are sensitive to the frequency band ranging just below 1 nanohertz to a few tens of microhertz. the discovery space of this band is potentially rich with populations of inspiraling supermassive black hole binaries, decaying cosmic string networks, relic post-inflation gws, and even non-gw imprints of axionic dark matter. this article aims to provide an understanding of the exciting open science questions in cosmology, galaxy evolution, and fundamental physics that will be addressed by the detection and study of gws through ptas. the focus of the article is on providing an understanding of the mechanisms by which ptas can address specific questions in these fields, and to outline some of the subtleties and difficulties in each case. the material included is weighted most heavily toward the questions which we expect will be answered in the near-term with ptas; however, we have made efforts to include most currently anticipated applications of nanohertz gws. | the astrophysics of nanohertz gravitational waves |
we present version 8 of the chianti database. this version includes a large amount of new data and ions, which represent a significant improvement in the soft x-ray, extreme uv (euv) and uv spectral regions, which several space missions currently cover. new data for neutrals and low charge states are also added. the data are assessed, but to improve the modelling of low-temperature plasma the effective collision strengths for most of the new datasets are not spline-fitted as previously, but are retained as calculated. this required a change of the format of the chianti electron excitation files. the format of the energy files has also been changed. excitation rates between all the levels are retained for most of the new datasets, so the data can in principle be used to model high-density plasma. in addition, the method for computing the differential emission measure used in the chianti software has been changed. | chianti - an atomic database for emission lines. version 8 |
the saturn-mass exoplanet wasp-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy1-4. however, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality5-9. here we present the transmission spectrum of wasp-39b obtained using the single-object slitless spectroscopy (soss) mode of the near infrared imager and slitless spectrograph (niriss) instrument on the jwst. this spectrum spans 0.6-2.8 μm in wavelength and shows several water-absorption bands, the potassium resonance doublet and signatures of clouds. the precision and broad wavelength coverage of niriss/soss allows us to break model degeneracies between cloud properties and the atmospheric composition of wasp-39b, favouring a heavy-element enhancement (`metallicity') of about 10-30 times the solar value, a sub-solar carbon-to-oxygen (c/o) ratio and a solar-to-super-solar potassium-to-oxygen (k/o) ratio. the observations are also best explained by wavelength-dependent, non-grey clouds with inhomogeneous coverageof the planet's terminator. | early release science of the exoplanet wasp-39b with jwst niriss |
context. a new class of exoplanets has emerged: the ultra hot jupiters, the hottest close-in gas giants. the majority of them have weaker-than-expected spectral features in the 1.1-1.7 μm bandpass probed by hst/wfc3 but stronger spectral features at longer wavelengths probed by spitzer. this led previous authors to puzzling conclusions about the thermal structures and chemical abundances of these planets.aims: we investigate how thermal dissociation, ionization, h- opacity, and clouds shape the thermal structures and spectral properties of ultra hot jupiters.methods: we use the sparc/mitgcm to model the atmospheres of four ultra hot jupiters and discuss more thoroughly the case of wasp-121b. we expand our findings to the whole population of ultra hot jupiters through analytical quantification of the thermal dissociation and its influence on the strength of spectral features.results: we predict that most molecules are thermally dissociated and alkalies are ionized in the dayside photospheres of ultra hot jupiters. this includes h2o, tio, vo, and h2 but not co, which has a stronger molecular bond. the vertical molecular gradient created by the dissociation significantly weakens the spectral features from h2o while the 4.5 μm co feature remains unchanged. the water band in the hst/wfc3 bandpass is further weakened by the continuous opacity of the h- ions. molecules are expected to recombine before reaching the limb, leading to order of magnitude variations of the chemical composition and cloud coverage between the limb and the dayside.conclusions: molecular dissociation provides a qualitative understanding of the lack of strong spectral features of water in the 1-2 μm bandpass observed in most ultra hot jupiters. quantitatively, our model does not provide a satisfactory match to the wasp-121b emission spectrum. together with wasp-33b and kepler-33ab, they seem the outliers among the population of ultra hot jupiters, in need of a more thorough understanding. | from thermal dissociation to condensation in the atmospheres of ultra hot jupiters: wasp-121b in context |
recent detection of gravitational waves from a neutron star (ns) merger event gw170817 and identification of an electromagnetic counterpart provide a unique opportunity to study the physical processes in ns mergers. to derive properties of ejected material from the ns merger, we perform radiative transfer simulations of kilonova, optical and near-infrared emissions powered by radioactive decays of r-process nuclei synthesized in the merger. we find that the observed near-infrared emission lasting for >10 d is explained by 0.03 m⊙ of ejecta containing lanthanide elements. however, the blue optical component observed at the initial phases requires an ejecta component with a relatively high electron fraction (ye). we show that both optical and near-infrared emissions are simultaneously reproduced by the ejecta with a medium ye of ∼0.25. we suggest that a dominant component powering the emission is post-merger ejecta, which exhibits that the mass ejection after the first dynamical ejection is quite efficient. our results indicate that ns mergers synthesize a wide range of r-process elements and strengthen the hypothesis that ns mergers are the origin of r-process elements in the universe. | kilonova from post-merger ejecta as an optical and near-infrared counterpart of gw170817 |
we present empirical measurements of the radii of 116 stars that host transiting planets. these radii are determined using only direct observables—the bolometric flux at earth, the effective temperature, and the parallax provided by the gaia first data release—and thus are virtually model independent, with extinction being the only free parameter. we also determine each star’s mass using our newly determined radius and the stellar density, a virtually model independent quantity itself from previously published transit analyses. these stellar radii and masses are in turn used to redetermine the transiting-planet radii and masses, again using only direct observables. the median uncertainties on the stellar radii and masses are 8% and 30%, respectively, and the resulting uncertainties on the planet radii and masses are 9% and 22%, respectively. these accuracies are generally larger than previously published model-dependent precisions of 5% and 6% on the planet radii and masses, respectively, but the newly determined values are purely empirical. we additionally report radii for 242 stars hosting radial-velocity (non-transiting) planets, with a median achieved accuracy of ≈2%. using our empirical stellar masses we verify that the majority of putative “retired a stars” in the sample are indeed more massive than ∼1.2 {m}⊙ . most importantly, the bolometric fluxes and angular radii reported here for a total of 498 planet host stars—with median accuracies of 1.7% and 1.8%, respectively—serve as a fundamental data set to permit the re-determination of transiting-planet radii and masses with the gaia second data release to ≈3% and ≈5% accuracy, better than currently published precisions, and determined in an entirely empirical fashion. | accurate empirical radii and masses of planets and their host stars with gaia parallaxes |
context. the kilo-degree survey (kids) is an ongoing optical wide-field imaging survey with the omegacam camera at the vlt survey telescope, specifically designed for measuring weak gravitational lensing by galaxies and large-scale structure. when completed it will consist of 1350 square degrees imaged in four filters (ugri).aims: here we present the fourth public data release which more than doubles the area of sky covered by data release 3. we also include aperture-matched zyjhks photometry from our partner viking survey on the vista telescope in the photometry catalogue. we illustrate the data quality and describe the catalogue content.methods: two dedicated pipelines are used for the production of the optical data. the astro-wise information system is used for the production of co-added images in the four survey bands, while a separate reduction of the r-band images using the theli pipeline is used to provide a source catalogue suitable for the core weak lensing science case. all data have been re-reduced for this data release using the latest versions of the pipelines. the viking photometry is obtained as forced photometry on the theli sources, using a re-reduction of the viking data that starts from the vista pawprints. modifications to the pipelines with respect to earlier releases are described in detail. the photometry is calibrated to the gaia dr2 g band using stellar locus regression.results: in this data release a total of 1006 square-degree survey tiles with stacked ugri images are made available, accompanied by weight maps, masks, and single-band source lists. we also provide a multi-band catalogue based on r-band detections, including homogenized photometry and photometric redshifts, for the whole dataset. mean limiting magnitudes (5σ in a 2″ aperture) and the tile-to-tile rms scatter are 24.23 ± 0.12, 25.12 ± 0.14, 25.02 ± 0.13, 23.68 ± 0.27 in ugri, respectively, and the mean r-band seeing is 0.70". | the fourth data release of the kilo-degree survey: ugri imaging and nine-band optical-ir photometry over 1000 square degrees |
the maximal gravitational mass of nonrotating neutron stars ($m_{\rm tov}$) is one of the key parameters of compact objects and only loose bounds can be set based on the first principle. with reliable measurements of the masses and/or radii of the neutron stars, $m_{\rm tov}$ can be robustly inferred from either the mass distribution of these objects or the reconstruction of the equation of state (eos) of the very dense matter. for the first time we take the advantages of both two approaches to have a precise inference of $m_{\rm tov}=2.25^{+0.08}_{-0.07}~m_\odot$ (68.3% credibility), with the updated neutron star mass measurement sample, the mass-tidal deformability data of gw170817, the mass-radius data of psr j0030+0451 and psr j0740+6620, as well as the theoretical information from the chiral effective theory ($\chi$eft) and perturbative quantum chromodynamics (pqcd) at low and very high energy densities, respectively. this narrow credible range is benefited from the suppression of the high $m_{\rm tov}$ by the pqcd constraint and the exclusion of the low $m_{\rm tov}$ by the mass function. three different eos reconstruction methods are adopted separately, and the resulting $m_{\rm tov}$ are found to be almost identical. this precisely evaluated $m_{\rm tov}$ suggests that the eos of neutron star matter is just moderately stiff and the $\sim 2.5-3m_\odot$ compact objects detected by the second generation gravitational wave detectors are most likely the lightest black holes. | maximum gravitational mass $m_{\\rm tov}=2.25^{+0.08}_{-0.07}m_\\odot$ inferred at about $3\\%$ precision with multimessenger data of neutron stars |
searching for distinctive signatures, which characterize different formation channels of binary black holes (bbhs), is a crucial step towards the interpretation of current and future gravitational wave detections. here, we investigate the demography of merging bbhs in young star clusters (scs), which are the nursery of massive stars. we performed 4 × 103n-body simulations of scs with metallicity z = 0.002, initial binary fraction 0.4, and fractal initial conditions, to mimic the clumpiness of star-forming regions. our simulations include a novel population-synthesis approach based on the code mobse. we find that sc dynamics does not affect the merger rate significantly, but leaves a strong fingerprint on the properties of merging bbhs. more than 50 per cent of merging bbhs in young scs form by dynamical exchanges in the first few myr. dynamically formed merging bbhs are significantly heavier than merging bbhs in isolated binaries: merging bbhs with total mass up to ∼120 m⊙ form in young scs, while the maximum total mass of merging bbhs in isolated binaries with the same metallicity is only ∼70 m⊙. merging bbhs born via dynamical exchanges tend to have smaller mass ratios than bbhs in isolated binaries. furthermore, sc dynamics speeds up the merger: the delay time between star formation and coalescence is significantly shorter in young scs. in our simulations, massive systems such as gw170729 form only via dynamical exchanges. finally ∼2 per cent of merging bbhs in young scs have mass in the pair-instability mass gap (∼60-120 m⊙). this represents a unique fingerprint of merging bbhs in scs. | merging black holes in young star clusters |
star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. in this review, we focus on the role of gravitational instability in this process. we begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small-scale turbulence-like density fluctuations, and fragmentation of the disk itself. we present the analytic theory that describes the linear growth phase of the instability supplemented with a survey of numerical simulations that aim to capture the nonlinear evolution. we emphasize the role of thermodynamics and large-scale infall in controlling the outcome of the instability. despite apparent controversies in the literature, we show a remarkable level of agreement between analytic predictions and numerical results. in the next part of our review, we focus on the astrophysical consequences of the instability. we show that the disks most likely to be gravitationally unstable are young and relatively massive compared with their host star, md/m*≥0.1. they will develop quasi-stable spiral arms that process infall from the background cloud. although instability is less likely at later times, once infall becomes less important, the manifestations of the instability are more varied. in this regime, the disk thermodynamics, often regulated by stellar irradiation, dictates the development and evolution of the instability. in some cases the instability may lead to fragmentation into bound companions. these companions are more likely to be brown dwarfs or stars than planetary mass objects. finally, we highlight open questions related to the development of a turbulent cascade in thin disks and the role of mode-mode coupling in setting the maximum angular momentum transport rate in thick disks. | gravitational instabilities in circumstellar disks |
recent population studies have searched for a subpopulation of primordial black holes (pbhs) in the gravitational-wave (gw) events so far detected by ligo/virgo/kagra (lvk), in most cases adopting a phenomenological pbh mass distribution. when deriving such a population from first principles in the standard scenario, however, the equation of state of the universe at the time of pbh formation may strongly affect the pbh abundance and mass distribution, which ultimately depend on the power spectrum of cosmological perturbations. here we improve on previous population studies on several aspects: (i) we adopt state-of-the-art pbh formation models describing the collapse of cosmological perturbations across the qcd epoch; (ii) we perform the first bayesian multipopulation inference on gw data including pbhs and directly using power spectrum parameters instead of phenomenological distributions; (iii) we critically confront the pbh scenario with lvk phenomenological models describing the gwtc-3 catalog both in the neutron-star and in the bh mass ranges, also considering pbhs as a subpopulation of the total events. our results confirm that lvk observations prevent the majority of the dark matter to be in the form of stellar mass pbhs. we find that the best-fit pbh model can comprise a small fraction of the total events, in particular it can naturally explain events in the mass gaps. if the lower mass-gap event gw190814 is interpreted as a pbh binary, we predict that lvk should detect up to a few subsolar mergers and one to ≈30 lower mass-gap events during the upcoming o4 and o5 runs. finally, mapping back the best-fit power spectrum into an ultra-slow-roll inflationary scenario, we show that the latter predicts detectable pbh mergers in the lvk band, a stochastic gw background detectable by current and future instruments, and may include the entirety of dark matter in asteroid-mass pbhs. | from inflation to black hole mergers and back again: gravitational-wave data-driven constraints on inflationary scenarios with a first-principle model of primordial black holes across the qcd epoch |
we experimentally study the response of star-shaped clusters of initially unentangled n =4 , 10, and 37 nuclear spin-1 /2 moments to an inexact π -pulse sequence and show that an ising coupling between the center and the satellite spins results in robust period-2 magnetization oscillations. the period is stable against bath effects, but the amplitude decays with a timescale that depends on the inexactness of the pulse. simulations reveal a semiclassical picture in which the rigidity of the period is due to a randomizing effect of the larmor precession under the magnetization of surrounding spins. the timescales with stable periodicity increase with net initial magnetization, even in the presence of perturbations, indicating a robust temporal ordered phase for large systems with finite magnetization per spin. | temporal order in periodically driven spins in star-shaped clusters |
we study the link between baryons and dark matter (dm) in 240 galaxies with spatially resolved kinematic data. our sample spans 9 dex in stellar mass and includes all morphological types. we consider (1) 153 late-type galaxies (ltgs; spirals and irregulars) with gas rotation curves from the sparc database, (2) 25 early-type galaxies (etgs; ellipticals and lenticulars) with stellar and h i data from atlas{}3{{d}} or x-ray data from chandra, and (3) 62 dwarf spheroidals (dsphs) with individual-star spectroscopy. we find that ltgs, etgs, and “classical” dsphs follow the same radial acceleration relation: the observed acceleration ({g}{obs}) correlates with that expected from the distribution of baryons ({g}{bar}) over 4 dex. the relation coincides with the 1:1 line (no dm) at high accelerations but systematically deviates from unity below a critical scale of ∼10-10 m s-2. the observed scatter is remarkably small (≲ 0.13 dex) and largely driven by observational uncertainties. the residuals do not correlate with any global or local galaxy property (e.g., baryonic mass, gas fraction, and radius). the radial acceleration relation is tantamount to a natural law: when the baryonic contribution is measured, the rotation curve follows, and vice versa. including ultrafaint dsphs, the relation may extend by another 2 dex and possibly flatten at {g}{bar}≲ {10}-12 m s-2, but these data are significantly more uncertain. the radial acceleration relation subsumes and generalizes several well-known dynamical properties of galaxies, like the tully-fisher and faber-jackson relations, the “baryon-halo” conspiracies, and renzo’s rule. | one law to rule them all: the radial acceleration relation of galaxies |
gravitational-wave detections are starting to allow us to probe the physical processes in the evolution of very massive stars through the imprints they leave on their final remnants. stellar evolution theory predicts the existence of a gap in the black hole mass distribution at high mass due to the effects of pair instability. previously, we showed that the location of the gap is robust against model uncertainties, but it does depend sensitively on the uncertain ${}^{12}{\rm{c}}{(\alpha ,\gamma )}^{16}{\rm{o}}$ rate. this rate is of great astrophysical significance and governs the production of oxygen at the expense of carbon. we use the open-source mesa stellar evolution code to evolve massive helium stars to probe the location of the mass gap. we find that the maximum black hole mass below the gap varies between $40\,{m}_{\odot }$ and $90\,{m}_{\odot }$ , depending on the strength of the uncertain ${}^{12}{\rm{c}}{(\alpha ,\gamma )}^{16}{\rm{o}}$ reaction rate. with the first 10 gravitational-wave detections of black holes, we constrain the astrophysical s-factor for ${}^{12}{\rm{c}}{(\alpha ,\gamma )}^{16}{\rm{o}}$ , at $300\,\mathrm{kev}$ , to ${s}_{300}\gt 175\,\,{\rm{kev}}\,{\rm{b}}$ at 68% confidence. with ${ \mathcal o }(50)$ detected binary black hole mergers, we expect to constrain the s-factor to within ±10-30 ${\rm{kev}}\,{\rm{b}}$ . we also highlight a role for independent constraints from electromagnetic transient surveys. the unambiguous detection of pulsational pair-instability supernovae would imply that ${s}_{300}\gt 79\,{\rm{kev}}\,{\rm{b}}$ . degeneracies with other model uncertainties need to be investigated further, but probing nuclear stellar astrophysics poses a promising science case for the future gravitational-wave detectors. | constraints from gravitational-wave detections of binary black hole mergers on the 12c(α, γ)16o rate |
we used high-precision radial velocity measurements of fgkm stars to determine the occurrence of giant planets as a function of orbital separation spanning 0.03-30 au. giant planets are more prevalent at orbital distances of 1-10 au compared to orbits interior or exterior of this range. the increase in planet occurrence at ~1 au by a factor of ~4 is highly statistically significant. a fall-off in giant planet occurrence at larger orbital distances is favored over models with flat or increasing occurrence. we measure ${14.1}_{-1.8}^{+2.0}$ giant planets per 100 stars with semimajor axes of 2-8 au and ${8.9}_{-2.4}^{+3.0}$ giant planets per 100 stars in the range 8-32 au, a decrease in occurrence with increasing orbital separation that is significant at the ~2σ level. we find that the occurrence rate of sub-jovian planets (0.1-1 jupiter masses) is also enhanced for 1-10 au orbits. this suggests that lower-mass planets may share the formation or migration mechanisms that drive the increased prevalence near the water-ice line for their jovian counterparts. our measurements of cold gas giant occurrence are consistent with the latest results from direct imaging surveys and gravitational lensing surveys despite different stellar samples. we corroborate previous findings that giant planet occurrence increases with stellar mass and metallicity. | california legacy survey. ii. occurrence of giant planets beyond the ice line |
debris disks are tenuous, dust-dominated disks commonly observed around stars over a wide range of ages. those around main sequence stars are analogous to the solar system's kuiper belt and zodiacal light. the dust in debris disks is believed to be continuously regenerated, originating primarily with collisions of planetesimals. observations of debris disks provide insight into the evolution of planetary systems; and the composition of dust, comets, and planetesimals outside the solar system; as well as placing constraints on the orbital architecture and potentially the masses of exoplanets that are not otherwise detectable. this review highlights recent advances in multiwavelength, high-resolution scattered light and thermal imaging that have revealed a complex and intricate diversity of structures in debris disks and discusses how modeling methods are evolving with the breadth and depth of the available observations. two rapidly advancing subfields highlighted in this review include observations of atomic and molecular gas around main sequence stars and variations in emission from debris disks on very short (days to years) timescales, providing evidence of non-steady-state collisional evolution particularly in young debris disks. | debris disks: structure, composition, and variability |
the rest-frame ultraviolet properties of galaxies during the first three billion years of cosmic time (redshift z > 4) indicate a rapid evolution in the dust obscuration of such galaxies. this evolution implies a change in the average properties of the interstellar medium, but the measurements are systematically uncertain owing to untested assumptions and the inability to detect heavily obscured regions of the galaxies. previous attempts to measure the interstellar medium directly in normal galaxies at these redshifts have failed for a number of reasons, with two notable exceptions. here we report measurements of the forbidden c ii emission (that is, [c ii]) from gas, and the far-infrared emission from dust, in nine typical star-forming galaxies about one billion years after the big bang (z ~ 5-6). we find that these galaxies have thermal emission that is less than 1/12 that of similar systems about two billion years later, and enhanced [c ii] emission relative to the far-infrared continuum, confirming a strong evolution in the properties of the interstellar medium in the early universe. the gas is distributed over scales of one to eight kiloparsecs, and shows diverse dynamics within the sample. these results are consistent with early galaxies having significantly less dust than typical galaxies seen at z < 3 and being comparable in dust content to local low-metallicity systems. | galaxies at redshifts 5 to 6 with systematically low dust content and high [c ii] emission |
we investigate the stellar populations for a sample of 161 massive, mainly quiescent galaxies at <z obs> = 0.8 with deep keck/deimos rest-frame optical spectroscopy (halo7d survey). with the fully bayesian framework prospector, we simultaneously fit the spectroscopic and photometric data with an advanced physical model (including nonparametric star formation histories, emission lines, variable dust attenuation law, and dust and active galactic nucleus emission), together with an uncertainty and outlier model. we show that both spectroscopy and photometry are needed to break the dust-age-metallicity degeneracy. we find a large diversity of star formation histories: although the most massive (m ⋆ > 2 × 1011 m ⊙) galaxies formed the earliest (formation redshift of z f ≈ 5-10 with a short star formation timescale of τ sf ≲ 1 gyr), lower-mass galaxies have a wide range of formation redshifts, leading to only a weak trend of z f with m ⋆. interestingly, several low-mass galaxies have formation redshifts of z f ≈ 5-8. star-forming galaxies evolve about the star-forming main sequence, crossing the ridgeline several times in their past. quiescent galaxies show a wide range and continuous distribution of quenching timescales (τ quench ≈ 0-5 gyr) with a median of $\langle {\tau }_{\mathrm{quench}}\rangle ={1.0}_{-0.9}^{+0.8}\,\mathrm{gyr}$ and of quenching epochs of z quench ≈ 0.8-5.0 ( $\langle {z}_{\mathrm{quench}}\rangle ={1.3}_{-0.4}^{+0.7}$ ). this large diversity of quenching timescales and epochs points toward a combination of internal and external quenching mechanisms. in our sample, rejuvenation and "late bloomers" are uncommon. in summary, our analysis supports the "grow-and-quench" framework and is consistent with a wide and continuously populated diversity of quenching timescales. | fast, slow, early, late: quenching massive galaxies at z ∼ 0.8 |
we have conducted 19 state-of-the-art 3d core-collapse supernova simulations spanning a broad range of progenitor masses. this is the largest collection of sophisticated 3d supernova simulations ever performed. we have found that while the majority of these models explode, not all do, and that even models in the middle of the available progenitor mass range may be less explodable. this does not mean that those models for which we did not witness explosion would not explode in nature, but that they are less prone to explosion than others. one consequence is that the 'compactness' measure is not a metric for explodability. we find that lower-mass massive star progenitors likely experience lower-energy explosions, while the higher-mass massive stars likely experience higher-energy explosions. moreover, most 3d explosions have a dominant dipole morphology, have a pinched, wasp-waist structure, and experience simultaneous accretion and explosion. we reproduce the general range of residual neutron-star masses inferred for the galactic neutron-star population. the most massive progenitor models, however, in particular vis à vis explosion energy, need to be continued for longer physical times to asymptote to their final states. we find that while the majority of the inner ejecta have ye = 0.5, there is a substantial proton-rich tail. this result has important implications for the nucleosynthetic yields as a function of progenitor. finally, we find that the non-exploding models eventually evolve into compact inner configurations that experience a quasi-periodic spiral sasi mode. we otherwise see little evidence of the sasi in the exploding models. | the overarching framework of core-collapse supernova explosions as revealed by 3d fornax simulations |
mergers of black hole-neutron star (bhns) binaries have now been observed by gravitational wave (gw) detectors with the recent announcement of gw200105 and gw200115. such observations not only provide confirmation that these systems exist but will also give unique insights into the death of massive stars, the evolution of binary systems and their possible association with gamma-ray bursts, r-process enrichment, and kilonovae. here, we perform binary population synthesis of isolated bhns systems in order to present their merger rate and characteristics for ground-based gw observatories. we present the results for 420 different model permutations that explore key uncertainties in our assumptions about massive binary star evolution (e.g. mass transfer, common-envelope evolution, supernovae), and the metallicity-specific star formation rate density, and characterize their relative impacts on our predictions. we find intrinsic local bhns merger rates spanning $\mathcal {r}_{\rm {m}}^0 \approx$ 4-830 $\, \rm {gpc}^{-3}$$\, \rm {yr}^{-1}$ for our full range of assumptions. this encompasses the rate inferred from recent bhns gw detections and would yield detection rates of $\mathcal {r}_{\rm {det}} \approx 1$-180$\, \rm {yr}^{-1}$ for a gw network consisting of ligo, virgo, and kagra at design sensitivity. we find that the binary evolution and metallicity-specific star formation rate density each impacts the predicted merger rates by order $\mathcal {o}(10)$. we also present predictions for the gw-detected bhns merger properties and find that all 420 model variations predict that $\lesssim 5{{\ \rm per\ cent}}$ of the bhns mergers have bh masses $m_{\rm {bh}} \gtrsim 18\, \rm {m}_{\odot }$, total masses $m_{\rm {tot}} \gtrsim 20\, \rm {m}_{\odot }$, chirp masses ${\mathcal {m}}_{\rm {c}} \gtrsim 5.5\, \rm {m}_{\odot }$, and mass ratios qf ≳ 12 or qf ≲ 2. moreover, we find that massive nss with $m_{\rm {ns}} \gt 2\, \rm {m}_{\odot }$ are expected to be commonly detected in bhns mergers in almost all our model variations. finally, a wide range of $\sim 0{{\ \rm per\ cent}}$ to $70{{\ \rm per\ cent}}$ of the bhns mergers are predicted to eject mass during the merger. our results highlight the importance of considering variations in binary evolution and cosmological models when predicting, and eventually evaluating, populations of bhns mergers. | impact of massive binary star and cosmic evolution on gravitational wave observations i: black hole-neutron star mergers |
compact stars may contain quark matter in their interiors at densities exceeding several times the nuclear saturation density. we explore models of such compact stars where there are two first-order phase transitions: the first from nuclear matter to a quark-matter phase, followed at a higher density by another first-order transition to a different quark-matter phase [e.g., from the two-flavor color-superconducting (2sc) to the color-flavor-locked (cfl) phase]. we show that this can give rise to two separate branches of hybrid stars, separated from each other and from the nuclear branch by instability regions, and, therefore, to a new family of compact stars, denser than the ordinary hybrid stars. in a range of parameters, one may obtain twin hybrid stars (hybrid stars with the same masses but different radii) and even triplets where three stars, with inner cores of nuclear matter, 2sc matter, and cfl matter, respectively, all have the same mass but different radii. | compact stars with sequential qcd phase transitions |
over the last few years, both atacama large millimeter/submillimeter array (alma) and spitzer observations have revealed a population of likely massive galaxies at z > 3 that was too faint to be detected inhubble space telescope(hst) rest-frame ultraviolet imaging. however, due to the very limited photometry for individual galaxies, the true nature of these so-called hst-dark galaxies has remained elusive. here, we present the first sample of such galaxies observed with very deep, high-resolution nircam imaging from the early release science programme ceers. 30 hst-dark sources are selected based on their red colours across 1.6-4.4 $\mu$m. their physical properties are derived from 12-band multiwavelength photometry, including ancillary hst imaging. we find that these galaxies are generally heavily dust-obscured (av ~ 2 mag), massive (log (m/m⊙) ~ 10), star-forming sources at z ~ 2-8 with an observed surface density of ~0.8 arcmin-2. this suggests that an important fraction of massive galaxies may have been missing from our cosmic census at z > 3 all the way into the epoch of reionization. the hst-dark sources lie on the main sequence of galaxies and add an obscured star formation rate density of $\mathrm{3.2^{+1.8}_{-1.3} \times 10^{-3} \,{\rm m}_{\odot }\,yr^{-1}\,mpc^{-3}}$ at z ~ 7, showing likely presence of dust in the epoch of reionization. our analysis shows the unique power of jwst to reveal this previously missing galaxy population and to provide a more complete census of galaxies at z = 2-8 based on rest-frame optical imaging. | unveiling the nature of infrared bright, optically dark galaxies with early jwst data |
we present results of a deep spectroscopic survey quantifying the statistics of the escape of ionizing radiation from star-forming galaxies at z ∼ 3. we measure the ratio of ionizing to non-ionizing uv flux density < {f}900{/f}1500{> }obs}, where f 900 is the mean flux density evaluated over the range [880, 910] å. we quantify the emergent ratio of ionizing to non-ionizing uv flux density by analyzing high signal-to-noise ratio composite spectra formed from subsamples with common observed properties and numbers sufficient to reduce the statistical uncertainty in the modeled igm+cgm correction to obtain precise values of < {f}900{/f}1500{> }out}, including a full-sample average < {f}900{/f}1500{> }out} = 0.057 ± 0.006. we show that < {f}900{/f}1500{> }out} increases monotonically with {w}λ ({ly}α ), inducing an inverse correlation with uv luminosity as a by-product. we fit the composite spectra using stellar spectral synthesis together with models of the ism in which a fraction fcof the stellar continuum is covered by gas with column density {n}{{h}{{i}}}. we show that the composite spectra simultaneously constrain the intrinsic properties of the stars (l 900/l 1500)int along with fc , {n}{{h}{{i}}}, e(b-v), and f esc,abs, the absolute escape fraction of ionizing photons. we find a sample-averaged f esc,abs = 0.09 ± 0.01, with subsamples falling along a linear relation < {f}esc,{abs}}> ≃ 0.75[{w}λ ({ly}α )/110 \mathringa ]. using the far-uv luminosity function, the distribution function n(w(lyα)), and the relationship between {w}λ ({ly}α ) and < {f}900{/f}1500{> }out}, we estimate the total ionizing emissivity of z ∼ 3 star-forming galaxies with m uv ≤ -19.5, which exceeds the contribution of quasi-stellar objects by a factor of ∼3, and accounts for ∼50% of the total ɛ lyc at z ∼ 3 estimated using indirect methods. 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 keck lyman continuum spectroscopic survey (klcs): the emergent ionizing spectrum of galaxies at z ∼ 3 |
planets form and obtain their compositions in disks of gas and dust around young stars. the chemical compositions of these planet-forming disks regulate all aspects of planetary compositions from bulk elemental inventories to access to water and reactive organics, i.e. a planet's hospitality to life and its chemical origins. disk chemical structures are in their turn governed by a combination of in situ chemical processes, and inheritance of molecules from the preceding evolutionary stages of the star formation process. in this review we present our current understanding of the chemical processes active in pre- and protostellar environments that set the initial conditions for disks, and the disk chemical processes that evolve the chemical conditions during the first million years of planet formation. we review recent observational, laboratory and theoretical discoveries that have led to the present view of the chemical environment within which planets form, and their effects on the compositions of nascent planetary systems. we also discuss the many unknowns that remain and outline some possible pathways to addressing them. | astrochemistry and compositions of planetary systems |
neutrino flavor evolution in core-collapse supernovae, neutron-star mergers, or the early universe is dominated by neutrino-neutrino refraction, often spawning ;self-induced flavor conversion,; i.e., shuffling of flavor among momentum modes. this effect is driven by collective run-away modes of the coupled ;flavor oscillators; and can spontaneously break the initial symmetries such as axial symmetry, homogeneity, isotropy, and even stationarity. moreover, the growth rates of unstable modes can be of the order of the neutrino-neutrino interaction energy instead of the much smaller vacuum oscillation frequency: self-induced flavor conversion does not always require neutrino masses. we illustrate these newly found phenomena in terms of simple toy models. what happens in realistic astrophysical settings is up to speculation at present. | collective neutrino flavor conversion: recent developments |
we present an analysis of spectroscopic and astrometric data from apogee-2 and gaia dr2 to identify structures toward the orion complex. by applying a hierarchical clustering algorithm to the six-dimensional stellar data, we identify spatially and/or kinematically distinct groups of young stellar objects with ages ranging from 1 to 12 myr. we also investigate the star-forming history within the orion complex and identify peculiar subclusters. with this method we reconstruct the older populations in the regions that are currently largely devoid of molecular gas, such as orion c (which includes the σ ori cluster) and orion d (the population that traces ori ob1a, ob1b, and orion x). we report on the distances, kinematics, and ages of the groups within the complex. the orion d group is in the process of expanding. on the other hand, orion b is still in the process of contraction. in λ ori the proper motions are consistent with a radial expansion due to an explosion from a supernova; the traceback age from the expansion exceeds the age of the youngest stars formed near the outer edges of the region, and their formation would have been triggered when they were halfway from the cluster center to their current positions. we also present a comparison between the parallax and proper-motion solutions obtained by gaia dr2 and those obtained toward star-forming regions by the very long baseline array. | the apogee-2 survey of the orion star-forming complex. ii. six-dimensional structure |
the oldest, most metal-poor stars in the galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical conditions of the earliest star-forming environments in the universe. we review the fields of stellar archaeology and dwarf galaxy archaeology by examining the chemical abundance measurements of various elements in extremely metal-poor stars. focus on the carbon-rich and carbon-normal halo star populations illustrates how these provide insight into the population iii star progenitors responsible for the first metal enrichment events. we extend the discussion to near-field cosmology, which is concerned with the formation of the first stars and galaxies, and how metal-poor stars can be used to constrain these processes. complementary abundance measurements in high-redshift gas clouds further help establish the early chemical evolution of the universe. the data appear consistent with the existence of two distinct channels of star formation at the earliest times. | near-field cosmology with extremely metal-poor stars |
we present a unified description of the scenario of global hierarchical collapse (ghc). ghc constitutes a flow regime of (non-homologous) collapses within collapses, in which all scales accrete from their parent structures, and small, dense regions begin to contract at later times, but on shorter time-scales than large, diffuse ones. the different time-scales allow for most of the clouds' mass to be dispersed by the feedback from the first massive stars, maintaining the cloud-scale star formation rate low. molecular clouds (mcs), clumps, and cores are not in equilibrium, but rather are either undergoing contraction or dispersal. the main features of ghc are as follows: (1) the gravitational contraction is initially very slow, and begins when the cloud still consists of mostly atomic gas. (2) star-forming mcs are in an essentially pressureless regime, causing filamentary accretion flows from the cloud to the core scale to arise spontaneously. (3) accreting objects have longer lifetimes than their own free-fall time, due to the continuous replenishment of material. (4) the clouds' total mass and its molecular and dense mass fractions increase over time. (5) the clouds' masses stop growing when feedback becomes important. (6) the first stars appear several megayears after global contraction began, and are of low mass; massive stars appear a few megayears later, in massive hubs. (7) the minimum fragment mass may well extend into the brown-dwarf regime. (8) bondi-hoyle-lyttleton-like accretion occurs at both the protostellar and the core scales, accounting for an imf with slope dn/dm ∝ m-2. (9) the extreme anisotropy of the filamentary network explains the difficulty in detecting large-scale infall signatures. (10) the balance between inertial and gravitationally driven motions in clumps evolves during the contraction, explaining the approach to apparent virial equilibrium, from supervirial states in low-column density clumps and from subvirial states in dense cores. (11) prestellar cores adopt bonnor-ebert-like profiles, but are contracting ever since when they may appear to be unbound. (12) stellar clusters develop radial age and mass segregation gradients. we also discuss the incompatibility between supersonic turbulence and the observed scalings in the molecular hierarchy. since gravitationally formed filaments do not develop shocks at their axes, we suggest that a diagnostic for the ghc scenario should be the absence of strong shocks in them. finally, we critically discuss some recent objections to the ghc mechanism. | global hierarchical collapse in molecular clouds. towards a comprehensive scenario |
we study molecular outflows in a sample of 45 local galaxies, both star forming and active galactic nucleus (agn), primarily by using co data from the atacama large millimeter/submillimeter array (alma) archive and from the literature. for a subsample, we also compare the molecular outflow with the ionized and neutral atomic phases. we infer an empirical analytical function relating the outflow rate simultaneously to the star formation rate (sfr), lagn, and galaxy stellar mass; this relation is much tighter than the relations with the individual quantities. the outflow kinetic power shows a larger scatter than in previous, more biased studies, spanning from 0.1 to 5 per cent of lagn, while the momentum rate ranges from 1 to 30 times lagn/c, indicating that these outflows can be both energy driven, but with a broad range of coupling efficiencies with the interstellar medium (ism), and radiation pressure driven. for about 10 per cent of the objects, the outflow energetics significantly exceed the maximum theoretical values; we interpret these as `fossil outflows' resulting from activity of a past strong agn, which has now faded. we estimate that, in the stellar mass range probed here (> 10^{10} m_{⊙}), less than 5 per cent of the outflowing gas escapes the galaxy. the molecular gas depletion time associated with the outflow can be as short as a few million years in powerful agn; however, the total gas (h2 + h i) depletion times are much longer. altogether, our findings suggest that even agn-driven outflows might be relatively ineffective in clearing galaxies of their entire gas content, although they are likely capable of clearing and quenching the central region. | cold molecular outflows in the local universe and their feedback effect on galaxies |
is the secondary component of gw190814 the lightest black hole or the heaviest neutron star ever discovered in a double compact-object system [abbott et al. astrophys. j. 896, l44 (2020), 10.3847/2041-8213/ab960f]? this is the central question animating this paper. covariant density functional theory provides a unique framework to investigate both the properties of finite nuclei and neutron stars, while enforcing causality at all densities. by tuning existing energy density functionals we were able to: (i) account for a 2.6 m⊙ neutron star, (ii) satisfy the original constraint on the tidal deformability of a 1.4 m⊙ neutron star, and (iii) reproduce ground-state properties of finite nuclei. yet, for the class of models explored in this work, we find that the stiffening of the equation of state required to support supermassive neutron stars is inconsistent with either constraints obtained from energetic heavy-ion collisions or from the low deformability of medium-mass stars. thus, we speculate that the maximum neutron star mass can not be significantly higher than the existing observational limit and that the 2.6 m⊙ compact object is likely to be the lightest black hole ever discovered. | gw190814: impact of a 2.6 solar mass neutron star on the nucleonic equations of state |
the mass accretion rate, ṁacc, is a key quantity for the understanding of the physical processes governing the evolution of accretion discs around young low-mass (m⋆ ≲ 2.0 m⊙) stars and substellar objects (ysos). we present here the results of a study of the stellar and accretion properties of the (almost) complete sample of class ii and transitional ysos in the lupus i, ii, iii and iv clouds, based on spectroscopic data acquired with the vlt/x-shooter spectrograph. our study combines the dataset from our previous work with new observations of 55 additional objects. we have investigated 92 yso candidates in total, 11 of which have been definitely identified with giant stars unrelated to lupus. the stellar and accretion properties of the 81 bona fide ysos, which represent more than 90% of the whole class ii and transition disc yso population in the aforementioned lupus clouds, have been homogeneously and self-consistently derived, allowing for an unbiased study of accretion and its relationship with stellar parameters. the accretion luminosity, lacc, increases with the stellar luminosity, l⋆, with an overall slope of 1.6, similar but with a smaller scatter than in previous studies. there is a significant lack of strong accretors below l⋆ ≈ 0.1 l⊙, where lacc is always lower than 0.01 l⋆. we argue that the lacc - l⋆ slope is not due to observational biases, but is a true property of the lupus ysos. the log ṁacc - log m⋆ correlation shows a statistically significant evidence of a break, with a steeper relation for m⋆ ≲ 0.2 m⊙ and a flatter slope for higher masses. the bimodality of the ṁacc - m⋆ relation is confirmed with four different evolutionary models used to derive the stellar mass. the bimodal behaviour of the observed relationship supports the importance of modelling self-gravity in the early evolution of the more massive discs, but other processes, such as photo-evaporation and planet formation during the yso's lifetime, may also lead to disc dispersal on different timescales depending on the stellar mass. the sample studied here more than doubles the number of ysos with homogeneously and simultaneously determined lacc and luminosity, lline, of many permitted emission lines. hence, we also refined the empirical relationships between lacc and lline on a more solid statistical basis. based on observations collected at the european southern observatory at paranal, under programs 084.c-0269(a), 085.c-0238(a), 086.c-0173(a), 087.c-0244(a), 089.c-0143(a), 095.c-0134(a), 097.c-0349(a), and archive data of programmes 085.c-0764(a) and 093.c-0506(a). | x-shooter spectroscopy of young stellar objects in lupus. accretion properties of class ii and transitional objects |
the sami galaxy survey will observe 3400 galaxies with the sydney-aao multi-object integral-field spectrograph (sami) on the anglo-australian telescope in a 3-yr survey which began in 2013. we present the throughput of the sami system, the science basis and specifications for the target selection, the survey observation plan and the combined properties of the selected galaxies. the survey includes four volume-limited galaxy samples based on cuts in a proxy for stellar mass, along with low-stellar-mass dwarf galaxies all selected from the galaxy and mass assembly (gama) survey. the gama regions were selected because of the vast array of ancillary data available, including ultraviolet through to radio bands. these fields are on the celestial equator at 9, 12 and 14.5 h, and cover a total of 144 deg2 (in gama-i). higher density environments are also included with the addition of eight clusters. the clusters have spectroscopy from 2-degree field galaxy redshift survey (2dfgrs) and sloan digital sky survey (sdss) and photometry in regions covered by the sdss and/or vlt survey telescope/atlas. the aim is to cover a broad range in stellar mass and environment, and therefore the primary survey targets cover redshifts 0.004 < z < 0.095, magnitudes rpet < 19.4, stellar masses 107-1012 m⊙, and environments from isolated field galaxies through groups to clusters of ∼1015 m⊙. | the sami galaxy survey: instrument specification and target selection |
recent developments in compact object astrophysics, especially the discovery of merging neutron stars by ligo, the imaging of the black hole in m87 by the event horizon telescope, and high- precision astrometry of the galactic center at close to the event horizon scale by the gravity experiment motivate the development of numerical source models that solve the equations of general relativistic magnetohydrodynamics (grmhd). here we compare grmhd solutions for the evolution of a magnetized accretion flow where turbulence is promoted by the magnetorotational instability from a set of nine grmhd codes: athena++, bhac, cosmos++, echo, h-amr, iharm3d, harm-noble, illinoisgrmhd, and koral. agreement among the codes improves as resolution increases, as measured by a consistently applied, specially developed set of code performance metrics. we conclude that the community of grmhd codes is mature, capable, and consistent on these test problems. | the event horizon general relativistic magnetohydrodynamic code comparison project |
a long-standing question in nuclear physics is whether chargeless nuclear systems can exist. to our knowledge, only neutron stars represent near-pure neutron systems, where neutrons are squeezed together by the gravitational force to very high densities. the experimental search for isolated multi-neutron systems has been an ongoing quest for several decades1, with a particular focus on the four-neutron system called the tetraneutron, resulting in only a few indications of its existence so far2-4, leaving the tetraneutron an elusive nuclear system for six decades. here we report on the observation of a resonance-like structure near threshold in the four-neutron system that is consistent with a quasi-bound tetraneutron state existing for a very short time. the measured energy and width of this state provide a key benchmark for our understanding of the nuclear force. the use of an experimental approach based on a knockout reaction at large momentum transfer with a radioactive high-energy 8he beam was key. | observation of a correlated free four-neutron system |
context. with the most recent gaia data release, the number of sources with complete 6d phase space information (position and velocity) has increased to well over 33 million stars, while stellar astrophysical parameters are provided for more than 470 million sources, and more than 11 million variable stars are identified.aims: using the astrophysical parameters and variability classifications provided in gaia dr3, we selected various stellar populations to explore and identify non-axisymmetric features in the disc of the milky way in configuration and velocity space.methods: using more about 580 000 sources identified as hot ob stars, together with 988 known open clusters younger than 100 myr, we mapped the spiral structure associated with star formation 4−5 kpc from the sun. we selected over 2800 classical cepheids younger than 200 myr that show spiral features extending as far as 10 kpc from the sun in the outer disc. we also identified more than 8.7 million sources on the red giant branch (rgb), of which 5.7 million have line-of-sight velocities. this later sample allows the velocity field of the milky way to be mapped as far as 8 kpc from the sun, including the inner disc.results: the spiral structure revealed by the young populations is consistent with recent results using gaia edr3 astrometry and source lists based on near-infrared photometry, showing the local (orion) arm to be at least 8 kpc long, and an outer arm consistent with what is seen in hi surveys, which seems to be a continuation of the perseus arm into the third quadrant. the subset of rgb stars with velocities clearly reveals the large-scale kinematic signature of the bar in the inner disc, as well as evidence of streaming motions in the outer disc that might be associated with spiral arms or bar resonances. a local comparison of the velocity field of the ob stars reveals similarities and differences with the rgb sample.conclusions: this cursory study of gaia dr3 data shows there is a rich bounty of kinematic information to be explored more deeply, which will undoubtedly lead us to a clearer understanding of the dynamical nature of the non-axisymmetric structures of the milky way. the data for tables 1 and 2, figs. 16, 17, 21, and b.1 are only available at the cds via anonymous ftp at cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/674/a37 | gaia data release 3. mapping the asymmetric disc of the milky way |
context. the motion of stars has been used to reveal details of the complex history of the milky way, in constant interaction with its environment. nevertheless, to reconstruct the galactic history puzzle in its entirety, the chemo-physical characterisation of stars is essential. previous gaia data releases were supported by a smaller, heterogeneous, and spatially biased mixture of chemical data from ground-based observations.aims: gaia data release 3 opens a new era of all-sky spectral analysis of stellar populations thanks to the nearly 5.6 million stars observed by the radial velocity spectrometer (rvs) and parametrised by the gsp-spec module. in this work, we aim to demonstrate the scientific quality of gaia's milky way chemical cartography through a chemo-dynamical analysis of disc and halo populations.methods: stellar atmospheric parameters and chemical abundances provided by gaia dr3 spectroscopy are combined with dr3 radial velocities and edr3 astrometry to analyse the relationships between chemistry and milky way structure, stellar kinematics, and orbital parameters.results: the all-sky gaia chemical cartography allows a powerful and precise chemo-dynamical view of the milky way with unprecedented spatial coverage and statistical robustness. first, it reveals the strong vertical symmetry of the galaxy and the flared structure of the disc. second, the observed kinematic disturbances of the disc - seen as phase space correlations - and kinematic or orbital substructures are associated with chemical patterns that favour stars with enhanced metallicities and lower [α/fe] abundance ratios compared to the median values in the radial distributions. this is detected both for young objects that trace the spiral arms and older populations. several α, iron-peak elements and at least one heavy element trace the thin and thick disc properties in the solar cylinder. third, young disc stars show a recent chemical impoverishment in several elements. fourth, the largest chemo-dynamical sample of open clusters analysed so far shows a steepening of the radial metallicity gradient with age, which is also observed in the young field population. finally, the gaia chemical data have the required coverage and precision to unveil galaxy accretion debris and heated disc stars on halo orbits through their [α/fe] ratio, and to allow the study of the chemo-dynamical properties of globular clusters.conclusions: gaia dr3 chemo-dynamical diagnostics open new horizons before the era of ground-based wide-field spectroscopic surveys. they unveil a complex milky way that is the outcome of an eventful evolution, shaping it to the present day. | gaia data release 3. chemical cartography of the milky way |
bayesian neural network (bnn) approach is employed to improve the nuclear mass predictions of various models. it is found that the noise error in the likelihood function plays an important role in the predictive performance of the bnn approach. by including a distribution for the noise error, an appropriate value can be found automatically in the sampling process, which optimizes the nuclear mass predictions. furthermore, two quantities related to nuclear pairing and shell effects are added to the input layer in addition to the proton and mass numbers. as a result, the theoretical accuracies are significantly improved not only for nuclear masses but also for single-nucleon separation energies. due to the inclusion of the shell effect, in the unknown region, the bnn approach predicts a similar shell-correction structure to that in the known region, e.g., the predictions of underestimation of nuclear mass around the magic numbers in the relativistic mean-field model. this manifests that better predictive performance can be achieved if more physical features are included in the bnn approach. | nuclear mass predictions based on bayesian neural network approach with pairing and shell effects |
we study the non-relativistic expansion of general relativity coupled to matter. this is done by expanding the metric and matter fields analytically in powers of 1/c2 where c is the speed of light. in order to perform this expansion it is shown to be very convenient to rewrite general relativity in terms of a timelike vielbein and a spatial metric. this expansion can be performed covariantly and off shell. we study the expansion of the einstein-hilbert action up to next-to-next-to-leading order. we couple this to different forms of matter: point particles, perfect fluids, scalar fields (including an off-shell derivation of the schrödinger-newton equation) and electrodynamics (both its electric and magnetic limits). we find that the role of matter is crucial in order to understand the properties of the newton-cartan geometry that emerges from the expansion of the metric. it turns out to be the matter that decides what type of clock form is allowed, i.e. whether we have absolute time or a global foliation of constant time hypersurfaces. we end by studying a variety of solutions of non-relativistic gravity coupled to perfect fluids. this includes the schwarzschild geometry, the tolman-oppenheimer-volkoff solution for a fluid star, the flrw cosmological solutions and anti-de sitter spacetimes. | non-relativistic gravity and its coupling to matter |
several studies have detected ly$\alpha$ from bright ($m_{uv}\lesssim-21.5$) galaxies during the early stages of reionization despite the significantly neutral igm. to explain these detections, it has been suggested that z>7 ly$\alpha$ emitters (laes) inhabit large, physical mpc (pmpc)-scale ionized regions. however, systematic searches for the overdensities of faint galaxies expected to be powering these ionized bubbles around laes have been challenging. here, we use ceers nircam imaging to investigate the possibility of galaxy overdensities associated with two very uv-bright laes at z=8.7 in the egs field. we design a color selection to identify objects at z=8.4-9.1, selecting 28 candidates (including the one lae in the footprint, egsy8p7). we model the seds of these objects and infer that all are moderately faint ($-21.2\lesssim m_{uv}\lesssim-19.1$) with stellar masses of $m_* \approx 10^{7.5 - 8.8}$ $m_\odot$. all are efficient ionizing agents ($\xi_{ion}^*\sim10^{25.5-26.0}$ hz erg$^{-1}$) and are generally morphologically simple with only one compact ($r_e\lesssim140$ to $\sim650$ pc) star-forming component. of the 27 objects besides egsy8p7, 13 lie within 5' of egsy8p7, leading to a $4\times$ overdensity in projection at separations <5' (1.4 pmpc in projection at z=8.7). separations of 10'-15' (2.7-4.1 projected pmpc) are consistent with an average field. the spatial distribution of our sample may qualitatively suggest a large ($r\geq2$ pmpc) ionized bubble encompassing both laes in the field, which is theoretically unexpected but may be possible for a galaxy population four times more numerous than the average to create given moderate escape fractions ($f_{esc}\gtrsim0.15$) over long times ($\gtrsim200$ myr). upcoming spectroscopic follow up will enable characterization of the size of any ionized bubble that may exist and the properties of the galaxies powering such a bubble. | insight from jwst/nircam into galaxy overdensities around bright ly$\\alpha$ emitters during reionization: implications for ionized bubbles at $z \\sim 9$ |
we present the host galaxies of four apparently non-repeating fast radio bursts (frbs), frbs 20181223c, 20190418a, 20191220a, and 20190425a, reported in the first canadian hydrogen intensity mapping experiment (chime/frb) catalog. our selection of these frbs is based on a planned hypothesis testing framework where we search all chime/frb catalog-1 events that have low extragalactic dispersion measure (< 100 pc cm$^{-3}$), with high galactic latitude (|b| > 10$°$) and saved baseband data. we associate the selected frbs to galaxies with moderate to high star-formation rates located at redshifts between 0.027 and 0.071. we also search for possible multi-messenger counterparts, including persistent compact radio and gravitational wave (gw) sources, and find none. utilizing the four frb hosts from this study along with the hosts of 14 published local universe frbs (z < 0.1) with robust host association, we conduct an frb host demographics analysis. we find all 18 local universe frb hosts in our sample to be spirals (or late-type galaxies), including the host of frb 20220509g, which was previously reported to be elliptical. using this observation, we scrutinize proposed frb source formation channels and argue that core-collapse supernovae are likely the dominant channel to form frb progenitors. moreover, we infer no significant difference in the host properties of repeating and apparently non-repeating frbs in our local universe frb host sample. finally, we find the burst rates of these four apparently non-repeating frbs to be consistent with those of the sample of localized repeating frbs observed by chime/frb. therefore, we encourage further monitoring of these frbs with more sensitive radio telescopes. | host galaxies for four nearby chime/frb sources and the local universe frb host galaxy population |
the study of galaxy evolution hinges on our ability to interpret multiwavelength galaxy observations in terms of their physical properties. to do this, we rely on spectral energy distribution (sed) models, which allow us to infer physical parameters from spectrophotometric data. in recent years, thanks to wide and deep multiwave band galaxy surveys, the volume of high-quality data have significantly increased. alongside the increased data, algorithms performing sed fitting have improved, including better modeling prescriptions, newer templates, and more extensive sampling in wavelength space. we present a comprehensive analysis of different sed-fitting codes including their methods and output with the aim of measuring the uncertainties caused by the modeling assumptions. we apply 14 of the most commonly used sed-fitting codes on samples from the candels photometric catalogs at z ~ 1 and z ~ 3. we find agreement on the stellar mass, while we observe some discrepancies in the star formation rate (sfr) and dust-attenuation results. to explore the differences and biases among the codes, we explore the impact of the various modeling assumptions as they are set in the codes (e.g., star formation histories, nebular, dust and active galactic nucleus models) on the derived stellar masses, sfrs, and avvalues. we then assess the difference among the codes on the sfr-stellar mass relation and we measure the contribution to the uncertainties by the modeling choices (i.e., the modeling uncertainties) in stellar mass (~0.1 dex), sfr (~0.3 dex), and dust attenuation (~0.3 mag). finally, we present some resources summarizing best practices in sed fitting. | the art of measuring physical parameters in galaxies: a critical assessment of spectral energy distribution fitting techniques |
the recent alma observations of the disk surrounding hl tau reveal a very complex dust spatial distribution. we present a radiative transfer model accounting for the observed gaps and bright rings as well as radial changes of the emissivity index. we find that the dust density is depleted by at least a factor of 10 in the main gaps compared to the surrounding rings. ring masses range from 10-100 m⊕ in dust, and we find that each of the deepest gaps is consistent with the removal of up to 40 m⊕ of dust. if this material has accumulated into rocky bodies, these would be close to the point of runaway gas accretion. our model indicates that the outermost ring is depleted in millimeter grains compared to the central rings. this suggests faster grain growth in the central regions and/or radial migration of the larger grains. the morphology of the gaps observed by alma—well separated and showing a high degree of contrast with the bright rings over all azimuths—indicates that the millimeter dust disk is geometrically thin (scale height ≈1 au at 100 au) and that a large amount of settling of large grains has already occurred. assuming a standard dust settling model, we find that the observations are consistent with a turbulent viscosity coefficient of a few 10-4. we estimate the gas/dust ratio in this thin layer to be of the order of 5 if the initial ratio is 100. the hco+ and co emission is consistent with gas in keplerian motion around a 1.7 m⊙ star at radii from ≤10-120 au. | dust and gas in the disk of hl tauri: surface density, dust settling, and dust-to-gas ratio |
context. mergers of two stellar-origin black holes are a prime source of gravitational waves and are under intensive investigation. one crucial ingredient in their modeling has been neglected: pair-instability pulsation supernovae with associated severe mass loss may suppress the formation of massive black holes, decreasing black-hole-merger rates for the highest black-hole masses.aims: we demonstrate the effects of pair-instability pulsation supernovae on merger rate and mass using populations of double black-hole binaries formed through the isolated binary classical evolution channel.methods: the mass loss from pair-instability pulsation supernova is estimated based on existing hydrodynamical calculations. this mass loss is incorporated into the startrack population synthesis code. startrack is used to generate double black-hole populations with and without pair-instability pulsation supernova mass loss.results: the mass loss associated with pair-instability pulsation supernovae limits the population i/ii stellar-origin black-hole mass to 50 m⊙, in tension with earlier predictions that the maximum black-hole mass could be as high as 100 m⊙. in our model, neutron stars form with mass 1-2 m⊙. we then encounter the first mass gap at 2-5 m⊙ with the compact object absence due to rapid supernova explosions, followed by the formation of black holes with mass 5-50 m⊙, with a second mass gap at 50-135 m⊙ created by pair-instability pulsation supernovae and by pair-instability supernovae. finally, black holes with masses above 135 m⊙ may potentially form to arbitrarily high mass limited only by the extent of the initial mass function and the strength of stellar winds. suppression of double black-hole-merger rates by pair-instability pulsation supernovae is negligible for our evolutionary channel. our standard evolutionary model, with the inclusion of pair-instability pulsation supernovae and pair-instability supernovae, is fully consistent with the laser interferometric gravitational-wave observatory (ligo) observations of black-hole mergers: gw150914, gw151226, and lvt151012. the ligo results are inconsistent with high (≳ 400 km s-1) black hole (bh) natal kicks. we predict the detection of several, and up to as many as ~60, bh-bh mergers with a total mass of 10-150 m⊙ (most likely range: 20-80 m⊙) in the forthcoming ~60 effective days of the ligo o2 observations, assuming the detectors reach the optimistic target o2 sensitivity. | the effect of pair-instability mass loss on black-hole mergers |
motivated by the recent detection of gravitational waves from the black hole binary merger gw150914, we study the dynamical evolution of (stellar-mass) black holes in galactic nuclei, where massive star clusters reside. with masses of ∼ {10}7 {m}⊙and sizes of only a few parsecs, nuclear star clusters (nscs) are the densest stellar systems observed in the local universe and represent a robust environment where black hole binaries can dynamically form, harden, and merge. we show that due to their large escape speeds, nscs can retain a large fraction of their merger remnants. successive mergers can then lead to significant growth and produce black hole mergers of several tens of solar masses similar to gw150914 and up to a few hundreds of solar masses, without the need to invoke extremely low metallicity environments. we use a semi-analytical approach to describe the dynamics of black holes in massive star clusters. our models give a black hole binary merger rate of ≈ 1.5 {{gpc}}-3 {{yr}}-1 from nscs, implying up to a few tens of possible detections per year with advanced ligo. moreover, we find a local merger rate of ∼ 1 {{gpc}}-3 {{yr}}-1 for high mass black hole binaries similar to gw150914; a merger rate comparable to or higher than that of similar binaries assembled dynamically in globular clusters (gcs). finally, we show that if all black holes receive high natal kicks, ≳ 50 {km} {{{s}}}-1, then nscs will dominate the local merger rate of binary black holes compared to either gcs or isolated binary evolution. | merging black hole binaries in galactic nuclei: implications for advanced-ligo detections |
the early release science results from jwst have yielded an unexpected abundance of high-redshift luminous galaxies that seems to be in tension with current theories of galaxy formation. however, it is currently difficult to draw definitive conclusions form these results as the sources have not yet been spectroscopically confirmed. it is in any case important to establish baseline predictions from current state-of-the-art galaxy formation models that can be compared and contrasted with these new measurements. in this work, we use the new large-volume ($l_\mathrm{box}\sim 740 \, \mathrm{cmpc}$) hydrodynamic simulation of the millenniumtng project, suitably scaled to match results from higher resolution - smaller volume simulations, to make predictions for the high-redshift (z ≳ 8) galaxy population and compare them to recent jwst observations. we show that the simulated galaxy population is broadly consistent with observations until z ~ 10. from z ≈ 10-12, the observations indicate a preference for a galaxy population that is largely dust-free, but is still consistent with the simulations. beyond z ≳ 12, however, our simulation results underpredict the abundance of luminous galaxies and their star-formation rates by almost an order of magnitude. this indicates either an incomplete understanding of the new jwst data or a need for more sophisticated galaxy formation models that account for additional physical processes such as population iii stars, variable stellar initial mass functions, or even deviations from the standard λcdm model. we emphasize that any new process invoked to explain this tension should only significantly influence the galaxy population beyond z ≳ 10, while leaving the successful galaxy formation predictions of the fiducial model intact below this redshift. | the millenniumtng project: the galaxy population at z ≥ 8 |
we present models of realistic globular clusters with post-newtonian dynamics for black holes. by modeling the relativistic accelerations and gravitational-wave emission in isolated binaries and during three- and four-body encounters, we find that nearly half of all binary black hole mergers occur inside the cluster, with about 10% of those mergers entering the ligo/virgo band with eccentricities greater than 0.1. in-cluster mergers lead to the birth of a second generation of black holes with larger masses and high spins, which, depending on the black hole natal spins, can sometimes be retained in the cluster and merge again. as a result, globular clusters can produce merging binaries with detectable spins regardless of the birth spins of black holes formed from massive stars. these second-generation black holes would also populate any upper mass gap created by pair-instability supernovae. | post-newtonian dynamics in dense star clusters: highly eccentric, highly spinning, and repeated binary black hole mergers |
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