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we present a comprehensive study of spectroscopic radius measurements of twelve neutron stars obtained during thermonuclear bursts or in quiescence. we incorporate, for the first time, a large number of systematic uncertainties in the measurement of the apparent angular sizes, eddington fluxes, and distances, in the composition of the interstellar medium, and in the flux calibration of x-ray detectors. we also take into account the results of recent theoretical calculations of rotational effects on neutron star radii, of atmospheric effects on surface spectra, and of relativistic corrections to the eddington critical flux. we employ bayesian statistical frameworks to obtain neutron star radii from the spectroscopic measurements as well as to infer the equation of state from the radius measurements. combining these with the results of experiments in the vicinity of nuclear saturation density and the observations of ∼ 2 {m}⊙neutron stars, we place strong and quantitative constraints on the properties of the equation of state between ≈ 2{--}8 times the nuclear saturation density. we find that around m=1.5{m}⊙ , the preferred equation of state predicts radii between 10.1 and 11.1 km. when interpreting the pressure constraints in the context of high density equations of state based on interacting nucleons, our results suggest a relatively weak contribution of the three-body interaction potential. | the dense matter equation of state from neutron star radius and mass measurements |
gravitational-wave astronomy has revolutionized humanity's view of the universe, a revolution driven by observations that no other field can make. this white paper describes an observatory that builds on decades of investment by the national science foundation and that will drive discovery for decades to come: cosmic explorer. major discoveries in astronomy are driven by three related improvements: better sensitivity, higher precision, and opening new observational windows. cosmic explorer promises all three and will deliver an order-of-magnitude greater sensitivity than ligo. cosmic explorer will push the gravitational-wave frontier to almost the edge of the observable universe using technologies that have been proven by ligo during its development. with the unprecedented sensitivity that only a new facility can deliver, cosmic explorer will make discoveries that cannot yet be anticipated, especially since gravitational waves are both synergistic with electromagnetic observations and can reach into regions of the universe that electromagnetic observations cannot explore. with cosmic explorer, scientists can use the universe as a laboratory to test the laws of physics and study the nature of matter. cosmic explorer allows the united states to continue its leading role in gravitational-wave science and the international network of next-generation observatories. with its extraordinary discovery potential, cosmic explorer will deliver revolutionary observations across astronomy, physics, and cosmology including: black holes and neutron stars throughout cosmic time, multi-messenger astrophysics and dynamics of dense matter, new probes of extreme astrophysics, fundamental physics and precision cosmology, dark matter and the early universe. | cosmic explorer: a submission to the nsf mpsac nggw subcommittee |
by numerically inverting the tolman-oppenheimer-volkov (tov) equation using an explicitly isospin-dependent parametric equation of state (eos) of dense neutron-rich nucleonic matter, a restricted eos parameter space is established using observational constraints on the radius, maximum mass, tidal deformability and causality condition of neutron stars (nss). the constraining band obtained for the pressure as a function of energy (baryon) density is in good agreement with that extracted recently by the ligo+virgo collaborations from their improved analyses of the ns tidal deformability in gw170817. rather robust upper and lower boundaries on nuclear symmetry energies are extracted from the observational constraints up to about twice the saturation density ρ0 of nuclear matter. more quantitatively, the symmetry energy at 2 ρ0 is constrained to esym(2 ρ0) =46 .9 ±10 .1 mev excluding many existing theoretical predictions scattered between esym(2 ρ0) =15 and 100 mev. moreover, by studying variations of the causality surface where the speed of sound equals that of light at central densities of the most massive neutron stars within the restricted eos parameter space, the absolutely maximum mass of neutron stars is found to be 2.40 m⊙ approximately independent of the eoss used. this limiting mass is consistent with findings of several recent analyses and numerical general relativity simulations about the maximum mass of the possible super-massive remanent produced in the immediate aftermath of gw170817. deformability | extracting nuclear symmetry energies at high densities from observations of neutron stars and gravitational waves |
stars and planets both form by accreting material from a surrounding disk. because they grow from the same material, theory predicts that there should be a relationship between their compositions. in this study, we search for a compositional link between rocky exoplanets and their host stars. we estimate the iron-mass fraction of rocky exoplanets from their masses and radii and compare it with the compositions of their host stars, which we assume reflect the compositions of the protoplanetary disks. we find a correlation (but not a 1:1 relationship) between these two quantities, with a slope of >4, which we interpret as being attributable to planet formation processes. super-earths and super-mercuries appear to be distinct populations with differing compositions, implying differences in their formation processes. | a compositional link between rocky exoplanets and their host stars |
we present a calibration of the tip of the red giant branch (trgb) in the large magellanic cloud (lmc) on the hubble space telescope (hst)/acs f814w system. we use archival hst observations to derive blending corrections and photometric transformations for two ground-based wide-area imaging surveys of the magellanic clouds. we show that these surveys are biased bright by up to ∼0.1 mag in the optical due to blending, and that the bias is a function of local stellar density. we correct the lmc trgb magnitudes from jang & lee and use the geometric distance from pietrzyński et al. to obtain an absolute trgb magnitude of {m}{{f}814{{w}}}=-3.97+/- 0.046 {mag}. applying this calibration to the trgb magnitudes from freedman et al. in sn ia hosts yields a value for the hubble constant of h 0 = 72.4 ± 2.0 km s-1 mpc-1 for their trgb+sne ia distance ladder. the difference in the trgb calibration and the value of h 0 derived here and by freedman et al. primarily results from their overestimate of the lmc extinction, caused by inconsistencies in their different sources of trgb photometry for the magellanic clouds. using the same source of photometry (ogle) for both clouds and applying the aforementioned corrections yields a value for the lmc i-band trgb extinction that is lower by 0.06 mag, consistent with independent ogle reddening maps used by us and by jang & lee to calibrate trgb and determine h 0. | consistent calibration of the tip of the red giant branch in the large magellanic cloud on the hubble space telescope photometric system and a redetermination of the hubble constant |
chianti contains a large quantity of atomic data for the analysis of astrophysical spectra. programs are available in idl and python to perform calculation of the expected emergent spectrum from these sources. the database includes atomic energy levels, wavelengths, radiative transition probabilities, rate coefficients for collisional excitation, ionization, and recombination, as well as data to calculate free-free, free-bound, and two-photon continuum emission. in version 9, we improve the modeling of the satellite lines at x-ray wavelengths by explicitly including autoionization and dielectronic recombination processes in the calculation of level populations for select members of the lithium isoelectronic sequence and fe xviii-xxiii. in addition, existing data sets are updated, new ions are added, and new total recombination rates for several fe ions are included. all data and idl programs are freely available at http://www.chiantidatabase.org or through solarsoft, and the python code chiantipy is also freely available at https://github.com/chianti-atomic/chiantipy. | chianti—an atomic database for emission lines. xv. version 9, improvements for the x-ray satellite lines |
the mean free path of ionizing photons, λmfp, is a key factor in the photoionization of the intergalactic medium (igm). at z ≳ 5, however, λmfp may be short enough that measurements towards qsos are biased by the qso proximity effect. we present new direct measurements of λmfp that address this bias and extend up to z ~ 6 for the first time. our measurements at z ~ 5 are based on data from the giant gemini gmos survey and new keck lris observations of low-luminosity qsos. at z ~ 6 we use qso spectra from keck esi and vlt x-shooter. we measure $\lambda _{\rm mfp} = 9.09^{+1.62}_{-1.28}$ proper mpc and $0.75^{+0.65}_{-0.45}$ proper mpc (68 per cent confidence) at z = 5.1 and 6.0, respectively. the results at z = 5.1 are consistent with existing measurements, suggesting that bias from the proximity effect is minor at this redshift. at z = 6.0, however, we find that neglecting the proximity effect biases the result high by a factor of two or more. our measurement at z = 6.0 falls well below extrapolations from lower redshifts, indicating rapid evolution in λmfp over 5 < z < 6. this evolution disfavours models in which reionization ended early enough that the igm had time to fully relax hydrodynamically by z = 6, but is qualitatively consistent with models wherein reionization completed at z = 6 or even significantly later. our mean free path results are most consistent with late reionization models wherein the igm is still 20 per cent neutral at z = 6, although our measurement at z = 6.0 is even lower than these models prefer. | the mean free path of ionizing photons at 5 < z < 6: evidence for rapid evolution near reionization |
in their recent study, labbé et al. used multi-band infrared images captured by the james webb space telescope (jwst) to discover a population of red massive galaxies that formed approximately 600 million years after the big bang. the authors reported an extraordinarily large density of these galaxies, with stellar masses exceeding $10^{10}$ solar masses, which, if confirmed, challenges the standard cosmological model as suggested by recent studies. however, this conclusion is disputed. we contend that during the early epochs of the universe the stellar mass-to-light ratio could not have reached the values reported by labbé et al. a model of galaxy formation based on standard cosmology provides support for this hypothesis, predicting the formation of massive galaxies with higher ultraviolet (uv) luminosity, which produce several hundred solar masses of stars per year and containing significant dust. these forecasts are consistent with the abundance of jwst/hst galaxies selected photometrically in the rest-frame uv wavelengths and with the properties of the recent spectroscopically-confirmed jwst/hst galaxies formed during that era. discrepancies with labbé et al. may arise from overestimation of the stellar masses, systematic uncertainties, absence of jwst/miri data, heavy dust extinction affecting uv luminosities, or misidentification of faint red agn galaxies at closer redshifts. the current jwst/hst results, combined with a realistic galaxy formation model, provide strong confirmation of the standard cosmology. | confirmation of the standard cosmological model from red massive galaxies $\\sim600$ myr after the big bang |
pair-instability and pulsational pair-instability supernovae (ppisne) have not been unambiguously observed so far. they are, however, promising candidates for the progenitors of the heaviest binary black hole (bbh) mergers detected. if these bbhs are the product of binary evolution, then ppisne could occur in very close binaries. motivated by this, we discuss the implications of a ppisn happening with a close binary companion and what impact these events have on the formation of merging bbhs through binary evolution. for this, we have computed a set of models of metal-poor (z ⊙/10) single helium stars using the mesa software instrument. for ppisn progenitors with pre-pulse masses >50 m ⊙ we find that, after a pulse, heat deposited throughout the layers of the star that remain bound causes it to expand to more than 100 r ⊙ for periods of 102-104 yr depending on the mass of the progenitor. this results in long-lived phases of roche lobe overflow or even common-envelope events if there is a close binary companion, leading to additional electromagnetic transients associated with ppisn eruptions. if we ignore the effect of these interactions, we find that mass loss from ppisne reduces the final bh spin by ∼30%, induces eccentricities below the threshold of detectability of the lisa observatory, and can produce a double-peaked distribution of measured chirp masses in bbh mergers observed by ground-based detectors. | pulsational pair-instability supernovae in very close binaries |
we present maps of the stellar streams detected in the gaia data release 2 (dr2) and early data release 3 (edr3) catalogs using the streamfinder algorithm. we also report the spectroscopic follow-up of the brighter dr2 stream members obtained with the high-resolution cfht/espadons and vlt/uves spectrographs as well as with the medium-resolution ntt/efosc2 spectrograph. two new stellar streams that do not have a clear progenitor are detected in dr2 (named hríd and gunnthrá), and seven are detected in edr3 (named gaia-6 to gaia-12). several candidate streams are also identified. the software also finds very long tidal tails associated with the 15 globular clusters: ngc 288, ngc 1261, ngc 1851, ngc 2298, ngc 2808, ngc 3201, m68, ωcen, ngc 5466, palomar 5, m5, ngc 6101, m92, ngc 6397, and ngc 7089. these stellar streams will be used in subsequent contributions in this series to chart the properties of the galactic acceleration field on ~100 pc to ~100 kpc scales. | charting the galactic acceleration field. i. a search for stellar streams with gaia dr2 and edr3 with follow-up from espadons and uves |
the set of data released as gaia early data release 3 (gaia edr3) on 3 december 2020 comprises: the full astrometric solution --- positions on the sky (α, δ), parallaxes, and proper motions --- for around 1.46 billion (1.46*109) sources, with a limiting magnitude of about g=~21 and a bright limit of about g=~3. the astrometric solution is accompanied with some new quality indicators, like ruwe, and source image descriptors. the full astrometric solution has been done as 5-parameter solution for 585 million sources and as 6-parameter solution for 882 million sources. in the 6-parameter solution, the additional fitted quantity is the so-called pseudo-colour that had to be included for sources without high-quality colour information. in addition, two-parameters solutions --- positions on the sky (α, δ) --- for around 344 million additional sources. g magnitudes for around 1.806 billion sources (with the known issue present in edr3 corrected in gaia dr3). gbp and grp magnitudes for around 1.54 billion and 1.55 billion sources, respectively. in gaia data release 3 (gaia dr3), the above set of data is complemented with new products released on 13 june 2022 (eas presentation a. vallenari): object classifications for 1.59 billion sources and astrophysical parameters (teff, logg, [m/h], ag, distance, etc.) from bp/rp spectra for 470 million objects, including mcmc samples for most sources with astrophysical parameters (eas presentation o.creevey). other astrophysical parameters from the bp/rp spectra include: spectral types (217 million stars) and emission-line star classifications (57,000 stars); spectroscopic parameters for 2.3 million hot stars, 94,000 ultra-cool stars, activity index for 1.3 million cool stars, and h-alpha emission for 235 million stars; evolutionary parameters (mass and age) for 128 million stars; astrophysical parameters for 348 million objects based on the assumption of an unresolved binary in the bp/rp spectra; self-organised map (outlier) analysis based on 56 million sources with the weakest object classifications. astrophysical parameters (teff, logg, [m/h], [x/m] for 12 elements, etc.) from rvs spectra for 5.5 million objects, including diffuse interstellar bands for 472,000 objects. all-sky total galactic extinction maps at 4 different spatial resolutions (healpix levels 6, 7, 8, and 9). mean bp/rp spectra for 219 million sources, most of them with g < 17.6 mag (eas presentation f. de angeli). mean rvs spectra for 1 million well-behaved objects (eas presentation p. sartoretti). mean radial velocities for 33 million stars and mean grvs magnitudes for 32 million objects with grvs<~14mag with effective temperatures (teff) in the range of ~3100 to 14500k (eas presentation p. sartoretti). rotational velocities for 3.5 million sources with grvs<~12mag. variability analysis, together with the underlying epoch photometry, for 10.5 million sources. apart from classification into 24 variability classes, detailed variability results are provided in separate tables for the following candidates (eas presentation l. eyer): cepheids (15,021 objects); compact companions (6306 objects); eclipsing binaries (2,184,477 objects); long-period variables (1,720,588 objects); microlensing events (363 objects); planetary transits (214 objects); rr lyrae stars (271,779 objects); short-timescale variables (471,679 objects); solar-like rotational modulation variables (474,026 objects); upper-main-sequence oscillators (54,476 objects); active galactic nuclei (872,228 objects). solar-system results for 158,000 sources (including 31 planetary satellites), with orbital solutions and individual epoch observations for 154,000 objects and with mean bp/rp reflectance spectra for more than 60,000 objects (eas presentation p. tanga). some 813,000 non-single stars, including amongst others non-single-star models for sources compatible with an astrometric acceleration solution, non-single-star orbital models for spectroscopic binaries compatible with a trend, and non-single-star orbital models for sources compatible with a two-body solution (eas presentation f. arenou). some 6.6 million quasar candidates with redshift estimates for most of them (eas presentation l. galluccio). some 1.1 million quasars analysed with 60,000 host galaxies detected and 15,000 surface brightness profiles of the host galaxy. some 4.8 million galaxy candidates with redshift estimates for more than 1 million objects (eas presentation l. galluccio). some 900,000 galaxies analysed with two surface brightness profiles. the gaia andromeda photometric survey (gaps), consisting of the photometric time series for all 1.2 million sources located in a 5.5-degree radius field centred on the andromeda galaxy. selected tables from gaia collaboration performance verification papers published with gaia dr3. all 2612 science alerts triggered in the period underlying gaia dr3. the new data set neither contains new astrometry nor new photometric calibrations such that the following elements are in common for and apply to both gaia edr3 and gaia dr3: about 1.61 million celestial reference frame (gaia-crf3) sources. cross-matches between gaia (e)dr3 sources on the one hand and hipparcos-2, tycho-2 + tdsc merged, 2mass psc (merged with 2mass xsc), sdss dr13, pan-starrs1 dr1, skymapper dr2, gsc 2.3, apass dr9, rave dr5, allwise, urat-1, and rave dr6 data on the other hand. additionally, a gaia dr2 to gaia (e)dr3 match table. full photometric passband definitions for g, gbp, grp, and grvs. more information is available here. please be aware that the photometric system for the g, gbp, and grp bands in gaia (e)dr3 is different from the photometric systems as used in gaia dr2 and in gaia dr1. simulated data from the gaia object generator (gog) and the gaia universe model snapshot (gums). the commanded scan law covering the gaia (e)dr3 data collection period. also the major periods where data was not sent to the ground or could not be processed are identified. all of the above combined makes up the full gaia data release 3. (16 data files). | vizier online data catalog: gaia dr3 part 1. main source (gaia collaboration, 2022) |
direct images of protoplanets embedded in disks around infant stars provide the key to understanding the formation of gas giant planets such as jupiter. using the subaru telescope and the hubble space telescope, we find evidence for a jovian protoplanet around ab aurigae orbiting at a wide projected separation (~93 au), probably responsible for multiple planet-induced features in the disk. its emission is reproducible as reprocessed radiation from an embedded protoplanet. we also identify two structures located at 430-580 au that are candidate sites of planet formation. these data reveal planet formation in the embedded phase and a protoplanet discovery at wide, >50 au separations characteristic of most imaged exoplanets. with at least one clump-like protoplanet and multiple spiral arms, the ab aur system may also provide the evidence for a long-considered alternative to the canonical model for jupiter's formation, namely disk (gravitational) instability. | images of embedded jovian planet formation at a wide separation around ab aurigae |
the coevolution of galaxies and their metal content serves as an important test for galaxy feedback models. we analyse the distribution and evolution of metals within the illustristng simulation suite with a focus on the gas-phase mass-metallicity relation (mzr). we find that the illustristng model broadly reproduces the slope and normalization evolution of the mzr across the redshift range 0 < z < 2 and mass range 109 < m*/m⊙ < 1010.5. we make predictions for the high-redshift (2 < z < 10) metal content of galaxies which is described by a gradual decline in the normalization of the metallicity with an average high-redshift (z > 2) evolution fit by d log(z)/dz ≈ -0.064. our simulations indicate that the metal retention efficiency of the interstellar medium (ism) is low: a majority of gas-phase metals (∼85 per cent at z = 0) live outside of the ism, either in an extended gas disc, the circumgalactic medium, or outside the halo. nevertheless, the redshift evolution in the simulated mzr normalization is driven by the higher gas fractions of high-redshift galaxies, not by changes to the metal retention efficiency. the scatter in the simulated mzr contains a clear correlation with the gas-mass or star formation rate of the system, in agreement with the observed fundamental metallicity relation. the scatter in the mzr is driven by a competition between periods of enrichment- and accretion-dominated metallicity evolution. we expect that while the normalization of the mzr declines with redshift, the slope of the correlation between metallicity and gas-mass at fixed stellar mass is not a strong function of redshift. our results indicate that the gas fraction dependence of `regulator' style models allows them to simultaneously explaining the shape, redshift evolution, and existence of correlated scatter with gas fraction about the mzr. | the evolution of the mass-metallicity relation and its scatter in illustristng |
we measure the hubble constant of the universe using spatial cross-correlation between gravitational wave (gw) sources without electromagnetic counterparts from the third gw transient catalog (gwtc-3), and the photometric galaxy surveys 2mpz and wise-supercosmos. using the eight well-localised gw events, we obtain hubble constant $h_0= 68.2_{-6.2}^{+26.0}$ km/s/mpc (median and 68.3$\%$ equal-tailed interval (eti)) after marginalizing over the matter density and the gw bias parameters. though the constraints are weak due to a limited number of gw sources and poor sky localization, they are not subject to assumptions regarding the gw mass distribution. by combining this measurement with the hubble constant measurement from binary neutron star gw170817, we find a value of hubble constant $h_0= 67.0_{-3.8}^{+6.3}$ km/s/mpc (median and 68.3$\%$ eti). | cross-correlating dark sirens and galaxies: measurement of $h_0$ from gwtc-3 of ligo-virgo-kagra |
we present the results of our year-long afterglow monitoring of gw 170817, the first binary neutron star merger detected by advanced laser interferometer gravitational-wave observatory (ligo) and advanced virgo. new observations with the australian telescope compact array and the chandra x-ray telescope were used to constrain its late-time behaviour. the broad-band emission, from radio to x-rays, is well-described by a simple power-law spectrum with index β ∼ 0.585 at all epochs. after an initial shallow rise ∝t0.9, the afterglow displayed a smooth turnover, reaching a peak x-ray luminosity of lx ≈ 5 × 1039 erg s-1 at 160 d, and has now entered a phase of rapid decline, approximately ∝t-2. the latest temporal trend challenges most models of choked jet/cocoon systems, and is instead consistent with the emergence of a relativistic structured jet seen at an angle of ≈22° from its axis. within such model, the properties of the explosion (such as its blast wave energy ek ≈ 2 × 1050 erg, jet width θc ≈ 4°, and ambient density n ≈ 3 × 10-3 cm-3) fit well within the range of properties of cosmological short gamma-ray bursts. | a year in the life of gw 170817: the rise and fall of a structured jet from a binary neutron star merger |
this letter presents the first experimental observation of the attractive strong interaction between a proton and a multistrange baryon (hyperon) ξ-. the result is extracted from two-particle correlations of combined p -ξ-⊕p ¯ -ξ¯ + pairs measured in p -pb collisions at √{snn }=5.02 tev at the lhc with alice. the measured correlation function is compared with the prediction obtained assuming only an attractive coulomb interaction and a standard deviation in the range [3.6, 5.3] is found. since the measured p -ξ-⊕p ¯ -ξ¯ + correlation is significantly enhanced with respect to the coulomb prediction, the presence of an additional, strong, attractive interaction is evident. the data are compatible with recent lattice calculations by the hal-qcd collaboration, with a standard deviation in the range [1.8, 3.7]. the lattice potential predicts a shallow repulsive ξ- interaction within pure neutron matter and this implies stiffer equations of state for neutron-rich matter including hyperons. implications of the strong interaction for the modeling of neutron stars are discussed. | first observation of an attractive interaction between a proton and a cascade baryon |
we introduce a family of equations of state (eos) for hybrid neutron star (ns) matter that is obtained by a two-zone parabolic interpolation between a soft hadronic eos at low densities and a set of stiff quark matter eos at high densities within a finite region of chemical potentials μh<μ <μq . fixing the hadronic eos as the apr one and choosing the color-superconducting, nonlocal njl model with two free parameters for the quark phase, we perform bayesian analyses with this two-parameter family of hybrid eos. using three different sets of observational constraints that include the mass of psr j0740+6620, the tidal deformability for gw170817, and the mass-radius relation for psr j0030+0451 from nicer as obligatory (set 1), while set 2 uses the possible upper limit on the maximum mass from gw170817 as an additional constraint and set 3 instead of the possibility that the lighter object in the asymmetric binary merger gw190814 is a neutron star. we confirm that in any case, the quark matter phase has to be color superconducting with the dimensionless diquark coupling approximately fulfilling the fierz relation ηd=0.75 and the most probable solutions exhibiting a proportionality between ηd and ηv, the coupling of the repulsive vector interaction that is required for a sufficiently large maximum mass. we used the bayesian analysis to investigate with the method of fictitious measurements the consequences of anticipating different radii for the massive 2 m⊙ psr j0740+6220 for the most likely equation of state. with the actual outcome of the nicer radius measurement on psr j0740+6220 we could conclude that for the most likely hybrid star eos would not support a maximum mass as large as 2.5 m⊙ so that the event gw190814 was a binary black hole merger. | bayesian analysis of multimessenger m-r data with interpolated hybrid eos |
galactic compact binaries with orbital periods shorter than a few hours emit detectable gravitational waves at low frequencies. their gravitational wave signals can be detected with the future laser interferometer space antenna (lisa). crucially, they may be useful in the early months of the mission operation in helping to validate lisa's performance in comparison to pre-launch expectations. we present an updated list of 55 candidate lisa binaries with measured properties, for which we derive distances based on gaia data release 3 astrometry. based on the known properties from electromagnetic observations, we predict the lisa detectability after 1, 3, 6, and 48 months with state-of-the-art bayesian analysis methods. we distinguish between verification and detectable binaries as being detectable after 3 and 48 months respectively. we find 18 verification binaries and 22 detectable sources, which triples the number of known lisa binaries over the last few years. these include detached double white dwarfs, am cvn binaries, one ultracompact x-ray binary and two hot subdwarf binaries. we find that across this sample the gravitational wave amplitude is expected to be measured to $\approx10\%$ on average, while the inclination is expected to be determined with $\approx15^\circ$ precision. for detectable binaries these average errors increase to $\approx50\%$ and to $\approx40^\circ$ respectively. | lisa galactic binaries with astrometry from gaia dr3 |
elements heavier than zinc are synthesized through the rapid (r) and slow (s) neutron-capture processes. the main site of production of the r-process elements (such as europium) has been debated for nearly 60 years. initial studies of trends in chemical abundances in old milky way halo stars suggested that these elements are produced continually, in sites such as core-collapse supernovae. but evidence from the local universe favours the idea that r-process production occurs mainly during rare events, such as neutron star mergers. the appearance of a plateau of europium abundance in some dwarf spheroidal galaxies has been suggested as evidence for rare r-process enrichment in the early universe, but only under the assumption that no gas accretes into those dwarf galaxies; gas accretion favours continual r-process enrichment in these systems. furthermore, the universal r-process pattern has not been cleanly identified in dwarf spheroidals. the smaller, chemically simpler, and more ancient ultrafaint dwarf galaxies assembled shortly after the first stars formed, and are ideal systems with which to study nucleosynthesis events such as the r-process. reticulum ii is one such galaxy. the abundances of non-neutron-capture elements in this galaxy (and others like it) are similar to those in other old stars. here, we report that seven of the nine brightest stars in reticulum ii, observed with high-resolution spectroscopy, show strong enhancements in heavy neutron-capture elements, with abundances that follow the universal r-process pattern beyond barium. the enhancement seen in this ‘r-process galaxy’ is two to three orders of magnitude higher than that detected in any other ultrafaint dwarf galaxy. this implies that a single, rare event produced the r-process material in reticulum ii. the r-process yield and event rate are incompatible with the source being ordinary core-collapse supernovae, but consistent with other possible sources, such as neutron star mergers. | r-process enrichment from a single event in an ancient dwarf galaxy |
axionlike dark matter whose symmetry breaking occurs after the end of inflation predicts enhanced primordial density fluctuations at small scales. this leads to dense axion minihalos (or miniclusters) forming early in the history of the universe. condensation of axions in the minihalos leads to the formation and subsequent growth of axion stars at the cores of these halos. if, like the qcd axion, the axionlike particle has attractive self-interactions there is a maximal mass for these stars, above which the star rapidly shrinks and converts an o (1 ) fraction of its mass into unbound relativistic axions. this process would leave a similar (although in principle distinct) signature in cosmological observables as a decaying dark matter fraction, and thus is strongly constrained. we place new limits on the properties of axionlike particles that are independent of their nongravitational couplings to the standard model. | recurrent axion stars collapse with dark radiation emission and their cosmological constraints |
this paper is the primary deliverable of the very first nasa living with a star institute working group, geomagnetically induced currents (gic) working group. the paper provides a broad overview of the current status and future challenges pertaining to the science, engineering, and applications of the gic problem. science is understood here as the basic space and earth sciences research that allows improved understanding and physics-based modeling of the physical processes behind gic. engineering, in turn, is understood here as the "impact" aspect of gic. applications are understood as the models, tools, and activities that can provide actionable information to entities such as power systems operators for mitigating the effects of gic and government agencies for managing any potential consequences from gic impact to critical infrastructure. applications can be considered the ultimate goal of our gic work. in assessing the status of the field, we quantify the readiness of various applications in the mitigation context. we use the applications readiness level (arl) concept to carry out the quantification. | geomagnetically induced currents: science, engineering, and applications readiness |
if dark matter is composed of axions, then axion stars form in the cores of dark matter halos. these stars are unstable above a critical mass, decaying to radio photons that heat the intergalactic medium, offering a new channel for axion indirect detection. we recently provided the first accurate calculation of the axion decay rate due to axion star mergers. in this work we show how existing data concerning the cmb optical depth leads to strong constraints on the axion photon coupling in the mass range $10^{-14}\,{\rm ev}\lesssim m_a\lesssim 10^{-8}\,{\rm ev}$. axion star decays lead to efficient reionization of the intergalactic medium during the dark ages. by comparing this non-standard reionization with planck legacy measurements of the thompson optical width, we show that couplings in the range $10^{-14}\,{\rm gev}^{-1} \lesssim g_{a\gamma\gamma} \lesssim 10^{-10}\,{\rm gev}^{-1}$ are excluded for our benchmark model of axion star abundance. future measurements of the 21cm emission of neutral hydrogen at high redshift could improve this limit by an order of magnitude or more, providing complementary indirect constraints on axion dark matter in parameter space also targeted by direct detection haloscopes. | axion star explosions: a new source for axion indirect detection |
mergers of binaries consisting of two neutron stars, or a black hole and a neutron star, offer a unique opportunity to study a range of physical and astrophysical processes using two different and almost orthogonal probes - gravitational waves (gw) and electromagnetic (em) emission. the gw signal probes the binary and the physical processes that take place during the last stages of the merger, while the em emission provides clues to the material that is thrown out following the merger. the accurate localization, which only the em emission can provide, also indicates the astrophysical setting in which the merger took place. in addition, the combination of the two signals provides constraints on the nature of gravity and on the expansion rate of the universe. the first detection of a binary neutron star merger by the ligo-virgo collaboration, gw170817, initiated the era of multi-messenger gw-em astrophysics and demonstrated the great promise it holds. the event produced an unprecedented data set, and although it was only a single event, it provided remarkable results that revolutionized our knowledge of neutron star mergers. gw170817 is especially exciting since we know that it is not one of a kind and that many more events will be detected during the next decade. in this review, i summarize, first, the theory of em emission from compact binary mergers, highlighting the unique information that the combined gw-em detection provides. i then describe the entire set of gw and em observations of gw170817, and summarize the range of insights that it offers. this includes clues about the role that similar events play in the r-process elements budget of the universe, the neutron star equation of state, the properties of the relativistic outflow that followed the merger, and the connection between neutron star binary mergers and short gamma-ray bursts. i conclude by discussing some of the future prospects of this new window that has been opened. | the electromagnetic counterparts of compact binary mergers |
we present a comprehensive catalog of observations and stellar population properties for 23 highly secure host galaxies of fast radio bursts (frbs). our sample comprises 6 repeating frbs and 17 apparent nonrepeaters. we present 82 new photometric and 8 new spectroscopic observations of these hosts. using stellar population synthesis modeling and employing nonparametric star formation histories (sfhs), we find that frb hosts have a median stellar mass of ≈109.9 m ⊙, mass-weighted age ≈5.1 gyr, and ongoing star formation rate ≈1.3 m ⊙ yr-1 but span wide ranges in all properties. classifying the hosts by degree of star formation, we find that 87% (20 of 23 hosts) are star-forming, two are transitioning, and one is quiescent. the majority trace the star-forming main sequence of galaxies, but at least three frbs in our sample originate in less-active environments (two nonrepeaters and one repeater). across all modeled properties, we find no statistically significant distinction between the hosts of repeaters and nonrepeaters. however, the hosts of repeating frbs generally extend to lower stellar masses, and the hosts of nonrepeaters arise in more optically luminous galaxies. while four of the galaxies with the clearest and most prolonged rises in their sfhs all host repeating frbs, demonstrating heightened star formation activity in the last ≲100 myr, one nonrepeating host shows this sfh as well. our results support progenitor models with short delay channels (i.e., magnetars formed via core-collapse supernova) for most frbs, but the presence of some frbs in less-active environments suggests a fraction form through more delayed channels. | the demographics, stellar populations, and star formation histories of fast radio burst host galaxies: implications for the progenitors |
close binaries suppress the formation of circumstellar (s-type) planets and therefore significantly bias the inferred planet occurrence rates and statistical trends. after compiling various radial velocity and high-resolution imaging surveys, we determine that binaries with a < 1 au fully suppress s-type planets, binaries with a = 10 au host close planets at 15$_{-12}^{+17}$ per cent the occurrence rate of single stars, and wide binaries with a > 200 au have a negligible effect on close planet formation. we show that f = 43 ± 7 per cent of solar-type primaries in magnitude-limited samples do not host close planets due to suppression by close stellar companions. by removing spectroscopic binaries from their samples, radial velocity surveys for giant planets boost their detection rates by a factor of 1/(1-f) = 1.8 ± 0.2 compared to transiting surveys. this selection bias fully accounts for the discrepancy in hot jupiter and close neptune occurrence rates inferred from these two detection methods. correcting for both planet suppression by close binaries and transit dilution by wide binaries, the occurrence rate of small planets orbiting single g-dwarfs is 2.1 ± 0.3 times larger than the rate inferred from all g-dwarfs in the kepler survey. additionally, about half (but not all) of the observed increase in small, short-period planets towards low-mass hosts can be explained by the corresponding decrease in the binary fraction. | impact of binary stars on planet statistics - i. planet occurrence rates and trends with stellar mass |
gravitational wave observations of gw170817 placed bounds on the tidal deformabilities of compact stars, allowing one to probe equations of state for matter at supranuclear densities. here we design new parametrizations for hybrid hadron-quark equations of state, which give rise to low-mass twin stars, and test them against gw170817. we find that gw170817 is consistent with the coalescence of a binary hybrid star-neutron star. we also test and find that the i-love-q relations for hybrid stars in the third family agree with those for purely hadronic and quark stars within ∼3 % for both slowly and rapidly rotating configurations, implying that these relations can be used to perform equation-of-state independent tests of general relativity and to break degeneracies in gravitational waveforms for hybrid stars in the third family as well. | implications from gw170817 and i-love-q relations for relativistic hybrid stars |
we utilize deep near-infrared survey data from the ultravista fourth data release (dr4) and the video survey, in combination with overlapping optical and spitzer data, to search for bright star-forming galaxies at z ≳ 7.5. using a full photometric redshift fitting analysis applied to the ∼6 deg^2 of imaging searched, we find 27 lyman break galaxies (lbgs), including 20 new sources, with best-fitting photometric redshifts in the range 7.4 < z < 9.1. from this sample, we derive the rest-frame uv luminosity function at z = 8 and z = 9 out to extremely bright uv magnitudes (muv ≃ -23) for the first time. we find an excess in the number density of bright galaxies in comparison to the typically assumed schechter functional form derived from fainter samples. combined with previous studies at lower redshift, our results show that there is little evolution in the number density of very bright (muv ∼ -23) lbgs between z ≃ 5 and z ≃ 9. the tentative detection of an lbg with best-fitting photometric redshift of z = 10.9 ± 1.0 in our data is consistent with the derived evolution. we show that a double power-law fit with a brightening characteristic magnitude (δm*/δz ≃ -0.5) and a steadily steepening bright-end slope (δβ/δz ≃ -0.5) provides a good description of the z > 5 data over a wide range in absolute uv magnitude (-23 < muv < -17). we postulate that the observed evolution can be explained by a lack of mass quenching at very high redshifts in combination with increasing dust obscuration within the first {∼}1 gyr of galaxy evolution. | a lack of evolution in the very bright end of the galaxy luminosity function from z ≃ 8 to 10 |
weave, the new wide-field, massively multiplexed spectroscopic survey facility for the william herschel telescope, will see first light in late 2022. weave comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (ifus), and a single large ifu. these fibre systems feed a dual-beam spectrograph covering the wavelength range 366-959 nm at r ~ 5000, or two shorter ranges at r ~ 20 000. after summarising the design and implementation of weave and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our galaxy's origins by completing gaia's phase-space information, providing metallicities to its limiting magnitude for ~3 million stars and detailed abundances for ~1.5 million brighter field and open-cluster stars; (ii) survey ~0.4 million galactic-plane oba stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ~400 neutral-hydrogen-selected galaxies with the ifus; (v) study properties and kinematics of stellar populations and ionised gas in z < 0.5 cluster galaxies; (vi) survey stellar populations and kinematics in ~25 000 field galaxies at 0.3 ≲ z ≲ 0.7; (vii) study the cosmic evolution of accretion and star formation using >1 million spectra of lofar-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at z > 2. finally, we describe the weave operational rehearsals using the weave simulator. | the wide-field, multiplexed, spectroscopic facility weave: survey design, overview, and simulated implementation |
the recent direct detection of gravitational waves from a neutron star merger with optical counterpart has been used to severely constrain models of dark energy that typically predict a modification of the gravitational wave speed. however, the energy scales observed at ligo, and the particular frequency of the neutron star event, lie very close to the strong coupling scale or cutoff associated with many dark energy models. while it is true that at very low energies one expects gravitational waves to travel at a speed different than light in these models, the same is no longer necessarily true as one reaches energy scales close to the cutoff. we show explicitly how this occurs in a simple model with a known partial uv completion. within the context of horndeski, we show how the operators that naturally lie at the cutoff scale can affect the speed of propagation of gravitational waves and bring it back to unity at ligo scales. we discuss how further missions including lisa and ptas could play an essential role in testing such models. | gravitational rainbows: ligo and dark energy at its cutoff |
the sun, as an active star, is the driver of energetic phenomena that structure interplanetary space and affect planetary atmospheres. the effects of space weather on earth and the solar system is of increasing importance as human spaceflight is preparing for lunar and mars missions. this review is focusing on the solar perspective of the space weather relevant phenomena, coronal mass ejections (cmes), flares, solar energetic particles (seps), and solar wind stream interaction regions (sir). with the advent of the stereo mission (launched in 2006), literally, new perspectives were provided that enabled for the first time to study coronal structures and the evolution of activity phenomena in three dimensions. new imaging capabilities, covering the entire sun-earth distance range, allowed to seamlessly connect cmes and their interplanetary counterparts measured in-situ (so called icmes). this vastly increased our knowledge and understanding of the dynamics of interplanetary space due to solar activity and fostered the development of space weather forecasting models. moreover, we are facing challenging times gathering new data from two extraordinary missions, nasa's parker solar probe (launched in 2018) and esa's solar orbiter (launched in 2020), that will in the near future provide more detailed insight into the solar wind evolution and image cmes from view points never approached before. the current review builds upon the living reviews article by schwenn from 2006, updating on the space weather relevant cme-flare-sep phenomena from the solar perspective, as observed from multiple viewpoints and their concomitant solar surface signatures. | space weather: the solar perspective |
concerning the significant increase in the negative effects of flash-floods worldwide, the main goal of this research is to evaluate the power of the analytical hierarchy process (ahp), fi (knn), k-star (ks) algorithms and their ensembles in flash-flood susceptibility mapping. to train the two stand-alone models and their ensembles, for the first stage, the areas affected in the past by torrential phenomena are identified using remote sensing techniques. approximately 70% of these areas are used as a training data set along with 10 flash-flood predictors. it should be remarked that the remote sensing techniques play a crucial role in obtaining eight out of 10 flash-flood conditioning factors. the predictive capability of predictors is evaluated through the information gain ratio (igr) method. as expected, the slope angle results in the factor with the highest predictive capability. the application of the ahp model implies the construction of ten pair-wise comparison matrices for calculating the normalized weights of each flash-flood predictor. the computed weights are used as input data in knn–ahp and ks–ahp ensemble models for calculating the flash-flood potential index (ffpi). the ffpi also is determined through knn and ks stand-alone models. the performance of the models is evaluated using statistical metrics (i.e., sensitivity, specificity and accuracy) while the validation of the results is done by constructing the receiver operating characteristics (roc) curve and area under curve (auc) values and by calculating the density of torrential pixels within ffpi classes. overall, the best performance is obtained by the knn–ahp ensemble model. | flash-flood susceptibility assessment using multi-criteria decision making and machine learning supported by remote sensing and gis techniques |
we revisit the global 21 cm signal calculation incorporating a possible radio background at early times, and find that the global 21 cm signal shows a much stronger absorption feature, which could enhance detection prospects for future 21 cm experiments. in light of recent reports of a possible low-frequency excess radio background, we propose that detailed 21 cm calculations should include a possible early radio background. | enhanced global signal of neutral hydrogen due to excess radiation at cosmic dawn |
all stellar-mass black holes have hitherto been identified by x-rays emitted from gas that is accreting onto the black hole from a companion star. these systems are all binaries with a black-hole mass that is less than 30 times that of the sun1-4. theory predicts, however, that x-ray-emitting systems form a minority of the total population of star-black-hole binaries5,6. when the black hole is not accreting gas, it can be found through radial-velocity measurements of the motion of the companion star. here we report radial-velocity measurements taken over two years of the galactic b-type star, lb-1. we find that the motion of the b star and an accompanying hα emission line require the presence of a dark companion with a mass of 68-13+11 solar masses, which can only be a black hole. the long orbital period of 78.9 days shows that this is a wide binary system. gravitational-wave experiments have detected black holes of similar mass, but the formation of such massive ones in a high-metallicity environment would be extremely challenging within current stellar evolution theories. | a wide star-black-hole binary system from radial-velocity measurements |
aims: several kinematic and chemical substructures have been recently found amongst milky way halo stars with retrograde motions. it is currently unclear how these various structures are related to each other. this letter aims to shed light on this issue.methods: we explore the retrograde halo with an augmented version of the gaia dr2 rvs sample, extended with data from three large spectroscopic surveys, namely rave, apogee, and lamost. in this dataset, we identify several structures using the hdbscan clustering algorithm. we discuss their properties and possible links using all the available chemical and dynamical information.results: in concordance with previous work, we find that stars with [fe/h] < -1 have more retrograde motions than those with [fe/h] > -1. the retrograde halo contains a mixture of debris from objects like gaia-enceladus, sequoia, and even the chemically defined thick disc. we find that the sequoia has a smaller range in orbital energies than previously suggested and is confined to high energy. sequoia could be a small galaxy in itself, but since it overlaps both in integrals-of-motion space and chemical abundance space with the less bound debris of gaia-enceladus, its nature cannot yet be fully settled. in the low-energy part of the halo, we find evidence for at least one more distinct structure: thamnos. stars in thamnos are on low-inclination, mildly eccentric retrograde orbits, moving at vϕ ≈ -150 km s-1, and are chemically distinct from the other structures.conclusions: even with the excellent gaia dr2 data, piecing together all the fragments found in the retrograde halo remains challenging. at this point, we are very much in need of large datasets with high-quality high-resolution spectra and tailored high-resolution hydrodynamical simulations of galaxy mergers. | multiple retrograde substructures in the galactic halo: a shattered view of galactic history |
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 (hera collaboration 2022a), we find at 95% confidence that $\delta^2(k = 0.34$ $h$ mpc$^{-1}$) $\leq 457$ mk$^2$ at $z = 7.9$ and that $\delta^2 (k = 0.36$ $h$ mpc$^{-1}) \leq 3,496$ mk$^2$ 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 (2022b), 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 the discovery of an extremely long (∼110 mpc h-1) and dark (τeff ≳ 7) lyα trough extending down to z ≃ 5.5 towards the zem ≃ 6.0 quasar ulas j0148+0600. we use these new data in combination with lyα forest measurements from 42 quasars at 4.5 ≤ zem ≤ 6.4 to conduct an updated analysis of the line-of-sight variance in the intergalactic lyα opacity over 4 ≤ z ≤ 6. we find that the scatter in transmission among lines of sight near z ∼ 6 significantly exceeds theoretical expectations for either a uniform ultraviolet background (uvb) or simple fluctuating uvb models in which the mean free path to ionizing photons is spatially invariant. the data, particularly near z ≃ 5.6-5.8, instead require fluctuations in the volume-weighted hydrogen neutral fraction that are a factor of 3 or more beyond those expected from density variations alone. we argue that these fluctuations are most likely driven by large-scale variations in the mean free path, consistent with expectations for the final stages of inhomogeneous hydrogen reionization. even by z ≃ 5.6, however, a large fraction of the data are consistent with a uniform uvb, and by z ∼ 5 the data are fully consistent with opacity fluctuations arising solely from the density field. this suggests that while reionization may be ongoing at z ∼ 6, it has fully completed by z ∼ 5. | evidence of patchy hydrogen reionization from an extreme lyα trough below redshift six |
review of the history of solar system elemental abundances with a new assessment of elemental and isotopic abundances from ci-chondrites and solar data. solar elemental abundances, or solar system elemental abundances refer to the complement of chemical elements in the entire solar system. the sun contains more than 99-percent of the mass in the solar system and therefore the composition of the sun is a good proxy for the composition of the overall solar system. the solar system composition can be taken as the overall composition of the molecular cloud within the interstellar medium from which the solar system formed 4.567 billion years ago. active research areas in astronomy and cosmochemistry model collapse of a molecular cloud of solar composition into a star with a planetary system, and the physical and chemical fractionation of the elements during planetary formation and differentiation. the solar system composition is the initial composition from which all solar system objects (the sun, terrestrial planets, gas giant planets, planetary satellites and moons, asteroids, kuiper-belt objects, and comets) were derived. (abstract truncated). | solar elemental abundances |
in this article, we have presented a static anisotropic solution of stellar compact objects for self-gravitating system by using minimal geometric deformation techniques in the framework of embedding class one space-time. for solving of this coupling system, we deform this system into two separate system through the geometric deformation of radial components for the source function λ (r ) by mapping: e-λ (r )→e-λ ~(r )+β g (r ) , where g(r) is deformation function. the first system corresponds to einstein's system which is solved by taking a particular generalized form for source function λ ~(r ) while another system is solved by choosing well-behaved deformation function g(r). to test the physical viability of this solution, we find complete thermodynamical observable as pressure, density, velocity, and equilibrium condition via. tov equation etc. in addition to the above, we have also obtained the moment of inertia (i), kepler frequency (v), compression modulus (ke) and stability for this coupling system. the m-r curve has been presented for obtaining the maximum mass and corresponding radius of the compact objects. | minimally deformed anisotropic model of class one space-time by gravitational decoupling |
we investigate properties of material ejected dynamically in the merger of black hole-neutron star binaries by numerical-relativity simulations. we systematically study the dependence of ejecta properties on the mass ratio of the binary, spin of the black hole, and equation of state of the neutron-star matter. dynamical mass ejection is driven primarily by tidal torque, and the ejecta is much more anisotropic than that from binary neutron star mergers. in particular, the dynamical ejecta is concentrated around the orbital plane with a half opening angle of 10°-20° and often sweeps out only a half of the plane. the ejecta mass can be as large as ∼0.1 m⊙, and the velocity is subrelativistic with ∼0.2 - 0.3 c for typical cases. the ratio of the ejecta mass to the bound mass (disk and fallback components) is larger, and the ejecta velocity is larger, for larger values of the binary mass ratio, i.e., for larger values of the black-hole mass. the remnant black hole-disk system receives a kick velocity of o (100 ) km s-1 due to the ejecta linear momentum, and this easily dominates the kick velocity due to gravitational radiation. structures of postmerger material, velocity distribution of the dynamical ejecta, fallback rates, and gravitational waves are also investigated. we also discuss the effect of ejecta anisotropy on electromagnetic counterparts, specifically a macronova/kilonova and synchrotron radio emission, developing analytic models. | dynamical mass ejection from black hole-neutron star binaries |
a critical challenge to the cold dark matter (cdm) paradigm is that there are fewer satellites observed around the milky way than found in simulations of dark matter substructure. we show that there is a match between the observed satellite counts corrected by the detection efficiency of the sloan digital sky survey (for luminosities l ≳340 l⊙ ) and the number of luminous satellites predicted by cdm, assuming an empirical relation between stellar mass and halo mass. the "missing satellites problem," cast in terms of number counts, is thus solved. we also show that warm dark matter models with a thermal relic mass smaller than 4 kev are in tension with satellite counts, putting pressure on the sterile neutrino interpretation of recent x-ray observations. importantly, the total number of milky way satellites depends sensitively on the spatial distribution of satellites, possibly leading to a "too many satellites" problem. measurements of completely dark halos below 1 08 m⊙, achievable with substructure lensing and stellar stream perturbations, are the next frontier for tests of cdm. | missing satellites problem: completeness corrections to the number of satellite galaxies in the milky way are consistent with cold dark matter predictions |
parametric models for galaxy star formation histories (sfhs) are widely used, though they are known to impose strong priors on physical parameters. this has consequences for measurements of the galaxy stellar-mass function, star formation rate density (sfrd), and star-forming main sequence (sfms). we investigate the effects of the exponentially declining, delayed exponentially declining, lognormal, and double power-law sfh models using bagpipes. we demonstrate that each of these models imposes strong priors on specific star formation rates (sfrs), potentially biasing the sfms, and also imposes a strong prior preference for young stellar populations. we show that stellar mass, sfr, and mass-weighted age inferences from high-quality mock photometry vary with the choice of sfh model by at least 0.1, 0.3, and 0.2 dex, respectively. however, the biases with respect to the true values depend more on the true sfh shape than the choice of model. we also demonstrate that photometric data cannot discriminate between sfh models, meaning that it is important to perform independent tests to find well-motivated priors. we finally fit a low-redshift, volume-complete sample of galaxies from the galaxy and mass assembly (gama) survey with each model. we demonstrate that our stellar masses and sfrs at redshift z ∼ 0.05 are consistent with other analyses. however, our inferred cosmic sfrds peak at z ∼ 0.4, approximately 6 gyr later than direct observations suggest, meaning that our mass-weighted ages are significantly underestimated. this makes the use of parametric sfh models for understanding mass assembly in galaxies challenging. in a companion paper, we consider nonparametric sfh models. | how to measure galaxy star formation histories. i. parametric models |
we report a new binary black hole merger in the publicly available ligo first observing run (o1) data release. the event has a false alarm rate of one per six years in the detector-frame chirp-mass range mdet∈[20 ,40 ]m⊙ in a new independent analysis pipeline that we developed. our best estimate of the probability that the event is of astrophysical origin is pastro∼0.71 . the estimated physical parameters of the event indicate that it is the merger of two massive black holes, mdet=3 1-3+2m⊙ with an effective spin parameter, χeff=0.8 1-0.21+0.15, making this the most highly spinning merger reported to date. it is also among the two highest redshift mergers observed so far. the high aligned spin of the merger supports the hypothesis that merging binary black holes can be created by binary stellar evolution. | highly spinning and aligned binary black hole merger in the advanced ligo first observing run |
using state-of-the-art dynamical simulations of globular clusters, including radiation reaction during black hole encounters and a cosmological model of star cluster formation, we create a realistic population of dynamically formed binary black hole mergers across cosmic space and time. we show that in the local universe, 10% of these binaries form as the result of gravitational-wave emission between unbound black holes during chaotic resonant encounters, with roughly half of those events having eccentricities detectable by current ground-based gravitational-wave detectors. the mergers that occur inside clusters typically have lower masses than binaries that were ejected from the cluster many gyrs ago. gravitational-wave captures from globular clusters contribute 1 - 2 gpc-3 yr-1 to the binary merger rate in the local universe, increasing to ≳10 gpc-3 yr-1 at z ∼3 . finally, we discuss some of the technical difficulties associated with post-newtonian scattering encounters, and how care must be taken when measuring the binary parameters during a dynamical capture. | post-newtonian dynamics in dense star clusters: formation, masses, and merger rates of highly-eccentric black hole binaries |
the kilonova emission observed following the binary neutron star merger event gw170817 provided the first direct evidence for the synthesis of heavy nuclei through the rapid neutron capture process (r process). the late-time transition in the spectral energy distribution to near-infrared wavelengths was interpreted as indicating the production of lanthanide nuclei, with atomic mass number a ≳140 . however, compelling evidence for the presence of even heavier third-peak (a ≈195 ) r -process elements (e.g., gold, platinum) or translead nuclei remains elusive. at early times (∼days ) most of the r -process heating arises from a large statistical ensemble of β decays, which thermalize efficiently while the ejecta is still dense, generating a heating rate that is reasonably approximated by a single power law. however, at later times of weeks to months, the decay energy input can also possibly be dominated by a discrete number of α decays, 223ra (half-life t1 /2=11.43 d ), 225ac (t1 /2=10.0 d , following the β decay of 225ra with t1 /2=14.9 d ), and the fissioning isotope 254cf (t1 /2=60.5 d ), which liberate more energy per decay and thermalize with greater efficiency than β -decay products. late-time nebular observations of kilonovae which constrain the radioactive power provide the potential to identify signatures of these individual isotopes, thus confirming the production of heavy nuclei. in order to constrain the bolometric light to the required accuracy, multiepoch and wideband observations are required with sensitive instruments like the james webb space telescope. in addition, by comparing the nuclear heating rate obtained with an abundance distribution that follows the solar r abundance pattern, to the bolometric lightcurve of at2017gfo, we find that the yet-uncertain r abundance of 72ge plays a decisive role in powering the lightcurve, if one assumes that gw170817 has produced a full range of the solar r abundances down to mass number a ∼70 . | fingerprints of heavy-element nucleosynthesis in the late-time lightcurves of kilonovae |
understanding the link between massive (≳30 m⊙) stellar black holes (bhs) and their progenitor stars is a crucial step to interpret observations of gravitational-wave events. in this paper, we discuss the final fate of very massive stars (vmss), with zero-age main sequence (zams) mass >150 m⊙, accounting for pulsational pair-instability supernovae (ppisne) and for pair-instability supernovae (pisne). we describe an updated version of our population synthesis code sevn, in which we added stellar evolution tracks for vmss with zams mass up to 350 m⊙ and we included analytical prescriptions for ppisne and pisne. we use the new version of sevn to study the bh mass spectrum at different metallicity z, ranging from z = 2.0 × 10-4 to 2.0 × 10-2. the main effect of ppisne and pisne is to favour the formation of bhs in the mass range of the first gravitational-wave event (gw150914), while they prevent the formation of remnants with mass 60-120 m⊙. in particular, we find that ppisne significantly enhance mass-loss of metal-poor (z ≤ 2.0 × 10-3) stars with zams mass 60 ≤ mzams/ m⊙ ≤ 125. in contrast, pisne become effective only for moderately metal-poor (z < 8.0 × 10-3) vmss. vmss with mzams ≳ 220 m⊙ and z < 10-3 do not undergo pisne and form intermediate-mass bhs (with mass ≳200 m⊙) via direct collapse. | very massive stars, pair-instability supernovae and intermediate-mass black holes with the sevn code |
the field of planet formation is in an exciting era, where recent observations of disks around low- to intermediate-mass stars made with state of the art interferometers and high-contrast optical and ir facilities have revealed a diversity of substructures, some possibly planet-related. it is therefore important to understand the physical and chemical nature of the protoplanetary building blocks, as well as their spatial distribution, to better understand planet formation. since ppvi, the field has seen tremendous improvements in observational capabilities, enabling both surveys of large samples of disks and high resolution imaging studies of a few bright disks. improvements in data quality and sample size have, however, opened up many fundamental questions about properties such as the mass budget of disks, its spatial distribution, and its radial extent. moreover, the vertical structure of disks has been studied in greater detail with spatially resolved observations, providing new insights on vertical layering and temperature stratification, yet also bringing rise to questions about other properties, such as material transport and viscosity. each one of these properties—disk mass, surface density distribution, outer radius, vertical extent, temperature structure, and transport—is of fundamental interest as they collectively set the stage for disk evolution and corresponding planet formation theories. in this chapter, we will review our understanding of the fundamental properties of disks including the relevant observational techniques to probe their nature, modeling methods, and the respective caveats. finally, we discuss the implications for theories of disk evolution and planet formation underlining what new questions have since arisen as our observational facilities have improved. | setting the stage for planet formation: measurements and implications of the fundamental disk properties |
we present two bright galaxy candidates at z ~ 12-13 identified in our h-dropout lyman break selection with 2.3 deg2 near-infrared deep imaging data. these galaxy candidates, selected after careful screening of foreground interlopers, have spectral energy distributions showing a sharp discontinuity around 1.7 μm, a flat continuum at 2-5 μm, and nondetections at <1.2 μm in the available photometric data sets, all of which are consistent with a z > 12 galaxy. an alma program targeting one of the candidates shows a tentative 4σ [o iii] 88 μm line at z = 13.27, in agreement with its photometric redshift estimate. the number density of the z ~ 12-13 candidates is comparable to that of bright z ~ 10 galaxies and is consistent with a recently proposed double-power-law luminosity function rather than the schechter function, indicating little evolution in the abundance of bright galaxies from z ~ 4 to 13. comparisons with theoretical models show that the models cannot reproduce the bright end of rest-frame ultraviolet luminosity functions at z ~ 10-13. combined with recent studies reporting similarly bright galaxies at z ~ 9-11 and mature stellar populations at z ~ 6-9, our results indicate the existence of a number of star-forming galaxies at z > 10, which will be detected with upcoming space missions such as the james webb space telescope, nancy grace roman space telescope, and grex-plus. | a search for h-dropout lyman break galaxies at z 12-16 |
making the most of the rapidly increasing population of gravitational-wave detections of black hole (bh) and neutron star (ns) mergers requires comparing observations with population synthesis predictions. in this work, we investigate the combined impact from the key uncertainties in population synthesis modelling of the isolated binary evolution channel: the physical processes in massive binary-star evolution and the star formation history as a function of metallicity, z, and redshift z, $\mathcal {s}(z,z)$. considering these uncertainties, we create 560 different publicly available model realizations and calculate the rate and distribution characteristics of detectable bhbh, bhns, and nsns mergers. we find that our stellar evolution and $\mathcal {s}(z,z)$ variations can combined impact the predicted intrinsic and detectable merger rates by factors in the range 102-104. we find that bhbh rates are dominantly impacted by $\mathcal {s}(z,z)$ variations, nsns rates by stellar evolution variations and bhns rates by both. we then consider the combined impact from all uncertainties considered in this work on the detectable mass distribution shapes (chirp mass, individual masses, and mass ratio). we find that the bhns mass distributions are predominantly impacted by massive binary-star evolution changes. for bhbh and nsns, we find that both uncertainties are important. we also find that the shape of the delay time and birth metallicity distributions are typically dominated by the choice of $\mathcal {s}(z,z)$ for bhbh, bhns, and nsns. we identify several examples of robust features in the mass distributions predicted by all 560 models, such that we expect more than 95 per cent of bhbh detections to contain a bh $\gtrsim 8\, \rm {m}_{\odot }$ and have mass ratios ≲ 4. our work demonstrates that it is essential to consider a wide range of allowed models to study double compact object merger rates and properties. conversely, larger observed samples could allow us to decipher currently unconstrained stages of stellar and binary evolution. | impact of massive binary star and cosmic evolution on gravitational wave observations - ii. double compact object rates and properties |
a knowledge of stellar ages is crucial for our understanding of many astrophysical phenomena, and yet ages can be difficult to determine. as they become older, stars lose mass and angular momentum, resulting in an observed slowdown in surface rotation. the technique of ‘gyrochronology’ uses the rotation period of a star to calculate its age. however, stars of known age must be used for calibration, and, until recently, the approach was untested for old stars (older than 1 gigayear, gyr). rotation periods are now known for stars in an open cluster of intermediate age (ngc 6819; 2.5 gyr old), and for old field stars whose ages have been determined with asteroseismology. the data for the cluster agree with previous period-age relations, but these relations fail to describe the asteroseismic sample. here we report stellar evolutionary modelling, and confirm the presence of unexpectedly rapid rotation in stars that are more evolved than the sun. we demonstrate that models that incorporate dramatically weakened magnetic braking for old stars can—unlike existing models—reproduce both the asteroseismic and the cluster data. our findings might suggest a fundamental change in the nature of ageing stellar dynamos, with the sun being close to the critical transition to much weaker magnetized winds. this weakened braking limits the diagnostic power of gyrochronology for those stars that are more than halfway through their main-sequence lifetimes. | weakened magnetic braking as the origin of anomalously rapid rotation in old field stars |
context. one of the long-term goals of exoplanet science is the atmospheric characterization of dozens of small exoplanets in order to understand their diversity and search for habitable worlds and potential biosignatures. achieving this goal requires a space mission of sufficient scale that can spatially separate the signals from exoplanets and their host stars and thus directly scrutinize the exoplanets and their atmospheres.aims: we seek to quantify the exoplanet detection performance of a space-based mid-infrared (mir) nulling interferometer that measures the thermal emission of exoplanets. we study the impact of various parameters and compare the performance with that of large single-aperture mission concepts that detect exoplanets in reflected light.methods: we have developed an instrument simulator that considers all major astrophysical noise sources and coupled it with monte carlo simulations of a synthetic exoplanet population around main-sequence stars within 20 pc of the sun. this allows us to quantify the number (and types) of exoplanets that our mission concept could detect. considering single visits only, we discuss two different scenarios for distributing 2.5 yr of an initial search phase among the stellar targets. different apertures sizes and wavelength ranges are investigated.results: an interferometer consisting of four 2 m apertures working in the 4-18.5 μ.m wavelength range with a total instrument throughput of 5% could detect up to ≈550 exoplanets with radii between 0.5 and 6 r⊕ with an integrated s/n ≥ 7. at least ≈160 of the detected exoplanets have radii ≤1.5 r⊕. depending on the observing scenario, ≈25-45 rocky exoplanets (objects with radii between 0.5 and 1.5 r⊕) orbiting within the empirical habitable zone (ehz) of their host stars are among the detections. with four 3.5 m apertures, the total number of detections can increase to up to ≈770, including ≈60-80 rocky ehz planets. with four times 1 m apertures, the maximum detection yield is ≈315 exoplanets, including ≤20 rocky ehz planets. the vast majority of small, temperate exoplanets are detected around m dwarfs. the impact of changing the wavelength range to 3-20 μm or 6-17 μm on the detection yield is negligible.conclusions: a large space-based mir nulling interferometer will be able to directly detect hundreds of small, nearby exoplanets, tens of which would be habitable world candidates. this shows that such a mission can compete with large single-aperture reflected light missions. further increasing the number of habitable world candidates, in particular around solar-type stars, appears possible via the implementation of a multi-visit strategy during the search phase. the high median s/n of most of the detected planets will allow for first estimates of their radii and effective temperatures and will help prioritize the targets for a second mission phase to obtain high-s/n thermal emission spectra, leveraging the superior diagnostic power of the mir regime compared to shorter wavelengths. | large interferometer for exoplanets (life). i. improved exoplanet detection yield estimates for a large mid-infrared space-interferometer mission |
the fundamental nature of dark matter is entirely unknown. a compelling candidate is twin higgs mirror matter, invisible hidden-sector cousins of the standard model particles and forces. this predicts mirror neutron stars made entirely of mirror nuclear matter. we find their structure using realistic equations of state, robustly modified based on first-principle quantum chromodynamic calculations, for the first time. this allows us to predict their gravitational wave signals, demonstrating an impressive discovery potential and ability to probe dark sectors connected to the hierarchy problem. | mirror neutron stars |
we present a new set of solar metallicity atmosphere and evolutionary models for very cool brown dwarfs and self-luminous giant exoplanets, which we term atmo 2020. atmosphere models are generated with our state-of-the-art 1d radiative-convective equilibrium code atmo, and are used as surface boundary conditions to calculate the interior structure and evolution of 0.001-0.075 m⊙ objects. our models include several key improvements to the input physics used in previous models available in the literature. most notably, the use of a new h-he equation of state including ab initio quantum molecular dynamics calculations has raised the mass by ~1-2% at the stellar-substellar boundary and has altered the cooling tracks around the hydrogen and deuterium burning minimum masses. a second key improvement concerns updated molecular opacities in our atmosphere model atmo, which now contains significantly more line transitions required to accurately capture the opacity in these hot atmospheres. this leads to warmer atmospheric temperature structures, further changing the cooling curves and predicted emission spectra of substellar objects. we present significant improvement for the treatment of the collisionally broadened potassium resonance doublet, and highlight the importance of these lines in shaping the red-optical and near-infrared spectrum of brown dwarfs. we generate three different grids of model simulations, one using equilibrium chemistry and two using non-equilibrium chemistry due to vertical mixing, all three computed self-consistently with the pressure-temperature structure of the atmosphere. we show the impact of vertical mixing on emission spectra and in colour-magnitude diagrams, highlighting how the 3.5-5.5 μm flux window can be used to calibrate vertical mixing in cool t-y spectral type objects. | a new set of atmosphere and evolution models for cool t-y brown dwarfs and giant exoplanets |
we describe the first observations of the same celestial object with gravitational waves and light. gw170817 was the first detection of a neutron star merger with gravitational waves. the detection of a spatially coincident weak burst of gamma-rays (grb 170817a) 1.7 s after the merger constituted the first electromagnetic detection of a gravitational wave source and established a connection between at least some cosmic short gamma-ray bursts (sgrbs) and binary neutron star mergers. a fast-evolving optical and near-infrared transient (at 2017gfo) associated with the event can be interpreted as resulting from the ejection of ∼0.05 m⊙ of material enriched in r-process elements, finally establishing binary neutron star mergers as at least one source of r-process nucleosynthesis. radio and x-ray observations revealed a long-rising source that peaked ∼160,d after the merger. combined with the apparent superluminal motion of the associated very long baseline interferometry source, these observations show that the merger produced a relativistic structured jet whose core was oriented ≈20 deg from the line of sight and with properties similar to sgrbs. the jet structure likely results from interaction between the jet and the merger ejecta. the electromagnetic and gravitational wave information can be combined to produce constraints on the expansion rate of the universe and the equation of state of dense nuclear matter. these multimessenger endeavors will be a major emphasis of future work. | first multimessenger observations of a neutron star merger |
recently the edges collaboration reported an anomalous absorption signal in the sky-averaged 21-cm spectrum around $z=17$. such a signal may be understood as an indication for an unexpected cooling of the hydrogen gas during or prior to the so called cosmic dawn era. here we explore the possibility that dark matter cooled the gas through velocity-dependent, rutherford-like interactions. we argue that such interactions require a light mediator that is highly constrained by 5th force experiments and limits from stellar cooling. consequently, only a hidden or the visible photon can in principle mediate such a force. neutral hydrogen thus plays a sub-leading role and the cooling occurs via the residual free electrons and protons. we find that these two scenarios are strongly constrained by the predicted dark matter self-interactions and by limits on millicharged dark matter respectively. we conclude that the 21-cm absorption line is unlikely to be the result of gas cooling via the scattering with a dominant component of the dark matter. an order 1\% subcomponent of millicharged dark matter remains a viable explanation. | strong constraints on light dark matter interpretation of the edges signal |
presented here is a review of present knowledge of the long-term behavior of solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method. the concept of solar activity is discussed along with an overview of the special indices used to quantify different aspects of variable solar activity, with special emphasis upon sunspot number. over long timescales, quantitative information about past solar activity can only be obtained using a method based upon indirect proxies, such as the cosmogenic isotopes ^{14}c and ^{10}be in natural stratified archives (e.g., tree rings or ice cores). we give an historical overview of the development of the proxy-based method for past solar-activity reconstruction over millennia, as well as a description of the modern state. special attention is paid to the verification and cross-calibration of reconstructions. it is argued that this method of cosmogenic isotopes makes a solid basis for studies of solar variability in the past on a long timescale (centuries to millennia) during the holocene. a separate section is devoted to reconstructions of strong solar energetic-particle (sep) events in the past, that suggest that the present-day average sep flux is broadly consistent with estimates on longer timescales, and that the occurrence of extra-strong events is unlikely. finally, the main features of the long-term evolution of solar magnetic activity, including the statistics of grand minima and maxima occurrence, are summarized and their possible implications, especially for solar/stellar dynamo theory, are discussed. | a history of solar activity over millennia |
stellar evolution theory predicts a "gap" in the black hole birth function caused by the pair instability. many presupernova stars that have a core mass below some limiting value, mlow, after all pulsational activity is finished, collapse to black holes, while more massive ones, up to some limiting value, mhigh, explode, promptly and completely, as pair-instability supernovae. previous work has suggested mlow ≈ 50 m⊙ and mhigh ≈ 130 m⊙. these calculations have been challenged by recent ligo observations that show many black holes merging with individual masses mlow ≳ 65 m⊙. here we explore four factors affecting the theoretical estimates for the boundaries of this mass gap: nuclear reaction rates, evolution in detached binaries, rotation, and hyper-eddington accretion after black hole birth. current uncertainties in reaction rates by themselves allow mlow to rise to 64 m⊙ and mhigh as large as 161 m⊙. rapid rotation could further increase mlow to ∼70 m⊙, depending on the treatment of magnetic torques. evolution in detached binaries and super-eddington accretion can, with great uncertainty, increase mlow still further. dimensionless kerr parameters close to unity are allowed for the more massive black holes produced in close binaries, though they are generally smaller. | the pair-instability mass gap for black holes |
aims: we study the evolution of the rotation and the high energy x-ray, extreme ultraviolet (euv), and ly-α emission for f, g, k, and m dwarfs, with masses between 0.1 and 1.2 m⊙, and provide a freely available set of evolutionary tracks for use in planetary atmosphere studies.methods: we develop a physical rotational evolution model constrained by observed rotation distributions in young stellar clusters. using rotation, x-ray, euv, and ly-α measurements, we derive empirical relations for the dependences of high energy emission on stellar parameters. our description of x-ray evolution is validated using measurements of x-ray distributions in young clusters.results: a star's x-ray, euv, and ly-α evolution is determined by its mass and initial rotation rate, with initial rotation being less important for lower mass stars. at all ages, solar mass stars are significantly more x-ray luminous than lower mass stars and stars that are born as rapid rotators remain highly active longer than those born as slow rotators. at all evolutionary stages, habitable zone planets receive higher x-ray and euv fluxes when orbiting lower mass stars due to their longer evolutionary timescales. the rates of flares follow similar evolutionary trends with higher mass stars flaring more often than lower mass stars at all ages, though habitable zone planets are likely influenced by flares more when orbiting lower mass stars.conclusions: our results show that single decay laws are insufficient to describe stellar activity evolution and highlight the need for a more comprehensive description based on the evolution of rotation that also includes the effects of short-term variability. planets at similar orbital distances from their host stars receive significantly more x-ray and euv energy over their lifetimes when orbiting higher mass stars. the common belief that m dwarfs are more x-ray and euv active than g dwarfs is justified only when considering the fluxes received by planets with similar effective temperatures, such as those in the habitable zone. our code for calculating stellar rotation and xuv evolution is available at https://github.com/colinphilipjohnstone/mors and an extensive grid of evolutionary tracks is available at https://zenodo.org/record/4266670#.x6rmuq4o9h5. | the active lives of stars: a complete description of the rotation and xuv evolution of f, g, k, and m dwarfs |
we measure the velocity dispersion, σ, and surface density, σ, of the molecular gas in nearby galaxies from co spectral line cubes with spatial resolution 45-120 pc, matched to the size of individual giant molecular clouds. combining 11 galaxies from the phangs-alma survey with four targets from the literature, we characterize ∼30,000 independent sightlines where co is detected at good significance. σ and σ show a strong positive correlation, with the best-fit power-law slope close to the expected value for resolved, self-gravitating clouds. this indicates only a weak variation in the virial parameter α vir ∝ σ 2/σ, which is ∼1.5-3.0 for most galaxies. we do, however, observe enormous variation in the internal turbulent pressure p turb ∝ σσ 2, which spans ∼5 dex across our sample. we find σ, σ, and p turb to be systematically larger in more massive galaxies. the same quantities appear enhanced in the central kiloparsec of strongly barred galaxies relative to their disks. based on sensitive maps of m31 and m33, the slope of the σ-σ relation flattens at σ ≲ 10 m ⊙ pc-2, leading to high σ for a given σ and high apparent α vir. this echoes results found in the milky way and likely originates from a combination of lower beam-filling factors and a stronger influence of local environment on the dynamical state of molecular gas in the low-density regime. | cloud-scale molecular gas properties in 15 nearby galaxies |
primordial black holes (pbhs) could provide the dark matter in various mass windows below 102 m⊙ and those of 30 m⊙ might explain the ligo events. pbhs much larger than this might have important consequences even if they provide only a small fraction of the dark matter. in particular, they could generate cosmological structure either individually through the `seed' effect or collectively through the `poisson' effect, thereby alleviating some problems associated with the standard cold dark matter scenario. if the pbhs all have a similar mass and make a small contribution to the dark matter, then the seed effect dominates on small scales, in which case pbhs could generate the supermassive black holes in galactic nuclei or even galaxies themselves. if they have a similar mass and provide the dark matter, the poisson effect dominates on all scales and the first bound clouds would form earlier than in the usual scenario, with interesting observational consequences. if the pbhs have an extended mass spectrum, which is more likely, they could fulfill all three roles - providing the dark matter, binding the first bound clouds, and generating galaxies. in this case, the galactic mass function naturally has the observed form, with the galaxy mass being simply related to the black hole mass. the stochastic gravitational wave background from the pbhs in this scenario would extend continuously from the ligo frequency to the lisa frequency, offering a potential goal for future surveys. | primordial black holes as generators of cosmic structures |
we report evidence from apogee for the presence of a new metal-poor stellar structure located within ∼4 kpc of the galactic centre. characterized by a chemical composition resembling those of low-mass satellites of the milky way, this new inner galaxy structure (igs) seems to be chemically and dynamically detached from more metal-rich populations in the inner galaxy. we conjecture that this structure is associated with an accretion event that likely occurred in the early life of the milky way. comparing the mean elemental abundances of this structure with predictions from cosmological numerical simulations, we estimate that the progenitor system had a stellar mass of ∼5 × 108 m⊙, or approximately twice the mass of the recently discovered gaia-enceladus/sausage system. we find that the accreted:in situ ratio within our metal-poor ([fe/h] < -0.8) bulge sample is somewhere between 1:3 and 1:2, confirming predictions of cosmological numerical simulations by various groups. | evidence from apogee for the presence of a major building block of the halo buried in the inner galaxy |
the use of type ia supernovae (sne ia) as cosmological tools has motivated significant effort to understand what drives the intrinsic scatter of sn ia distance modulus residuals after standardization, characterize the distribution of sn ia colors, and explain why properties of the host galaxies of the sne correlate with sn ia distance modulus residuals. we use a compiled sample of ∼1450 spectroscopically confirmed photometric light curves of sne ia and propose a solution to these three problems simultaneously that also explains an empirical 11σ detection of the dependence of hubble residual scatter on sn ia color. we introduce a physical model of color where intrinsic sn ia colors with a relatively weak correlation with luminosity are combined with extrinsic dust-like colors (e(b - v)) with a wide range of extinction parameter values (rv). this model captures the observed trends of hubble residual scatter and indicates that the dominant component of sn ia intrinsic scatter is variation in rv. we also find that the recovered e(b - v) and rv distributions differ based on global host-galaxy stellar mass, and this explains the observed correlation (γ) between mass and hubble residuals seen in past analyses, as well as an observed 4.5σ dependence of γ on sn ia color. this finding removes any need to ascribe different intrinsic luminosities to different progenitor systems. finally, we measure biases in the equation of state of dark energy (w) up to ∣δw∣ = 0.04 by replacing previous models of sn color with our dust-based model; this bias is larger than any systematic uncertainty in previous sn ia cosmological analyses. | it's dust: solving the mysteries of the intrinsic scatter and host-galaxy dependence of standardized type ia supernova brightnesses |
spectroscopic surveys of the milky way's stars have revealed spatial, chemical, and kinematical structures that encode its history. in this work, we study their origins using a cosmological zoom simulation, vintergatan, of a milky way-mass disc galaxy. we find that in connection to the last major merger at z ∼ 1.5, cosmological accretion leads to the rapid formation of an outer, metal-poor, low-[α/fe] gas disc around the inner, metal-rich galaxy containing the old high-[α/fe] stars. this event leads to a bimodality in [α/fe] over a range of [fe/h]. a detailed analysis of how the galaxy evolves since z ∼ 1 is presented. we demonstrate the way in which inside-out growth shapes the radial surface density and metallicity profile and how radial migration preferentially relocates stars from the inner disc to the outer disc. secular disc heating is found to give rise to increasing velocity dispersions and scale heights with stellar age, which together with disc flaring explains several trends observed in the milky way, including shallower radial [fe/h] profiles above the mid-plane. we show how the galaxy formation scenario imprints non-trivial mappings between structural associations (i.e. thick and thin discs), velocity dispersions, α-enhancements, and ages of stars; e.g. the most metal-poor stars in the low-[α/fe] sequence are found to have a scale height comparable to old high-[α/fe] stars. finally, we illustrate how at low spatial resolution, comparable to the thickness of the galaxy, the proposed pathway to distinct sequences in [α/fe]-[fe/h] cannot be captured. | vintergatan - i. the origins of chemically, kinematically, and structurally distinct discs in a simulated milky way-mass galaxy |
the supernova impostor sn 2010da located in the nearby galaxy ngc 300, later identified as a likely supergiant b[e] high-mass x-ray binary, was simultaneously observed by nustar and xmm-newton between 2016 december 16 and 20, over a total time span of ∼310 ks. we report the discovery of a strong periodic modulation in the x-ray flux with a pulse period of 31.6 s and a very rapid spin-up, and confirm therefore that the compact object is a neutron star. we find that the spin period is changing from 31.71 s to 31.54 s over that period, with a spin-up rate of -5.56 × 10-7 s s-1, likely the largest ever observed from an accreting neutron star. the spectrum is described by a power-law and a disc blackbody model, leading to a 0.3-30 kev unabsorbed luminosity of 4.7 × 1039 erg s-1. applying our best-fitting model successfully to the spectra of an xmm-newton observation from 2010, suggests that the lower fluxes of ngc 300 ulx1 reported from observations around that time are caused by a large amount of absorption, while the intrinsic luminosity was similar as seen in 2016. a more constant luminosity level is also consistent with the long-term pulse period evolution approaching an equilibrium value asymptotically. we conclude that the source is another candidate for the new class of ultraluminous x-ray pulsars. | discovery of pulsations from ngc 300 ulx1 and its fast period evolution |
the transiting exoplanet survey satellite (tess) is finding transiting planet candidates around bright, nearby stars across the entire sky. the large field of view, however, results in low spatial resolution; therefore, multiple stars contribute to almost every tess light curve. high angular resolution imaging can detect the previously unknown companions to planetary candidate hosts that dilute the transit depths, lead to host star ambiguity, and, in some cases, are the source of false-positive transit signals. we use speckle imaging on the southern astrophysical research (soar) telescope to search for companions to 542 tess planet candidate hosts in the southern sky. we provide correction factors for the 117 systems with resolved companions due to photometric contamination. the contamination in tess due to close binaries is similar to that found in surveys of kepler planet candidates. for the solar-type population, we find a deep deficit of close binary systems with projected stellar separations less than 100 au among planet candidate hosts (44 observed binaries compared to 124 expected based on field binary statistics). the close binary suppression among tess planet candidate hosts is similar to that seen for the more distant kepler population. we also find a large surplus of tess planet candidates in wide binary systems detected in both soar and gaia dr2 (119 observed binaries compared to 77 expected). these wide binaries almost exclusively host giant planets, however, suggesting that orbital migration caused by perturbations from the stellar companion may lead to planet-planet scattering and suppress the population of small planets in wide binaries. both trends are also apparent in the m dwarf planet candidate hosts. | soar tess survey. i. sculpting of tess planetary systems by stellar companions |
we present an improved measurement of the hubble constant (h0) using the `inverse distance ladder' method, which adds the information from 207 type ia supernovae (sne ia) from the dark energy survey (des) at redshift 0.018 < z < 0.85 to existing distance measurements of 122 low-redshift (z < 0.07) sne ia (low-z) and measurements of baryon acoustic oscillations (baos). whereas traditional measurements of h0 with sne ia use a distance ladder of parallax and cepheid variable stars, the inverse distance ladder relies on absolute distance measurements from the baos to calibrate the intrinsic magnitude of the sne ia. we find h0 = 67.8 ± 1.3 km s-1 mpc-1 (statistical and systematic uncertainties, 68 per cent confidence). our measurement makes minimal assumptions about the underlying cosmological model, and our analysis was blinded to reduce confirmation bias. we examine possible systematic uncertainties and all are below the statistical uncertainties. our h0 value is consistent with estimates derived from the cosmic microwave background assuming a λcdm universe. | first cosmological results using type ia supernovae from the dark energy survey: measurement of the hubble constant |
the aavso photometric all sky survey (apass) project is designed to bridge the gap between the shallow tycho2 two-bandpass photometric catalog that is complete to v=11 and the deeper, but less spatially-complete catalogs like sdss or panstarrs. it can be used for calibration of a specific field; for obtaining spectral information about single sources, determining reddening in a small area of the sky; or even obtaining current-epoch astrometry for rapidly moving objects. the survey is being performed at two locations: near weed, new mexico in the northern hemisphere; and at ctio in the southern hemisphere. each site consists of dual bore-sighted 20cm telescopes on a single mount, designed to obtain two bandpasses of information simultaneously. each telescope covers 9 square degrees of sky with 2.5arcsec pixels, with the main survey taken with b,v,g',r',i' filters and covering the magnitude range 10<v<17. a bright extension is underway, saturating at v=7 and extending the wavelength coverage from u' to y. the current catalog is data release 9 and contains approximately 62 million stars. the american association of variable star observers is responsible for the overall management of the survey; a team of professional astronomers participate in the data analysis. the project was initially funded by the robert martin ayers sciences fund, with a follow-on grant from the national science foundation. (1 data file). | vizier online data catalog: aavso photometric all sky survey (apass) dr9 (henden+, 2016) |
advanced ligo detectors at hanford and livingston made two confirmed and one marginal detection of binary black holes during their first observing run. the first event, gw150914, was from the merger of two black holes much heavier that those whose masses have been estimated so far, indicating a formation scenario that might differ from "ordinary" stellar evolution. one possibility is that these heavy black holes resulted from a previous merger. when the progenitors of a black hole binary merger result from previous mergers, they should (on average) merge later, be more massive, and have spin magnitudes clustered around a dimensionless spin ∼0.7 . here we ask the following question: can gravitational-wave observations determine whether merging black holes were born from the collapse of massive stars ("first generation"), rather than being the end product of earlier mergers ("second generation")? we construct simple, observationally motivated populations of black hole binaries, and we use bayesian model selection to show that measurements of the masses, luminosity distance (or redshift), and "effective spin" of black hole binaries can indeed distinguish between these different formation scenarios. | are merging black holes born from stellar collapse or previous mergers? |
giant planets acquire gas, ices and rocks during the early formation stages of planetary systems and thus inform us on the formation process itself. proceeding from inside out, examining the connections between the deep interiors and the observable atmospheres, linking detailed measurements on giant planets in the solar system to the wealth of data on brown dwarfs and giant exoplanets, we aim to provide global constraints on interiors structure and composition for models of the formation of these planets. new developments after the juno and cassini missions point to both jupiter and saturn having strong compositional gradients and stable regions from the atmosphere to the deep interior. this is also the case of uranus and neptune, based on available, limited data on these planets. giant exoplanets and brown dwarfs provide us with new opportunities to link atmospheric abundances to bulk, interior abundances \rev{and to link these abundances and isotopic ratios to formation scenarios. analysing the wealth of data becoming available} will require new models accounting for the complexity of the planetary interiors and atmospheres | giant planets from the inside-out |
star formation histories (sfh) of early (6$<z<$12) galaxies have been found to be highly stochastic in both simulations and observations, while at $z\lesssim$6 the presence of a main sequence (ms) of star-forming galaxies imply secular processes at play. in this work, we aim at characterising the sfh variability of early galaxies as a function of their stellar mass and redshift. we use the jades public catalogue and derive the physical properties of the galaxies as well as their sfh using the spectral energy distribution modelling code cigale. to this aim, we implement a non-parametric sfh with a flat prior allowing for as much stochasticity as possible. we use the sfr gradient, an indicator of the movement of galaxies on the sfr-$m_\ast$ plane, linked to the recent sfh of galaxies. this dynamical approach of the relation between the sfr and stellar mass allows us to show that, at $z>9$, 87% of massive galaxies, ($\log(m_\ast/m_\odot)\gtrsim$9), have sfr gradients consistent with a stochastic star-formation activity during the last 100 myr, while this fraction drops to 15% at $z<7$. on the other hand, we see an increasing fraction of galaxies with a star-formation activity following a common stream on the sfr-$m_\ast$ plane with cosmic time, indicating that a secular mode of star-formation is emerging. we place our results in the context of the observed excess of uv emission as probed by the uv luminosity function at $z\gtrsim10$, by estimating $\sigma_{uv}$, the dispersion of the uv absolute magnitude distribution, to be of the order of 1.2mag and compare it with predictions from the literature. in conclusion, we find a transition of star-formation mode happening around $z\sim9$: galaxies with stochastic sfhs dominates at $z\gtrsim9$, although this level of stochasticity is too low to reach those invoked by recent models to reproduce the observed uv luminosity function. | identification of a transition from stochastic to secular star formation around $z=9$ with jwst |
we propose the existence of a lower bound on the energy of pure neutron matter (pnm) on the basis of unitary-gas considerations. we discuss its justification from experimental studies of cold atoms as well as from theoretical studies of neutron matter. we demonstrate that this bound results in limits to the density-dependent symmetry energy, which is the difference between the energies of symmetric nuclear matter and pnm. in particular, this bound leads to a lower limit to the volume symmetry energy parameter s 0. in addition, for assumed values of s 0 above this minimum, this bound implies both upper and lower limits to the symmetry energy slope parameter l ,which describes the lowest-order density dependence of the symmetry energy. a lower bound on neutron-matter incompressibility is also obtained. these bounds are found to be consistent with both recent calculations of the energies of pnm and constraints from nuclear experiments. our results are significant because several equations of state that are currently used in astrophysical simulations of supernovae and neutron star mergers, as well as in nuclear physics simulations of heavy-ion collisions, have symmetry energy parameters that violate these bounds. furthermore, below the nuclear saturation density, the bound on neutron-matter energies leads to a lower limit to the density-dependent symmetry energy, which leads to upper limits to the nuclear surface symmetry parameter and the neutron-star crust-core boundary. we also obtain a lower limit to the neutron-skin thicknesses of neutron-rich nuclei. above the nuclear saturation density, the bound on neutron-matter energies also leads to an upper limit to the symmetry energy, with implications for neutron-star cooling via the direct urca process. | symmetry parameter constraints from a lower bound on neutron-matter energy |
solar eruptions are spectacular magnetic explosions in the sun's corona, and how they are initiated remains unclear. prevailing theories often rely on special magnetic topologies that may not generally exist in the pre-eruption source region of corona. here, using fully three-dimensional magnetohydrodynamic simulations with high accuracy, we show that solar eruptions can be initiated in a single bipolar configuration with no additional special topology. through photospheric shearing motion alone, an electric current sheet forms in the highly sheared core field of the magnetic arcade during its quasi-static evolution. once magnetic reconnection sets in, the whole arcade is expelled impulsively, forming a fast-expanding twisted flux rope with a highly turbulent reconnecting region underneath. the simplicity and efficacy of this scenario argue strongly for its fundamental importance in the initiation of solar eruptions. | a fundamental mechanism of solar eruption initiation |
the first generation of stars, often called population iii (or pop iii), form from metal-free primordial gas at redshifts z ∼ 30 and below. they dominate the cosmic star-formation history until z ∼ 15-20, at which point the formation of metal-enriched population ii stars takes over. we review current theoretical models for the formation, properties, and impact of pop iii stars and discuss existing and future observational constraints. key takeaways from this review include the following: <label>■</label>primordial gas is highly susceptible to fragmentation and pop iii stars form as members of small clusters with a logarithmically flat mass function.<label>■</label>feedback from massive pop iii stars plays a central role in regulating subsequent star formation, but major uncertainties remain regarding its immediate impact.<label>■</label>in extreme conditions, supermassive pop iii stars can form, reaching masses of several 105mȯ. their remnants may be the seeds of the supermassive black holes observed in high-redshift quasars.<label>■</label>direct observations of pop iii stars in the early universe remain extremely challenging. indirect constraints from the global 21-cm signal or gravitational waves are more promising.<label>■</label>stellar archeological surveys allow us to constrain both the low-mass and the high-mass ends of the pop iii mass distribution. observations suggest that most massive pop iii stars end their lives as core-collapse supernovae rather than as pair-instability supernovae. | the first stars: formation, properties, and impact |
with just a month of data, jwst is already transforming our view of the universe, revealing and resolving starlight in unprecedented populations of galaxies. although "hst-dark" galaxies have previously been detected at long wavelengths, these observations generally suffer from a lack of spatial resolution, which limits our ability to characterize their sizes and morphologies. here we report on a first view of starlight from a subset of the hst-dark population that is bright with jwst/nircam (4.4 μm < 24.5 mag) and very faint or even invisible with hst (<1.6 μm). in this letter we focus on a dramatic and unanticipated population of physically extended galaxies (≳0.″25). these 12 galaxies have photometric redshifts 2 < z < 6, high stellar masses m ⋆ ≳ 1010 m ⊙, and significant dust-attenuated star formation. surprisingly, the galaxies have elongated projected axis ratios at 4.4 μm, suggesting that the population is disk dominated or prolate and we hence refer to them as ultrared flattened objects. most of the galaxies appear red at all radii, suggesting significant dust attenuation throughout. with r e (f444w) ~ 1-2 kpc, the galaxies are similar in size to compact massive galaxies at z ~ 2 and the cores of massive galaxies and s0s at z ~ 0. the stellar masses, sizes, and morphologies of the sample suggest that some could be progenitors of lenticular or fast-rotating galaxies in the local universe. the existence of this population suggests that our previous censuses of the universe may have missed massive, dusty edge-on disks, in addition to dust-obscured starbursts. | jwst reveals a population of ultrared, flattened galaxies at 2 ≲ z ≲ 6 previously missed by hst |
in recent years, machine learning has emerged as a powerful computational tool and novel problem-solving perspective for physics, offering new avenues for studying strongly interacting qcd matter properties under extreme conditions. this review article aims to provide an overview of the current state of this intersection of fields, focusing on the application of machine learning to theoretical studies in high energy nuclear physics. it covers diverse aspects, including heavy ion collisions, lattice field theory, and neutron stars, and discuss how machine learning can be used to explore and facilitate the physics goals of understanding qcd matter. the review also provides a commonality overview from a methodology perspective, from data-driven perspective to physics-driven perspective. we conclude by discussing the challenges and future prospects of machine learning applications in high energy nuclear physics, also underscoring the importance of incorporating physics priors into the purely data-driven learning toolbox. this review highlights the critical role of machine learning as a valuable computational paradigm for advancing physics exploration in high energy nuclear physics. | exploring qcd matter in extreme conditions with machine learning |
we present results on the morphological and structural evolution of a total of 3956 galaxies observed with jwst at 1.5 < z < 6.5 in the jwst ceers observations that overlap with the candels egs field. this is the biggest visually classified sample observed with jwst yet, ~20 times larger than previous studies, and allows us to examine in detail how galaxy structure has changed over this critical epoch. all sources were classified by six individual classifiers using a simple classification scheme aimed at producing disk/spheroid/peculiar classifications, whereby we determine how the relative number of these morphologies has evolved since the universe's first billion years. additionally, we explore structural and quantitative morphology measurements using morfometryka, and show that galaxies with m * > 109 m ⊙ at z > 3 are not dominated by irregular and peculiar structures, either visually or quantitatively, as previously thought. we find a strong dominance of morphologically selected disk galaxies up to z = 6 in this mass range. we also find that the stellar mass and star formation rate densities are dominated by disk galaxies up to z ~ 6, demonstrating that most stars in the universe were likely formed in a disk galaxy. we compare our results to theory to show that the fraction of types we find is predicted by cosmological simulations, and that the hubble sequence was already in place as early as one billion years after the big bang. additionally, we make our visual classifications public for the community. | the jwst hubble sequence: the rest-frame optical evolution of galaxy structure at 1.5 < z < 6.5 |
astrophysical processes such as feedback from supernovae and active galactic nuclei modify the properties and spatial distribution of dark matter, gas, and galaxies in a poorly understood way. this uncertainty is one of the main theoretical obstacles to extract information from cosmological surveys. we use 2,000 state-of-the-art hydrodynamic simulations from the camels project spanning a wide variety of cosmological and astrophysical models and generate hundreds of thousands of 2-dimensional maps for 13 different fields: from dark matter to gas and stellar properties. we use these maps to train convolutional neural networks to extract the maximum amount of cosmological information while marginalizing over astrophysical effects at the field level. although our maps only cover a small area of $(25~h^{-1}{\rm mpc})^2$, and the different fields are contaminated by astrophysical effects in very different ways, our networks can infer the values of $\omega_{\rm m}$ and $\sigma_8$ with a few percent level precision for most of the fields. we find that the marginalization performed by the network retains a wealth of cosmological information compared to a model trained on maps from gravity-only n-body simulations that are not contaminated by astrophysical effects. finally, we train our networks on multifields -- 2d maps that contain several fields as different colors or channels -- and find that not only they can infer the value of all parameters with higher accuracy than networks trained on individual fields, but they can constrain the value of $\omega_{\rm m}$ with higher accuracy than the maps from the n-body simulations. | multifield cosmology with artificial intelligence |
we investigate the neutron star (ns) equation of state (eos) by incorporating multi-messenger data of gw170817, psr j0030+0451, psr j0740+6620, and state-of-the-art theoretical progresses, including the information from chiral effective field theory ($\chi$eft) and perturbative quantum chromodynamics (pqcd) calculation. taking advantage of the various structures sampling by a single-layer feed-forward neural network model embedded in the bayesian nonparametric inference, the structure of ns matter's sound speed $c_{\rm s}$ is explored in a model-agnostic way. it is found that a peak structure is common in the $c_{\rm s}^2$ posterior, locating at $2.4-4.8\rho_{\rm sat}$ (nuclear saturation density) and $c_{\rm s}^2$ exceeds ${c^{2}}/{3}$ at 90\% credibility. the non-monotonic behavior suggests evidence of the state deviating from hadronic matter inside the very massive nss. assuming the new/exotic state is featured as it is softer than typical hadronic models or even with hyperons, we find that a sizable ($\geq 10^{-3}m_\odot$) exotic core, likely made of quark matter, is plausible for the ns with a gravitational mass above about $0.98m_{\rm tov}$, where $m_{\rm tov}$ represents the maximum gravitational mass of a non-rotating cold ns. the inferred $m_{\rm tov} = 2.18^{+0.27}_{-0.13}m_\odot$ (90\% credibility) is well consistent with the value of $2.17^{+0.15}_{-0.12}m_\odot$ estimated independently with gw170817/grb 170817a/at2017gfo assuming a temporary supramassive ns remnant formed after the merger. psr j0740+6620, the most massive ns detected so far, may host an exotic core with a probability of $\approx 0.36$. | plausible presence of new state in neutron stars with masses above 0.98mtov |
stellar evolution theory predicts multiple pathways to the explosive deaths of stars as supernovae. locating and characterizing the progenitors of well-studied supernovae is important to constrain the theory and to justify and design future surveys to improve on progenitor detections. here we report the serendipitous preexplosion imaging, by the hubble space telescope, of sn 2023ixf, one of the nearest extragalactic supernovae ever discovered, in the galaxy m101. the extremely red color and absolute magnitude ${m}_{{\rm{f}}814{\rm{w}}}=-{5.11}_{-0.47}^{+0.65}$ mag suggest that the progenitor was a red supergiant. comparison with stellar evolutionary isochrones suggests it is within the relatively low initial mass range of ~8-10 m ⊙ and that there is likely a lot of dust present at the supernova site. | possible detection of the progenitor of the type ii supernova sn 2023ixf |
we present the identification of 42 narrow-line active galactic nuclei (type-2 agn) candidates in the two deepest observations of the jades spectroscopic survey with jwst/nirspec. the spectral coverage and the depth of our observations allow us to select narrow-line agns based on both rest-frame optical and uv emission lines up to z=10. due to the metallicity decrease of galaxies, at $z>3$ the standard optical diagnostic diagrams (n2-bpt or s2-vo87) become unable to distinguish many agn from other sources of photoionisation. therefore, we also use high ionisation lines, such as heii$\lambda$4686, heii$\lambda$1640, neiv$\lambda$2422, nev$\lambda$3420, and nv$\lambda$1240, also in combination with other uv transitions, to trace the presence of agn. out of a parent sample of 209 galaxies, we identify 42 type-2 agn (although 10 of them are tentative), giving a fraction of galaxies in jades hosting type-2 agn of about $20\pm3$\%, which does not evolve significantly in the redshift range between 2 and 10. the selected type-2 agn have estimated bolometric luminosities of $10^{41.3-44.9}$ erg s$^{-1}$ and host-galaxy stellar masses of $10^{7.2-9.3}$ m$_{\odot}$. the star formation rates of the selected agn host galaxies are consistent with those of the star-forming main sequence. the agn host galaxies at z=4-6 contribute $\sim$8-30 \% to the uv luminosity function, slightly increasing with uv luminosity. | jades: a large population of obscured, narrow line agn at high redshift |
we report the discovery of a remarkable lyα emitting galaxy at z = 7.2782, jades-gs+53.16746−27.7720 (shortened to jades-gs-z7-la), with rest-frame equivalent width, ew0(lyα) = 388.0 ± 88.8 å and uv magnitude −17.0. the spectroscopic redshift is confirmed via rest-frame optical lines [o ii], hβ and [o iii] in its jwst/nirspec micro-shutter assembly (msa) spectrum. the lyα line is detected in both lower resolution (r ∼ 100) prism as well as medium resolution (r ∼ 1000) g140m grating spectra. the line spread function-deconvolved lyα full width at half maximum in the grating is 383.9 ± 56.2 km s−1 and the lyα velocity offset compared to the systemic redshift is 113.3 ± 80.0 km s−1, indicative of very little neutral gas or dust within the galaxy. we estimate the lyα escape fraction to be > 70%. jades-gs-z7-la has a [o iii]/[o ii] ratio (o32) of 11.1 ± 2.2 and a ([o iii] + [o ii])/hβ ratio (r23) of 11.2 ± 2.6, consistent with low metallicity and high ionization parameters. deep nircam imaging also revealed a close companion source (separated by 0.23″), which exhibits similar photometry to that of jades-gs-z7-la, with a photometric excess in the f410m nircam image consistent with [o iii] + hβ emission at the same redshift. the spectral energy distribution of jades-gs-z7-la indicates a "bursty" star formation history, with a low stellar mass of ≈107 m⊙. assuming that the lyα transmission through the intergalactic medium is the same as its measured escape fraction, an ionized region of size > 1.5 pmpc is needed to explain the high lyα ew and low velocity offset compared to systemic seen in jades-gs-z7-la. owing to its uv-faintness, we show that it is incapable of single-handedly ionizing a region large enough to explain its lyα emission. therefore, we suggest that jades-gs-z7-la (and possibly the companion source) may be a part of a larger overdensity, presenting direct evidence of overlapping ionized bubbles at z > 7. | jades: discovery of extremely high equivalent width lyman-α emission from a faint galaxy within an ionized bubble at z = 7.3 |
we present a spatially resolved study of stellar populations in 6 galaxies with stellar masses $m_*\sim10^{10}m_\odot$ at $z\sim3.7$ using 14-filter jwst/nircam imaging from the jades and jems surveys. the 6 galaxies are visually selected to have clumpy substructures with distinct colors over rest-frame $3600-4100$å, including a bright dominant stellar core that is close to their stellar-light centroids. with 23-filter photometry from hst to jwst, we measure the stellar-population properties of individual structural components via sed fitting using prospector. we find that the central stellar cores are $\gtrsim2$ times more massive than the toomre mass, indicating they may not form via in-situ fragmentation. the stellar cores have stellar ages of $0.4-0.7$ gyr that are similar to the timescale of clump inward migration due to dynamical friction, suggesting that they likely instead formed through the coalescence of giant stellar clumps. while they have not yet quenched, the 6 galaxies are below the star-forming main sequence by $0.2-0.7$ dex. within each galaxy, we find that the specific star formation rate is lower in the central stellar core, and the stellar-mass surface density of the core is already similar to quenched galaxies of the same masses and redshifts. meanwhile, the stellar ages of the cores are either comparable to or younger than the extended, smooth parts of the galaxies. our findings are consistent with model predictions of the gas-rich compaction scenario for the buildup of galaxies' central regions at high redshifts. we are likely witnessing the coeval formation of dense central cores, along with the onset of galaxy-wide quenching at $z>3$. | jades + jems: a detailed look at the buildup of central stellar cores and suppression of star formation in galaxies at redshifts 3 < z < 4.5 |
we investigate close encounters by stellar mass black holes (bhs) in the gaseous discs of active galactic nuclei (agn) as a potential formation channel of binary black holes (bbhs). we perform a series of 2d isothermal viscous hydrodynamical simulations within a shearing box prescription using the eulerian grid code \texttt{athena++}. we co-evolve the embedded bhs with the gas keeping track of the energetic dissipation and torquing of the bbh by gas gravitation and inertial forces. to probe the dependence of capture on the initial conditions, we discuss a suite of 345 simulations spanning local agn disc density ($\rho_0$) and impact parameter ($b$) space. we identify a clear region in $b - \rho_0$ space where gas assisted bbh capture is efficient. we find that the presence of gas leads to strong energetic dissipation during close encounters between unbound bhs, forming stably bound eccentric bbhs. we find that the gas dissipation during close encounters increases for systems with increased disc density and deeper periapsis passages $r_p$, fitting a power law such that $\delta e \propto \rho_0^{\alpha}r_p^{\beta}$ where $\{\alpha,\beta\} = \{1.01\pm0.04,-0.43\pm0.03\}$. alternatively, the gas dissipation is approximately $\delta e = 4.3 m_\text{d} v_\text{h} v_p$, where $m_\text{d} $ is the mass of a single bh minidisc just prior to the encounter when the binary separation is $2r_\text{h}$ (two binary hill radii), $v_\text{h}$ and $v_p$ are the relative bh velocities at $2r_\text{h}$ and at the first closest approach, respectively. we derive a prescription for capture which can be used in semi-analytical models of agn. we do not find the dissipative dynamics observed in these systems to be in agreement with the simple gas dynamical friction models often used in the literature. | gas assisted binary black hole formation in agn discs |
we present nustar observations of the nearby sn 2023ixf in m101 (d = 6.9 mpc) that provide the earliest hard x-ray detection of a nonrelativistic stellar explosion to date at δ t ≈ 4 days and δ t ≈ 11 days. the spectra are well described by a hot thermal bremsstrahlung continuum with t > 25 kev shining through a thick neutral medium with a neutral hydrogen column that decreases with time (initial n hint = 2.6 × 1023 cm-2). a prominent neutral fe kα emission line is clearly detected, similar to other strongly interacting supernovae (sne) such as sn 2010jl. the rapidly decreasing intrinsic absorption with time suggests the presence of a dense but confined circumstellar medium (csm). the absorbed broadband x-ray luminosity (0.3-79 kev) is lx≈ 2.5 × 1040 erg s-1 during both epochs, with the increase in overall x-ray flux related to the decrease in the absorbing column. interpreting these observations in the context of thermal bremsstrahlung radiation originating from the interaction of the sn shock with a dense medium we infer large particle densities in excess of n csm ≈ 4 × 108 cm-3 at r < 1015 cm, corresponding to an enhanced progenitor mass-loss rate of $\dot{m}\approx 3\times {10}^{-4}$ m ⊙ yr-1 for an assumed wind velocity of vw= 50 km s-1. | early hard x-rays from the nearby core-collapse supernova sn 2023ixf |
we present the mufasa suite of cosmological hydrodynamic simulations, which employs the gizmo meshless finite mass (mfm) code including h2-based star formation, nine-element chemical evolution, two-phase kinetic outflows following scalings from the feedback in realistic environments zoom simulations, and evolving halo mass-based quenching. our fiducial (50 h-1 mpc)3 volume is evolved to z = 0 with a quarter billion elements. the predicted galaxy stellar mass functions (gsmfs) reproduces observations from z = 4 → 0 to ≲ 1.2σ in cosmic variance, providing an unprecedented match to this key diagnostic. the cosmic star formation history and stellar mass growth show general agreement with data, with a strong archaeological downsizing trend such that dwarf galaxies form the majority of their stars after z ∼ 1. we run 25 and 12.5 h-1 mpc volumes to z = 2 with identical feedback prescriptions, the latter resolving all hydrogen-cooling haloes, and the three runs display fair resolution convergence. the specific star formation rates broadly agree with data at z = 0, but are underpredicted at z ∼ 2 by a factor of 3, re-emphasizing a longstanding puzzle in galaxy evolution models. we compare runs using mfm and two flavours of smoothed particle hydrodynamics, and show that the gsmf is sensitive to hydrodynamics methodology at the ∼×2 level, which is sub-dominant to choices for parametrizing feedback. | mufasa: galaxy formation simulations with meshless hydrodynamics |
the first neutron star (ns) merger observed by advanced ligo and virgo, gw170817, and its fireworks of electromagnetic counterparts across the entire electromagnetic spectrum marked the beginning of multi-messenger astronomy and astrophysics with gravitational waves. the ultraviolet, optical, and near-infrared emission was consistent with being powered by the radioactive decay of nuclei synthesized in the merger ejecta by the rapid neutron capture process (r-process). starting from an outline of the inferred properties of this "kilonova" emission, i discuss possible astrophysical sites for r-process nucleosynthesis in ns mergers, arguing that the heaviest r-process elements synthesized in this event most likely originated in outflows from a post-merger accretion disk. i compare the inferred properties of r-process element production in gw170817 to current observational constraints on galactic heavy r-process nucleosynthesis and discuss challenges merger-only models face in explaining the r-process content of our galaxy. based on the observational properties of gw170817 and recent theoretical progress on r-process nucleosynthesis in collapsars, i then show how gw170817 points to collapsars as the dominant source of r-process enrichment in the milky way. these rare core-collapse events arguably better satisfy existing constraints and overcome problems related to r-process enrichment in various environments that ns mergers face. finally, i comment on the universality of the r-process and on how variations in light r-process elements can be obtained both in ns mergers and collapsars. | gw170817 -the first observed neutron star merger and its kilonova: implications for the astrophysical site of the r-process |
we present the first generalization of navier-stokes theory to relativity that satisfies all of the following properties: (a) the system coupled to einstein's equations is causal and strongly hyperbolic; (b) equilibrium states are stable; (c) all leading dissipative contributions are present, i.e., shear viscosity, bulk viscosity, and thermal conductivity; (d) non-zero baryon number is included; (e) entropy production is non-negative in the regime of validity of the theory; (f) all of the above holds in the nonlinear regime without any simplifying symmetry assumptions. these properties are accomplished using a generalization of eckart's theory containing only the hydrodynamic variables, so that no new extended degrees of freedom are needed as in müller-israel-stewart theories. property (b), in particular, follows from a more general result that we also establish, namely, sufficient conditions that when added to stability in the fluid's rest frame imply stability in any reference frame obtained via a lorentz transformation. all our results are mathematically rigorously established. the framework presented here provides the starting point for systematic investigations of general-relativistic viscous phenomena in neutron star mergers. | first-order general-relativistic viscous fluid dynamics |
we analytically solve the problem of bose star growth in the bath of gravitationally interacting particles. we find that after nucleation of this object the bath is described by a self-similar solution of kinetic equation. together with the conservation laws, this fixes mass evolution of the bose star. our theory explains, in particular, the slowdown of the star growth at a certain "core-halo" mass, but also predicts formation of heavier and lighter objects in magistral dark matter models. the developed "adiabatic" approach to self-similarity may be of interest for kinetic theory in general. | self-similar growth of bose stars |
we present the properties of milky way- and andromeda-like (mw/m31-like) galaxies simulated within tng50, the highest-resolution run of the illustristng suite of $\lambda$cdm magneto-hydrodynamical simulations. we introduce our fiducial selection for mw/m31 analogs, which we propose for direct usage as well as for reference in future analyses. tng50 contains 198 mw/m31 analogs, i.e. galaxies with stellar disky morphology, with a stellar mass in the range of $m_* = 10^{10.5 - 11.2}$ msun, and within a mw-like mpc-scale environment at z=0. these are resolved with baryonic (dark matter) mass resolution of $8.5\times10^4$ msun ($4.5\times10^5$ msun) and $\sim150$ pc of average spatial resolution in the star-forming regions: we therefore expand by many factors (2 orders of magnitude) the sample size of cosmologically-simulated analogs with similar ($\times 10$ better) numerical resolution. the majority of tng50 mw/m31 analogs at $z=0$ exhibit a bar, 60 per cent are star-forming, the sample includes 3 local group (lg)-like systems, and a number of galaxies host one or more satellites as massive as e.g. the magellanic clouds. even within such a relatively narrow selection, tng50 reveals a great diversity in galaxy and halo properties, as well as in past histories. within the tng50 sample, it is possible to identify several simulated galaxies whose integral and structural properties are consistent, one or more at a time, with those measured for the galaxy and andromeda. with this paper, we document and release a series of broadly applicable data products that build upon the illustristng public release and aim to facilitate easy access and analysis by public users. these include datacubes across snapshots ($0 \le z \le 7$) for each tng50 mw/m31-like galaxy, and a series of value-added catalogs that will be continually expanded to provide a convenient and up to date community resource. | milky way and andromeda analogs from the tng50 simulation |
recent discoveries of a significant population of bright galaxies at cosmic dawn $\left(z\gtrsim 10\right)$ have enabled critical tests of cosmological galaxy formation models. in particular, the bright end of the galaxys' uv luminosity functions (uvlfs) appear higher than predicted by many models. using approximately 25,000 galaxy snapshots at 8 ≤ z ≤ 12 in a suite of fire-2 cosmological "zoom-in" simulations from the feedback in realistic environments (fire) project, we show that the observed abundance of uv-bright galaxies at cosmic dawn is reproduced in these simulations with a multichannel implementation of standard stellar feedback processes, without any fine-tuning. notably, we find no need to invoke previously suggested modifications, such as a nonstandard cosmology, a top-heavy stellar initial mass function, or a strongly enhanced star formation efficiency. we contrast the uvlfs predicted by bursty star formation in these original simulations to those derived from star formation histories (sfhs) smoothed over prescribed timescales (e.g., 100 myr). the comparison demonstrates that the strongly time-variable sfhs predicted by the fire simulations play a key role in correctly reproducing the observed, bright-end uvlfs at cosmic dawn: the bursty sfhs induce order-or-magnitude changes in the abundance of uv-bright (m uv ≲ -20) galaxies at z ≳ 10. the predicted bright-end uvlfs are consistent with both the spectroscopically confirmed population and the photometrically selected candidates. we also find good agreement between the predicted and observationally inferred integrated uv luminosity densities, which evolve more weakly with redshift in fire than suggested by some other models. | bursty star formation naturally explains the abundance of bright galaxies at cosmic dawn |
in this article, we explore some emerging properties of the stellar objects in the frame of the $f(r,t)$ gravity by employing the well-known karmarkar condition, where $r$ and $t$ represent ricci scalar and trace of energy momentum tensor respectively. it is worthy to highlight here that we assume the exponential type model of $f(r,t)$ theory of gravity $f(r,t)=r+\alpha(e^{-\beta r}-1)+\gamma t$ along with the matter lagrangian $\mathcal{l}_{m}=-\frac{1}{3}(p_{r}+2 p_{t})$ to classify the complete set of modified field equations. we demonstrate the embedded class-i technique by using the static spherically symmetric line element along with anisotropic fluid matter distribution. further, to achieve our goal, we consider a specific expression of metric potential $g_{rr}$, already presented in literature, and proceed by using the karmarkar condition to obtain the second metric potential. in particular, we use four different compact stars, namely $lmc~x-4,$ $exo~1785-248,$ $cen~x-3$ and $4u~1820-30$ and compute the corresponding values of the unknown parameters appearing in metric potentials. moreover, we conduct various physical evolutions such as graphical nature of energy density and pressure progression, energy constraints, mass function, adiabatic index, stability and equilibrium conditions to ensure the viability and consistency of our proposed model. our analysis indicates that the obtained anisotropic outcomes are physically acceptable with the finest degree of accuracy. | study of embedded class-i fluid spheres in f(r,t) gravity with karmarkar condition |
the search for habitable environments and biomarkers in exoplanetary atmospheres is the holy grail of exoplanet science. the detection of atmospheric signatures of habitable earth-like exoplanets is challenging owing to their small planet-star size contrast and thin atmospheres with high mean molecular weight. recently, a new class of habitable exoplanets, called hycean worlds, has been proposed, defined as temperate ocean-covered worlds with h2-rich atmospheres. their large sizes and extended atmospheres, compared to rocky planets of the same mass, make hycean worlds significantly more accessible to atmospheric spectroscopy with jwst. here we report a transmission spectrum of the candidate hycean world k2-18 b, observed with the jwst niriss and nirspec instruments in the 0.9-5.2 μm range. the spectrum reveals strong detections of methane (ch4) and carbon dioxide (co2) at 5σ and 3σ confidence, respectively, with high volume mixing ratios of ~1% each in a h2-rich atmosphere. the abundant ch4 and co2, along with the nondetection of ammonia (nh3), are consistent with chemical predictions for an ocean under a temperate h2-rich atmosphere on k2-18 b. the spectrum also suggests potential signs of dimethyl sulfide (dms), which has been predicted to be an observable biomarker in hycean worlds, motivating considerations of possible biological activity on the planet. the detection of ch4 resolves the long-standing missing methane problem for temperate exoplanets and the degeneracy in the atmospheric composition of k2-18 b from previous observations. we discuss possible implications of the findings, open questions, and future observations to explore this new regime in the search for life elsewhere. | carbon-bearing molecules in a possible hycean atmosphere |
exoplanet discoveries of recent years have provided a great deal of new data for studying the bulk compositions of giant planets. here we identify 47 transiting giant planets (20 m ⊕ < m < 20 m j) whose stellar insolations are low enough (f * < 2 × 108 erg s-1 cm-2, or roughly t eff < 1000) that they are not affected by the hot-jupiter radius inflation mechanism(s). we compute a set of new thermal and structural evolution models and use these models in comparison with properties of the 47 transiting planets (mass, radius, age) to determine their heavy element masses. a clear correlation emerges between the planetary heavy element mass mzand the total planet mass, approximately of the form {m}z\propto \sqrt{m}. this finding is consistent with the core-accretion model of planet formation. we also study how stellar metallicity [fe/h] affects planetary metal-enrichment and find a weaker correlation than has previously been reported from studies with smaller sample sizes. we confirm a strong relationship between the planetary metal-enrichment relative to the parent star z planet/z star and the planetary mass, but see no relation in z planet/z star with planet orbital properties or stellar mass. the large heavy element masses of many planets (>50 m ⊕) suggest significant amounts of heavy elements in h/he envelopes, rather than cores, such that metal-enriched giant planet atmospheres should be the rule. we also discuss a model of core-accretion planet formation in a one-dimensional disk and show that it agrees well with our derived relation between mass and z planet/z star. | the mass-metallicity relation for giant planets |
in this paper, we present the galex-sdss-wise legacy catalog (gswlc), a catalog of physical properties (stellar masses, dust attenuations, and star formation rates [sfrs]) for ∼700,000 galaxies with sloan digital sky survey (sdss) redshifts below 0.3. gswlc contains galaxies within the galaxy evolution explorer footprint, regardless of a uv detection, covering 90% of sdss. the physical properties were obtained from uv/optical spectral energy distribution (sed) fitting following bayesian methodology of salim et al., with improvements such as blending corrections for low-resolution uv photometry, flexible dust attenuation laws, and emission-line corrections. gswlc also includes mid-ir sfrs derived from ir templates based on 22 μ {{m}} wide-field infrared survey explorer observations. these estimates are independent of uv/optical sed fitting, in order to separate possible systematics. the paper argues that the comparison of specific sfrs (ssfrs) is more informative and physically motivated than the comparison of sfrs. the ssfrs resulting from the uv/optical sed fitting are compared to the mid-ir ssfrs and to ssfrs from three published catalogs. for “main-sequence” galaxies with no active galactic nucleus (agn) all ssfrs are in very good agreement (within 0.1 dex on average). in particular, the widely used aperture-corrected sfrs from the mpa/jhu catalog show no systematic offsets, in contrast to some integral field spectroscopy results. for galaxies below the main sequence (log ssfr < -11), mid-ir (s)sfrs based on fixed luminosity-sfr conversion are severely biased (up to 2 dex) because the dust is primarily heated by old stars. furthermore, mid-ir (s)sfrs are overestimated by up to 0.6 dex for galaxies with agns, presumably due to nonstellar dust heating. uv/optical (s)sfrs are thus preferred to ir-based (s)sfrs for quenched galaxies and those that host agns. | galex-sdss-wise legacy catalog (gswlc): star formation rates, stellar masses, and dust attenuations of 700,000 low-redshift galaxies |
the evolution of helium stars with initial masses in the range 1.6-120 {m}⊙is studied, including the effects of mass loss by winds. these stars are assumed to form in binary systems when their expanding hydrogenic envelopes are promptly lost just after helium ignition. significant differences are found with single-star evolution, chiefly because the helium core loses mass during helium burning rather than gaining it from hydrogen shell burning. consequently, presupernova stars for a given initial mass function have considerably smaller mass when they die and will be easier to explode. even accounting for this difference, the helium stars with mass loss develop more centrally condensed cores that should explode more easily than their single-star counterparts. the production of low-mass black holes may be diminished. helium stars with initial masses below 3.2 {m}⊙experience significant radius expansion after helium depletion, reaching blue supergiant proportions. this could trigger additional mass exchange or affect the light curve of the supernova. the most common black hole mass produced in binaries is estimated to be about 9 {m}⊙ . a new maximum mass for black holes derived from pulsational pair-instability supernovae is derived, 46 {m}⊙ , and a new potential gap at 10-12 {m}⊙is noted. models pertinent to sn 2014ft are presented, and a library of presupernova models is generated. | the evolution of massive helium stars, including mass loss |
we introduce project nihao (numerical investigation of a hundred astrophysical objects), a set of 100 cosmological zoom-in hydrodynamical simulations performed using the gasoline code, with an improved implementation of the sph algorithm. the haloes in our study range from dwarf (m200 ∼ 5 × 109 m⊙) to milky way (m200 ∼ 2 × 1012 m⊙) masses, and represent an unbiased sampling of merger histories, concentrations and spin parameters. the particle masses and force softenings are chosen to resolve the mass profile to below 1 per cent of the virial radius at all masses, ensuring that galaxy half-light radii are well resolved. using the same treatment of star formation and stellar feedback for every object, the simulated galaxies reproduce the observed inefficiency of galaxy formation across cosmic time as expressed through the stellar mass versus halo mass relation, and the star formation rate versus stellar mass relation. we thus conclude that stellar feedback is the chief piece of physics required to limit the efficiency of star formation in galaxies less massive than the milky way. | nihao project - i. reproducing the inefficiency of galaxy formation across cosmic time with a large sample of cosmological hydrodynamical simulations |
context. open clusters are key targets for studies of galaxy structure and evolution, and stellar physics. since the gaia data release 2 (dr2), the discovery of undetected clusters has shown that previous surveys were incomplete.aims: our aim is to exploit the big data capabilities of machine learning to detect new open clusters in gaia dr2, and to complete the open cluster sample to enable further studies of the galactic disc.methods: we use a machine-learning based methodology to systematically search the galactic disc for overdensities in the astrometric space and identify the open clusters using photometric information. first, we used an unsupervised clustering algorithm, dbscan, to blindly search for these overdensities in gaia dr2 (l, b, ϖ, μα*, μδ), and then we used a deep learning artificial neural network trained on colour-magnitude diagrams to identify isochrone patterns in these overdensities, and to confirm them as open clusters.results: we find 582 new open clusters distributed along the galactic disc in the region |b| < 20°. we detect substructure in complex regions, and identify the tidal tails of a disrupting cluster ubc 274 of ∼3 gyr located at ∼2 kpc.conclusions: adapting the mentioned methodology to a big data environment allows us to target the search using the physical properties of open clusters instead of being driven by computational limitations. this blind search for open clusters in the galactic disc increases the number of known open clusters by 45%. full table 1 and table 2 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/635/a45 | hunting for open clusters in gaia dr2: 582 new open clusters in the galactic disc |
the first four gravitational wave events detected by ligo were all interpreted as merging black hole binaries (bhbs), opening a new perspective on the study of such systems. here we use our new population-synthesis code mobse, an upgraded version of bse, to investigate the demography of merging bhbs. mobse includes metallicity-dependent prescriptions for mass-loss of massive hot stars. it also accounts for the impact of the electron-scattering eddington factor on mass-loss. we perform >108 simulations of isolated massive binaries, with 12 different metallicities, to study the impact of mass-loss, core-collapse supernovae and common envelope on merging bhbs. accounting for the dependence of stellar winds on the eddington factor leads to the formation of black holes (bhs) with mass up to 65 m⊙ at metallicity z ∼ 0.0002. however, most bhs in merging bhbs have masses ≲ 40 m⊙. we find merging bhbs with mass ratios in the 0.1-1.0 range, even if mass ratios >0.6 are more likely. we predict that systems like gw150914, gw170814 and gw170104 can form only from progenitors with metallicity z ≤ 0.006, z ≤ 0.008 and z ≤ 0.012, respectively. most merging bhbs have gone through a common envelope phase, but up to ∼17 per cent merging bhbs at low metallicity did not undergo any common envelope phase. we find a much higher number of mergers from metal-poor progenitors than from metal-rich ones: the number of bhb mergers per unit mass is ∼10-4 m_{⊙}^{-1} at low metallicity (z = 0.0002-0.002) and drops to ∼10-7 m_{⊙}^{-1} at high metallicity (z ∼ 0.02). | merging black hole binaries: the effects of progenitor's metallicity, mass-loss rate and eddington factor |
the search for life in the universe is a fundamental problem of astrobiology and modern science. the current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. to specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (hzs) around g-k-m dwarf stars including our young sun. global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. a key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and earth sciences. the assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the hz to the biogenic zone and provide new observational strategies for searching for signatures of life. the major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the nasa nexus for exoplanetary system science funded workshop 'exoplanetary space weather, climate and habitability' and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology. | impact of space weather on climate and habitability of terrestrial-type exoplanets |
annular structures (rings and gaps) in disks around pre-main-sequence stars have been detected in abundance towards class ii protostellar objects that are approximately 1,000,000 years old1. these structures are often interpreted as evidence of planet formation1-3, with planetary-mass bodies carving rings and gaps in the disk4. this implies that planet formation may already be underway in even younger disks in the class i phase, when the protostar is still embedded in a larger-scale dense envelope of gas and dust5. only within the past decade have detailed properties of disks in the earliest star-forming phases been observed6,7. here we report 1.3-millimetre dust emission observations with a resolution of five astronomical units that show four annular substructures in the disk of the young (less than 500,000 years old)8 protostar irs 63. irs 63 is a single class i source located in the nearby ophiuchus molecular cloud at a distance of 144 parsecs9, and is one of the brightest class i protostars at millimetre wavelengths. irs 63 also has a relatively large disk compared to other young disks (greater than 50 astronomical units)10. multiple annular substructures observed towards disks at young ages can act as an early foothold for dust-grain growth, which is a prerequisite of planet formation. whether or not planets already exist in the disk of irs 63, it is clear that the planet-formation process begins in the initial protostellar phases, earlier than predicted by current planet-formation theories11. | four annular structures in a protostellar disk less than 500,000 years old |
during 2014 and 2015, nasa's neutron star interior composition explorer (nicer) mission proceeded success- fully through phase c, design and development. an x-ray (0.2-12 kev) astrophysics payload destined for the international space station, nicer is manifested for launch in early 2017 on the commercial resupply services spacex-11 flight. its scientific objectives are to investigate the internal structure, dynamics, and energetics of neutron stars, the densest objects in the universe. during phase c, flight components including optics, detectors, the optical bench, pointing actuators, electronics, and others were subjected to environmental testing and integrated to form the flight payload. a custom-built facility was used to co-align and integrate the x-ray "con- centrator" optics and silicon-drift detectors. ground calibration provided robust performance measures of the optical (at nasa's goddard space flight center) and detector (at the massachusetts institute of technology) subsystems, while comprehensive functional tests prior to payload-level environmental testing met all instrument performance requirements. we describe here the implementation of nicer's major subsystems, summarize their performance and calibration, and outline the component-level testing that was successfully applied. | the neutron star interior composition explorer (nicer): design and development |
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