abstract
stringlengths 3
192k
| title
stringlengths 4
857
|
|---|---|
this paper presents a table with estimates of the absolute magnitude of the sun and the conversions from vegamag to the ab and st systems for several wide-band filters used in ground-based and space-based observatories. these estimates use the dustless spectral energy distribution (sed) of vega, calibrated absolutely using the sed of sirius, to set the vegamag zero-points and a composite spectrum of the sun that coadds space-based observations from the ultraviolet to the near-infrared with models of the solar atmosphere. the uncertainty of the absolute magnitudes is estimated by comparing the synthetic colors with photometric measurements of solar analogs and is found to be ∼0.02 mag. combined with the uncertainty of ∼2% in the calibration of the vega sed, the errors of these absolute magnitudes are ∼3%-4%. using these seds, for three of the most utilized filters in extragalactic work the estimated absolute magnitudes of the sun are mb= 5.44, mv= 4.81, and mk= 3.27 mag in the vegamag system and mb= 5.31, mv= 4.80, and mk= 5.08 mag in ab. | the absolute magnitude of the sun in several filters |
two neutron stars merging together generate a gravitational wave signal and have also been predicted to emit electromagnetic radiation. when the gravitational wave event gw170817 was detected, astronomers rushed to search for the source using conventional telescopes (see the introduction by smith). coulter et al. describe how the one-meter two-hemispheres (1m2h) collaboration was the first to locate the electromagnetic source. drout et al. present the 1m2h measurements of its optical and infrared brightness, and shappee et al. report their spectroscopy of the event, which is unlike previously detected astronomical transient sources. kilpatrick et al. show how these observations can be explained by an explosion known as a kilonova, which produces large quantities of heavy elements in nuclear reactions. | early spectra of the gravitational wave source gw170817: evolution of a neutron star merger |
finite-density lattice qcd aims for the first-principle study of qcd at finite density, which describes the system consisting of many quarks. the main targets are systems such as quark-gluon plasma, nuclei, and neutron stars. explaining macroscopic physics from the microscopic theory is a natural path in the development of physics. to understand the strong interaction completely, we have to solve finite-density qcd. each of the systems mentioned above has open problems which cannot easily be accessed by experiment or observation, so it is important to make progress in finite-density lattice qcd. in this article, we summarize the past development and current status of the field of finite-density lattice qcd. the difficulty in the study of theories with the sign problem is that the numerical methods which are correct in principle do not necessarily work in practice and it is hard to know when it fails. we will introduce various approaches in this article, but all of them have pitfalls, which lead to unphysical results unless we study carefully. we will explain what kinds of studies were done in the past, to what extent they succeeded, and what kinds of obstacles they encountered, and why the approaches are correct in principle can lead to wrong answers. in this way, we would like to provide lessons from the past for ambitious researchers who plan to work on the finite-density lattice qcd. | finite-density lattice qcd and sign problem: current status and open problems |
in this review, i will discuss the comparison between model results and observational data for the milky way, the predictive power of such models as well as their limits. such a comparison, known as galactic archaeology, allows us to impose constraints on stellar nucleosynthesis and timescales of formation of the various galactic components (halo, bulge, thick disk and thin disk). | modelling the chemical evolution of the milky way |
we report a robust sample of 10 massive quiescent galaxies at redshift, z > 3, selected using the first data from the jwst cosmic evolution early release science programme. three of these galaxies are at 4 < z < 5, constituting the best evidence to date for quiescent galaxies significantly before z = 4. these extreme galaxies have stellar masses in the range log10(m*/m⊙) = 10.1-11.1, and formed the bulk of their mass around z ≃ 10, with two objects having star formation histories that suggest they had already reached log10(m*/m⊙) > 10 by z ≳ 8. we report number densities for our sample, demonstrating that, based on the small area of jwst imaging so far available, previous work appears to have underestimated the number of quiescent galaxies at 3 < z < 4 by a factor of 3-5, due to a lack of ultra-deep imaging data at $\lambda \gt 2\, \mu$m. this result deepens the existing tension between observations and theoretical models, which already struggle to reproduce previous estimates of z > 3 quiescent galaxy number densities. upcoming wider-area jwst imaging surveys will provide larger samples of such galaxies and more robust number densities, as well as providing opportunities to search for quiescent galaxies at z > 5. the galaxies we report are excellent potential targets for jwst nirspec spectroscopy, which will be required to understand in detail their physical properties, providing deeper insights into the processes responsible for forming massive galaxies and quenching star formation during the first billion years. | a surprising abundance of massive quiescent galaxies at 3 < z < 5 in the first data from jwst ceers |
context. the inner regions of the envelopes surrounding young protostars are characterized by a complex chemistry, with prebiotic molecules present on the scales where protoplanetary disks eventually may form. the atacama large millimeter/submillimeter array (alma) provides an unprecedented view of these regions zooming in on solar system scales of nearby protostars and mapping the emission from rare species.aims: the goal is to introduce a systematic survey, the protostellar interferometric line survey (pils), of the chemical complexity of one of the nearby astrochemical templates, the class 0 protostellar binary iras 16293-2422, using alma in order to understand the origin of the complex molecules formed in its vicinity. in addition to presenting the overall survey, the analysis in this paper focuses on new results for the prebiotic molecule glycolaldehyde, its isomers, and rarer isotopologues and other related molecules.methods: an unbiased spectral survey of iras 16293-2422 covering the full frequency range from 329 to 363 ghz (0.8 mm) has been obtained with alma, in addition to a few targeted observations at 3.0 and 1.3 mm. the data consist of full maps of the protostellar binary system with an angular resolution of 0.5'' (60 au diameter), a spectral resolution of 0.2 km s-1, and a sensitivity of 4-5 mjy beam-1 km s-1, which is approximately two orders of magnitude better than any previous studies.results: more than 10 000 features are detected toward one component in the protostellar binary, corresponding to an average line density of approximately one line per 3 km s-1. glycolaldehyde; its isomers, methyl formate and acetic acid; and its reduced alcohol, ethylene glycol, are clearly detected and their emission well-modeled with an excitation temperature of 300 k. for ethylene glycol both lowest state conformers, agg' and ggg', are detected, the latter for the first time in the interstellar medium (ism). the abundance of glycolaldehyde is comparable to or slightly larger than that of ethylene glycol. in comparison to the galactic center these two species are over-abundant relative to methanol, possibly an indication of formation of the species at low temperatures in co-rich ices during the infall of the material toward the central protostar. both 13c and the deuterated isotopologues of glycolaldehyde are detected, also for the first time ever in the ism. for the deuterated species, a d/h ratio of ≈5% is found with no differences between the deuteration in the different functional groups of glycolaldehyde, in contrast to previous estimates for methanol and recent suggestions of significant equilibration between water and -oh functional groups at high temperatures. measurements of the 13c-species lead to a 12c:13c ratio of ≈30, lower than the typical ism value. this low ratio may reflect an enhancement of 13co in the ice due to either ion-molecule reactions in the gas before freeze-out or to differences in the temperatures where 12co and 13co ices sublimate.conclusions: the results reinforce the importance of low-temperature grain surface chemistry for the formation of prebiotic molecules seen here in the gas after sublimation of the entire ice mantle. systematic surveys of the molecules thought to be chemically related, as well as the accurate measurements of their isotopic composition, hold strong promise for understanding the origin of prebiotic molecules in the earliest stages of young stars. | the alma protostellar interferometric line survey (pils). first results from an unbiased submillimeter wavelength line survey of the class 0 protostellar binary iras 16293-2422 with alma |
it is predicted that the spectrum of radio emission from the whole sky should show a dip arising from the action of the light from the first stars on the hydrogen atoms in the surrounding gas, which causes the 21-cm line to appear in absorption against the cosmic microwave background. bowman et al. 2018 identified a broad flat-bottomed absorption profile centred at 78 mhz, which could be this feature, although the depth of the profile is much larger than expected. we have examined the modelling process they used and find that their data implies unphysical parameters for the foreground emission and also that their solution is not unique in the sense that we found other simple formulations for the signal that are different in shape but that also fit their data. we argue that this calls into question the interpretation of these data as an unambiguous detection of the cosmological 21-cm absorption signature. | concerns about modelling of the edges data |
we present a comparison between several simulation codes designed to study the core-collapse supernova mechanism. we pay close attention to controlling the initial conditions and input physics in order to ensure a meaningful and informative comparison. our goal is three-fold. first, we aim to demonstrate the current level of agreement between various groups studying the core-collapse supernova central engine. second, we desire to form a strong basis for future simulation codes and methods to compare to. lastly, we want this work to be a stepping stone for future work exploring more complex simulations of core-collapse supernovae, i.e., simulations in multiple dimensions and simulations with modern neutrino and nuclear physics. we compare the early (first ∼500 ms after core bounce) spherically-symmetric evolution of a 20 m ⊙ progenitor star from six different core-collapse supernovae codes: 3dnsne-idsa, agile-boltztran, flash, fornax, gr1d, and prometheus-vertex. given the diversity of neutrino transport and hydrodynamic methods employed, we find excellent agreement in many critical quantities, including the shock radius evolution and the amount of neutrino heating. our results provide an excellent starting point from which to extend this comparison to higher dimensions and compare the development of hydrodynamic instabilities that are crucial to the supernova explosion mechanism, such as turbulence and convection. | global comparison of core-collapse supernova simulations in spherical symmetry |
time-delay cosmography of lensed quasars has achieved 2.4% precision on the measurement of the hubble constant, h0. as part of an ongoing effort to uncover and control systematic uncertainties, we investigate three potential sources: 1- stellar kinematics, 2- line-of-sight effects, and 3- the deflector mass model. to meet this goal in a quantitative way, we reproduced the h0licow/sharp/strides (hereafter tdcosmo) procedures on a set of real and simulated data, and we find the following. first, stellar kinematics cannot be a dominant source of error or bias since we find that a systematic change of 10% of measured velocity dispersion leads to only a 0.7% shift on h0 from the seven lenses analyzed by tdcosmo. second, we find no bias to arise from incorrect estimation of the line-of-sight effects. third, we show that elliptical composite (stars + dark matter halo), power-law, and cored power-law mass profiles have the flexibility to yield a broad range in h0 values. however, the tdcosmo procedures that model the data with both composite and power-law mass profiles are informative. if the models agree, as we observe in real systems owing to the "bulge-halo" conspiracy, h0 is recovered precisely and accurately by both models. if the two models disagree, as in the case of some pathological models illustrated here, the tdcosmo procedure either discriminates between them through the goodness of fit, or it accounts for the discrepancy in the final error bars provided by the analysis. this conclusion is consistent with a reanalysis of six of the tdcosmo (real) lenses: the composite model yields h0 = 74.0-1.8+1.7 km s-1 mpc-1, while the power-law model yields 74.2-1.6+1.6 km s-1 mpc-1. in conclusion, we find no evidence of bias or errors larger than the current statistical uncertainties reported by tdcosmo. | tdcosmo. i. an exploration of systematic uncertainties in the inference of h0 from time-delay cosmography |
context. the post-asymptotic giant branch (agb) phase is arguably one of the least understood phases of the evolution of low- and intermediate- mass stars. the two grids of models presently available are based on outdated micro- and macrophysics and do not agree with each other. studies of the central stars of planetary nebulae (cspne) and post-agb stars in different stellar populations point to significant discrepancies with the theoretical predictions of post-agb models.aims: we study the timescales of post-agb and cspne in the context of our present understanding of the micro- and macrophysics of stars. we want to assess whether new post-agb models, based on the latter improvements in tp-agb modeling, can help us to understand the discrepancies between observation and theory and within theory itself. in addition, we aim to understand the impact of the previous agb evolution for post-agb phases.methods: we computed a grid of post-agb full evolutionary sequences that include all previous evolutionary stages from the zero age main sequence to the white dwarf phase. we computed models for initial masses between 0.8 and 4 m⊙ and for a wide range of initial metallicities (z0 = 0.02, 0.01, 0.001, 0.0001). this allowed us to provide post-agb timescales and properties for h-burning post-agb objects with masses in the relevant range for the formation of planetary nebulae (~0.5-0.8 m⊙). we included an updated treatment of the constitutive microphysics and included an updated description of the mixing processes and winds that play a key role during the thermal pulses (tp) on the agb phase.results: we present a new grid of models for post-agb stars that take into account the improvements in the modeling of agb stars in recent decades. these new models are particularly suited to be inputs in studies of the formation of planetary nebulae and for the determination of the properties of cspne from their observational parameters. we find post-agb timescales that are at least approximately three to ten times shorter than those of old post-agb stellar evolution models. this is true for the whole mass and metallicity range. the new models are also ~0.1-0.3 dex brighter than the previous models with similar remnant masses. post-agb timescales only show a mild dependence on metallicity.conclusions: the shorter post-agb timescales derived in the present work are in agreement with recent semiempirical determinations of the post-agb timescales from the cspne in the galactic bulge. the lower number of post-agb and cspne predicted by the new models might help to alleviate some of the discrepancies found in the literature. as a result of the very different post-agb crossing times, initial final mass relation and luminosities of the present models, the new models will have a significant impact on the predictions for the formation of planetary nebulae and the planetary nebulae luminosity function. in particular, the new models should help to understand the formation of low-mass cspne as inferred from asteroseismic and spectroscopic determinations. tables containing the evolution of luminosity, temperature, surface gravity, and other relevant quantities are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/588/a25 | new models for the evolution of post-asymptotic giant branch stars and central stars of planetary nebulae |
we review the current status and recent progress of microscopic many-body approaches and phenomenological models, which are employed to construct the equation of state of neutron stars. the equation of state is relevant for the description of their structure and dynamical properties, and it rules also the dynamics of core-collapse supernovae and binary neutron star mergers. we describe neutron star matter assuming that the main degrees of freedom are nucleons and hyperons, disregarding the appearance of quark matter. we compare the theoretical predictions of the different equation-of-state models with the currently available data coming from both terrestrial laboratory experiments and recent astrophysical observations. we also analyze the importance of the nuclear strong interaction and equation of state for the cooling properties of neutron stars. we discuss the main open challenges in the description of the equation of state, mainly focusing on the limits of the different many-body techniques, the so-called "hyperon puzzle," and the dependence of the direct urca processes on the equation of state. | neutron stars and the nuclear equation of state |
magnetars are the strongest magnets in the present universe and the combination of extreme magnetic field, gravity and density makes them unique laboratories to probe current physical theories (from quantum electrodynamics to general relativity) in the strong field limit. magnetars are observed as peculiar, burst-active x-ray pulsars, the anomalous x-ray pulsars (axps) and the soft gamma repeaters (sgrs); the latter emitted also three ‘giant flares’, extremely powerful events during which luminosities can reach up to 1047erg s-1 for about one second. the last five years have witnessed an explosion in magnetar research which has led, among other things, to the discovery of transient, or ‘outbursting’, and ‘low-field’ magnetars. substantial progress has been made also on the theoretical side. quite detailed models for explaining the magnetars’ persistent x-ray emission, the properties of the bursts, the flux evolution in transient sources have been developed and confronted with observations. new insight on neutron star asteroseismology has been gained through improved models of magnetar oscillations. the long-debated issue of magnetic field decay in neutron stars has been addressed, and its importance recognized in relation to the evolution of magnetars and to the links among magnetars and other families of isolated neutron stars. the aim of this paper is to present a comprehensive overview in which the observational results are discussed in the light of the most up-to-date theoretical models and their implications. this addresses not only the particular case of magnetar sources, but the more fundamental issue of how physics in strong magnetic fields can be constrained by the observations of these unique sources. | magnetars: the physics behind observations. a review |
we present multiple ultrahigh resolution cosmological hydrodynamic simulations of m⋆ ≃ 104-6.3 m⊙ dwarf galaxies that form within two mvir = 109.5-10 m⊙ dark matter halo initial conditions. our simulations rely on the feedback in realistic environments (fire) implementation of star formation feedback and were run with high enough force and mass resolution to directly resolve structure on the ∼200 pc scales. the resultant galaxies sit on the m⋆ versus mvir relation required to match the local group stellar mass function via abundance matching. they have bursty star formation histories and also form with half-light radii and metallicities that broadly match those observed for local dwarfs at the same stellar mass. we demonstrate that it is possible to create a large (∼1 kpc) constant-density dark matter core in a cosmological simulation of an m⋆ ≃ 106.3 m⊙ dwarf galaxy within a typical mvir = 1010 m⊙ halo - precisely the scale of interest for resolving the `too big to fail' problem. however, these large cores are not ubiquitous and appear to correlate closely with the star formation histories of the dwarfs: dark matter cores are largest in systems that form their stars late (z ≲ 2), after the early epoch of cusp building mergers has ended. our m⋆ ≃ 104 m⊙ dwarf retains a cuspy dark matter halo density profile that matches that of a dark-matter-only run of the same system. though ancient, most of the stars in our ultrafaint form after reionization; the ultraviolet field acts mainly to suppress fresh gas accretion, not to boil away gas that is already present in the protodwarf. | forged in fire: cusps, cores and baryons in low-mass dwarf galaxies |
alma observations of the long wavelength dust continuum are used to estimate the interstellar medium (ism) masses in a sample of 708 galaxies at z = 0.3 to 4.5 in the cosmos field. the galaxy sample has known far-infrared luminosities and, hence, star formation rates (sfrs) and stellar masses ({m}* ) from the optical-infrared spectrum fitting. the galaxies sample sfrs from the main sequence (ms) to 50 times above the ms. the derived ism masses are used to determine the dependence of gas mass on redshift, {m}* , and specific sfr (ssfr) relative to the ms. the ism masses increase approximately with the 0.63 power of the rate of increase in sfrs with redshift and the 0.32 power of the ssfr/ssfrms. the sf efficiencies also increase as the 0.36 power of the sfr redshift evolution and the 0.7 power of the elevation above the ms; thus the increased activities at early epochs are driven by both increased ism masses and sf efficiency. using the derived ism mass function, we estimate the accretion rates of gas required to maintain continuity of the ms evolution (> 100 {m}⊙yr-1 at z > 2.5). simple power-law dependencies are similarly derived for the gas accretion rates. we argue that the overall evolution of galaxies is driven by the rates of gas accretion. the cosmic evolution of total ism mass is estimated and linked to the evolution of sf and active galactic nucleus activity at early epochs. | evolution of interstellar medium, star formation, and accretion at high redshift |
we employ polarization-resolved electronic raman spectroscopy and density functional theory to study the primary and secondary order parameters, as well as their interplay, in the charge density wave (cdw) state of the kagome metal a v3sb5 . previous x-ray diffraction data at 15 k established that the cdw order in csv3sb5 comprises of a 2 ×2 ×4 structure: one layer of inverse-star-of-david and three consecutive layers of star-of-david pattern. we analyze the lattice distortions based on the 2 ×2 ×4 structure at 15 k, and find that the u1 lattice distortion is the primarylike (leading) order parameter while m1+ and l2− distortions are secondarylike order parameters for vanadium displacements. this conclusion is confirmed by the calculation of bare susceptibility χ0'(q ) that shows a broad peak at around qz=0.25 along the hexagonal brillouin zone face central line (u line). we also identify several phonon modes emerging in the cdw state, which are lattice vibration modes related to v and sb atoms as well as alkali-metal atoms. the detailed temperature evolution of these modes' frequencies, half-width at half-maximums, and integrated intensities support a phase diagram with two successive structural phase transitions in csv3sb5 : the first one with a primarylike order parameter appearing at ts=94 k and the second isostructural one appearing at around t*=70 k . furthermore, the t dependence of the integrated intensity for these modes shows two types of behavior below ts: the low-energy modes show a plateaulike behavior below t* while the high-energy modes monotonically increase below ts. these two behaviors are captured by the landau free-energy model incorporating the interplay between the primarylike and the secondarylike order parameters via trilinear coupling. especially, the sign of the trilinear term that couples order parameters with different wave vectors determines whether the primarylike and secondarylike order parameters cooperate or compete with each other, thus determining the shape of the t dependence of the intensities of bragg peak in x-ray data and the amplitude modes in raman data below ts. these results provide an accurate basis for studying the interplay between multiple cdw order parameters in kagome metal systems. | charge density wave order in the kagome metal a v3sb5 (a =cs ,rb ,k ) |
we derive the probability for a newly formed binary black hole (bbh) to undergo an eccentric gravitational wave (gw) merger during binary-single interactions inside a stellar cluster. by integrating over the hardening interactions such a bbh must undergo before ejection, we find that the observable rate of bbh mergers with eccentricity >0.1 at 10 hz relative to the rate of circular mergers can be as high as ∼5 % for a typical globular cluster (gc). this further suggests that bbh mergers forming through gw captures in binary-single interactions, eccentric or not, are likely to constitute ∼10 % of the total bbh merger rate from gcs. such gw capture mergers can only be probed with an n -body code that includes general relativistic corrections, which explains why recent newtonian cluster studies have not been able to resolve this population. finally, we show that the relative rate of eccentric bbh mergers depends on the compactness of their host cluster, suggesting that an observed eccentricity distribution can be used to probe the origin of bbh mergers. | eccentric black hole mergers forming in globular clusters |
we present new stellar mass functions at z ~ 6, z ~ 7, z ~ 8, z ~ 9 and, for the first time, z ~ 10, constructed from ~800 lyman-break galaxies previously identified over the extreme deep field and hubble ultra-deep field parallel fields and the five cosmic assembly near-infrared deep extragalactic legacy survey fields. our study is distinctive due to (1) the much deeper (~200 hr) wide-area spitzer/infrared array camera (irac) imaging at 3.6 μm and 4.5 μm from the great observatories origins deep survey re-ionization era wide-area treasury from spitzer program (greats) and (2) consideration of z ~ 6-10 sources over a 3× larger area than those of previous hubble space telescope+spitzer studies. the spitzer/irac data enable ≥2σ rest-frame optical detections for an unprecedented 50% of galaxies down to a stellar mass limit of $\sim {10}^{8}{{ \mathcal m }}_{\odot }$ across all redshifts. schechter fits to our volume densities suggest a combined evolution in the characteristic mass ${{ \mathcal m }}^{* }$ and normalization factor φ* between z ~ 6 and z ~ 8. the stellar mass density (smd) increases by ~1000× in the ~500 myr between z ~ 10 and z ~ 6, with indications of a steeper evolution between z ~ 10 and z ~ 8, similar to the previously reported trend of the star formation rate density. strikingly, abundance matching to the bolshoi-planck simulation indicates halo mass densities evolving at approximately the same rate as the smd between z ~ 10 and z ~ 4. our results show that the stellar-to-halo mass ratios, a proxy for the star formation efficiency, do not change significantly over the huge stellar mass buildup occurred from z ~ 10 to z ~ 6, indicating that the assembly of stellar mass closely mirrors the buildup in halo mass in the first ~1 gyr of cosmic history. the james webb space telescope is poised to extend these results into the "first galaxy" epoch at z ≳ 10. | galaxy stellar mass functions from z 10 to z 6 using the deepest spitzer/infrared array camera data: no significant evolution in the stellar-to-halo mass ratio of galaxies in the first gigayear of cosmic time |
we investigate the evolution of galaxy masses and star formation rates in the evolution and assembly of galaxies and their environment (eagle) simulations. these comprise a suite of hydrodynamical simulations in a λ cold dark matter cosmogony with subgrid models for radiative cooling, star formation, stellar mass-loss and feedback from stars and accreting black holes. the subgrid feedback was calibrated to reproduce the observed present-day galaxy stellar mass function and galaxy sizes. here, we demonstrate that the simulations reproduce the observed growth of the stellar mass density to within 20 per cent. the simulations also track the observed evolution of the galaxy stellar mass function out to redshift z = 7, with differences comparable to the plausible uncertainties in the interpretation of the data. just as with observed galaxies, the specific star formation rates of simulated galaxies are bimodal, with distinct star forming and passive sequences. the specific star formation rates of star-forming galaxies are typically 0.2 to 0.5 dex lower than observed, but the evolution of the rates track the observations closely. the unprecedented level of agreement between simulation and data across cosmic time makes eagle a powerful resource to understand the physical processes that govern galaxy formation. | evolution of galaxy stellar masses and star formation rates in the eagle simulations |
context. the gaia second data release (dr2) presents a first mapping of full-sky rr lyrae stars and cepheids observed by the spacecraft during the initial 22 months of science operations.aims: the specific objects study (sos) pipeline, developed to validate and fully characterise cepheids and rr lyrae stars (sos cep&rrl) observed by gaia, has been presented in the documentation and papers accompanying the gaia first data release. here we describe how the sos pipeline was modified to allow for processing the gaia multi-band (g, gbp, and grp) time-series photometry of all-sky candidate variables and produce specific results for confirmed rr lyrae stars and cepheids that are published in the dr2 catalogue.methods: the sos cep&rrl processing uses tools such as the period-amplitude and the period-luminosity relations in the g band. for the analysis of the gaia dr2 candidates we also used tools based on the gbp and grp photometry, such as the period-wesenheit relation in (g, grp).results: multi-band time-series photometry and characterisation by the sos cep&rrl pipeline are published in gaia dr2 for 150 359 such variables (9575 classified as cepheids and 140 784 as rr lyrae stars) distributed throughout the sky. the sample includes variables in 87 globular clusters and 14 dwarf galaxies (the magellanic clouds, 5 classical and 7 ultra-faint dwarfs). to the best of our knowledge, as of 25 april 2018, the variability of 50 570 of these sources (350 cepheids and 50 220 rr lyrae stars) has not been reported before in the literature, therefore they are likely new discoveries by gaia. an estimate of the interstellar absorption is published for 54 272 fundamental-mode rr lyrae stars from a relation based on the g-band amplitude and the pulsation period. metallicities derived from the fourier parameters of the light curves are also released for 64 932 rr lyrae stars and 3738 fundamental-mode classical cepheids with periods shorter than 6.3 days. full table c.1 is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/622/a60 | gaia data release 2. specific characterisation and validation of all-sky cepheids and rr lyrae stars |
the variable stars in the vsx catalogue are derived from a multitude of inhomogeneous data sources and classification tools. this inhomogeneity complicates our understanding of variable star types, statistics, and properties, and it directly affects attempts to build training sets for current (and next) generation all-sky, time-domain surveys. we homogeneously analyse the all-sky automated survey for supernovae (asas-sn) v-band light curves of {∼ }412 000 variables from the vsx catalogue. the variables are classified using an updated random forest classifier with an f1 score of 99.4 per cent and refinement criteria for individual classifications. we have derived periods for {∼ }52 000 variables in the vsx catalogue that lack a period, and have reclassified {∼ } 17 000 sources into new broad variability groups with high confidence. we have also reclassified {∼ } 94 000 known variables with miscellaneous/generic classifications. the light curves, classifications, and a range of properties of the variables are all available through the asas-sn variable stars database (https://asas-sn.osu.edu/variables). we also include the v-band light curves for a set of ∼4000 rare variables and transient sources, including cataclysmic variables, symbiotic binaries, and flare stars. | the asas-sn catalogue of variable stars - ii. uniform classification of 412 000 known variables |
nuclear star clusters around a central massive black hole (mbh) are expected to be abundant in stellar black hole (bh) remnants and bh-bh binaries. these binaries form a hierarchical triple system with the central mbh, and gravitational perturbations from the mbh can cause high-eccentricity excitation in the bh-bh binary orbit. during this process, the eccentricity may approach unity, and the pericenter distance may become sufficiently small so that gravitational-wave emission drives the bh-bh binary to merge. in this work, we construct a simple proof-of-concept model for this process, and specifically, we study the eccentric kozai-lidov mechanism in unequal-mass, soft bh-bh binaries. our model is based on a set of monte carlo simulations for bh-bh binaries in galactic nuclei, taking into account quadrupole- and octupole-level secular perturbations, general relativistic precession, and gravitational-wave emission. for a typical steady-state number of bh-bh binaries, our model predicts a total merger rate of ∼1-3 {gpc} -3 {yr} -1, depending on the assumed density profile in the nucleus. thus, our mechanism could potentially compete with other dynamical formation processes for merging bh-bh binaries, such as the interactions of stellar bhs in globular clusters or in nuclear star clusters without an mbh. | black hole mergers in galactic nuclei induced by the eccentric kozai-lidov effect |
the aless survey has followed up on a sample of 122 sub-millimeter sources in the extended chandra deep field south at 870 μm with the atacama large millimeter array (alma), allowing us to pinpoint the positions of sub-millimeter galaxies (smgs) to ∼0.3 arcsec and to find their precise counterparts at different wavelengths. this enabled the first compilation of the multi-wavelength spectral energy distributions (seds) of a statistically reliable survey of smgs. in this paper, we present a new calibration of the magphys sed modeling code that is optimized to fit these ultraviolet-to-radio seds of z\gt 1 star-forming galaxies using an energy balance technique to connect the emission from stellar populations, dust attenuation, and dust emission in a physically consistent way. we derive statistically and physically robust estimates of the photometric redshifts and physical parameters (such as stellar masses, dust attenuation, star formation rates (sfrs), and dust masses) for the aless smgs. we find that the aless smgs have median stellar mass {m}*=8.9+/- 0.1× {10}10 {m}⊙ , median sfr =\280+/- 70 {m}⊙{{yr}}-1, median overall v-band dust attenuation {a}v=1.9+/- 0.2 mag, median dust mass {m}{dust}=(5.6+/- 1.0)× {10}8 {m}⊙ , and median average dust temperature {t}{dust}≃ 40 k. we find that the average intrinsic sed of the aless smgs resembles that of local ultra-luminous infrared galaxies in the infrared range, but the stellar emission of our average smg is brighter and bluer, indicating lower dust attenuation, possibly because they are more extended. we explore how the average seds vary with different parameters (redshift, sub-millimeter flux, dust attenuation, and total infrared luminosity), and we provide a new set of smg templates that can be used to interpret other smg observations. to put the aless smgs into context, we compare their stellar masses and sfrs with those of less actively star-forming galaxies at the same redshifts. we find that at z≃ 2, about half of the smgs lie above the star-forming main sequence (with sfrs three times larger than normal galaxies of the same stellar mass), while half are consistent with being at the high-mass end of the main sequence. at higher redshifts (z≃ 3.5), the smgs tend to have higher sfrs and stellar masses, but the fraction of smgs that lie significantly above the main sequence decreases to less than a third. | an alma survey of sub-millimeter galaxies in the extended chandra deep field south: physical properties derived from ultraviolet-to-radio modeling |
we present a catalog of stellar properties for a large sample of 6676 evolved stars with apache point observatory galactic evolution experiment spectroscopic parameters and kepler asteroseismic data analyzed using five independent techniques. our data include evolutionary state, surface gravity, mean density, mass, radius, age, and the spectroscopic and asteroseismic measurements used to derive them. we employ a new empirical approach for combining asteroseismic measurements from different methods, calibrating the inferred stellar parameters, and estimating uncertainties. with high statistical significance, we find that asteroseismic parameters inferred from the different pipelines have systematic offsets that are not removed by accounting for differences in their solar reference values. we include theoretically motivated corrections to the large frequency spacing (δν) scaling relation, and we calibrate the zero-point of the frequency of the maximum power (ν max) relation to be consistent with masses and radii for members of star clusters. for most targets, the parameters returned by different pipelines are in much better agreement than would be expected from the pipeline-predicted random errors, but 22% of them had at least one method not return a result and a much larger measurement dispersion. this supports the usage of multiple analysis techniques for asteroseismic stellar population studies. the measured dispersion in mass estimates for fundamental calibrators is consistent with our error model, which yields median random and systematic mass uncertainties for rgb stars of order 4%. median random and systematic mass uncertainties are at the 9% and 8% level, respectively, for red clump stars. | the second apokasc catalog: the empirical approach |
we explore the predictions for detectable gravitational-wave signals from merging binary black holes formed through chemically homogeneous evolution in massive short-period stellar binaries. we find that ∼500 events per year could be detected with advanced ground-based detectors operating at full sensitivity. we analyse the distribution of detectable events, and conclude that there is a very strong preference for detecting events with nearly equal components (mass ratio >0.66 at 90 per cent confidence in our default model) and high masses (total source-frame mass between 57 and 103 m⊙ at 90 per cent confidence). we consider multiple alternative variations to analyse the sensitivity to uncertainties in the evolutionary physics and cosmological parameters, and conclude that while the rates are sensitive to assumed variations, the mass distributions are robust predictions. finally, we consider the recently reported results of the analysis of the first 16 double-coincident days of the o1 ligo (laser interferometer gravitational-wave observatory) observing run, and find that this formation channel is fully consistent with the inferred parameters of the gw150914 binary black hole detection and the inferred merger rate. | the chemically homogeneous evolutionary channel for binary black hole mergers: rates and properties of gravitational-wave events detectable by advanced ligo |
high-contrast adaptive optics (ao) imaging is a powerful technique to probe the architectures of planetary systems from the outside-in and survey the atmospheres of self-luminous giant planets. direct imaging has rapidly matured over the past decade and especially the last few years with the advent of high-order ao systems, dedicated planet-finding instruments with specialized coronagraphs, and innovative observing and post-processing strategies to suppress speckle noise. this review summarizes recent progress in high-contrast imaging with particular emphasis on observational results, discoveries near and below the deuterium-burning limit, and a practical overview of large-scale surveys and dedicated instruments. i conclude with a statistical meta-analysis of deep imaging surveys in the literature. based on observations of 384 unique and single young (≈5-300 myr) stars spanning stellar masses between 0.1 and 3.0 m ⊙, the overall occurrence rate of 5-13 m jup companions at orbital distances of 30-300 au is {0.6}-0.5+0.7 % assuming hot-start evolutionary models. the most massive giant planets regularly accessible to direct imaging are about as rare as hot jupiters are around sun-like stars. dividing this sample into individual stellar mass bins does not reveal any statistically significant trend in planet frequency with host mass: giant planets are found around {2.8}-2.3+3.7 % of ba stars, <4.1% of fgk stars, and <3.9% of m dwarfs. looking forward, extreme ao systems and the next generation of ground- and space-based telescopes with smaller inner working angles and deeper detection limits will increase the pace of discovery to ultimately map the demographics, composition, evolution, and origin of planets spanning a broad range of masses and ages. | imaging extrasolar giant planets |
the trappist-1 system is the first transiting planet system found orbiting an ultracool dwarf star 1 . at least seven planets similar in radius to earth were previously found to transit this host star 2 . subsequently, trappist-1 was observed as part of the k2 mission and, with these new data, we report the measurement of an 18.77 day orbital period for the outermost transiting planet, trappist-1 h, which was previously unconstrained. this value matches our theoretical expectations based on laplace relations 3and places trappist-1 h as the seventh member of a complex chain, with three-body resonances linking every member. we find that trappist-1 h has a radius of 0.752 r ⊕ and an equilibrium temperature of 173 k. we have also measured the rotational period of the star to be 3.3 days and detected a number of flares consistent with a low-activity, middle-aged, late m dwarf. | a seven-planet resonant chain in trappist-1 |
the neutron star interior composition explorer collaboration recently published a joint estimate of the mass and the radius of psr j0030+0451, derived via x-ray pulse-profile modeling. raaijmakers et al. explored the implications of this measurement for the dense matter equation of state (eos) using two parameterizations of the high-density eos: a piecewise-polytropic model, and a model based on the speed of sound in neutron stars (nss). in this work we obtain further constraints on the eos following this approach, but we also include information about the tidal deformability of nss from the gravitational wave signal of the compact binary merger gw170817. we compare the constraints on the eos to those set by the recent measurement of a 2.14 m⊙ pulsar, included as a likelihood function approximated by a gaussian, and find a small increase in information gain. to show the flexibility of our method, we also explore the possibility that gw170817 was a ns-black hole merger, which yields weaker constraints on the eos. | constraining the dense matter equation of state with joint analysis of nicer and ligo/virgo measurements |
magnetars younger than one century are expected to be hyperactive: besides winds powered by rotation, they can generate frequent magnetic flares, which launch powerful blast waves into the wind. the resulting magnetized shocks act as masers producing bright radio emission. this theoretical picture predicts radio bursts with the following properties. (1) ghz radio emission occurs at radii $r\sim {10}^{14}\,\mathrm{cm}$ and lasts $\lesssim 1$ ms in the observer's time. (2) induced scattering in the surrounding wind does not suppress the radio burst. (3) the emission has linear polarization set by the magnetar rotation axis. (4) the emission drifts to lower frequencies during the burst, and its duration broadens at lower frequencies. (5) blast waves in inhomogeneous winds may emit variable radio bursts; periodicity might appear on submillisecond timescales if the magnetar rotates with a ∼1 s period. however, the observed burst structure is likely changed by lensing effects during propagation through the host galaxy. (6) the magnetar bursts should repeat, with rare ultrastrong events (possibly up to ∼1043 erg in radio waves) or more frequent weak bursts. (7) when a repeating magnetic flare strikes the wind bubble in the tail of a previous flare, the radio burst turns into a bright optical burst lasting $\lesssim 1\,{\rm{s}}$ . locations of hyperactive magnetars in their host galaxies depend on how they form: magnetars created in supernova explosions will trace star formation regions, and magnetars formed in mergers of compact objects will be offset. the merger magnetars are expected to be particularly hyperactive. | blast waves from magnetar flares and fast radio bursts |
in this paper we present the mosfire deep evolution field (mosdef) survey. the mosdef survey aims to obtain moderate-resolution (r = 3000-3650) rest-frame optical spectra (∼3700-7000 å) for ∼1500 galaxies at 1.37≤ z≤ 3.80 in three well-studied candels fields: aegis, cosmos, and goods-n. targets are selected in three redshift intervals: 1.37≤ z≤ 1.70, 2.09≤ z≤ 2.61, and 2.95≤ z≤ 3.80, down to fixed {h}{ab} (f160w) magnitudes of 24.0, 24.5, and 25.0, respectively, using the photometric and spectroscopic catalogs from the 3d-hst survey. we target both strong nebular emission lines (e.g., [o ii] λ λ 3727,3730, hβ, [o iii] λ λ 4960,5008, hα, [n ii] λ λ 6550,6585, and [s ii] λ λ 6718,6733) and stellar continuum and absorption features (e.g., balmer lines, ca-ii h and k, mgb, 4000 å break). here we present an overview of our survey, the observational strategy, the data reduction and analysis, and the sample characteristics based on spectra obtained during the first 24 nights. to date, we have completed 21 masks, obtaining spectra for 591 galaxies. for ∼80% of the targets we derive a robust redshift from either emission or absorption lines. in addition, we confirm 55 additional galaxies, which were serendipitously detected. the mosdef galaxy sample includes unobscured star-forming, dusty star-forming, and quiescent galaxies and spans a wide range in stellar mass (∼ {10}9-{10}11.5 {m}⊙ ) and star formation rate (∼ {10}0-{10}3 {m}⊙{{yr}}-1). the spectroscopically confirmed sample is roughly representative of an h-band limited galaxy sample at these redshifts. with its large sample size, broad diversity in galaxy properties, and wealth of available ancillary data, mosdef will transform our understanding of the stellar, gaseous, metal, dust, and black hole content of galaxies during the time when the universe was most active. | the mosfire deep evolution field (mosdef) survey: rest-frame optical spectroscopy for ~1500 h-selected galaxies at 1.37 < z < 3.8 |
we explore the consequences of imposing robust thermodynamic constraints arising from perturbative quantum chromodynamics (qcd) when inferring the dense-matter equation-of-state (eos). we find that the termination density, up to which the eos modeling is performed in an inference setup, strongly affects the constraining power of the qcd input. this sensitivity in the constraining power arises from eoss that have a specific form, with drastic softening immediately above the termination density followed by a strong stiffening. we also perform explicit modeling of the eos down from perturbative-qcd densities to construct a new qcd likelihood function that incorporates additional perturbative-qcd calculations of the sound speed and is insensitive to the termination density, which we make publicly available. | equation of state at neutron-star densities and beyond from perturbative qcd |
axions can be copiously produced in localized regions of neutron star magnetospheres where the ambient plasma is unable to efficiently screen the induced electric field. as these axions stream away from the neutron star they can resonantly transition into photons, generating a large broadband contribution to the neutron star's intrinsic radio flux. in this letter, we develop a comprehensive end-to-end framework to model this process from the initial production of axions to the final detection of radio photons, and derive constraints on the axion-photon coupling, ga γ γ, using observations of 27 nearby pulsars. we study the modeling uncertainty in the sourced axion spectrum by comparing predictions from 2.5 dimensional particle-in-cell simulations with those derived using a semianalytic model; these results show remarkable agreement, leading to constraints on the axion-photon coupling that typically differ by a factor of no more than ∼2 . the limits presented here are the strongest to date for axion masses 10-8 ev ≲ma≲10-5 ev , and crucially do not rely on the assumption that axions are dark matter. | novel constraints on axions produced in pulsar polar-cap cascades |
we present the first comprehensive halo occupation distribution (hod) analysis of the desi one-percent survey luminous red galaxy (lrg) and quasi-stellar object (qso) samples. we constrain the hod of each sample and test possible hod extensions by fitting the redshift-space galaxy 2-point correlation functions in 0.15 < r < 32 mpc/h in a set of fiducial redshift bins. we use abacussummit cubic boxes at planck 2018 cosmology as model templates and forward model galaxy clustering with the abacushod package. we achieve good fits with a standard hod model with velocity bias, and we find no evidence for galaxy assembly bias or satellite profile modulation at the current level of statistical uncertainty. for lrgs in 0.4 < z < 0.6, we infer a satellite fraction of fsat = 11+-1%, a mean halo mass of log10 mh = 13.40+0.02-0.02, and a linear bias of blin = 1.93+0.06-0.04. for lrgs in 0.6 < z < 0.8, we find fsat = 14+-1%, log10 mh = 13.24+0.02-0.02, and blin = 2.08+0.03-0.03. for qsos, we infer fsat = 3+8-2%, log10 mh = 12.65+0.09-0.04, and blin = 2.63+0.37-0.26 in redshift range 0.8 < z < 2.1. using these fits, we generate a large suite of high-fidelity galaxy mocks. we also study the redshift-evolution of the desi lrg sample from z = 0.4 up to z = 1.1, revealing significant and interesting trends in mean halo mass, linear bias, and satellite fraction. | the desi one-percent survey: exploring the halo occupation distribution of luminous red galaxies and quasi-stellar objects with abacussummit |
the apache point observatory galactic evolution experiment (apogee), part of the sloan digital sky survey iii, explores the stellar populations of the milky way using the sloan 2.5-m telescope linked to a high resolution (r ∼ 22,500), near-infrared (1.51-1.70 μm) spectrograph with 300 optical fibers. for over 150,000 predominantly red giant branch stars that apogee targeted across the galactic bulge, disks and halo, the collected high signal-to-noise ratio (>100 per half-resolution element) spectra provide accurate (∼0.1 km s-1) rvs, stellar atmospheric parameters, and precise (≲0.1 dex) chemical abundances for about 15 chemical species. here we describe the basic apogee data reduction software that reduces multiple 3d raw data cubes into calibrated, well-sampled, combined 1d spectra, as implemented for the sdss-iii/apogee data releases (dr10, dr11 and dr12). the processing of the near-ir spectral data of apogee presents some challenges for reduction, including automated sky subtraction and telluric correction over a 3°-diameter field and the combination of spectrally dithered spectra. we also discuss areas for future improvement. | the data reduction pipeline for the apache point observatory galactic evolution experiment |
the manga survey (mapping nearby galaxies at apache point observatory) is one of three core programs in the sloan digital sky survey iv. it is obtaining integral field spectroscopy for 10,000 nearby galaxies at a spectral resolution of r ∼ 2000 from 3622 to 10354 å. the design of the survey is driven by a set of science requirements on the precision of estimates of the following properties: star formation rate surface density, gas metallicity, stellar population age, metallicity, and abundance ratio, and their gradients; stellar and gas kinematics; and enclosed gravitational mass as a function of radius. we describe how these science requirements set the depth of the observations and dictate sample selection. the majority of targeted galaxies are selected to ensure uniform spatial coverage in units of effective radius (re ) while maximizing spatial resolution. about two-thirds of the sample is covered out to 1.5re(primary sample), and one-third of the sample is covered to 2.5re(secondary sample). we describe the survey execution with details that would be useful in the design of similar future surveys. we also present statistics on the achieved data quality, specifically the point-spread function, sampling uniformity, spectral resolution, sky subtraction, and flux calibration. for our primary sample, the median r-band signal-to-noise ratio is ∼70 per 1.4 å pixel for spectra stacked between 1reand 1.5re . measurements of various galaxy properties from the first-year data show that we are meeting or exceeding the defined requirements for the majority of our science goals. | sdss-iv manga ifs galaxy survey—survey design, execution, and initial data quality |
white dwarfs are a class of stars with unique physical properties. they present many challenging problems whose solution requires advanced theories of dense matter, state-of-the-art experimental techniques, and extensive computing efforts. new ground- and space-based observatories will soon provide an increasingly detailed view of white dwarf stars and reveal new phenomena that will challenge our models. this review is an introduction to the nature of white dwarfs, the physical processes that determine their structure and evolution, and the physical conditions they span. we discuss a wide variety of currently unsolved or partially resolved problems in their constitutive physics that are broadly related to equations of state, transport processes and opacities. | current challenges in the physics of white dwarf stars |
context. the gaia early data release 3 contained the positions, parallaxes, and proper motions of 1.5 billion sources, some of which did not show a good fit to the `single star' model. binarity is one of the causes of this.aims: four million of these stars were selected and various models were tested to detect binary stars and to derive their parameters.methods: we used a preliminary treatment to discard the partially resolved double stars and to correct the transits for perspective acceleration. we then investigated whether the measurements show a good fit to an acceleration model with or without jerk. we tried the orbital model when the fit of any acceleration model was beyond our acceptance criteria. we also tried a variability-induced mover (vim) model when the star was photometrically variable. a final selection was made in order to keep only solutions that probably correspond to the real nature of the stars.results: following our analysis, 338 215 acceleration solutions, about 165 500 orbital solutions, and 869 vim solutions were retained. in addition, formulae for calculating the uncertainties of the campbell orbital elements from orbital solutions expressed in thiele-innes elements are given in an appendix. | gaia data release 3. astrometric binary star processing |
the presence of a stellar bar in a disc galaxy indicates that the galaxy hosts a dynamically settled disc and that bar-driven processes are taking place in shaping the evolution of the galaxy. studying the cosmic evolution of the bar fraction in disc galaxies is therefore essential to understand galaxy evolution in general. previous studies have found, using the hubble space telescope (hst), that the bar fraction significantly declines from the local universe to redshifts near one. using the first four pointings from the james webb space telescope (jwst) cosmic evolution early release science survey (ceers) and the initial public observations for the public release imaging for extragalactic research (primer), we extend the studies on the bar fraction in disc galaxies to redshifts $1 \leq z \leq 3$, i.e., for the first time beyond redshift two. we only use galaxies that are also present in the cosmic assembly near-ir deep extragalactic legacy survey (candels) on the extended groth strip (egs) and ultra deep survey (uds) hst observations. an optimised sample of 768 close-to-face-on galaxies is visually classified to find the fraction of bars in disc galaxies in two redshift bins: $1 \leq z \leq 2$ and $2 < z \leq 3$. the bar fraction decreases from $\sim 18.9^{+ 9.7}_{- 9.4}$ per cent to $\sim 6.6^{+ 7.1}_{- 5.9}$ per cent (from the lower to the higher redshift bin), but is $\sim 3 - 4$ times greater than the bar fraction found in previous studies using bluer hst filters. our results show that bar-driven evolution commences at early cosmic times and that dynamically settled discs are already present at a lookback time of $\sim 11$ gyrs. | a jwst investigation into the bar fraction at redshifts 1 < z < 3 |
we select galaxies from the illustristng hydrodynamical simulations (m_stars> 10^9 m_⊙ at 0 ≤ z ≤ 2) and characterize the shapes and evolutions of their uvj and star formation rate-stellar mass (sfr-mstars) diagrams. we quantify the systematic uncertainties related to different criteria to classify star-forming versus quiescent galaxies, different sfr estimates, and by accounting for the star formation measured within different physical apertures. the tng model returns the observed features of the uvj diagram at z ≤ 2, with a clear separation between two classes of galaxies. it also returns a tight star-forming main sequence (ms) for m_stars< 10^{10.5} (m_⊙) with a ∼0.3 dex scatter at z ∼ 0 in our fiducial choices. if a uvj-based cut is adopted, the tng ms exhibits a downwardly bending at stellar masses of about 1010.5-10.7 m⊙. moreover, the model predicts that {∼ }80 (50) per cent of 1010.5-11 m⊙ galaxies at z = 0 (z = 2) are quiescent and the numbers of quenched galaxies at intermediate redshifts and high masses are in better agreement with observational estimates than previous models. however, shorter sfr-averaging time-scales imply higher normalizations and scatter of the ms, while smaller apertures lead to underestimating the galaxy sfrs: overall we estimate the inspected systematic uncertainties to sum up to about 0.2-0.3 dex in the locus of the ms and to about 15 percentage points in the fraction of quenched galaxies. while tng colour distributions are clearly bimodal, this is not the case for the sfr logarithmic distributions in bins of stellar mass (sfr ≳ 10-3 m⊙yr-1). finally, the slope and z = 0 normalization of the tng ms are consistent with observational findings; however, the locus of the tng ms remains lower by about 0.2-0.5 dex at 0.75 ≤ z < 2 than the available observational estimates taken at face value. | the star formation activity of illustristng galaxies: main sequence, uvj diagram, quenched fractions, and systematics |
here we present high-resolution (15-24 au) observations of co isotopologue lines from the molecules with alma on planet-forming scales (maps) alma large program. our analysis employs observations of the (j = 2-1) and (1-0) lines of 13co and c18o and the (j = 1-0) line of c17o for five protoplanetary disks. we retrieve co gas density distributions, using three independent methods: (1) a thermochemical modeling framework based on the co data, the broadband spectral energy distribution, and the millimeter continuum emission; (2) an empirical temperature distribution based on optically thick co lines; and (3) a direct fit to the c17o hyperfine lines. results from these methods generally show excellent agreement. the co gas column density profiles of the five disks show significant variations in the absolute value and the radial shape. assuming a gas-to-dust mass ratio of 100, all five disks have a global co-to-h2 abundance 10-100 times lower than the interstellar medium ratio. the co gas distributions between 150 and 400 au match well with models of viscous disks, supporting the long-standing theory. co gas gaps appear to be correlated with continuum gap locations, but some deep continuum gaps do not have corresponding co gaps. the relative depths of co and dust gaps are generally consistent with predictions of planet-disk interactions, but some co gaps are 5-10 times shallower than predictions based on dust gaps. this paper is part of the maps special issue of the astrophysical journal supplement. | molecules with alma at planet-forming scales (maps). v. co gas distributions |
gas stripping phenomena in galaxies with muse (gasp) is a new integral-field spectroscopic survey with muse at the vlt aimed at studying gas removal processes in galaxies. we present an overview of the survey and show a first example of a galaxy undergoing strong gas stripping. gasp is obtaining deep muse data for 114 galaxies at z = 0.04-0.07 with stellar masses in the range {10}9.2{--}{10}11.5 {m}⊙in different environments (galaxy clusters and groups over more than four orders of magnitude in halo mass). gasp targets galaxies with optical signatures of unilateral debris or tails reminiscent of gas-stripping processes (“jellyfish galaxies”), as well as a control sample of disk galaxies with no morphological anomalies. gasp is the only existing integral field unit (ifu) survey covering both the main galaxy body and the outskirts and surroundings, where the ifu data can reveal the presence and origin of the outer gas. to demonstrate gasp’s ability to probe the physics of gas and stars, we show the complete analysis of a textbook case of a jellyfish galaxy, jo206. this is a massive galaxy (9× {10}10 {m}⊙ ) in a low-mass cluster (σ ∼ 500 {km} {{{s}}}-1) at a small projected clustercentric radius and a high relative velocity, with ≥90 kpc long tentacles of ionized gas stripped away by ram pressure. we present the spatially resolved kinematics and physical properties of the gas and stars and depict the evolutionary history of this galaxy. | gasp. i. gas stripping phenomena in galaxies with muse |
the disk substructures at high angular resolution project (dsharp) is the largest homogeneous high-resolution (∼0.″035, or ∼5 au) disk continuum imaging survey with the atacama large millimeter/submillimeter array (alma) so far. in the coming years, many more disks will be mapped with alma at similar resolution. interpreting the results in terms of the properties and quantities of the emitting dusty material is, however, a very non-trivial task. this is in part due to the uncertainty in the dust opacities, an uncertainty that is not likely to be resolved any time soon. it is also partly due to the fact that, as the dsharp survey has shown, these disk often contain regions of intermediate to high optical depth, even at millimeter wavelengths and at relatively large radius in the disk. this makes the interpretation challenging, in particular if the grains are large and have a large albedo. on the other hand, the highly structured features seen in the dsharp survey, of which strong indications were already seen in earlier observations, provide a unique opportunity to study the dust growth and dynamics. to provide continuity within the dsharp project, its follow-up projects, and projects by other teams interested in these data, we present here the methods and opacity choices used within the dsharp collaboration to link the measured intensity iνto dust surface density σ d . | the disk substructures at high angular resolution project (dsharp). v. interpreting alma maps of protoplanetary disks in terms of a dust model |
with the first observation of a binary neutron star merger through gravitational waves and light, gw170817, compact binary mergers have now taken the center stage in nuclear astrophysics. they are thought to be one of the main astrophysical sites of production of r-process elements, and merger observations have become a fundamental tool to constrain the properties of matter. here, we review our current understanding of the dynamics of neutron star mergers in general and of gw170817 in particular. we discuss the physical processes governing the inspiral, merger, and postmerger evolution, and we highlight the connections between these processes, the dynamics, and the multimessenger observables. finally, we discuss open questions and issues in the field and the need to address them through a combination of better theoretical models and new observations. | the dynamics of binary neutron star mergers and gw170817 |
measuring the metallicity and carbon-to-oxygen (c/o) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. transmission spectroscopy (for example, refs. 1,2) provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution and high precision, which, together, are not achievable with previous observatories. now that jwst has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. here we report time-series observations of the transiting exoplanet wasp-39b using jwst's near infrared camera (nircam). the long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0-4.0 micrometres, exhibit minimal systematics and reveal well defined molecular absorption features in the planet's spectrum. specifically, we detect gaseous water in the atmosphere and place an upper limit on the abundance of methane. the otherwise prominent carbon dioxide feature at 2.8 micrometres is largely masked by water. the best-fit chemical equilibrium models favour an atmospheric metallicity of 1-100-times solar (that is, an enrichment of elements heavier than helium relative to the sun) and a substellar c/o ratio. the inferred high metallicity and low c/o ratio may indicate significant accretion of solid materials during planet formation (for example, refs. 3,4,) or disequilibrium processes in the upper atmosphere (for example, refs. 5,6). | early release science of the exoplanet wasp-39b with jwst nircam |
we analyze the rest-frame near-uv and optical nebular spectra of three z > 7 galaxies from the early release observations taken with the near-infrared spectrograph (nirspec) on the james webb space telescope (jwst). these three high-z galaxies show the detection of several strong emission nebular lines, including the temperature-sensitive [o iii] λ4363 line, allowing us to directly determine the nebular conditions and abundances for o/h, c/o, and ne/o. we derive o/h abundances and ionization parameters that are generally consistent with other recent analyses. we analyze the mass-metallicity relationship (i.e., slope) and its redshift evolution by comparing between the three z > 7 galaxies and local star-forming galaxies. we also detect the c iii] λλ1907, 1909 emission in a z > 8 galaxy from which we determine the most distant c/o abundance to date. this valuable detection of log(c/o) = -0.83 ± 0.38 provides the first test of c/o redshift evolution out to high redshift. for neon, we use the high-ionization [ne iii] λ3869 line to measure the first ne/o abundances at z > 7, finding no evolution in this α-element ratio. we explore the tentative detection of [fe ii] and [fe iii] lines in a z > 8 galaxy, which would indicate a rapid buildup of metals. importantly, we demonstrate that properly flux-calibrated and higher-s/n spectra are crucial to robustly determine the abundance pattern in z > 7 galaxies with nirspec/jwst. | a first look at the abundance pattern-o/h, c/o, and ne/o-in z > 7 galaxies with jwst/nirspec |
the dark energy spectroscopic instrument (desi) survey will measure large-scale structures using quasars as direct tracers of dark matter in the redshift range 0.9 < z < 2.1 and using lyα forests in quasar spectra at z > 2.1. we present several methods to select candidate quasars for desi, using input photometric imaging in three optical bands (g, r, z) from the desi legacy imaging surveys and two infrared bands (w1, w2) from the wide-field infrared survey explorer. these methods were extensively tested during the survey validation of desi. in this paper, we report on the results obtained with the different methods and present the selection we optimized for the desi main survey. the final quasar target selection is based on a random forest algorithm and selects quasars in the magnitude range of 16.5 < r < 23. visual selection of ultra-deep observations indicates that the main selection consists of 71% quasars, 16% galaxies, 6% stars, and 7% inconclusive spectra. using the spectra based on this selection, we build an automated quasar catalog that achieves a fraction of true qsos higher than 99% for a nominal effective exposure time of ~1000 s. with a 310 deg-2 target density, the main selection allows desi to select more than 200 deg-2 quasars (including 60 deg-2 quasars with z > 2.1), exceeding the project requirements by 20%. the redshift distribution of the selected quasars is in excellent agreement with quasar luminosity function predictions. | target selection and validation of desi quasars |
we present the analysis of five black hole candidates identified from gravitational microlensing surveys. hubble space telescope astrometric data and densely sampled light curves from ground-based microlensing surveys are fit with a single-source, single-lens microlensing model in order to measure the mass and luminosity of each lens and determine if it is a black hole. one of the five targets (ogle-2011-blg-0462/moa-2011-blg-191 or ob110462 for short) shows a significant >1 mas coherent astrometric shift, little to no lens flux, and has an inferred lens mass of 1.6-4.4 m ⊙. this makes ob110462 the first definitive discovery of a compact object through astrometric microlensing and it is most likely either a neutron star or a low-mass black hole. this compact-object lens is relatively nearby (0.70-1.92 kpc) and has a slow transverse motion of <30 km s-1. ob110462 shows significant tension between models well fit to photometry versus astrometry, making it currently difficult to distinguish between a neutron star and a black hole. additional observations and modeling with more complex system geometries, such as binary sources, are needed to resolve the puzzling nature of this object. for the remaining four candidates, the lens masses are <2m ⊙, and they are unlikely to be black holes; two of the four are likely white dwarfs or neutron stars. we compare the full sample of five candidates to theoretical expectations on the number of black holes in the milky way (~108) and find reasonable agreement given the small sample size. | an isolated mass-gap black hole or neutron star detected with astrometric microlensing |
we assess a model of late cosmic reionization in which the ionizing background radiation arises entirely from high-redshift quasars and other active galactic nuclei (agns). the low optical depth to thomson scattering reported by the planck collaboration pushes the redshift of instantaneous reionization down to z={8.8}-1.4+1.7 and greatly reduces the need for significant lyman-continuum emission at very early times. we show that if recent claims of a numerous population of faint agns at z = 4-6 are upheld and the high inferred agn comoving emissivity at these epochs persists to higher, z ≳ 10, redshifts, then active galaxies may drive the reionization of hydrogen and helium with little contribution from normal star-forming galaxies. we discuss an agn-dominated scenario that satisfies a number of observational constraints: the h i photoionization rate is relatively flat over the range 2 < z < 5, hydrogen gets fully reionized by z ≃ 5.7, and the integrated thomson scattering optical depth is τ ≃ 0.056, in agreement with measurements based on the lyα opacity of the intergalactic medium (igm) and cosmic microwave background polarization. it is a prediction of the model that helium gets doubly reionized before redshift 4, the heat input from helium reionization dominates the thermal balance of the igm after hydrogen reionization, and z > 5 agns provide a significant fraction of the unresolved x-ray background at 2 kev. singly and doubly ionized helium contribute about 13% to τ, and the he iii volume fraction is already 50% when hydrogen becomes fully reionized. | cosmic reionization after planck: could quasars do it all? |
using the spinning worldline quantum field theory formalism we calculate the quadratic-in-spin momentum impulse δ piμ and spin kick δ aiμ from a scattering of two arbitrarily oriented spinning massive bodies (black holes or neutron stars) in a weak gravitational background up to third post-minkowskian (pm) order (g3). two-loop feynman integrals are performed in the potential region, yielding conservative results. for spins aligned to the orbital angular momentum we find a conservative scattering angle that is fully consistent with state-of-the-art post-newtonian results. using the 2pm radiated angular momentum previously obtained by plefka, steinhoff, and the present authors, we generalize the angle to include radiation-reaction effects, in which case it avoids divergences in the high-energy limit. | conservative and radiative dynamics of spinning bodies at third post-minkowskian order using worldline quantum field theory |
we describe a stream-based analysis pipeline to detect gravitational waves from the merger of binary neutron stars, binary black holes, and neutron-star-black-hole binaries within ∼1 min of the arrival of the merger signal at earth. such low-latency detection is crucial for the prompt response by electromagnetic facilities in order to observe any fading electromagnetic counterparts that might be produced by mergers involving at least one neutron star. even for systems expected not to produce counterparts, low-latency analysis of the data is useful for deciding when not to point telescopes, and as feedback to observatory operations. analysts using this pipeline were the first to identify gw151226, the second gravitational-wave event ever detected. the pipeline also operates in an offline mode, in which it incorporates more refined information about data quality and employs acausal methods that are inapplicable to the online mode. the pipeline's offline mode was used in the detection of the first two gravitational-wave events, gw150914 and gw151226, as well as the identification of a third candidate, lvt151012. | analysis framework for the prompt discovery of compact binary mergers in gravitational-wave data |
the heating of the solar chromosphere and corona to the observed high temperatures, imply the presence of ongoing heating that balances the strong radiative and thermal conduction losses expected in the solar atmosphere. it has been theorized for decades that the required heating mechanisms of the chromospheric and coronal parts of the active regions, quiet-sun, and coronal holes are associated with the solar magnetic fields. however, the exact physical process that transport and dissipate the magnetic energy which ultimately leads to the solar plasma heating are not yet fully understood. the current understanding of coronal heating relies on two main mechanism: reconnection and mhd waves that may have various degrees of importance in different coronal regions. in this review we focus on recent advances in our understanding of mhd wave heating mechanisms. first, we focus on giving an overview of observational results, where we show that different wave modes have been discovered in the corona in the last decade, many of which are associated with a significant energy flux, either generated in situ or pumped from the lower solar atmosphere. afterwards, we summarise the recent findings of numerical modelling of waves, motivated by the observational results. despite the advances, only 3d mhd models with alfvén wave heating in an unstructured corona can explain the observed coronal temperatures compatible with the quiet sun, while 3d mhd wave heating models including cross-field density structuring are not yet able to account for the heating of coronal loops in active regions to their observed temperature. | coronal heating by mhd waves |
context. absorption by molecules in the earth's atmosphere strongly affects ground-based astronomical observations. the resulting absorption line strength and shape depend on the highly variable physical state of the atmosphere, i.e. pressure, temperature, and mixing ratio of the different molecules involved. usually, supplementary observations of so-called telluric standard stars (tss) are needed to correct for this effect, which is expensive in terms of telescope time. we have developed the software package molecfit to provide synthetic transmission spectra based on parameters obtained by fitting narrow ranges of the observed spectra of scientific objects. these spectra are calculated by means of the radiative transfer code lblrtm and an atmospheric model. in this way, the telluric absorption correction for suitable objects can be performed without any additional calibration observations of tss.aims: we evaluate the quality of the telluric absorption correction using molecfit with a set of archival eso-vlt/x-shooter visible and near-infrared spectra.methods: thanks to the wavelength coverage from the u to the k band, x-shooter is well suited to investigate the quality of the telluric absorption correction with respect to the observing conditions, the instrumental set-up, input parameters of the code, the signal-to-noise of the input spectrum, and the atmospheric profiles. these investigations are based on two figures of merit, ioff and ires, that describe the systematic offsets and the remaining small-scale residuals of the corrections. we also compare the quality of the telluric absorption correction achieved with molecfit to the classical method based on a telluric standard star.results: the evaluation of the telluric correction with molecfit shows a convincing removal of atmospheric absorption features. the comparison with the classical method reveals that molecfit performs better because it is not prone to the bad continuum reconstruction, noise, and intrinsic spectral features introduced by the telluric standard star.conclusions: fitted synthetic transmission spectra are an excellent alternative to the correction based on telluric standard stars. moreover, molecfit offers wide flexibility for adaption to various instruments and observing sites. http://www.eso.org/sci/software/pipelines/skytools/ | molecfit: a general tool for telluric absorption correction. ii. quantitative evaluation on eso-vlt/x-shooterspectra |
x-ray pulsars (xrps) are accreting strongly magnetised neutron stars (nss) in binary systems with, as a rule, massive optical companions. very reach phenomenology and high observed flux put them into the focus of observational and theoretical studies since the first x-ray instruments were launched into space. the main attracting characteristic of nss in this kind of system is the magnetic field strength at their surface, about or even higher than $10^{12}\,{\rm g}$, that is about six orders of magnitude stronger than what is attainable in terrestrial laboratories. although accreting xrps were discovered about 50 years ago, the details of the physical mechanisms responsible for their properties are still under debate. here we review recent progress in observational and theoretical investigations of xrps as a unique laboratory for studies of fundamental physics (plasma physics, qed and radiative processes) under extreme conditions of ultra-strong magnetic field, high temperature, and enormous mass density. | accreting strongly magnetised neutron stars: x-ray pulsars |
a new table of the nuclear equation of state (eos) based on realistic nuclear potentials is constructed for core-collapse supernova numerical simulations. adopting the eos of uniform nuclear matter constructed by two of the present authors with the cluster variational method starting from the argonne v18 and urbana ix nuclear potentials, the thomas-fermi calculation is performed to obtain the minimized free energy of a wigner-seitz cell in non-uniform nuclear matter. as a preparation for the thomas-fermi calculation, the eos of uniform nuclear matter is modified so as to remove the effects of deuteron cluster formation in uniform matter at low densities. mixing of alpha particles is also taken into account following the procedure used by shen et al. (1998, 2011). the critical densities with respect to the phase transition from non-uniform to uniform phase with the present eos are slightly higher than those with the shen eos at small proton fractions. the critical temperature with respect to the liquid-gas phase transition decreases with the proton fraction in a more gradual manner than in the shen eos. furthermore, the mass and proton numbers of nuclides appearing in non-uniform nuclear matter with small proton fractions are larger than those of the shen eos. these results are consequences of the fact that the density derivative coefficient of the symmetry energy of our eos is smaller than that of the shen eos. | nuclear equation of state for core-collapse supernova simulations with realistic nuclear forces |
we present a sample of nearby dwarf galaxies with radio-selected accreting massive black holes (bhs), the majority of which are non-nuclear. we observed 111 galaxies using sensitive, high-resolution observations from the karl g. jansky very large array (vla) in its most extended a-configuration at x band (∼8-12 ghz), yielding a typical angular resolution of ∼0.″25 and rms noise of ∼15 μjy. our targets were selected by crossmatching galaxies with stellar masses m ⋆ ≤ 3 × 109 m ⊙ and redshifts z < 0.055 in the nasa-sloan atlas with the vla faint images of the radio sky at twenty centimeters survey. with our new high-resolution vla observations, we detect compact radio sources toward 39 galaxies and carefully evaluate possible origins for the radio emission, including thermal h ii regions, supernova remnants, younger radio supernovae, background interlopers, and active galactic nuclei (agns) in the target galaxies. we find that 13 dwarf galaxies almost certainly host active massive bhs, despite the fact that only one object was previously identified as having optical signatures of an agn. we also identify a candidate dual radio agn in a more massive galaxy system. the majority of the radio-detected bhs are offset from the center of the host galaxies, with some systems showing signs of interactions/mergers. our results indicate that massive bhs need not always live in the nuclei of dwarf galaxies, confirming predictions from simulations. moreover, searches attempting to constrain bh seed formation using observations of dwarf galaxies need to account for such a population of “wandering” bhs. | a new sample of (wandering) massive black holes in dwarf galaxies from high-resolution radio observations |
we perform a search for stellar streams around the milky way using the first 3 yr of multiband optical imaging data from the dark energy survey (des). we use des data covering ∼5000 deg2 to a depth of g > 23.5 with a relative photometric calibration uncertainty of <1%. this data set yields unprecedented sensitivity to the stellar density field in the southern celestial hemisphere, enabling the detection of faint stellar streams to a heliocentric distance of ∼50 kpc. we search for stellar streams using a matched filter in color-magnitude space derived from a synthetic isochrone of an old, metal-poor stellar population. our detection technique recovers four previously known thin stellar streams: phoenix, atlas, tucana iii, and a possible extension of molonglo. in addition, we report the discovery of 11 new stellar streams. in general, the new streams detected by des are fainter, more distant, and lower surface brightness than streams detected by similar techniques in previous photometric surveys. as a by-product of our stellar stream search, we find evidence for extratidal stellar structure associated with four globular clusters: ngc 288, ngc 1261, ngc 1851, and ngc 1904. the ever-growing sample of stellar streams will provide insight into the formation of the galactic stellar halo, the milky way gravitational potential, and the large- and small-scale distribution of dark matter around the milky way. | stellar streams discovered in the dark energy survey |
type ia supernovae (sne ia) play a key role in the fields of astrophysics and cosmology. it is widely accepted that sne ia arise from thermonuclear explosions of white dwarfs (wds) in binary systems. however, there is no consensus on the fundamental aspects of the nature of sn ia progenitors and their actual explosion mechanism. this fundamentally flaws our understanding of these important astrophysical objects. in this review, we outline the diversity of sne ia and the proposed progenitor models and explosion mechanisms. we discuss the recent theoretical and observational progress in addressing the sn ia progenitor and explosion mechanism in terms of the observables at various stages of the explosion, including rates and delay times, pre-explosion companion stars, ejecta-companion interaction, early excess emission, early radio/x-ray emission from circumstellar material interaction, surviving companion stars, late-time spectra and photometry, polarization signals and supernova remnant properties. despite the efforts from both the theoretical and observational sides, questions of how the wds reach an explosive state and what progenitor systems are more likely to produce sne ia remain open. no single published model is able to consistently explain all observational features and the full diversity of sne ia. this may indicate that either a new progenitor paradigm or an improvement in current models is needed if all sne ia arise from the same origin. an alternative scenario is that different progenitor channels and explosion mechanisms contribute to sne ia. in the next decade, the ongoing campaigns with the james webb space telescope, gaia and the zwicky transient facility, and upcoming extensive projects with the vera c. rubin observatory's legacy survey of space and time and the square kilometre array will allow us to conduct not only studies of individual sne ia in unprecedented detail but also systematic investigations for different subclasses of sne ia. this will advance theory and observations of sne ia sufficiently far to gain a deeper understanding of their origin and explosion mechanism. | type ia supernova explosions in binary systems: a review |
probing the connection between a star’s metallicity and the presence and properties of any associated planets offers an observational link between conditions during the epoch of planet formation and mature planetary systems. we explore this connection by analyzing the metallicities of kepler target stars and the subset of stars found to host transiting planets. after correcting for survey incompleteness, we measure planet occurrence: the number of planets per 100 stars with a given metallicity m. planet occurrence correlates with metallicity for some, but not all, planet sizes and orbital periods. for warm super-earths having p = 10-100 days and {r}p = 1.0-1.7 {r}\oplus , planet occurrence is nearly constant over metallicities spanning -0.4 to +0.4 dex. we find 20 warm super-earths per 100 stars, regardless of metallicity. in contrast, the occurrence of warm sub-neptunes ({r}p = 1.7-4.0 {r}\oplus ) doubles over that same metallicity interval, from 20 to 40 planets per 100 stars. we model the distribution of planets as {df}\propto {10}β m{dm}, where β characterizes the strength of any metallicity correlation. this correlation steepens with decreasing orbital period and increasing planet size. for warm super-earths β = -{0.3}-0.2+0.2, while for hot jupiters β = +{3.4}-0.8+0.9. high metallicities in protoplanetary disks may increase the mass of the largest rocky cores or the speed at which they are assembled, enhancing the production of planets larger than 1.7 {r}\oplus . the association between high metallicity and short-period planets may reflect disk density profiles that facilitate the inward migration of solids or higher rates of planet-planet scattering. | the california-kepler survey. iv. metal-rich stars host a greater diversity of planets |
jwst observations have revealed a population of galaxies bright enough that potentially challenge standard galaxy formation models in the λ cold dark matter (λcdm) cosmology. using a minimal empirical framework, we investigate the influence of variability on the rest-frame ultra-violet (uv) luminosity function of galaxies at z ≥ 9. our study differentiates between the median uv radiation yield and the variability of uv luminosities of galaxies at a fixed dark matter halo mass. we primarily focus on the latter effect, which depends on halo assembly and galaxy formation processes and can significantly increase the abundance of uv-bright galaxies due to the upscatter of galaxies in lower-mass haloes. we find that a relatively low level of variability, σuv ≈ 0.75 mag, matches the observational constraints at z ≈ 9. however, increasingly larger σuv is necessary when moving to higher redshifts, reaching $\sigma _{\rm uv} \approx 2.0\, (2.5)\, {\rm mag}$ at z ≈ 12 (16). this implied variability is consistent with expectations of physical processes in high-redshift galaxies such as bursty star formation and dust clearance during strong feedback cycles. photometric constraints from jwst at z ≳ 9 therefore can be reconciled with a standard λcdm-based galaxy formation model calibrated at lower redshifts without the need for adjustments to the median uv radiation yield. | the impact of uv variability on the abundance of bright galaxies at z ≥ 9 |
disks of gas and dust surrounding young stars are the birthplace of planets. however, the direct detection of protoplanets forming within disks has proved elusive to date. we present the detection of a large, localized deviation from keplerian velocity in the protoplanetary disk surrounding the young star hd 163296. the observed velocity pattern is consistent with the dynamical effect of a two-jupiter-mass planet orbiting at a radius ≈260 au from the star. | kinematic evidence for an embedded protoplanet in a circumstellar disk |
thus far, judging the fate of a massive star (either a neutron star [ns] or a black hole) solely by its structure prior to core collapse has been ambiguous. our work and previous attempts find a nonmonotonic variation of successful and failed supernovae with zero-age main-sequence mass, for which no single structural parameter can serve as a good predictive measure. however, we identify two parameters computed from the pre-collapse structure of the progenitor, which in combination allow for a clear separation of exploding and nonexploding cases with only a few exceptions (∼1%-2.5%) in our set of 621 investigated stellar models. one parameter is m4, defining the normalized enclosed mass for a dimensionless entropy per nucleon of s = 4, and the other is {μ }4\equiv ({dm}/{m}⊙ )/({dr}/1000 {km}){| }s=4, being the normalized mass derivative at this location. the two parameters μ4 and m4μ4 can be directly linked to the mass-infall rate, \dot{m}, of the collapsing star and the electron-type neutrino luminosity of the accreting proto-ns, {l}{ν e}\propto {m}{ns}\dot{m}, which play a crucial role in the “critical luminosity” concept for the theoretical description of neutrino-driven explosions as runaway phenomena of the stalled accretion shock. all models were evolved employing the approach of ugliano et al. for simulating neutrino-driven explosions in spherical symmetry. the neutrino emission of the accretion layer is approximated by a gray transport solver, while the uncertain neutrino emission of the 1.1 m⊙ proto-ns core is parameterized by an analytic model. the free parameters connected to the core-boundary prescription are calibrated to reproduce the observables of sn 1987a for five different progenitor models. | a two-parameter criterion for classifying the explodability of massive stars by the neutrino-driven mechanism |
the number of known periodic variables has grown rapidly in recent years. thanks to its large field of view and faint limiting magnitude, the zwicky transient facility (ztf) offers a unique opportunity to detect variable stars in the northern sky. here, we exploit ztf data release 2 (dr2) to search for and classify variables down to r ∼ 20.6 mag. we classify 781,602 periodic variables into 11 main types using an improved classification method. comparison with previously published catalogs shows that 621,702 objects (79.5%) are newly discovered or newly classified, including ∼700 cepheids, ∼5000 rr lyrae stars, ∼15,000 δ scuti variables, ∼350,000 eclipsing binaries, ∼100,000 long-period variables, and about 150,000 rotational variables. the typical misclassification rate and period accuracy are on the order of 2% and 99%, respectively. 74% of our variables are located at galactic latitudes, $| b| \lt 10^\circ $ . this large sample of cepheids, rr lyrae, δ scuti stars, and contact (ew-type) eclipsing binaries is helpful to investigate the galaxy's disk structure and evolution with an improved completeness, areal coverage, and age resolution. specifically, the northern warp and the disk's edge at distances of 15-20 kpc are significantly better covered than previously. among rotational variables, rs canum venaticorum and by draconis-type variables can be separated easily. our knowledge of stellar chromospheric activity would benefit greatly from a statistical analysis of these types of variables. | the zwicky transient facility catalog of periodic variable stars |
in the first billion years after the big bang, sources of ultraviolet (uv) photons are believed to have ionized intergalactic hydrogen, rendering the universe transparent to uv radiation. galaxies brighter than the characteristic luminosity l* (refs. 1,2) do not provide enough ionizing photons to drive this cosmic reionization. fainter galaxies are thought to dominate the photon budget; however, they are surrounded by neutral gas that prevents the escape of the lyman-α photons, which has been the dominant way to identify them so far. jd1 was previously identified as a triply-imaged galaxy with a magnification factor of 13 provided by the foreground cluster abell 2744 (ref. 3), and a photometric redshift of z ≈ 10. here we report the spectroscopic confirmation of this very low luminosity (≈0.05 l*) galaxy at z = 9.79, observed 480 myr after the big bang, by means of the identification of the lyman break and redward continuum, as well as multiple ≳4σ emission lines, with the near-infrared spectrograph (nirspec) and near-infrared camera (nircam) instruments. the combination of the james webb space telescope (jwst) and gravitational lensing shows that this ultra-faint galaxy (muv = −17.35)—with a luminosity typical of the sources responsible for cosmic reionization—has a compact (≈150 pc) and complex morphology, low stellar mass (107.19 m⊙) and subsolar (≈0.6 z⊙) gas-phase metallicity. | the nature of an ultra-faint galaxy in the cosmic dark ages seen with jwst |
we quantify the distribution of [o iii]+h β line strengths at z ≃ 7 using a sample of 20 bright ( $\mathrm{m}_{\mathrm{uv}}^{}$ ≲ -21) galaxies. we select these systems over wide-area fields (2.3 deg2 total) using a new colour-selection that precisely selects galaxies at z ≃ 6.63-6.83, a redshift range where blue spitzer/irac [3.6]-[4.5] colours unambiguously indicate strong [o iii]+h β emission. these 20 galaxies suggest a lognormal [o iii]+h β ew distribution with median ew = 759 $^{+112}_{-113}$ å and standard deviation = 0.26 $^{+0.06}_{-0.05}$ dex. we find no evidence for strong variation in this ew distribution with uv luminosity. the typical [o iii]+h β ew at z ≃ 7 implied by our sample is considerably larger than that in massive star-forming galaxies at z ≃ 2, consistent with a shift towards larger average ssfr (4.4 gyr-1) and lower metallicities (0.16 z⊙). we also find evidence for the emergence of a population with yet more extreme nebular emission ([o iii]+h β ew > 1200 å) that is rarely seen at lower redshifts. these objects have extremely large ssfr (>30 gyr-1), as would be expected for systems undergoing a burst or upturn in star formation. while this may be a short-lived phase, our results suggest that 20 per cent of the z ≃ 7 population has such extreme nebular emission, implying that galaxies likely undergo intense star formation episodes regularly at z > 6. we argue that this population may be among the most effective ionizing agents in the reionization era, both in terms of photon production efficiency and escape fraction. we furthermore suggest that galaxies passing through this large ssfr phase are likely to be very efficient in forming bound star clusters. | the [o iii]+h β equivalent width distribution at z ≃ 7: implications for the contribution of galaxies to reionization |
the binary neutron star merger gw170817 was the first multi-messenger event observed in both gravitational and electromagnetic waves1,2. the electromagnetic signal began approximately two seconds post-merger with a weak, short burst of gamma rays3, which was followed over the next hours and days by the ultraviolet, optical and near-infrared emission from a radioactively powered kilonova4-11. later, non-thermal rising x-ray and radio emission was observed12,13. the low luminosity of the gamma rays and the rising non-thermal flux from the source at late times could indicate that we are outside the opening angle of the beamed relativistic jet. alternatively, the emission could be arising from a cocoon of material formed from the interaction between a jet and the merger ejecta13-15. here we present late-time optical detections and deep near-infrared limits on the emission from gw170817 at 110 days post-merger. our new observations are at odds with expectations of late-time emission from kilonova models, being too bright and blue16,17. instead, the emission arises from the interaction between the relativistic ejecta of gw170817 and the interstellar medium. we show that this emission matches the expectations of a gaussian-structured relativistic jet, which would have launched a high-luminosity, short gamma-ray burst to an aligned observer. however, other jet structure or cocoon models can also match current data—the future evolution of the afterglow will directly distinguish the origin of the emission. | the optical afterglow of the short gamma-ray burst associated with gw170817 |
we review the physics potential of a next generation search for solar axions: the international axion observatory (iaxo) . endowed with a sensitivity to discover axion-like particles (alps) with a coupling to photons as small as gaγ~ 10-12 gev-1, or to electrons gae~10-13, iaxo has the potential to find the qcd axion in the 1 mev~1 ev mass range where it solves the strong cp problem, can account for the cold dark matter of the universe and be responsible for the anomalous cooling observed in a number of stellar systems. at the same time, iaxo will have enough sensitivity to detect lower mass axions invoked to explain: 1) the origin of the anomalous "transparency" of the universe to gamma-rays, 2) the observed soft x-ray excess from galaxy clusters or 3) some inflationary models. in addition, we review string theory axions with parameters accessible by iaxo and discuss their potential role in cosmology as dark matter and dark radiation as well as their connections to the above mentioned conundrums. | physics potential of the international axion observatory (iaxo) |
during its two-year prime mission, the transiting exoplanet survey satellite (tess) will perform a time-series photometric survey covering over 80% of the sky. this survey comprises observations of 26 24° × 96° sectors that are each monitored continuously for approximately 27 days. the main goal of tess is to find transiting planets around 200,000 pre-selected stars for which fixed aperture photometry is recorded every two minutes. however, tess is also recording and delivering full-frame images (ffis) of each detector at a 30-minutes cadence. we have created an open-source tool, eleanor, to produce light curves for objects in the tess ffis. here, we describe the methods used in eleanor to produce light curves that are optimized for planet searches. the tool performs background subtraction; aperture and point-spread function photometry; decorrelation of instrument systematics; and cotrending using principal component analysis. we recover known transiting exoplanets in the ffis to validate the pipeline and perform a limited search for new planet candidates in sector 1. our tests indicate that eleanor produces light curves with significantly less scatter than other tools that have been used in the literature. cadence-stacked images, and raw and detrended eleanor light curves for each analyzed star will be hosted on mikulski archive for space telescopes, with planet candidates on exofop-tess as community tess objects of interest. this work confirms the promise that the tess ffis will enable the detection of thousands of new exoplanets and a broad range of time domain astrophysics. | eleanor: an open-source tool for extracting light curves from the tess full-frame images |
fast radio bursts are bright, unresolved, non-repeating, broadband, millisecond flashes, found primarily at high galactic latitudes, with dispersion measures much larger than expected for a galactic source. the inferred all-sky burst rate is comparable to the core-collapse supernova rate out to redshift 0.5. if the observed dispersion measures are assumed to be dominated by the intergalactic medium, the sources are at cosmological distances with redshifts of 0.2 to 1 (refs 10 and 11). these parameters are consistent with a wide range of source models. one fast burst revealed circular polarization of the radio emission, but no linear polarization was detected, and hence no faraday rotation measure could be determined. here we report the examination of archival data revealing faraday rotation in the fast radio burst frb 110523. its radio flux and dispersion measure are consistent with values from previously reported bursts and, accounting for a galactic contribution to the dispersion and using a model of intergalactic electron density, we place the source at a maximum redshift of 0.5. the burst has a much higher rotation measure than expected for this line of sight through the milky way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. the pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy. the detection in this instance of magnetization and scattering that are both local to the source favours models involving young stellar populations such as magnetars over models involving the mergers of older neutron stars, which are more likely to be located in low-density regions of the host galaxy. | dense magnetized plasma associated with a fast radio burst |
the physics of star formation and the deposition of mass, momentum and energy into the interstellar medium by massive stars (`feedback') are the main uncertainties in modern cosmological simulations of galaxy formation and evolution1,2. these processes determine the properties of galaxies3,4 but are poorly understood on the scale of individual giant molecular clouds (less than 100 parsecs)5,6, which are resolved in modern galaxy formation simulations7,8. the key question is why the timescale for depleting molecular gas through star formation in galaxies (about 2 billion years)9,10 exceeds the cloud dynamical timescale by two orders of magnitude11. either most of a cloud's mass is converted into stars over many dynamical times12 or only a small fraction turns into stars before the cloud is dispersed on a dynamical timescale13,14. here we report high-angular-resolution observations of the nearby flocculent spiral galaxy ngc 300. we find that the molecular gas and high-mass star formation on the scale of giant molecular clouds are spatially decorrelated, in contrast to their tight correlation on galactic scales5. we demonstrate that this decorrelation implies rapid evolutionary cycling between clouds, star formation and feedback. we apply a statistical method15,16 to quantify the evolutionary timeline and find that star formation is regulated by efficient stellar feedback, which drives cloud dispersal on short timescales (around 1.5 million years). the rapid feedback arises from radiation and stellar winds, before supernova explosions can occur. this feedback limits cloud lifetimes to about one dynamical timescale (about 10 million years), with integrated star formation efficiencies of only 2 to 3 per cent. our findings reveal that galaxies consist of building blocks undergoing vigorous, feedback-driven life cycles that vary with the galactic environment and collectively define how galaxies form stars. | fast and inefficient star formation due to short-lived molecular clouds and rapid feedback |
context. the spectroscopy made easy (sme) package has become a popular tool for analyzing stellar spectra, often in connection with large surveys or exoplanet research. sme has evolved significantly since it was first described in 1996, but many of the original caveats and potholes still haunt users. the main drivers for this paper are complexity of the modeling task, the large user community, and the massive effort that has gone into sme.aims: we do not intend to give a comprehensive introduction to stellar atmospheres, but will describe changes to key components of sme: the equation of state, opacities, and radiative transfer. we will describe the analysis and fitting procedure and investigate various error sources that affect inferred parameters.methods: we review the current status of sme, emphasizing new algorithms and methods. we describe some best practices for using the package, based on lessons learned over two decades of sme usage. we present a new way to assess uncertainties in derived stellar parameters.results: improvements made to sme, better line data, and new model atmospheres yield more realistic stellar spectra, but in many cases systematic errors still dominate over measurement uncertainty. future enhancements are outlined. | spectroscopy made easy: evolution |
phangs-hst is an ultraviolet-optical imaging survey of 38 spiral galaxies within ~20 mpc. combined with the phangs-alma, phangs-muse surveys and other multiwavelength data, the data set will provide an unprecedented look into the connections between young stars, h ii regions, and cold molecular gas in these nearby star-forming galaxies. accurate distances are needed to transform measured observables into physical parameters (e.g. brightness to luminosity, angular to physical sizes of molecular clouds, star clusters and associations). phangs-hst has obtained parallel acs imaging of the galaxy haloes in the f606w and f814w bands. where possible, we use these parallel fields to derive tip of the red giant branch (trgb) distances to these galaxies. in this paper, we present trgb distances for 10 phangs galaxies from ~4 to ~15 mpc, based on the first year of phangs-hst observations. four of these represent the first published trgb distance measurements (ic 5332, ngc 2835, ngc 4298, and ngc 4321), and seven of which are the best available distances to these targets. we also provide a compilation of distances for the 118 galaxies in the full phangs sample, which have been adopted for the first phangs-alma public data release. | distances to phangs galaxies: new tip of the red giant branch measurements and adopted distances |
the density dependence of nuclear symmetry energy is among the most uncertain parts of the equation of state (eos) of dense neutron-rich nuclear matter. it is currently poorly known especially at suprasaturation densities partially because of our poor knowledge about isovector nuclear interactions at short distances. because of its broad impacts on many interesting issues, pinning down the density dependence of nuclear symmetry energy has been a longstanding and shared goal of both astrophysics and nuclear physics. new observational data of neutron stars including their masses, radii, and tidal deformations since gw170817 have helped improve our knowledge about nuclear symmetry energy, especially at high densities. based on various model analyses of these new data by many people in the nuclear astrophysics community, while our brief review might be incomplete and biased unintentionally, we learned in particular the following: (1) the slope parameter l of nuclear symmetry energy at saturation density ρ0 of nuclear matter from 24 new analyses of neutron star observables was about l≈57.7±19 mev at a 68% confidence level, consistent with its fiducial value from surveys of over 50 earlier analyses of both terrestrial and astrophysical data within error bars. (2) the curvature ksym of nuclear symmetry energy at ρ0 from 16 new analyses of neutron star observables was about ksym≈‑107±88 mev at a 68% confidence level, in very good agreement with the systematics of earlier analyses. (3) the magnitude of nuclear symmetry energy at 2ρ0, i.e., esym(2ρ0)≈51±13 mev at a 68% confidence level, was extracted from nine new analyses of neutron star observables, consistent with the results from earlier analyses of heavy-ion reactions and the latest predictions of the state-of-the-art nuclear many-body theories. (4) while the available data from canonical neutron stars did not provide tight constraints on nuclear symmetry energy at densities above about 2ρ0, the lower radius boundary r2.01=12.2 km from nicer's very recent observation of psr j0740+6620 of mass 2.08±0.07m⊙ and radius r=12.2–16.3 km at a 68% confidence level set a tight lower limit for nuclear symmetry energy at densities above 2ρ0. (5) bayesian inferences of nuclear symmetry energy using models encapsulating a first-order hadron–quark phase transition from observables of canonical neutron stars indicated that the phase transition shifted appreciably both l and ksym to higher values, but with larger uncertainties compared to analyses assuming no such phase transition. (6) the high-density behavior of nuclear symmetry energy significantly affected the minimum frequency necessary to rotationally support gw190814's secondary component of mass (2.50–2.67) m⊙ as the fastest and most massive pulsar discovered so far. overall, thanks to the hard work of many people in the astrophysics and nuclear physics community, new data of neutron star observations since the discovery of gw170817 have significantly enriched our knowledge about the symmetry energy of dense neutron-rich nuclear matter. | progress in constraining nuclear symmetry energy using neutron star observables since gw170817 |
we give an overview and describe the rationale, methods, and first results from nircam images of the jwst "prime extragalactic areas for reionization and lensing science" (pearls) project. pearls uses up to eight nircam filters to survey several prime extragalactic survey areas: two fields at the north ecliptic pole (nep); seven gravitationally lensing clusters; two high redshift protoclusters; and the iconic backlit vv 191 galaxy system to map its dust attenuation. pearls also includes niriss spectra for one of the nep fields and nirspec spectra of two high-redshift quasars. the main goal of pearls is to study the epoch of galaxy assembly, active galactic nucleus (agn) growth, and first light. five fields-the jwst nep time-domain field (tdf), irac dark field, and three lensing clusters-will be observed in up to four epochs over a year. the cadence and sensitivity of the imaging data are ideally suited to find faint variable objects such as weak agn, high-redshift supernovae, and cluster caustic transits. both nep fields have sightlines through our galaxy, providing significant numbers of very faint brown dwarfs whose proper motions can be studied. observations from the first spoke in the nep tdf are public. this paper presents our first pearls observations, their nircam data reduction and analysis, our first object catalogs, the 0.9-4.5 μm galaxy counts and integrated galaxy light. we assess the jwst sky brightness in 13 nircam filters, yielding our first constraints to diffuse light at 0.9-4.5 μm. pearls is designed to be of lasting benefit to the community. | jwst pearls. prime extragalactic areas for reionization and lensing science: project overview and first results |
aims: during the last ~50 years, the population of black hole candidates in x-ray binaries has increased considerably, with 59 galactic objects being detected in transient low-mass x-ray binaries, as well as a few in persistent systems (including ~5 extragalactic binaries).methods: we collect near-infrared, optical, and x-ray information spread over hundreds of references to study the population of black holes in x-ray transients as a whole.results: we present the most updated catalogue of black hole transients. this contains x-ray, optical, and near-infrared observations, together with their astrometric and dynamical properties. the catalogue provides new and useful information in both statistical and observational parameters and provides a thorough and complete overview of the black hole population in the milky way. analysing the distances and spatial distribution of the observed systems, we estimate a total population of ~1300 galactic black hole transients. this means that we have only discovered less than ~5% of the total galactic distribution. the complete version of this catalogue will be continuously updated at https://www.astro.puc.cl/blackcat and in the virtual observatory, including finding charts and data in other wavelengths.tables a.1 to a.4 are also available in electronic form at the cds via anonymous ftp to (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/587/a61 | blackcat: a catalogue of stellar-mass black holes in x-ray transients |
aims: we present the detailed characterisation of a sample of 56 sources serendipitously detected in alma band 7 as part of the alma large program to investigate cii at early times (alpine). these sources, detected in cosmos and ecdfs, have been used to derive the total infrared luminosity function (lf) and to estimate the cosmic star formation rate density (sfrd) up to z ≃ 6.methods: we looked for counterparts of the alma sources in all the available multi-wavelength (from hst to vla) and photometric redshift catalogues. we also made use of deeper ultravista and spitzer source lists and maps to identify optically dark sources with no matches in the public catalogues. we used the sources with estimated redshifts to derive the 250 μm rest-frame and total infrared (8-1000 μm) lfs from z ≃ 0.5 to 6.results: our alma blind survey (860 μm flux density range: ∼0.3-12.5 mjy) allows us to further push the study of the nature and evolution of dusty galaxies at high-z, identifying luminous and massive sources to redshifts and faint luminosities never probed before by any far-infrared surveys. the alpine data are the first ones to sample the faint end of the infrared lf, showing little evolution from z ≃ 2.5 to z ≃ 6, and a "flat" slope up to the highest redshifts (i.e. 4.5 < z < 6). the sfrd obtained by integrating the luminosity function remains almost constant between z ≃ 2 and z ≃ 6, and significantly higher than the optical or ultra-violet derivations, showing a significant contribution of dusty galaxies and obscured star formation at high-z. about 14% of all the alpine serendipitous continuum sources are found to be optically and near-infrared (near-ir) dark (to a depth ks ∼ 24.9 mag). six show a counterpart only in the mid-ir and no hst or near-ir identification, while two are detected as [c ii] emitters at z ≃ 5. the six hst+near-ir dark galaxies with mid-ir counterparts are found to contribute about 17% of the total sfrd at z ≃ 5 and to dominate the high-mass end of the stellar mass function at z > 3. | the alpine-alma [cii] survey. the nature, luminosity function, and star formation history of dusty galaxies up to z ≃ 6 |
one of the most striking observations made by parker solar probe during its first solar encounter is the omnipresence of rapid polarity reversals in a magnetic field that is otherwise mostly radial. these so-called switchbacks strongly affect the dynamics of the magnetic field. we concentrate here on their macroscopic properties. first, we find that these structures are self-similar, and have neither a characteristic magnitude, nor a characteristic duration. their waiting time statistics show evidence of aggregation. the associated long memory resides in their occurrence rate, and is not inherent to the background fluctuations. interestingly, the spectral properties of inertial range turbulence differ inside and outside of switchback structures; in the latter the 1/f range extends to higher frequencies. these results suggest that outside of these structures we are in the presence of lower-amplitude fluctuations with a shorter turbulent inertial range. we conjecture that these correspond to a pristine solar wind. | switchbacks in the near-sun magnetic field: long memory and impact on the turbulence cascade |
aims: we perform a comprehensive determination of the systemic proper motions of 74 dwarf galaxies and dwarf galaxy candidates in the local group based on gaia early data release 3. the outputs of the analysis for each galaxy, including probabilities of membership, will be made publicly available. the analysis is augmented by a determination of the orbital properties of galaxies within 500 kpc.methods: we adopt a flexible bayesian methodology presented in the literature, which takes into account the location of the stars on the sky, on the colour-magnitude diagram, and on the proper motion plane. we applied some modifications, in particular to the way the colour-magnitude diagram and spectroscopic information are factored in, for example, by including stars in several evolution phases. the bulk motions were integrated in three gravitational potentials: two where the milky way was treated in isolation and has a mass 0.9 & 1.6 × 1012 m⊙, and a time-varying potential, which includes the infall of a massive large magellanic cloud (lmc).results: we were able to determine bulk proper motions for 73 systems, and we consider 66 to be reliable measurements. for the first time, systemic motions are presented for galaxies out to a distance of 1.4 mpc in the ngc 3109 association. the inclusion of the infall of a massive lmc significantly modifies the orbital trajectories of the objects, with respect to orbit integration in static milky-way-only potentials, and this leads to six galaxies likely being associated with the lmc, three possibly being associated with it, and one recently captured object. we discuss the results of the orbit integration in the context of the relation of the galaxies to the system of milky way satellites, implications for the too-big-to-fail problem, the impact on star formation histories, and tidal disruption. tables of probabilities of membership are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/657/a54 | gaia early dr3 systemic motions of local group dwarf galaxies and orbital properties with a massive large magellanic cloud |
the identification of the main contributors to the locally observed fluxes of cosmic rays is a prime objective in the resolution of the long-standing enigma of the source of cosmic rays. we report on a compelling similarity of the energy and radial distributions of multi-tev cosmic rays extracted from observations of very-high-energy γ-rays towards the galactic centre and two prominent clusters of young massive stars, cygnus ob2 and westerlund 1. we interpret this resemblance as evidence that cosmic rays responsible for the diffuse very-high-energy γ-ray emission from the galactic centre are accelerated by the ultracompact stellar clusters located in the heart of the galactic centre. the derived 1/r decrement of the cosmic ray density with the distance from a star cluster is a distinct signature of continuous cosmic ray injection into the interstellar medium over a few million years. the lack of brightening of the γ-ray images towards the stellar clusters excludes the leptonic origin of γ-ray radiation. the hard, ∝e-2.3-type, power-law energy spectra of parent protons continues up to 1 pev. the efficiency of conversion of the kinetic energy of stellar winds to cosmic rays can be as high as 10%, implying that young massive stars may operate as proton pevatrons with a dominant contribution to the flux of the highest-energy galactic cosmic rays. | massive stars as major factories of galactic cosmic rays |
new millisecond pulsars (msps) in compact binaries provide a good opportunity to search for the most massive neutron stars. their main-sequence companion stars are often strongly irradiated by the pulsar, displacing the effective center of light from their barycenter and making mass measurements uncertain. we present a series of optical spectroscopic and photometric observations of psr j2215+5135, a “redback” binary msp in a 4.14 hr orbit, and measure a drastic temperature contrast between the dark/cold (t n = 5660{}-380+260 k) and bright/hot (t d = 8080{}-280+470 k) sides of the companion star. we find that the radial velocities depend systematically on the atmospheric absorption lines used to measure them. namely, the semi-amplitude of the radial velocity curve (rvc) of j2215 measured with magnesium triplet lines is systematically higher than that measured with hydrogen balmer lines, by 10%. we interpret this as a consequence of strong irradiation, whereby metallic lines dominate the dark side of the companion (which moves faster) and balmer lines trace its bright (slower) side. further, using a physical model of an irradiated star to fit simultaneously the two-species rvcs and the three-band light curves, we find a center-of-mass velocity of k 2 = 412.3 ± 5.0 km s-1 and an orbital inclination i = 63.°9{}-2.7+2.4. our model is able to reproduce the observed fluxes and velocities without invoking irradiation by an extended source. we measure masses of m 1 = 2.27{}-0.15+0.17 m ⊙ and m 2 = 0.33{}-0.02+0.03 m ⊙ for the neutron star and the companion star, respectively. if confirmed, such a massive pulsar would rule out some of the proposed equations of state for the neutron star interior. | peering into the dark side: magnesium lines establish a massive neutron star in psr j2215+5135 |
we present an updated model of the cosmic ionizing background from the uv to the x-rays. relative to our previous model, the new model provides a better match to a large number of up-to-date empirical constraints, including: (1) new galaxy and agn luminosity functions; (2) stellar spectra including binary stars; (3) obscured and unobscured agn; (4) a measurement of the non-ionizing uv background; (5) measurements of the intergalactic h i and he ii photoionization rates at z ∼ 0-6; (6) the local x-ray background; and (7) improved measurements of the intergalactic opacity. in this model, agn dominate the h i ionizing background at z ≲ 3 and star-forming galaxies dominate it at higher redshifts. combined with the steeply declining agn luminosity function beyond z ∼ 2, the slow evolution of the h i ionization rate inferred from the high-redshift h i ly α forest requires an escape fraction from star-forming galaxies that increases with redshift (a population-averaged escape fraction of $\approx 1{{\ \rm per\ cent}}$ suffices to ionize the intergalactic medium at z = 3 when including the contribution from agn). we provide effective photoionization and photoheating rates calibrated to match the planck 2018 reionization optical depth and recent constraints from the he ii ly α forest in hydrodynamic simulations. | a cosmic uv/x-ray background model update |
in quantum fluids, the quantization of circulation forbids the diffusion of a vortex swirling flow seen in classical viscous fluids. yet, accelerating quantum vortices may lose their energy into acoustic radiations1,2, similar to the way electric charges decelerate on emitting photons. the dissipation of vortex energy underlies central problems in quantum hydrodynamics3, such as the decay of quantum turbulence, highly relevant to systems as varied as neutron stars, superfluid helium and atomic condensates4,5. a deep understanding of the elementary mechanisms behind irreversible vortex dynamics has been a goal for decades3,6, but it is complicated by the shortage of conclusive experimental signatures7. here we address this challenge by realizing a programmable vortex collider in a planar, homogeneous atomic fermi superfluid with tunable inter-particle interactions. we create on-demand vortex configurations and monitor their evolution, taking advantage of the accessible time and length scales of ultracold fermi gases8,9. engineering collisions within and between vortex-antivortex pairs allows us to decouple relaxation of the vortex energy due to sound emission and that due to interactions with normal fluid (that is, mutual friction). we directly visualize how the annihilation of vortex dipoles radiates a sound pulse. further, our few-vortex experiments extending across different superfluid regimes reveal non-universal dissipative dynamics, suggesting that fermionic quasiparticles localized inside the vortex core contribute significantly to dissipation, thereby opening the route to exploring new pathways for quantum turbulence decay, vortex by vortex. | sound emission and annihilations in a programmable quantum vortex collider |
in the violent post-merger of binary neutron-star mergers strong oscillations are present that impact the emitted gravitational-wave (gw) signal. the frequencies, temperatures and densities involved in these oscillations allow for violations of the chemical equilibrium promoted by weak-interactions, thus leading to a nonzero bulk viscosity that can impact dynamics and gw signals. we present the first simulations of binary neutron-star mergers employing the self-consistent and second-order formulation of the equations of relativistic hydrodynamics for dissipative fluids proposed by müller, israel and stewart. with the spirit of obtaining a first assessment of the impact of bulk viscosity on the structure and radiative efficiency of the merger remnant we adopt a simplified approach for the viscosity, which we assume to be constant within the stars, but which we vary in strength for different binaries, thus exploring the possible behaviours and obtaining strict upper limits. in this way, we find that large bulk viscosities are very effective at damping the collision-and-bounce oscillations that characterize the dynamics of the stellar cores right after the merger. as a result, the $m=2$ deformations and the gravitational-radiation efficiency of the remnant are considerably reduced, with qualitative and quantitative changes in the post-merger spectrum that can be large in the case of the most extreme configurations. overall, our crude but self-consistent results indicate that bulk viscosity reduces the energy radiated in gws by $\lesssim 1\%$ in the (realistic) scenario of small viscosity, and by $\lesssim 15\%$ in the (unrealistic) scenario of large viscosity. | impact of bulk viscosity on the post-merger gravitational-wave signal from merging neutron stars |
accurately understanding the equation of state (eos) of high-density, zero-temperature quark matter plays an essential role in constraining the behavior of dense strongly interacting matter inside the cores of neutron stars. in this letter, we study the weak-coupling expansion of the eos of cold quark matter and derive the complete, gauge-invariant contributions from the long-wavelength, dynamically screened gluonic sector at next-to-next-to-next-to-leading order (n3lo) in the strong coupling constant αs. this elevates the eos result to the o (αs3ln αs) level, leaving only one unknown constant from the unscreened sector at n3lo, and places it on par with its high-temperature counterpart from 2003. | equation of state of cold quark matter to o (αs3ln αs) |
we perform a general-relativistic neutrino-radiation magnetohydrodynamic simulation of a one second-long binary neutron star merger on the japanese supercomputer fugaku using about 85 million cpu hours with 20 736 cpus. we consider an asymmetric binary neutron star merger with masses of 1.2 m⊙ and 1.5 m⊙ and a "soft" equation of state sfho. it results in a short-lived remnant with the lifetime of ≈0.017 s , and subsequent massive torus formation with the mass of ≈0.05 m⊙ after the remnant collapses to a black hole. for the first time, we find that after the dynamical mass ejection, which drives the fast tail and mildly relativistic components, the postmerger mass ejection from the massive torus takes place due to the magnetorotational instability-driven turbulent viscosity in a single simulation and the two ejecta components are seen in the distributions of the electron fraction and velocity with distinct features. | self-consistent picture of the mass ejection from a one second long binary neutron star merger leaving a short-lived remnant in a general-relativistic neutrino-radiation magnetohydrodynamic simulation |
it is a major open question which physical processes stop gas accretion on to giant molecular clouds (gmcs) and limit the efficiency at which gas is converted into stars. while feedback from supernova explosions has been the popular feedback mechanism included in simulations of galaxy formation and evolution, 'early' feedback mechanisms such as stellar winds, photoionization, and radiation pressure are expected to play an important role in dispersing the gas after the onset of star formation. these feedback processes typically take place on small scales (~10-100 pc) and their effects have therefore been difficult to constrain in environments other than the milky way. we apply a novel statistical method to ~1 arcsec resolution maps of co and h α across a sample of nine nearby galaxies, to measure the time over which gmcs are dispersed by feedback from young, high-mass stars, as a function of the galactic environment. we find that gmcs are typically dispersed within ~3 myr on average after the emergence of unembedded high-mass stars, with variations within galaxies associated with morphological features rather than radial trends. comparison with analytical predictions demonstrates that, independently of the environment, early feedback mechanisms (particularly photoionization and stellar winds) play a crucial role in dispersing gmcs and limiting their star formation efficiency in nearby galaxies. finally, we show that the efficiency at which the energy injected by these early feedback mechanisms couples with the parent gmc is relatively low (a few tens of per cent), such that the vast majority of momentum and energy emitted by the young stellar populations escapes the parent gmc. | pre-supernova feedback mechanisms drive the destruction of molecular clouds in nearby star-forming disc galaxies |
we report the most sensitive upper limits to date on the 21 cm epoch of reionization power spectrum using 94 nights of observing with phase i of the hydrogen epoch of reionization array (hera). using similar analysis techniques as in previously reported limits, we find at 95% confidence that δ2(k = 0.34 h mpc-1) ≤ 457 mk2 at z = 7.9 and that δ2(k = 0.36 h mpc-1) ≤ 3496 mk2 at z = 10.4, an improvement by a factor of 2.1 and 2.6, respectively. these limits are mostly consistent with thermal noise over a wide range of k after our data quality cuts, despite performing a relatively conservative analysis designed to minimize signal loss. our results are validated with both statistical tests on the data and end-to-end pipeline simulations. we also report updated constraints on the astrophysics of reionization and the cosmic dawn. using multiple independent modeling and inference techniques previously employed by hera collaboration, we find that the intergalactic medium must have been heated above the adiabatic cooling limit at least as early as z = 10.4, ruling out a broad set of so-called "cold reionization" scenarios. if this heating is due to high-mass x-ray binaries during the cosmic dawn, as is generally believed, our result's 99% credible interval excludes the local relationship between soft x-ray luminosity and star formation and thus requires heating driven by evolved low-metallicity stars. | improved constraints on the 21 cm eor power spectrum and the x-ray heating of the igm with hera phase i observations |
we report on radio and x-ray observations of the only known repeating fast radio burst (frb) source, frb 121102. we have detected six additional radio bursts from this source: five with the green bank telescope at 2 ghz, and one at 1.4 ghz with the arecibo observatory, for a total of 17 bursts from this source. all have dispersion measures consistent with a single value (∼559 pc cm-3) that is three times the predicted maximum galactic contribution. the 2 ghz bursts have highly variable spectra like those at 1.4 ghz, indicating that the frequency structure seen across the individual 1.4 and 2 ghz bandpasses is part of a wideband process. x-ray observations of the frb 121102 field with the swift and chandra observatories show at least one possible counterpart; however, the probability of chance superposition is high. a radio imaging observation of the field with the jansky very large array at 1.6 ghz yields a 5σ upper limit of 0.3 mjy on any point-source continuum emission. this upper limit, combined with archival wide-field infrared survey explorer 22 μm and iphas hα surveys, rules out the presence of an intervening galactic h ii region. we update our estimate of the frb detection rate in the palfa survey to be {1.1}-1.0+3.7× {10}4 frbs sky-1 day-1 (95% confidence) for peak flux density at 1.4 ghz above 300 mjy. we find that the intrinsic widths of the 12 frb 121102 bursts from arecibo are, on average, significantly longer than the intrinsic widths of the 13 single-component frbs detected with the parkes telescope. | the repeating fast radio burst frb 121102: multi-wavelength observations and additional bursts |
a black hole x-ray binary (xrb) system forms when gas is stripped from a normal star and accretes onto a black hole, which heats the gas sufficiently to emit x-rays. we report a polarimetric observation of the xrb cygnus x-1 using the imaging x-ray polarimetry explorer. the electric field position angle aligns with the outflowing jet, indicating that the jet is launched from the inner x-ray–emitting region. the polarization degree is 4.01 ± 0.20% at 2 to 8 kiloelectronvolts, implying that the accretion disk is viewed closer to edge-on than the binary orbit. these observations reveal that hot x-ray–emitting plasma is spatially extended in a plane perpendicular to, not parallel to, the jet axis. | polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary cygnus x-1 |
the large synoptic survey telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our solar system, galaxy and universe, across half the sky and over ten years of repeated observation. however, exactly how the lsst observations will be taken (the observing strategy or "cadence") is not yet finalized. in this dynamically-evolving community white paper, we explore how the detailed performance of the anticipated science investigations is expected to depend on small changes to the lsst observing strategy. using realistic simulations of the lsst schedule and observation properties, we design and compute diagnostic metrics and figures of merit that provide quantitative evaluations of different observing strategies, analyzing their impact on a wide range of proposed science projects. this is work in progress: we are using this white paper to communicate to each other the relative merits of the observing strategy choices that could be made, in an effort to maximize the scientific value of the survey. the investigation of some science cases leads to suggestions for new strategies that could be simulated and potentially adopted. notably, we find motivation for exploring departures from a spatially uniform annual tiling of the sky: focusing instead on different parts of the survey area in different years in a "rolling cadence" is likely to have significant benefits for a number of time domain and moving object astronomy projects. the communal assembly of a suite of quantified and homogeneously coded metrics is the vital first step towards an automated, systematic, science-based assessment of any given cadence simulation, that will enable the scheduling of the lsst to be as well-informed as possible. | science-driven optimization of the lsst observing strategy |
we present high-resolution rotation curves and mass models of 26 dwarf galaxies from “local irregulars that trace luminosity extremes, the h i nearby galaxy survey” (little things). little things is a high-resolution (∼6″ angular; <2.6 km s-1 velocity resolution) very large array h i survey for nearby dwarf galaxies in the local volume within 11 mpc. the high-resolution h i observations enable us to derive reliable rotation curves of the sample galaxies in a homogeneous and consistent manner. the rotation curves are then combined with spitzer archival 3.6 μm and ancillary optical u, b, and v images to construct mass models of the galaxies. this high quality multi-wavelength data set significantly reduces observational uncertainties and thus allows us to examine the mass distribution in the galaxies in detail. we decompose the rotation curves in terms of the dynamical contributions by baryons and dark matter (dm) halos, and compare the latter with those of dwarf galaxies from things as well as λcdm smoothed particle hydrodynamic (sph) simulations in which the effect of baryonic feedback processes is included. being generally consistent with things and simulated dwarf galaxies, most of the little things sample galaxies show a linear increase of the rotation curve in their inner regions, which gives shallower logarithmic inner slopes α of their dm density profiles. the mean value of the slopes of the 26 little things dwarf galaxies is α =-0.32+/- 0.24 which is in accordance with the previous results found for low surface brightness galaxies (α =-0.2+/- 0.2) as well as the seven things dwarf galaxies (α =-0.29+/- 0.07). however, this significantly deviates from the cusp-like dm distribution predicted by dm-only λcdm simulations. instead our results are more in line with the shallower slopes found in the λcdm sph simulations of dwarf galaxies in which the effect of baryonic feedback processes is included. in addition, we discuss the central dm distribution of ddo 210 whose stellar mass is relatively low in our sample to examine the scenario of inefficient supernova feedback in low mass dwarf galaxies predicted from recent λcdm sph simulations of dwarf galaxies where central cusps still remain. | high-resolution mass models of dwarf galaxies from little things |
fast radio bursts (frbs) are extragalactic radio flashes of unknown physical origin. their high luminosities and short durations require extreme energy densities, such as those found in the vicinity of neutron stars and black holes. studying the burst intensities and polarimetric properties on a wide range of timescales, from milliseconds down to nanoseconds, is key to understanding the emission mechanism. however, high-time-resolution studies of frbs are limited by their unpredictable activity levels, available instrumentation and temporal broadening in the intervening ionized medium. here we show that the repeating frb 20200120e can produce isolated shots of emission as short as about 60 nanoseconds in duration, with brightness temperatures as high as 3 × 1041 k (excluding relativistic effects), comparable with `nano-shots' from the crab pulsar. comparing both the range of timescales and luminosities, we find that frb 20200120e observationally bridges the gap between known galactic young pulsars and magnetars and the much more distant extragalactic frbs. this suggests a common magnetically powered emission mechanism spanning many orders of magnitude in timescale and luminosity. in this article, we probe a relatively unexplored region of the short-duration transient phase space; we highlight that there probably exists a population of ultrafast radio transients at nanosecond to microsecond timescales, which current frb searches are insensitive to. | burst timescales and luminosities as links between young pulsars and fast radio bursts |
the ligo/virgo collaboration has recently observed gw190521, the first binary black hole merger with at least the primary component mass in the mass gap predicted by the pair-instability supernova theory. this observation disfavors the standard stellar-origin formation scenario for the heavier black hole, motivating alternative hypotheses. we show that gw190521 cannot be explained within the primordial black hole (pbh) scenario if pbhs do not accrete during their cosmological evolution, since this would require an abundance which is already in tension with current constraints. on the other hand, gw190521 may have a primordial origin if pbhs accrete efficiently before the reionization epoch. | gw190521 mass gap event and the primordial black hole scenario |
for decades we have known that the sun lies within the local bubble, a cavity of low-density, high-temperature plasma surrounded by a shell of cold, neutral gas and dust1-3. however, the precise shape and extent of this shell4,5, the impetus and timescale for its formation6,7, and its relationship to nearby star formation8 have remained uncertain, largely due to low-resolution models of the local interstellar medium. here we report an analysis of the three-dimensional positions, shapes and motions of dense gas and young stars within 200 pc of the sun, using new spatial9-11 and dynamical constraints12. we find that nearly all of the star-forming complexes in the solar vicinity lie on the surface of the local bubble and that their young stars show outward expansion mainly perpendicular to the bubble's surface. tracebacks of these young stars' motions support a picture in which the origin of the local bubble was a burst of stellar birth and then death (supernovae) taking place near the bubble's centre beginning approximately 14 myr ago. the expansion of the local bubble created by the supernovae swept up the ambient interstellar medium into an extended shell that has now fragmented and collapsed into the most prominent nearby molecular clouds, in turn providing robust observational support for the theory of supernova-driven star formation. | star formation near the sun is driven by expansion of the local bubble |
the laser interferometer gravitational wave observatory (ligo) consists of two widely separated 4 km laser interferometers designed to detect gravitational waves from distant astrophysical sources in the frequency range from 10 hz to 10 khz. the first observation run of the advanced ligo detectors started in september 2015 and ended in january 2016. a strain sensitivity of better than 10-23/√{hz } was achieved around 100 hz. understanding both the fundamental and the technical noise sources was critical for increasing the astrophysical strain sensitivity. the average distance at which coalescing binary black hole systems with individual masses of 30 m⊙ could be detected above a signal-to-noise ratio (snr) of 8 was 1.3 gpc, and the range for binary neutron star inspirals was about 75 mpc. with respect to the initial detectors, the observable volume of the universe increased by a factor 69 and 43, respectively. these improvements helped advanced ligo to detect the gravitational wave signal from the binary black hole coalescence, known as gw150914. | sensitivity of the advanced ligo detectors at the beginning of gravitational wave astronomy |
the description of nuclei starting from the constituent nucleons and the realistic interactions among them has been a long-standing goal in nuclear physics. in addition to the complex nature of the nuclear forces, with two-, three- and possibly higher many-nucleon components, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. in recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from qcd-employing hamiltonians constructed within chiral effective field theory. after a brief overview of the field, we focus on ab initio many-body approaches—built upon the no-core shell model—that are capable of simultaneously describing both bound and scattering nuclear states, and present results for resonances in light nuclei, reactions important for astrophysics and fusion research. in particular, we review recent calculations of resonances in the 6he halo nucleus, of five- and six-nucleon scattering, and an investigation of the role of chiral three-nucleon interactions in the structure of 9be. further, we discuss applications to the 7be {({{p}},γ )}8{{b}} radiative capture. finally, we highlight our efforts to describe transfer reactions including the 3h{({{d}},{{n}})}4he fusion. | unified ab initio approaches to nuclear structure and reactions |
we present the stellar population content of early-type galaxies from the atlas3d survey. using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (ssp) models to derive ssp-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star formation histories, mass-weighted average values of age, metallicity, and half-mass formation time-scales. using homogeneously derived effective radii and dynamically determined galaxy masses, we present the distribution of stellar population parameters on the mass plane (mjam, σe, r^maj_e), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. from non-parametric star formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. assuming that our sample represents most of the stellar content of today's local universe, approximately 50 per cent of all stars formed within the first 2 gyr following the big bang. most of these stars reside today in the most massive galaxies (>1010.5 m⊙), which themselves formed 90 per cent of their stars by z ∼ 2. the lower mass objects, in contrast, have formed barely half their stars in this time interval. stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. in the highest density regions of our volume (dominated by the virgo cluster), galaxies are older, alpha-enhanced, and have shorter star formation histories with respect to lower density regions. | the atlas3d project - xxx. star formation histories and stellar population scaling relations of early-type galaxies |
the persistent radio counterpart of fast radio burst (frb) 121102 is estimated to have n∼ {10}52 particles, energy {e}n∼ {10}48 erg, and size r∼ {10}17 cm. the source can be nebula inflated and heated by an intermittent outflow from a magnetar—a neutron star powered by its magnetic (rather than rotational) energy. the object is young and frequently liberating energy in magnetic flares driven by accelerated ambipolar diffusion in the neutron star core, feeding the nebula and producing bright millisecond bursts. the particle number in the nebula is consistent with ion ejecta from giant flares. the nebula may also contain the freeze-out of electron-positron pairs {n}+/- ∼ {10}51 created months after the neutron star birth; the same mechanism offers an explanation for {n}+/-in the crab nebula. the persistent source around frb 121102 is likely heated by magnetic dissipation and internal waves excited by the magnetar ejecta. the volumetric heating by waves explains the nebula’s enormous efficiency in producing radio emission. the repeating radio bursts are suggested to occur much closer to the magnetar, as a result of ultrarelativistic internal shocks in the magnetar wind, which are launched by the magnetospheric flares. the shocks are mediated by larmor rotation, which forms a ghz maser with the observed ms duration. furthermore, the flare ejecta can become charge-starved and then convert to electromagnetic waves. | a flaring magnetar in frb 121102? |
we use globular cluster data from the resolved stellar populations early release science (ers) program to validate the flux calibration for the near infrared camera (nircam) on the james webb space telescope. we find a significant flux offset between the eight short wavelength detectors, ranging from 1% to 23% (~0.01-0.2 mag) that affects all nircam imaging observations. we deliver improved zero-points for the ers filters and show that alternate zero-points derived by the community also improve the calibration significantly. we also find that the detector offsets appear to be time variable by up to at least 0.1 mag. | the jwst resolved stellar populations early release science program. i. nircam flux calibration |
we present a robust sample of very high redshift galaxy candidates from the first epoch of jwst/nircam imaging from the next generation deep extragalactic exploratory public (ngdeep) survey. the ngdeep nircam imaging, spanning 9.7 arcmin2 in the hubble ultra deep field parallel field 2, reaches m = 30.4 (5σ, point-source, 2″ diameter apertures corrected to total) in f277w, making it the deepest public jwst go imaging data set to date. we describe our detailed data reduction process of the six-filter broadband jwst/nircam imaging, incorporating custom corrections for systematic effects to produce high-quality calibrated images. using robust photometric redshift selection criteria, we identify a sample of 38 z ≳ 9 galaxy candidates. these objects span a redshift range of z = 8.5-15.8 and apparent magnitudes of m f277w = 27-30.5 ab mag, reaching ~1.5 mag deeper than previous public jwst imaging surveys. we calculate the rest-frame ultraviolet luminosity function at z ~ 9 and 11 and present a new measurement of the luminosity function faint-end slope at z ~ 11. we find a faint-end slope of α = -2.5 ± 0.4 and -2.2 ± 0.2 at z ~ 9 and 11, respectively. this is consistent with no significant evolution in the faint-end slope and number density from z = 9 to 11. comparing our results with theoretical predictions, we find that some models produce better agreement at the faint end than the bright end. these results will help to constrain how stellar feedback impacts star formation at these early epochs. | ngdeep epoch 1: the faint end of the luminosity function at z 9-12 from ultradeep jwst imaging |
detections from the repeating fast radio burst frb 121102 are clustered in time, noticeable even in the earliest repeat bursts. recently, it was argued that the source activity is periodic, suggesting that the clustering reflected a not-yet-identified periodicity. we performed an extensive multiwavelength campaign with the effelsberg telescope, the green bank telescope, and the arecibo observatory to shadow the gran telescope canaria (optical), nustar (x-ray) and integral (γ-ray). we detected 36 bursts with effelsberg, one with a pulse width of 39 ms, the widest burst ever detected from frb 121102. with one burst detected during simultaneous nustar observations, we place a 5σ upper limit of 5 × 1047 erg on the 3-79 kev energy of an x-ray burst counterpart. we tested the periodicity hypothesis using 165 h of effelsberg observations and find a periodicity of 161 ± 5 d. we predict the source to be active from 2020 july 9 to october 14 and subsequently from 2020 december 17 to 2021 march 24. we compare the wait times between consecutive bursts within a single observation to weibull and poisson distributions. we conclude that the strong clustering was indeed a consequence of a periodic activity and show that if the few events with millisecond separation are excluded, the arrival times are poisson distributed. we model the bursts' cumulative energy distribution with energies from ∼1038-1039 erg and find that it is well described by a power law with slope of γ = -1.1 ± 0.2. we propose that a single power law might be a poor descriptor of the data over many orders of magnitude. | repeating behaviour of frb 121102: periodicity, waiting times, and energy distribution |
context. planetary formation and evolution is a combination of multiple interlinked processes. constraining the mechanisms observationally requires statistical comparison to a large diversity of planetary systems.aims: we want to understand global observable consequences of different physical processes (accretion, migration, and interactions) and initial properties (like disc masses and metallicities) on the demographics of the planetary population. we also want to study the convergence of our scheme with respect to one initial condition, the initial number of planetary embryo in each disc.methods: we selected distributions of initial conditions that are representative of known protoplanetary discs. then, we used the generation iii bern model to perform planetary population synthesis. we synthesise five populations with each a different initial number of moon-mass embryos per disc: 1, 10, 20, 50, and 100. the last is our nominal population consisting of 1000 stars (systems) that was used for an extensive statistical analysis of planetary systems around 1 m⊙ stars.results: the properties of giant planets do not change much as long as there are at least ten embryos in each system. the study of giants can thus be done with simulations requiring less computational resources. for inner terrestrial planets, only the 100-embryos population is able to attain the giant-impact stage. in that population, each planetary system contains, on average, eight planets more massive than 1 m⊕. the fraction of systems with giants planets at all orbital distances is 18%, but only 1.6% are at >10 au. systems with giants contain on average 1.6 such planets. the planetary mass function varies as m−2 between 5 and 50 m⊕. both at lower and higher masses, it follows approximately m−1. the frequency of terrestrial and super-earth planets peaks at a stellar [fe/h] of −0.2 and 0.0, respectively, being limited at lower [fe/h] by a lack of building blocks, and by (for them) detrimental growth of more massive dynamically active planets at higher [fe/h]. the frequency of more massive planets (neptunian, giants) increases monotonically with [fe/h]. the fast migration of planets in the 5-50 m⊕ range is reduced by the presence of multiple lower-mass inner planets in the multi-embryos populations. to assess the impact of parameters and model assumptions, we also study two non-nominal populations: insitu formation without gas-driven migration, and a different initial planetesimal surface density.conclusions: we present one of the most comprehensive simulations of (exo)planetary system formation and evolution to date. for observations, the syntheses provides a large data set to search for comparison synthetic planetary systems that show how these systems have come into existence. the systems, including their full formation and evolution tracks are available online. for theory, they provide the framework to observationally test the global statistical consequences of theoretical models for specific physical processes. this is an important ingredient towards the development of a standard model of planetary formation and evolution. the data supporting these findings are available online at http://dace.unige.ch under section `formation & evolution'. | the new generation planetary population synthesis (ngpps). ii. planetary population of solar-like stars and overview of statistical results |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.