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the third gravitational-wave transient catalog (gwtc-3) describes signals detected with advanced ligo and advanced virgo up to the end of their third observing run. updating the previous gwtc-2.1, we present candidate gravitational waves from compact binary coalescences during the second half of the third observing run (o3b) between 1 november 2019, 15 ∶00 coordinated universal time (utc) and 27 march 2020, 17 ∶00 utc. there are 35 compact binary coalescence candidates identified by at least one of our search algorithms with a probability of astrophysical origin pastro>0.5 . of these, 18 were previously reported as low-latency public alerts, and 17 are reported here for the first time. based upon estimates for the component masses, our o3b candidates with pastro>0.5 are consistent with gravitational-wave signals from binary black holes or neutron-star-black-hole binaries, and we identify none from binary neutron stars. however, from the gravitational-wave data alone, we are not able to measure matter effects that distinguish whether the binary components are neutron stars or black holes. the range of inferred component masses is similar to that found with previous catalogs, but the o3b candidates include the first confident observations of neutron-star-black-hole binaries. including the 35 candidates from o3b in addition to those from gwtc-2.1, gwtc-3 contains 90 candidates found by our analysis with pastro>0.5 across the first three observing runs. these observations of compact binary coalescences present an unprecedented view of the properties of black holes and neutron stars.

gwtc-3: compact binary coalescences observed by ligo and virgo during the second part of the third observing run

context. we present the second gaia data release, gaia dr2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. in addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system.aims: a summary of the contents of gaia dr2 is presented, accompanied by a discussion on the differences with respect to gaia dr1 and an overview of the main limitations which are still present in the survey. recommendations are made on the responsible use of gaia dr2 results.methods: the raw data collected with the gaia instruments during the first 22 months of the mission have been processed by the gaia data processing and analysis consortium (dpac) and turned into this second data release, which represents a major advance with respect to gaia dr1 in terms of completeness, performance, and richness of the data products.results: gaia dr2 contains celestial positions and the apparent brightness in g for approximately 1.7 billion sources. for 1.3 billion of those sources, parallaxes and proper motions are in addition available. the sample of sources for which variability information is provided is expanded to 0.5 million stars. this data release contains four new elements: broad-band colour information in the form of the apparent brightness in the gbp (330-680 nm) and grp (630-1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. finally, gaia dr2 also represents a new materialisation of the celestial reference frame in the optical, the gaia-crf2, which is the first optical reference frame based solely on extragalactic sources. there are notable changes in the photometric system and the catalogue source list with respect to gaia dr1, and we stress the need to consider the two data releases as independent.conclusions: gaia dr2 represents a major achievement for the gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the gaia survey which covers a very substantial fraction of the volume of our galaxy.

gaia data release 2. summary of the contents and survey properties

on september 14, 2015 at 09:50:45 utc the two detectors of the laser interferometer gravitational-wave observatory simultaneously observed a transient gravitational-wave signal. the signal sweeps upwards in frequency from 35 to 250 hz with a peak gravitational-wave strain of 1.0 ×10-21. it matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. the signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1 σ . the source lies at a luminosity distance of 41 0-180+160 mpc corresponding to a redshift z =0.0 9-0.04+0.03 . in the source frame, the initial black hole masses are 3 6-4+5m⊙ and 2 9-4+4m⊙ , and the final black hole mass is 6 2-4+4m⊙ , with 3. 0-0.5+0.5m⊙ c2 radiated in gravitational waves. all uncertainties define 90% credible intervals. these observations demonstrate the existence of binary stellar-mass black hole systems. this is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

observation of gravitational waves from a binary black hole merger

we present the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1 m⊙ during the first and second observing runs of the advanced gravitational-wave detector network. during the first observing run (o 1 ), from september 12, 2015 to january 19, 2016, gravitational waves from three binary black hole mergers were detected. the second observing run (o 2 ), which ran from november 30, 2016 to august 25, 2017, saw the first detection of gravitational waves from a binary neutron star inspiral, in addition to the observation of gravitational waves from a total of seven binary black hole mergers, four of which we report here for the first time: gw170729, gw170809, gw170818, and gw170823. for all significant gravitational-wave events, we provide estimates of the source properties. the detected binary black holes have total masses between 18.6-0.7+3.2 m⊙ and 84.4-11.1+15.8 m⊙ and range in distance between 320-110+120 and 2840-1360+1400 mpc . no neutron star-black hole mergers were detected. in addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false-alarm rate less than 1 per 30 days. from these results over the first two observing runs, which include approximately one gravitational-wave detection per 15 days of data searched, we infer merger rates at the 90% confidence intervals of 110 -3840 gpc-3 y-1 for binary neutron stars and 9.7 -101 gpc-3 y-1 for binary black holes assuming fixed population distributions and determine a neutron star-black hole merger rate 90% upper limit of 610 gpc-3 y-1 .

gwtc-1: a gravitational-wave transient catalog of compact binary mergers observed by ligo and virgo during the first and second observing runs

on august 17, 2017 at 12∶41:04 utc the advanced ligo and advanced virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. the signal, gw170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0 ×104 years . we infer the component masses of the binary to be between 0.86 and 2.26 m⊙ , in agreement with masses of known neutron stars. restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17 - 1.60 m⊙ , with the total mass of the system 2.7 4-0.01+0.04m⊙ . the source was localized within a sky region of 28 deg2 (90% probability) and had a luminosity distance of 4 0-14+8 mpc , the closest and most precisely localized gravitational-wave signal yet. the association with the γ -ray burst grb 170817a, detected by fermi-gbm 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ -ray bursts. subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. this unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.

gw170817: observation of gravitational waves from a binary neutron star inspiral

context. we present the early installment of the third gaia data release, gaia edr3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the list of radial velocities from gaia dr2.aims: a summary of the contents of gaia edr3 is presented, accompanied by a discussion on the differences with respect to gaia dr2 and an overview of the main limitations which are present in the survey. recommendations are made on the responsible use of gaia edr3 results.methods: the raw data collected with the gaia instruments during the first 34 months of the mission have been processed by the gaia data processing and analysis consortium and turned into this early third data release, which represents a major advance with respect to gaia dr2 in terms of astrometric and photometric precision, accuracy, and homogeneity.results: gaia edr3 contains celestial positions and the apparent brightness in g for approximately 1.8 billion sources. for 1.5 billion of those sources, parallaxes, proper motions, and the (gbp − grp) colour are also available. the passbands for g, gbp, and grp are provided as part of the release. for ease of use, the 7 million radial velocities from gaia dr2 are included in this release, after the removal of a small number of spurious values. new radial velocities will appear as part of gaia dr3. finally, gaia edr3 represents an updated materialisation of the celestial reference frame (crf) in the optical, the gaia-crf3, which is based solely on extragalactic sources. the creation of the source list for gaia edr3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. the source list is largely the same as that for gaia dr2, but it does feature new sources and there are some notable changes. the source list will not change for gaia dr3.conclusions: gaia edr3 represents a significant advance over gaia dr2, with parallax precisions increased by 30 per cent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30-40% for the parallaxes and by a factor ~2.5 for the proper motions. the photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. a single passband for g, gbp, and grp is valid over the entire magnitude and colour range, with no systematics above the 1% level

gaia early data release 3. summary of the contents and survey properties

context. we present the third data release of the european space agency's gaia mission, gaia dr3. this release includes a large variety of new data products, notably a much expanded radial velocity survey and a very extensive astrophysical characterisation of gaia sources.aims: we outline the content and the properties of gaia dr3, providing an overview of the main improvements in the data processing in comparison with previous data releases (where applicable) and a brief discussion of the limitations of the data in this release.methods: the gaia dr3 catalogue is the outcome of the processing of raw data collected with the gaia instruments during the first 34 months of the mission by the gaia data processing and analysis consortium.results: the gaia dr3 catalogue contains the same source list, celestial positions, proper motions, parallaxes, and broad band photometry in the g, gbp, and grp pass-bands already present in the early third data release, gaia edr3. gaia dr3 introduces an impressive wealth of new data products. more than 33 million objects in the ranges grvs < 14 and 3100 < teff < 14 500, have new determinations of their mean radial velocities based on data collected by gaia. we provide grvs magnitudes for most sources with radial velocities, and a line broadening parameter is listed for a subset of these. mean gaia spectra are made available to the community. the gaia dr3 catalogue includes about 1 million mean spectra from the radial velocity spectrometer, and about 220 million low-resolution blue and red prism photometer bp/rp mean spectra. the results of the analysis of epoch photometry are provided for some 10 million sources across 24 variability types. gaia dr3 includes astrophysical parameters and source class probabilities for about 470 million and 1500 million sources, respectively, including stars, galaxies, and quasars. orbital elements and trend parameters are provided for some 800 000 astrometric, spectroscopic and eclipsing binaries. more than 150 000 solar system objects, including new discoveries, with preliminary orbital solutions and individual epoch observations are part of this release. reflectance spectra derived from the epoch bp/rp spectral data are published for about 60 000 asteroids. finally, an additional data set is provided, namely the gaia andromeda photometric survey, consisting of the photometric time series for all sources located in a 5.5 degree radius field centred on the andromeda galaxy.conclusions: this data release represents a major advance with respect to gaia dr2 and gaia edr3 because of the unprecedented quantity, quality, and variety of source astrophysical data. to date this is the largest collection of all-sky spectrophotometry, radial velocities, variables, and astrophysical parameters derived from both low- and high-resolution spectra and includes a spectrophotometric and dynamical survey of ssos of the highest accuracy. the non-single star content surpasses the existing data by orders of magnitude. the quasar host and galaxy light profile collection is the first such survey that is all sky and space based. the astrophysical information provided in gaia dr3 will unleash the full potential of gaia's exquisite astrometric, photometric, and radial velocity surveys.

gaia data release 3. summary of the content and survey properties

pan-starrs1 has carried out a set of distinct synoptic imaging sky surveys including the $3\pi$ steradian survey and the medium deep survey in 5 bands ($grizy_{p1}$). the mean 5$\sigma$ point source limiting sensitivities in the stacked 3$\pi$ steradian survey in $grizy_{p1}$ are (23.3, 23.2, 23.1, 22.3, 21.4) respectively. the upper bound on the systematic uncertainty in the photometric calibration across the sky is 7-12 millimag depending on the bandpass. the systematic uncertainty of the astrometric calibration using the gaia frame comes from a comparison of the results with gaia: the standard deviation of the mean and median residuals ($ \delta ra, \delta dec $) are (2.3, 1.7) milliarcsec, and (3.1, 4.8) milliarcsec respectively. the pan-starrs system and the design of the ps1 surveys are described and an overview of the resulting image and catalog data products and their basic characteristics are described together with a summary of important results. the images, reduced data products, and derived data products from the pan-starrs1 surveys are available to the community from the mikulski archive for space telescopes (mast) at stsci.

the pan-starrs1 surveys

we report on the population properties of compact binary mergers inferred from gravitational-wave observations of these systems during the first three ligo-virgo observing runs. the gravitational-wave transient catalog 3 (gwtc-3) contains signals consistent with three classes of binary mergers: binary black hole, binary neutron star, and neutron star-black hole mergers. we infer the binary neutron star merger rate to be between 10 and 1700 gpc−3 yr−1 and the neutron star-black hole merger rate to be between 7.8 and 140 gpc−3 yr−1 , assuming a constant rate density in the comoving frame and taking the union of 90% credible intervals for methods used in this work. we infer the binary black hole merger rate, allowing for evolution with redshift, to be between 17.9 and 44 gpc-3 yr-1 at a fiducial redshift (z =0.2 ). the rate of binary black hole mergers is observed to increase with redshift at a rate proportional to (1 +z )κ with κ =2. 9-1.8+1.7 for z ≲1 . using both binary neutron star and neutron star-black hole binaries, we obtain a broad, relatively flat neutron star mass distribution extending from 1.2-0.2+0.1 to 2.0-0.3+0.3m⊙. we confidently determine that the merger rate as a function of mass sharply declines after the expected maximum neutron star mass, but cannot yet confirm or rule out the existence of a lower mass gap between neutron stars and black holes. we also find the binary black hole mass distribution has localized over- and underdensities relative to a power-law distribution, with peaks emerging at chirp masses of 8.3-0.5+0.3 and 27.9-1.8+1.9m⊙. while we continue to find that the mass distribution of a binary's more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above approximately 60 m⊙, which would indicate the presence of a upper mass gap. observed black hole spins are small, with half of spin magnitudes below χi≈0.25 . while the majority of spins are preferentially aligned with the orbital angular momentum, we infer evidence of antialigned spins among the binary population. we observe an increase in spin magnitude for systems with more unequal-mass ratio. we also observe evidence of misalignment of spins relative to the orbital angular momentum.

population of merging compact binaries inferred using gravitational waves through gwtc-3

we describe here the most ambitious survey currently planned in the optical, the large synoptic survey telescope (lsst). the lsst design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the solar system, exploring the transient optical sky, and mapping the milky way. lsst will be a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from cerro pachón in northern chile. the telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg2 field of view, a 3.2-gigapixel camera, and six filters (ugrizy) covering the wavelength range 320-1050 nm. the project is in the construction phase and will begin regular survey operations by 2022. about 90% of the observing time will be devoted to a deep-wide-fast survey mode that will uniformly observe a 18,000 deg2 region about 800 times (summed over all six bands) during the anticipated 10 yr of operations and will yield a co-added map to r ∼ 27.5. these data will result in databases including about 32 trillion observations of 20 billion galaxies and a similar number of stars, and they will serve the majority of the primary science programs. the remaining 10% of the observing time will be allocated to special projects such as very deep and very fast time domain surveys, whose details are currently under discussion. we illustrate how the lsst science drivers led to these choices of system parameters, and we describe the expected data products and their characteristics.

lsst: from science drivers to reference design and anticipated data products

we report on gravitational-wave discoveries from compact binary coalescences detected by advanced ligo and advanced virgo in the first half of the third observing run (o3a) between 1 april 2019 15 ∶00 utc and 1 october 2019 15 ∶00 utc. by imposing a false-alarm-rate threshold of two per year in each of the four search pipelines that constitute our search, we present 39 candidate gravitational-wave events. at this threshold, we expect a contamination fraction of less than 10%. of these, 26 candidate events were reported previously in near-real time through gamma-ray coordinates network notices and circulars; 13 are reported here for the first time. the catalog contains events whose sources are black hole binary mergers up to a redshift of approximately 0.8, as well as events whose components cannot be unambiguously identified as black holes or neutron stars. for the latter group, we are unable to determine the nature based on estimates of the component masses and spins from gravitational-wave data alone. the range of candidate event masses which are unambiguously identified as binary black holes (both objects ≥3 m⊙) is increased compared to gwtc-1, with total masses from approximately 14 m⊙ for gw190924_021846 to approximately 150 m⊙ for gw190521. for the first time, this catalog includes binary systems with significantly asymmetric mass ratios, which had not been observed in data taken before april 2019. we also find that 11 of the 39 events detected since april 2019 have positive effective inspiral spins under our default prior (at 90% credibility), while none exhibit negative effective inspiral spin. given the increased sensitivity of advanced ligo and advanced virgo, the detection of 39 candidate events in approximately 26 weeks of data (approximately 1.5 per week) is consistent with gwtc-1.

gwtc-2: compact binary coalescences observed by ligo and virgo during the first half of the third observing run

on 2017 august 17 a binary neutron star coalescence candidate (later designated gw170817) with merger time 12:41:04 utc was observed through gravitational waves by the advanced ligo and advanced virgo detectors. the fermi gamma-ray burst monitor independently detected a gamma-ray burst (grb 170817a) with a time delay of ∼ 1.7 {{s}} with respect to the merger time. from the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of {40}-8+8 mpc and with component masses consistent with neutron stars. the component masses were later measured to be in the range 0.86 to 2.26 {m}⊙ . an extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (sss17a, now with the iau identification of at 2017gfo) in ngc 4993 (at ∼ 40 {{mpc}}) less than 11 hours after the merger by the one-meter, two hemisphere (1m2h) team using the 1 m swope telescope. the optical transient was independently detected by multiple teams within an hour. subsequent observations targeted the object and its environment. early ultraviolet observations revealed a blue transient that faded within 48 hours. optical and infrared observations showed a redward evolution over ∼10 days. following early non-detections, x-ray and radio emission were discovered at the transient's position ∼ 9 and ∼ 16 days, respectively, after the merger. both the x-ray and radio emission likely arise from a physical process that is distinct from the one that generates the uv/optical/near-infrared emission. no ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. these observations support the hypothesis that gw170817 was produced by the merger of two neutron stars in ngc 4993 followed by a short gamma-ray burst (grb 170817a) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta. any correspondence should be addressed to .

multi-messenger observations of a binary neutron star merger

observing and timing a group of millisecond pulsars with high rotational stability enables the direct detection of gravitational waves (gws). the gw signals can be identified from the spatial correlations encoded in the times-of-arrival of widely spaced pulsar-pairs. the chinese pulsar timing array (cpta) is a collaboration aiming at the direct gw detection with observations carried out using chinese radio telescopes. this short article serves as a "table of contents" for a forthcoming series of papers related to the cpta data release 1 (cpta dr1) which uses observations from the five-hundred-meter aperture spherical radio telescope. here, after summarizing the time span and accuracy of cpta dr1, we report the key results of our statistical inference finding a correlated signal with amplitude $\mathrm{log}{a}_{{\rm{c}}}=-14.4{\,}_{-2.8}^{+1.0}$ for spectral index in the range of α ∈ [ - 1.8, 1.5] assuming a gw background (gwb) induced quadrupolar correlation. the search for the hellings-downs (hd) correlation curve is also presented, where some evidence for the hd correlation has been found that a 4.6σ statistical significance is achieved using the discrete frequency method around the frequency of 14 nhz. we expect that the future international pulsar timing array data analysis and the next cpta data release will be more sensitive to the nhz gwb, which could verify the current results.

searching for the nano-hertz stochastic gravitational wave background with the chinese pulsar timing array data release i

on 2017 august 17, the gravitational-wave event gw170817 was observed by the advanced ligo and virgo detectors, and the gamma-ray burst (grb) grb 170817a was observed independently by the fermi gamma-ray burst monitor, and the anti-coincidence shield for the spectrometer for the international gamma-ray astrophysics laboratory. the probability of the near-simultaneous temporal and spatial observation of grb 170817a and gw170817 occurring by chance is 5.0× {10}-8. we therefore confirm binary neutron star mergers as a progenitor of short grbs. the association of gw170817 and grb 170817a provides new insight into fundamental physics and the origin of short grbs. we use the observed time delay of (+1.74+/- 0.05) {{s}} between grb 170817a and gw170817 to: (i) constrain the difference between the speed of gravity and the speed of light to be between -3× {10}-15 and +7× {10}-16 times the speed of light, (ii) place new bounds on the violation of lorentz invariance, (iii) present a new test of the equivalence principle by constraining the shapiro delay between gravitational and electromagnetic radiation. we also use the time delay to constrain the size and bulk lorentz factor of the region emitting the gamma-rays. grb 170817a is the closest short grb with a known distance, but is between 2 and 6 orders of magnitude less energetic than other bursts with measured redshift. a new generation of gamma-ray detectors, and subthreshold searches in existing detectors, will be essential to detect similar short bursts at greater distances. finally, we predict a joint detection rate for the fermi gamma-ray burst monitor and the advanced ligo and virgo detectors of 0.1-1.4 per year during the 2018-2019 observing run and 0.3-1.7 per year at design sensitivity.

gravitational waves and gamma-rays from a binary neutron star merger: gw170817 and grb 170817a

we report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. the signal, gw151226, was observed by the twin detectors of the laser interferometer gravitational-wave observatory (ligo) on december 26, 2015 at 03:38:53 utc. the signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. subsequent off-line analyses recovered gw151226 with a network signal-to-noise ratio of 13 and a significance greater than 5 σ . the signal persisted in the ligo frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 hz, and reached a peak gravitational strain of 3. 4-0.9+0.7×10-22 . the inferred source-frame initial black hole masses are 14.2-3.7+8.3 m⊙ and 7. 5-2.3+2.3 m⊙, and the final black hole mass is 20.8-1.7+6.1 m⊙. we find that at least one of the component black holes has spin greater than 0.2. this source is located at a luminosity distance of 44 0-190+180 mpc corresponding to a redshift of 0.0 9-0.04+0.03. all uncertainties define a 90% credible interval. this second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

gw151226: observation of gravitational waves from a 22-solar-mass binary black hole coalescence

axions comprise a broad class of particles that can play a major role in explaining the unknown aspects of cosmology. they are also well-motivated within high energy physics, appearing in theories related to cp-violation in the standard model, supersymmetric theories, and theories with extra-dimensions, including string theory, and so axion cosmology offers us a unique view onto these theories. i review the motivation and models for axions in particle physics and string theory. i then present a comprehensive and pedagogical view on the cosmology and astrophysics of axion-like particles, starting from inflation and progressing via bbn, the cmb, reionization and structure formation, up to the present-day universe. topics covered include: axion dark matter (dm); direct and indirect detection of axions, reviewing existing and future experiments; axions as dark radiation; axions and the cosmological constant problem; decays of heavy axions; axions and stellar astrophysics; black hole superradiance; axions and astrophysical magnetic fields; axion inflation, and axion dm as an indirect probe of inflation. a major focus is on the population of ultralight axions created via vacuum realignment, and its role as a dm candidate with distinctive phenomenology. cosmological observations place robust constraints on the axion mass and relic density in this scenario, and i review where such constraints come from. i next cover aspects of galaxy formation with axion dm, and ways this can be used to further search for evidence of axions. an absolute lower bound on dm particle mass is established. it is ma > 10-24ev from linear observables, extending to ma ≳ 10-22ev from non-linear observables, and has the potential to reach ma ≳ 10-18ev in the future. these bounds are weaker if the axion is not all of the dm, giving rise to limits on the relic density at low mass. this leads to the exciting possibility that the effects of axion dm on structure formation could one day be detected, and the axion mass and relic density measured from cosmological observables.

axion cosmology

we present the first event horizon telescope (eht) observations of sagittarius a* (sgr a*), the galactic center source associated with a supermassive black hole. these observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of λ = 1.3 mm. the eht data resolve a compact emission region with intrahour variability. a variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of 51.8 ± 2.3 μas (68% credible interval). the ring has modest azimuthal brightness asymmetry and a comparatively dim interior. using a large suite of numerical simulations, we demonstrate that the eht images of sgr a* are consistent with the expected appearance of a kerr black hole with mass ~4 × 106 m ⊙, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. our model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50°), as well as nonspinning black holes and those with retrograde accretion disks. our results provide direct evidence for the presence of a supermassive black hole at the center of the milky way, and for the first time we connect the predictions from dynamical measurements of stellar orbits on scales of 103-105 gravitational radii to event-horizon-scale images and variability. furthermore, a comparison with the eht results for the supermassive black hole m87* shows consistency with the predictions of general relativity spanning over three orders of magnitude in central mass.

first sagittarius a* event horizon telescope results. i. the shadow of the supermassive black hole in the center of the milky way

on august 17, 2017, the advanced ligo and advanced virgo gravitational-wave detectors observed a low-mass compact binary inspiral. the initial sky localization of the source of the gravitational-wave signal, gw170817, allowed electromagnetic observatories to identify ngc 4993 as the host galaxy. in this work, we improve initial estimates of the binary's properties, including component masses, spins, and tidal parameters, using the known source location, improved modeling, and recalibrated virgo data. we extend the range of gravitational-wave frequencies considered down to 23 hz, compared to 30 hz in the initial analysis. we also compare results inferred using several signal models, which are more accurate and incorporate additional physical effects as compared to the initial analysis. we improve the localization of the gravitational-wave source to a 90% credible region of 16 deg2 . we find tighter constraints on the masses, spins, and tidal parameters, and continue to find no evidence for nonzero component spins. the component masses are inferred to lie between 1.00 and 1.89 m⊙ when allowing for large component spins, and to lie between 1.16 and 1.60 m⊙ (with a total mass 2.73-0.01+0.04 m⊙ ) when the spins are restricted to be within the range observed in galactic binary neutron stars. using a precessing model and allowing for large component spins, we constrain the dimensionless spins of the components to be less than 0.50 for the primary and 0.61 for the secondary. under minimal assumptions about the nature of the compact objects, our constraints for the tidal deformability parameter λ ∼ are (0,630) when we allow for large component spins, and 300-230+420 (using a 90% highest posterior density interval) when restricting the magnitude of the component spins, ruling out several equation-of-state models at the 90% credible level. finally, with ligo and geo600 data, we use a bayesian analysis to place upper limits on the amplitude and spectral energy density of a possible postmerger signal.

properties of the binary neutron star merger gw170817

we present an improved determination of the hubble constant from hubble space telescope (hst) observations of 70 long-period cepheids in the large magellanic cloud (lmc). these were obtained with the same wfc3 photometric system used to measure extragalactic cepheids in the hosts of sne ia. gyroscopic control of hst was employed to reduce overheads while collecting a large sample of widely separated cepheids. the cepheid period-luminosity relation provides a zero-point-independent link with 0.4% precision between the new 1.2% geometric distance to the lmc from detached eclipsing binaries (debs) measured by pietrzyński et al. and the luminosity of sne ia. measurements and analysis of the lmc cepheids were completed prior to knowledge of the new deb lmc distance. combined with a refined calibration of the count-rate linearity of wfc3-ir with 0.1% precision, these three improved elements together reduce the overall uncertainty in the geometric calibration of the cepheid distance ladder based on the lmc from 2.5% to 1.3%. using only the lmc debs to calibrate the ladder, we find h 0 = 74.22 ± 1.82 km s-1 mpc-1 including systematic uncertainties, 3% higher than before for this particular anchor. combining the lmc debs, masers in ngc 4258, and milky way parallaxes yields our best estimate: h 0 = 74.03 ± 1.42 km s-1 mpc-1, including systematics, an uncertainty of 1.91%-15% lower than our best previous result. removing any one of these anchors changes h 0 by less than 0.7%. the difference between h 0 measured locally and the value inferred from planck cmb and λcdm is 6.6 ± 1.5 km s-1 mpc-1 or 4.4σ (p = 99.999% for gaussian errors) in significance, raising the discrepancy beyond a plausible level of chance. we summarize independent tests showing that this discrepancy is not attributable to an error in any one source or measurement, increasing the odds that it results from a cosmological feature beyond λcdm.

large magellanic cloud cepheid standards provide a 1% foundation for the determination of the hubble constant and stronger evidence for physics beyond λcdm

the ever-increasing number of detections of gravitational waves (gws) from compact binaries by the advanced ligo and advanced virgo detectors allows us to perform ever-more sensitive tests of general relativity (gr) in the dynamical and strong-field regime of gravity. we perform a suite of tests of gr using the compact binary signals observed during the second half of the third observing run of those detectors. we restrict our analysis to the 15 confident signals that have false alarm rates $\leq 10^{-3}\, {\rm yr}^{-1}$. in addition to signals consistent with binary black hole (bh) mergers, the new events include gw200115_042309, a signal consistent with a neutron star--bh merger. we find the residual power, after subtracting the best fit waveform from the data for each event, to be consistent with the detector noise. additionally, we find all the post-newtonian deformation coefficients to be consistent with the predictions from gr, with an improvement by a factor of ~2 in the -1pn parameter. we also find that the spin-induced quadrupole moments of the binary bh constituents are consistent with those of kerr bhs in gr. we find no evidence for dispersion of gws, non-gr modes of polarization, or post-merger echoes in the events that were analyzed. we update the bound on the mass of the graviton, at 90% credibility, to $m_g \leq 1.27 \times 10^{-23} \mathrm{ev}/c^2$. the final mass and final spin as inferred from the pre-merger and post-merger parts of the waveform are consistent with each other. the studies of the properties of the remnant bhs, including deviations of the quasi-normal mode frequencies and damping times, show consistency with the predictions of gr. in addition to considering signals individually, we also combine results from the catalog of gw signals to calculate more precise population constraints. we find no evidence in support of physics beyond gr.

tests of general relativity with gwtc-3

we report the observation of a compact binary coalescence involving a 22.2-24.3 m⊙ black hole and a compact object with a mass of 2.50-2.67 m⊙ (all measurements quoted at the 90% credible level). the gravitational-wave signal, gw190814, was observed during ligo's and virgo's third observing run on 2019 august 14 at 21:10:39 utc and has a signal-to-noise ratio of 25 in the three-detector network. the source was localized to 18.5 deg2 at a distance of ${241}_{-45}^{+41}$ mpc; no electromagnetic counterpart has been confirmed to date. the source has the most unequal mass ratio yet measured with gravitational waves, ${0.112}_{-0.009}^{+0.008}$ , and its secondary component is either the lightest black hole or the heaviest neutron star ever discovered in a double compact-object system. the dimensionless spin of the primary black hole is tightly constrained to ≤0.07. tests of general relativity reveal no measurable deviations from the theory, and its prediction of higher-multipole emission is confirmed at high confidence. we estimate a merger rate density of 1-23 gpc-3 yr-1 for the new class of binary coalescence sources that gw190814 represents. astrophysical models predict that binaries with mass ratios similar to this event can form through several channels, but are unlikely to have formed in globular clusters. however, the combination of mass ratio, component masses, and the inferred merger rate for this event challenges all current models of the formation and mass distribution of compact-object binaries.

gw190814: gravitational waves from the coalescence of a 23 solar mass black hole with a 2.6 solar mass compact object

stellar distances constitute a foundational pillar of astrophysics. the publication of 1.47 billion stellar parallaxes from gaia is a major contribution to this. despite gaia's precision, the majority of these stars are so distant or faint that their fractional parallax uncertainties are large, thereby precluding a simple inversion of parallax to provide a distance. here we take a probabilistic approach to estimating stellar distances that uses a prior constructed from a three-dimensional model of our galaxy. this model includes interstellar extinction and gaia's variable magnitude limit. we infer two types of distance. the first, geometric, uses the parallax with a direction-dependent prior on distance. the second, photogeometric, additionally uses the color and apparent magnitude of a star, by exploiting the fact that stars of a given color have a restricted range of probable absolute magnitudes (plus extinction). tests on simulated data and external validations show that the photogeometric estimates generally have higher accuracy and precision for stars with poor parallaxes. we provide a catalog of 1.47 billion geometric and 1.35 billion photogeometric distances together with asymmetric uncertainty measures. our estimates are quantiles of a posterior probability distribution, so they transform invariably and can therefore also be used directly in the distance modulus ( $5{\mathrm{log}}_{10}r\,-\,5$ ). the catalog may be downloaded or queried using adql at various sites (see http://www.mpia.de/~calj/gedr3_distances.html), where it can also be cross-matched with the gaia catalog.

estimating distances from parallaxes. v. geometric and photogeometric distances to 1.47 billion stars in gaia early data release 3

we describe the observation of gw170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. the signal was measured on january 4, 2017 at 10∶11:58.6 utc by the twin advanced detectors of the laser interferometer gravitational-wave observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years. the inferred component black hole masses are 31. 2-6.0+8.4m⊙ and 19. 4-5.9+5.3 m⊙ (at the 90% credible level). the black hole spins are best constrained through measurement of the effective inspiral spin parameter, a mass-weighted combination of the spin components perpendicular to the orbital plane, χeff=-0.1 2-0.30+0.21 . this result implies that spin configurations with both component spins positively aligned with the orbital angular momentum are disfavored. the source luminosity distance is 88 0-390+450 mpc corresponding to a redshift of z =0.1 8-0.07+0.08 . we constrain the magnitude of modifications to the gravitational-wave dispersion relation and perform null tests of general relativity. assuming that gravitons are dispersed in vacuum like massive particles, we bound the graviton mass to mg≤7.7 ×10-23 ev /c2 . in all cases, we find that gw170104 is consistent with general relativity.

gw170104: observation of a 50-solar-mass binary black hole coalescence at redshift 0.2

on 17 august 2017, the ligo and virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. the detection of this gravitational-wave signal, gw170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. the initial, minimal-assumption analysis of the ligo and virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation of state and have spins within the range observed in galactic binary neutron stars. our analysis employs two methods: the use of equation-of-state-insensitive relations between various macroscopic properties of the neutron stars and the use of an efficient parametrization of the defining function p (ρ ) of the equation of state itself. from the ligo and virgo data alone and the first method, we measure the two neutron star radii as r1=10.8-1.7+2.0 km for the heavier star and r2=10.7-1.5+2.1 km for the lighter star at the 90% credible level. if we additionally require that the equation of state supports neutron stars with masses larger than 1.97 m⊙ as required from electromagnetic observations and employ the equation-of-state parametrization, we further constrain r1=11.9-1.4+1.4 km and r2=11.9-1.4+1.4 km at the 90% credible level. finally, we obtain constraints on p (ρ ) at supranuclear densities, with pressure at twice nuclear saturation density measured at 3.5-1.7+2.7×1034 dyn cm-2 at the 90% level.

gw170817: measurements of neutron star radii and equation of state

on 2019 april 25, the ligo livingston detector observed a compact binary coalescence with signal-to-noise ratio 12.9. the virgo detector was also taking data that did not contribute to detection due to a low signal-to-noise ratio, but were used for subsequent parameter estimation. the 90% credible intervals for the component masses range from 1.12 to 2.52 m⊙ (1.46-1.87 m⊙ if we restrict the dimensionless component spin magnitudes to be smaller than 0.05). these mass parameters are consistent with the individual binary components being neutron stars. however, both the source-frame chirp mass 1.44-0.02+0.02 m⊙ and the total mass 3.4-0.1+0.3 m⊙ of this system are significantly larger than those of any other known binary neutron star (bns) system. the possibility that one or both binary components of the system are black holes cannot be ruled out from gravitational-wave data. we discuss possible origins of the system based on its inconsistency with the known galactic bns population. under the assumption that the signal was produced by a bns coalescence, the local rate of neutron star mergers is updated to 250-2810 gpc-3yr-1.

gw190425: observation of a compact binary coalescence with total mass ∼ 3.4 m⊙

we present 12 new agn at 4<z<7 in the jades survey (in addition to the previously identified agn in gn-z11 at z=10.6) revealed through the detection of a broad line region as seen in halpha. the depth of jades, together with the use of three different spectral resolutions, enables us to probe a lower mass regime relative to previous studies. in a few cases we find evidence for two broad components of halpha which suggests that these could be candidate merging black holes (bhs). the inferred bh masses range between 8 x 10^7 msun down to 4 x 10^5 msun, interestingly probing the regime expected for direct collapse black holes (dcbhs). the inferred agn bolometric luminosities (~10^44-10^45 erg/s) imply accretion rates that are < 0.5 times the eddington rate in most cases. however, small bhs, with m_bh ~ 10^6 msun, tend to accrete at eddington or super-eddington rates. these bh at z~4-11 are over-massive relative to their host galaxies stellar masses when compared to the local m_bh-mstar relation, and even approaching m_bh~mstar, as expected for dcbhs and super-eddington scenarios. however, we find that these early bhs tend to be more consistent with the local relation between m_bh and velocity dispersion, as well as between m_bh and dynamical mass, suggesting that these are more fundamental and universal relations. on the bpt excitation-diagnostic diagram these agn are located in the region that is that is locally occupied by star-forming galaxies, implying that they would be missed by the standard classification techniques if they did not display broad lines. their location on the diagram is consistent with what expected for agn hosted in metal poor galaxies (z ~ 0.1-0.2 zsun). the fraction of broad line agn with l_agn > 10^44 erg/s, among galaxies in the redshift range 4<z<6, is about 10%, suggesting that the contribution of agn and their hosts to the reionization of the universe is > 10%.

jades. the diverse population of infant black holes at 4<z<11: merging, tiny, poor, but mighty

we introduce the virgo consortium's evolution and assembly of galaxies and their environments (eagle) project, a suite of hydrodynamical simulations that follow the formation of galaxies and supermassive black holes in cosmologically representative volumes of a standard λ cold dark matter universe. we discuss the limitations of such simulations in light of their finite resolution and poorly constrained subgrid physics, and how these affect their predictive power. one major improvement is our treatment of feedback from massive stars and active galactic nuclei (agn) in which thermal energy is injected into the gas without the need to turn off cooling or decouple hydrodynamical forces, allowing winds to develop without predetermined speed or mass loading factors. because the feedback efficiencies cannot be predicted from first principles, we calibrate them to the present-day galaxy stellar mass function and the amplitude of the galaxy-central black hole mass relation, also taking galaxy sizes into account. the observed galaxy stellar mass function is reproduced to ≲ 0.2 dex over the full resolved mass range, 108 < m*/m⊙ ≲ 1011, a level of agreement close to that attained by semi-analytic models, and unprecedented for hydrodynamical simulations. we compare our results to a representative set of low-redshift observables not considered in the calibration, and find good agreement with the observed galaxy specific star formation rates, passive fractions, tully-fisher relation, total stellar luminosities of galaxy clusters, and column density distributions of intergalactic c iv and o vi. while the mass-metallicity relations for gas and stars are consistent with observations for m* ≳ 109 m⊙ (m* ≳ 1010 m⊙ at intermediate resolution), they are insufficiently steep at lower masses. for the reference model, the gas fractions and temperatures are too high for clusters of galaxies, but for galaxy groups these discrepancies can be resolved by adopting a higher heating temperature in the subgrid prescription for agn feedback. the eagle simulation suite, which also includes physics variations and higher resolution zoomed-in volumes described elsewhere, constitutes a valuable new resource for studies of galaxy formation.

the eagle project: simulating the evolution and assembly of galaxies and their environments

the transiting exoplanet survey satellite (tess) will search for planets transiting bright and nearby stars. tess has been selected by nasa for launch in 2017 as an astrophysics explorer mission. the spacecraft will be placed into a highly elliptical 13.7-day orbit around the earth. during its 2-year mission, tess will employ four wide-field optical charge-coupled device cameras to monitor at least 200,000 main-sequence dwarf stars with ic≈4-13 for temporary drops in brightness caused by planetary transits. each star will be observed for an interval ranging from 1 month to 1 year, depending mainly on the star's ecliptic latitude. the longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the james webb space telescope. brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. tess stars will be 10 to 100 times brighter than those surveyed by the pioneering kepler mission. this will make tess planets easier to characterize with follow-up observations. tess is expected to find more than a thousand planets smaller than neptune, including dozens that are comparable in size to the earth. public data releases will occur every 4 months, inviting immediate community-wide efforts to study the new planets. the tess legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.

transiting exoplanet survey satellite (tess)

despite its importance to our understanding of physics at supranuclear densities, the equation of state (eos) of matter deep within neutron stars remains poorly understood. millisecond pulsars (msps) are among the most useful astrophysical objects in the universe for testing fundamental physics, and place some of the most stringent constraints on this high-density eos. pulsar timing—the process of accounting for every rotation of a pulsar over long time periods—can precisely measure a wide variety of physical phenomena, including those that allow the measurement of the masses of the components of a pulsar binary system1. one of these, called relativistic shapiro delay2, can yield precise masses for both an msp and its companion; however, it is only easily observed in a small subset of high-precision, highly inclined (nearly edge-on) binary pulsar systems. by combining data from the north american nanohertz observatory for gravitational waves (nanograv) 12.5-yr data set with recent orbital-phase-specific observations using the green bank telescope, we have measured the mass of the msp j0740+6620 to be 2 .14-0.09 +0 .10 ? m⊙ (68.3% credibility interval; the 95.4% credibility interval is 2 .14-0.18 +0 .20 ? m⊙). it is highly likely to be the most massive neutron star yet observed, and serves as a strong constraint on the neutron star interior eos.

relativistic shapiro delay measurements of an extremely massive millisecond pulsar

for the vast majority of stars in the second gaia data release, reliable distances cannot be obtained by inverting the parallax. a correct inference procedure must instead be used to account for the nonlinearity of the transformation and the asymmetry of the resulting probability distribution. here, we infer distances to essentially all 1.33 billion stars with parallaxes published in the second gaia data release. this is done using a weak distance prior that varies smoothly as a function of galactic longitude and latitude according to a galaxy model. the irreducible uncertainty in the distance estimate is characterized by the lower and upper bounds of an asymmetric confidence interval. although more precise distances can be estimated for a subset of the stars using additional data (such as photometry), our goal is to provide purely geometric distance estimates, independent of assumptions about the physical properties of, or interstellar extinction toward, individual stars. we analyze the characteristics of the catalog and validate it using clusters. the catalog can be queried using adql at http://gaia.ari.uni-heidelberg.de/tap.html (which also hosts the gaia catalog) and downloaded from http://www.mpia.de/~calj/gdr2_distances.html.

estimating distance from parallaxes. iv. distances to 1.33 billion stars in gaia data release 2

on august 14, 2017 at 10∶30:43 utc, the advanced virgo detector and the two advanced ligo detectors coherently observed a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes, with a false-alarm rate of ≲1 in 27 000 years. the signal was observed with a three-detector network matched-filter signal-to-noise ratio of 18. the inferred masses of the initial black holes are 30. 5-3.0+5.7m⊙ and 25 .3-4.2+2.8m⊙ (at the 90% credible level). the luminosity distance of the source is 54 0-210+130 mpc , corresponding to a redshift of z =0.1 1-0.04+0.03. a network of three detectors improves the sky localization of the source, reducing the area of the 90% credible region from 1160 deg2 using only the two ligo detectors to 60 deg2 using all three detectors. for the first time, we can test the nature of gravitational-wave polarizations from the antenna response of the ligo-virgo network, thus enabling a new class of phenomenological tests of gravity.

gw170814: a three-detector observation of gravitational waves from a binary black hole coalescence

psr j0740+6620 has a gravitational mass of 2.08 ± 0.07 m⊙, which is the highest reliably determined mass of any neutron star. as a result, a measurement of its radius will provide unique insight into the properties of neutron star core matter at high densities. here we report a radius measurement based on fits of rotating hot spot patterns to neutron star interior composition explorer (nicer) and x-ray multi-mirror (xmm-newton) x-ray observations. we find that the equatorial circumferential radius of psr j0740+6620 is ${13.7}_{-1.5}^{+2.6}$ km (68%). we apply our measurement, combined with the previous nicer mass and radius measurement of psr j0030+0451, the masses of two other ~2 m⊙ pulsars, and the tidal deformability constraints from two gravitational wave events, to three different frameworks for equation-of-state modeling, and find consistent results at ~1.5-5 times nuclear saturation density. for a given framework, when all measurements are included, the radius of a 1.4 m⊙ neutron star is known to ±4% (68% credibility) and the radius of a 2.08 m⊙ neutron star is known to ±5%. the full radius range that spans the ±1σ credible intervals of all the radius estimates in the three frameworks is 12.45 ± 0.65 km for a 1.4 m⊙ neutron star and 12.35 ± 0.75 km for a 2.08 m⊙ neutron star.

the radius of psr j0740+6620 from nicer and xmm-newton data

we report on bayesian estimation of the radius, mass, and hot surface regions of the massive millisecond pulsar psr j0740+6620, conditional on pulse-profile modeling of neutron star interior composition explorer x-ray timing instrument event data. we condition on informative pulsar mass, distance, and orbital inclination priors derived from the joint north american nanohertz observatory for gravitational waves and canadian hydrogen intensity mapping experiment/pulsar wideband radio timing measurements of fonseca et al. we use xmm-newton european photon imaging camera spectroscopic event data to inform our x-ray likelihood function. the prior support of the pulsar radius is truncated at 16 km to ensure coverage of current dense matter models. we assume conservative priors on instrument calibration uncertainty. we constrain the equatorial radius and mass of psr j0740+6620 to be ${12.39}_{-0.98}^{+1.30}$ km and ${2.072}_{-0.066}^{+0.067}$ m⊙ respectively, each reported as the posterior credible interval bounded by the 16% and 84% quantiles, conditional on surface hot regions that are non-overlapping spherical caps of fully ionized hydrogen atmosphere with uniform effective temperature; a posteriori, the temperature is ${\mathrm{log}}_{10}(t\,[{\rm{k}}])={5.99}_{-0.06}^{+0.05}$ for each hot region. all software for the x-ray modeling framework is open-source and all data, model, and sample information is publicly available, including analysis notebooks and model modules in the python language. our marginal likelihood function of mass and equatorial radius is proportional to the marginal joint posterior density of those parameters (within the prior support) and can thus be computed from the posterior samples.

a nicer view of the massive pulsar psr j0740+6620 informed by radio timing and xmm-newton spectroscopy

we review the landscape of qcd axion models. theoretical constructions that extend the window for the axion mass and couplings beyond conventional regions are highlighted and classified. bounds from cosmology, astrophysics and experimental searches are reexamined and updated.

corrigendum to "the landscape of qcd axion models" [phys. rep. 870 (2020) 1-117]

this paper documents the 16th data release (dr16) from the sloan digital sky surveys (sdss), the fourth and penultimate from the fourth phase (sdss-iv). this is the first release of data from the southern hemisphere survey of the apache point observatory galactic evolution experiment 2 (apogee-2); new data from apogee-2 north are also included. dr16 is also notable as the final data release for the main cosmological program of the extended baryon oscillation spectroscopic survey (eboss), and all raw and reduced spectra from that project are released here. dr16 also includes all the data from the time domain spectroscopic survey and new data from the spectroscopic identification of erosita survey programs, both of which were co-observed on eboss plates. dr16 has no new data from the mapping nearby galaxies at apache point observatory (manga) survey (or the manga stellar library "mastar"). we also preview future sdss-v operations (due to start in 2020), and summarize plans for the final sdss-iv data release (dr17).

the 16th data release of the sloan digital sky surveys: first release from the apogee-2 southern survey and full release of eboss spectra

we substantially update the capabilities of the open-source software instrument modules for experiments in stellar astrophysics (mesa). mesa can now simultaneously evolve an interacting pair of differentially rotating stars undergoing transfer and loss of mass and angular momentum, greatly enhancing the prior ability to model binary evolution. new mesa capabilities in fully coupled calculation of nuclear networks with hundreds of isotopes now allow mesa to accurately simulate the advanced burning stages needed to construct supernova progenitor models. implicit hydrodynamics with shocks can now be treated with mesa, enabling modeling of the entire massive star lifecycle, from pre-main-sequence evolution to the onset of core collapse and nucleosynthesis from the resulting explosion. coupling of the gyre non-adiabatic pulsation instrument with mesa allows for new explorations of the instability strips for massive stars while also accelerating the astrophysical use of asteroseismology data. we improve the treatment of mass accretion, giving more accurate and robust near-surface profiles. a new mesa capability to calculate weak reaction rates “on-the-fly” from input nuclear data allows better simulation of accretion induced collapse of massive white dwarfs and the fate of some massive stars. we discuss the ongoing challenge of chemical diffusion in the strongly coupled plasma regime, and exhibit improvements in mesa that now allow for the simulation of radiative levitation of heavy elements in hot stars. we close by noting that the mesa software infrastructure provides bit-for-bit consistency for all results across all the supported platforms, a profound enabling capability for accelerating mesa's development.

modules for experiments in stellar astrophysics (mesa): binaries, pulsations, and explosions

this report describes the 2014 study by the science definition team (sdt) of the wide-field infrared survey telescope (wfirst) mission. it is a space observatory that will address the most compelling scientific problems in dark energy, exoplanets and general astrophysics using a 2.4-m telescope with a wide-field infrared instrument and an optical coronagraph. the astro2010 decadal survey recommended a wide field infrared survey telescope as its top priority for a new large space mission. as conceived by the decadal survey, wfirst would carry out a dark energy science program, a microlensing program to determine the demographics of exoplanets, and a general observing program utilizing its ultra wide field. in october 2012, nasa chartered a science definition team (sdt) to produce, in collaboration with the wfirst study office at gsfc and the program office at jpl, a design reference mission (drm) for an implementation of wfirst using one of the 2.4-m, hubble-quality telescope assemblies recently made available to nasa. this drm builds on the work of the earlier wfirst sdt, reported by green et al. (2012) and the previous wfirst-2.4 drm, reported by spergel et. (2013). the 2.4-m primary mirror enables a mission with greater sensitivity and higher angular resolution than the 1.3-m and 1.1-m designs considered previously, increasing both the science return of the primary surveys and the capabilities of wfirst as a guest observer facility. the addition of an on-axis coronagraphic instrument to the baseline design enables imaging and spectroscopic studies of planets around nearby stars.

wide-field infrarred survey telescope-astrophysics focused telescope assets wfirst-afta 2015 report

context. at about 1000 days after the launch of gaia we present the first gaia data release, gaia dr1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.aims: a summary of gaia dr1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.methods: the raw data collected by gaia during the first 14 months of the mission have been processed by the gaia data processing and analysis consortium (dpac) and turned into an astrometric and photometric catalogue.results: gaia dr1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the hipparcos and tycho-2 catalogues - a realisation of the tycho-gaia astrometric solution (tgas) - and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. the second component is the photometric data set, consisting of mean g-band magnitudes for all sources. the g-band light curves and the characteristics of 3000 cepheid and rr lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. for the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr-1 for the proper motions. a systematic component of 0.3 mas should be added to the parallax uncertainties. for the subset of 94 000 hipparcos stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr-1. for the secondary astrometric data set, the typical uncertainty of the positions is 10 mas. the median uncertainties on the mean g-band magnitudes range from the mmag level to 0.03 mag over the magnitude range 5 to 20.7.conclusions: gaia dr1 is an important milestone ahead of the next gaia data release, which will feature five-parameter astrometry for all sources. extensive validation shows that gaia dr1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. nevertheless, the very preliminary nature of this first gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.

gaia data release 1. summary of the astrometric, photometric, and survey properties

we report on the population of 47 compact binary mergers detected with a false-alarm rate of < $1\,{\mathrm{yr}}^{-1}$ in the second ligo-virgo gravitational-wave transient catalog. we observe several characteristics of the merging binary black hole (bbh) population not discernible until now. first, the primary mass spectrum contains structure beyond a power law with a sharp high-mass cutoff; it is more consistent with a broken power law with a break at ${39.7}_{-9.1}^{+20.3}\,\,{m}_{\odot }$ or a power law with a gaussian feature peaking at ${33.1}_{-5.6}^{+4.0}\,\,{m}_{\odot }$ (90% credible interval). while the primary mass distribution must extend to $\sim 65\,{m}_{\odot }$ or beyond, only ${2.9}_{-1.7}^{+3.5} \% $ of systems have primary masses greater than $45\,{m}_{\odot }$ . second, we find that a fraction of bbh systems have component spins misaligned with the orbital angular momentum, giving rise to precession of the orbital plane. moreover, $12$ %- $44$ % of bbh systems have spins tilted by more than 90°, giving rise to a negative effective inspiral spin parameter, ${\chi }_{\mathrm{eff}}$ . under the assumption that such systems can only be formed by dynamical interactions, we infer that between 25% and 93% of bbhs with nonvanishing $| {\chi }_{\mathrm{eff}}| \gt 0.01$ are dynamically assembled. third, we estimate merger rates, finding ${{ \mathcal r }}_{\mathrm{bbh}}={23.9}_{-8.6}^{+14.3}\,\,{\mathrm{gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ for bbhs and ${{ \mathcal r }}_{\mathrm{bns}}={320}_{-240}^{+490}\,\,{\mathrm{gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ for binary neutron stars. we find that the bbh rate likely increases with redshift ( $85 \% $ credibility) but not faster than the star formation rate ( $86 \% $ credibility). additionally, we examine recent exceptional events in the context of our population models, finding that the asymmetric masses of gw190412 and the high component masses of gw190521 are consistent with our models, but the low secondary mass of gw190814 makes it an outlier.

population properties of compact objects from the second ligo-virgo gravitational-wave transient catalog

we report a precision measurement of the parity-violating asymmetry apv in the elastic scattering of longitudinally polarized electrons from 208pb. we measure apv=550 ±16 (stat) ±8 (syst) parts per billion, leading to an extraction of the neutral weak form factor fw(q2=0.00616 gev2)=0.368 ±0.013 . combined with our previous measurement, the extracted neutron skin thickness is rn-rp=0.283 ±0.071 fm . the result also yields the first significant direct measurement of the interior weak density of 208pb : ρw0=-0.0796 ±0.0036 (exp)±0.0013 (theo) fm-3 leading to the interior baryon density ρb0=0.1480 ±0.0036 (exp)±0.0013 (theo) fm-3 . the measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.

accurate determination of the neutron skin thickness of 208pb through parity-violation in electron scattering

neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists because their attributes can be used to determine the properties of the dense matter in their cores. one of the most informative approaches for determining the equation of state (eos) of this dense matter is to measure both a star’s equatorial circumferential radius reand its gravitational mass m. here we report estimates of the mass and radius of the isolated 205.53 hz millisecond pulsar psr j0030+0451 obtained using a bayesian inference approach to analyze its energy-dependent thermal x-ray waveform, which was observed using the neutron star interior composition explorer (nicer). this approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. we explored a variety of emission patterns on the stellar surface. our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using nicer. the radius and mass estimates given by this model are {r}e={13.02}-1.06+1.24 km and m={1.44}-0.14+0.15 {m}⊙(68%). the independent analysis reported in the companion paper by riley et al. explores different emitting spot models, but finds spot shapes and locations and estimates of reand m that are consistent with those found in this work. we show that our measurements of reand m for psr j0030+0451 improve the astrophysical constraints on the eos of cold, catalyzed matter above nuclear saturation density.

psr j0030+0451 mass and radius from nicer data and implications for the properties of neutron star matter

this is the first of a series of papers presenting the modules for experiments in stellar astrophysics (mesa) isochrones and stellar tracks (mist) project, a new comprehensive set of stellar evolutionary tracks and isochrones computed using mesa, a state-of-the-art open-source 1d stellar evolution package. in this work, we present models with solar-scaled abundance ratios covering a wide range of ages (5≤slant {log}({age}) [{year}]≤slant 10.3), masses (0.1≤slant m/{m}⊙ ≤slant 300), and metallicities (-2.0≤slant [{{z}}/{{h}}]≤slant 0.5). the models are self-consistently and continuously evolved from the pre-main sequence (pms) to the end of hydrogen burning, the white dwarf cooling sequence, or the end of carbon burning, depending on the initial mass. we also provide a grid of models evolved from the pms to the end of core helium burning for -4.0≤slant [{{z}}/{{h}}]\lt -2.0. we showcase extensive comparisons with observational constraints as well as with some of the most widely used existing models in the literature. the evolutionary tracks and isochrones can be downloaded from the project website at http://waps.cfa.harvard.edu/mist/.

mesa isochrones and stellar tracks (mist). i. solar-scaled models

the third generation of the sloan digital sky survey (sdss-iii) took data from 2008 to 2014 using the original sdss wide-field imager, the original and an upgraded multi-object fiber-fed optical spectrograph, a new near-infrared high-resolution spectrograph, and a novel optical interferometer. all of the data from sdss-iii are now made public. in particular, this paper describes data release 11 (dr11) including all data acquired through 2013 july, and data release 12 (dr12) adding data acquired through 2014 july (including all data included in previous data releases), marking the end of sdss-iii observing. relative to our previous public release (dr10), dr12 adds one million new spectra of galaxies and quasars from the baryon oscillation spectroscopic survey (boss) over an additional 3000 deg2 of sky, more than triples the number of h-band spectra of stars as part of the apache point observatory (apo) galactic evolution experiment (apogee), and includes repeated accurate radial velocity measurements of 5500 stars from the multi-object apo radial velocity exoplanet large-area survey (marvels). the apogee outputs now include the measured abundances of 15 different elements for each star. in total, sdss-iii added 5200 deg2 of ugriz imaging; 155,520 spectra of 138,099 stars as part of the sloan exploration of galactic understanding and evolution 2 (segue-2) survey; 2,497,484 boss spectra of 1,372,737 galaxies, 294,512 quasars, and 247,216 stars over 9376 deg2; 618,080 apogee spectra of 156,593 stars; and 197,040 marvels spectra of 5513 stars. since its first light in 1998, sdss has imaged over 1/3 of the celestial sphere in five bands and obtained over five million astronomical spectra.

the eleventh and twelfth data releases of the sloan digital sky survey: final data from sdss-iii

this paper documents the seventeenth data release (dr17) from the sloan digital sky surveys; the fifth and final release from the fourth phase (sdss-iv). dr17 contains the complete release of the mapping nearby galaxies at apache point observatory (manga) survey, which reached its goal of surveying over 10,000 nearby galaxies. the complete release of the manga stellar library accompanies this data, providing observations of almost 30,000 stars through the manga instrument during bright time. dr17 also contains the complete release of the apache point observatory galactic evolution experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. the main sample from the extended baryon oscillation spectroscopic survey (eboss), as well as the subsurvey time domain spectroscopic survey data were fully released in dr16. new single-fiber optical spectroscopy released in dr17 is from the spectroscipic identification of erosita survey subsurvey and the eboss-rm program. along with the primary data sets, dr17 includes 25 new or updated value-added catalogs. this paper concludes the release of sdss-iv survey data. sdss continues into its fifth phase with observations already underway for the milky way mapper, local volume mapper, and black hole mapper surveys.

the seventeenth data release of the sloan digital sky surveys: complete release of manga, mastar, and apogee-2 data

we report on bayesian parameter estimation of the mass and equatorial radius of the millisecond pulsar psr j0030+0451, conditional on pulse-profile modeling of neutron star interior composition explorer x-ray spectral-timing event data. we perform relativistic ray-tracing of thermal emission from hot regions of the pulsar’s surface. we assume two distinct hot regions based on two clear pulsed components in the phase-folded pulse-profile data; we explore a number of forms (morphologies and topologies) for each hot region, inferring their parameters in addition to the stellar mass and radius. for the family of models considered, the evidence (prior predictive probability of the data) strongly favors a model that permits both hot regions to be located in the same rotational hemisphere. models wherein both hot regions are assumed to be simply connected circular single-temperature spots, in particular those where the spots are assumed to be reflection-symmetric with respect to the stellar origin, are strongly disfavored. for the inferred configuration, one hot region subtends an angular extent of only a few degrees (in spherical coordinates with origin at the stellar center) and we are insensitive to other structural details; the second hot region is far more azimuthally extended in the form of a narrow arc, thus requiring a larger number of parameters to describe. the inferred mass m and equatorial radius r eq are, respectively, {1.34}-0.16+0.15 {m}⊙and {12.71}-1.19+1.14 {km}, while the compactness {gm}/{r}eq}{c}2={0.156}-0.010+0.008 is more tightly constrained; the credible interval bounds reported here are approximately the 16% and 84% quantiles in marginal posterior mass.

a nicer view of psr j0030+0451: millisecond pulsar parameter estimation

on the strength of a double nobel prize winning experiment (super)kamiokande and an extremely successful long baseline neutrino programme, the third generation water cherenkov detector, hyper-kamiokande, is being developed by an international collaboration as a leading worldwide experiment based in japan. the hyper-kamiokande detector will be hosted in the tochibora mine, about 295 km away from the j-parc proton accelerator research complex in tokai, japan. the currently existing accelerator will be steadily upgraded to reach a mw beam by the start of the experiment. a suite of near detectors will be vital to constrain the beam for neutrino oscillation measurements. a new cavern will be excavated at the tochibora mine to host the detector. the experiment will be the largest underground water cherenkov detector in the world and will be instrumented with new technology photosensors, faster and with higher quantum efficiency than the ones in super-kamiokande. the science that will be developed will be able to shape the future theoretical framework and generations of experiments. hyper-kamiokande will be able to measure with the highest precision the leptonic cp violation that could explain the baryon asymmetry in the universe. the experiment also has a demonstrated excellent capability to search for proton decay, providing a significant improvement in discovery sensitivity over current searches for the proton lifetime. the atmospheric neutrinos will allow to determine the neutrino mass ordering and, together with the beam, able to precisely test the three-flavour neutrino oscillation paradigm and search for new phenomena. a strong astrophysical programme will be carried out at the experiment that will detect supernova neutrinos and will measure precisely solar neutrino oscillation.

hyper-kamiokande design report

the jiangmen underground neutrino observatory (juno), a 20 kton multi-purpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy (mh) as a primary physics goal. the excellent energy resolution and the large fiducial volume anticipated for the juno detector offer exciting opportunities for addressing many important topics in neutrino and astro-particle physics. in this document, we present the physics motivations and the anticipated performance of the juno detector for various proposed measurements. following an introduction summarizing the current status and open issues in neutrino physics, we discuss how the detection of antineutrinos generated by a cluster of nuclear power plants allows the determination of the neutrino mh at a 3-4σ significance with six years of running of juno. the measurement of antineutrino spectrum with excellent energy resolution will also lead to the precise determination of the neutrino oscillation parameters {{sin}}2{θ }12, {{δ }}{m}212, and | {{δ }}{m}{ee}2| to an accuracy of better than 1%, which will play a crucial role in the future unitarity test of the mnsp matrix. the juno detector is capable of observing not only antineutrinos from the power plants, but also neutrinos/antineutrinos from terrestrial and extra-terrestrial sources, including supernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos, atmospheric neutrinos, and solar neutrinos. as a result of juno's large size, excellent energy resolution, and vertex reconstruction capability, interesting new data on these topics can be collected. for example, a neutrino burst from a typical core-collapse supernova at a distance of 10 kpc would lead to ∼5000 inverse-beta-decay events and ∼2000 all-flavor neutrino-proton es events in juno, which are of crucial importance for understanding the mechanism of supernova explosion and for exploring novel phenomena such as collective neutrino oscillations. detection of neutrinos from all past core-collapse supernova explosions in the visible universe with juno would further provide valuable information on the cosmic star-formation rate and the average core-collapse neutrino energy spectrum. antineutrinos originating from the radioactive decay of uranium and thorium in the earth can be detected in juno with a rate of ∼400 events per year, significantly improving the statistics of existing geoneutrino event samples. atmospheric neutrino events collected in juno can provide independent inputs for determining the mh and the octant of the {θ }23 mixing angle. detection of the 7be and 8b solar neutrino events at juno would shed new light on the solar metallicity problem and examine the transition region between the vacuum and matter dominated neutrino oscillations. regarding light sterile neutrino topics, sterile neutrinos with {10}-5 {{{ev}}}2\lt {{δ }}{m}412\lt {10}-2 {{{ev}}}2 and a sufficiently large mixing angle {θ }14 could be identified through a precise measurement of the reactor antineutrino energy spectrum. meanwhile, juno can also provide us excellent opportunities to test the ev-scale sterile neutrino hypothesis, using either the radioactive neutrino sources or a cyclotron-produced neutrino beam. the juno detector is also sensitive to several other beyondthe-standard-model physics. examples include the search for proton decay via the p\to {k}++\bar{ν } decay channel, search for neutrinos resulting from dark-matter annihilation in the sun, search for violation of lorentz invariance via the sidereal modulation of the reactor neutrino event rate, and search for the effects of non-standard interactions. the proposed construction of the juno detector will provide a unique facility to address many outstanding crucial questions in particle and astrophysics in a timely and cost-effective fashion. it holds the great potential for further advancing our quest to understanding the fundamental properties of neutrinos, one of the building blocks of our universe.

neutrino physics with juno

we update the capabilities of the software instrument modules for experiments in stellar astrophysics (mesa) and enhance its ease of use and availability. our new approach to locating convective boundaries is consistent with the physics of convection, and yields reliable values of the convective-core mass during both hydrogen- and helium-burning phases. stars with m< 8 m⊙ become white dwarfs and cool to the point where the electrons are degenerate and the ions are strongly coupled, a realm now available to study with mesa due to improved treatments of element diffusion, latent heat release, and blending of equations of state. studies of the final fates of massive stars are extended in mesa by our addition of an approximate riemann solver that captures shocks and conserves energy to high accuracy during dynamic epochs. we also introduce a 1d capability for modeling the effects of rayleigh-taylor instabilities that, in combination with the coupling to a public version of the stella radiation transfer instrument, creates new avenues for exploring type ii supernova properties. these capabilities are exhibited with exploratory models of pair-instability supernovae, pulsational pair-instability supernovae, and the formation of stellar-mass black holes. the applicability of mesa is now widened by the capability to import multidimensional hydrodynamic models into mesa. we close by introducing software modules for handling floating point exceptions and stellar model optimization, as well as four new software tools - mesa-web, mesa-docker, pymesa, and mesastar.org - to enhance mesa's education and research impact.

modules for experiments in stellar astrophysics (mesa): convective boundaries, element diffusion, and massive star explosions

we introduce an updated physical model to simulate the formation and evolution of galaxies in cosmological, large-scale gravity+magnetohydrodynamical simulations with the moving mesh code arepo. the overall framework builds upon the successes of the illustris galaxy formation model, and includes prescriptions for star formation, stellar evolution, chemical enrichment, primordial and metal-line cooling of the gas, stellar feedback with galactic outflows, and black hole formation, growth and multimode feedback. in this paper, we give a comprehensive description of the physical and numerical advances that form the core of the illustristng (the next generation) framework. we focus on the revised implementation of the galactic winds, of which we modify the directionality, velocity, thermal content and energy scalings, and explore its effects on the galaxy population. as described in earlier works, the model also includes a new black-hole-driven kinetic feedback at low accretion rates, magnetohydrodynamics and improvements to the numerical scheme. using a suite of (25 mpc h-1)3 cosmological boxes, we assess the outcome of the new model at our fiducial resolution. the presence of a self-consistently amplified magnetic field is shown to have an important impact on the stellar content of 1012 m⊙ haloes and above. finally, we demonstrate that the new galactic winds promise to solve key problems identified in illustris in matching observational constraints and affecting the stellar content and sizes of the low-mass end of the galaxy population.

simulating galaxy formation with the illustristng model

characterising the prevalence and properties of faint active galactic nuclei (agn) in the early universe is key for understanding the formation of supermassive black holes (smbhs) and determining their role in cosmic reionization. we perform a spectroscopic search for broad h$\alpha$ emitters at $z\approx4-6$ using deep jwst/nircam imaging and wide field slitless spectroscopy from the eiger and fresco surveys. we identify 20 h$\alpha$ lines at $z=4.2-5.5$ that have broad components with line widths from $\sim1200-3700$ km s$^{-1}$, contributing $\sim30-90$ % of the total line flux. we interpret these broad components as being powered by accretion onto smbhs with implied masses $\sim10^{7-8}$ m$_{\odot}$. in the uv luminosity range m$_{\rm uv}=-21$ to $-18$, we measure number densities of $\approx10^{-5}$ cmpc$^{-3}$. this is an order of magnitude higher than expected from extrapolating quasar uv luminosity functions. yet, such agn are found in only $<1$ % of star-forming galaxies at $z\sim5$. the smbh mass function agrees with large cosmological simulations. in two objects we detect narrow red- and blue-shifted h$\alpha$ absorption indicative, respectively, of dense gas fueling smbh growth and outflows. we may be witnessing early agn feedback that will clear dust-free pathways through which more massive blue quasars are seen. we uncover a strong correlation between reddening and the fraction of total galaxy luminosity arising from faint agn. this implies that early smbh growth is highly obscured and that faint agn are only minor contributors to cosmic reionization.

little red dots: an abundant population of faint agn at z~5 revealed by the eiger and fresco jwst surveys

we present possible observing scenarios for the advanced ligo, advanced virgo and kagra gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. we estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. we report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. the ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90 % credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. determining the sky position of a significant fraction of detected signals to areas of 5-20 deg2 requires at least three detectors of sensitivity within a factor of ∼2 of each other and with a broad frequency bandwidth. when all detectors, including kagra and the third ligo detector in india, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

prospects for observing and localizing gravitational-wave transients with advanced ligo, advanced virgo and kagra

we update the capabilities of the open-knowledge software instrument modules for experiments in stellar astrophysics (mesa). rsp is a new functionality in mesastar that models the nonlinear radial stellar pulsations that characterize rr lyrae, cepheids, and other classes of variable stars. we significantly enhance numerical energy conservation capabilities, including during mass changes. for example, this enables calculations through the he flash that conserve energy to better than 0.001%. to improve the modeling of rotating stars in mesa, we introduce a new approach to modifying the pressure and temperature equations of stellar structure, as well as a formulation of the projection effects of gravity darkening. a new scheme for tracking convective boundaries yields reliable values of the convective core mass and allows the natural emergence of adiabatic semiconvection regions during both core hydrogen- and helium-burning phases. we quantify the parallel performance of mesa on current-generation multicore architectures and demonstrate improvements in the computational efficiency of radiative levitation. we report updates to the equation of state and nuclear reaction physics modules. we briefly discuss the current treatment of fallback in core-collapse supernova models and the thermodynamic evolution of supernova explosions. we close by discussing the new mesa testhub software infrastructure to enhance source code development.

modules for experiments in stellar astrophysics (mesa): pulsating variable stars, rotation, convective boundaries, and energy conservation

we report the observation of gravitational waves from two compact binary coalescences in ligo's and virgo's third observing run with properties consistent with neutron star-black hole (nsbh) binaries. the two events are named gw200105_162426 and gw200115_042309, abbreviated as gw200105 and gw200115; the first was observed by ligo livingston and virgo and the second by all three ligo-virgo detectors. the source of gw200105 has component masses $8.{9}_{-1.5}^{+1.2}$ and $1.{9}_{-0.2}^{+0.3}\,{m}_{\odot }$ , whereas the source of gw200115 has component masses $5.{7}_{-2.1}^{+1.8}$ and $1.{5}_{-0.3}^{+0.7}\,{m}_{\odot }$ (all measurements quoted at the 90% credible level). the probability that the secondary's mass is below the maximal mass of a neutron star is 89%-96% and 87%-98%, respectively, for gw200105 and gw200115, with the ranges arising from different astrophysical assumptions. the source luminosity distances are ${280}_{-110}^{+110}$ and ${300}_{-100}^{+150}\,\mathrm{mpc}$ , respectively. the magnitude of the primary spin of gw200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. for gw200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. we are unable to constrain the spin or tidal deformation of the secondary component for either event. we infer an nsbh merger rate density of ${45}_{-33}^{+75}\,{\mathrm{gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ when assuming that gw200105 and gw200115 are representative of the nsbh population or ${130}_{-69}^{+112}\,{\mathrm{gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ under the assumption of a broader distribution of component masses.

observation of gravitational waves from two neutron star-black hole coalescences

context. gaia early data release 3 (gaia edr3) gives trigonometric parallaxes for nearly 1.5 billion sources. inspection of the edr3 data for sources identified as quasars reveals that their parallaxes are biased, that is, they are systematically offset from the expected distribution around zero, by a few tens of microarcseconds.aims: we attempt to map the main dependences of the parallax bias in edr3. in principle, this could provide a recipe for correcting the edr3 parallaxes.methods: quasars provide the most direct way for estimating the parallax bias for faint sources. in order to extend this to brighter sources and a broader range of colours, we used differential methods based on physical pairs (binaries) and sources in the large magellanic cloud. the functional forms of the dependences were explored by mapping the systematic differences between edr3 and dr2 parallaxes.results: the parallax bias is found to depend in a non-trivial way on (at least) the magnitude, colour, and ecliptic latitude of the source. different dependences apply to the five- and six-parameter solutions in edr3. while it is not possible to derive a definitive recipe for the parallax correction, we give tentative expressions to be used at the researcher's discretion and point out some possible paths towards future improvements.

gaia early data release 3. parallax bias versus magnitude, colour, and position

hypothetical low-mass particles, such as axions, provide a compelling explanation for the dark matter in the universe. such particles are expected to emerge abundantly from the hot interior of stars. to test this prediction, the cern axion solar telescope (cast) uses a 9 t refurbished large hadron collider test magnet directed towards the sun. in the strong magnetic field, solar axions can be converted to x-ray photons which can be recorded by x-ray detectors. in the 2013-2015 run, thanks to low-background detectors and a new x-ray telescope, the signal-to-noise ratio was increased by about a factor of three. here, we report the best limit on the axion-photon coupling strength (0.66 × 10-10 gev-1 at 95% confidence level) set by cast, which now reaches similar levels to the most restrictive astrophysical bounds.

new cast limit on the axion-photon interaction

we report results from continued timing observations of psr j0740+6620, a high-mass, 2.8 ms radio pulsar in orbit with a likely ultracool white dwarf companion. our data set consists of combined pulse arrival-time measurements made with the 100 m green bank telescope and the canadian hydrogen intensity mapping experiment telescope. we explore the significance of timing-based phenomena arising from general relativistic dynamics and variations in pulse dispersion. when using various statistical methods, we find that combining ~1.5 yr of additional, high-cadence timing data with previous measurements confirms and improves on previous estimates of relativistic effects within the psr j0740+6620 system, with the pulsar mass ${m}_{p}=\,{2.08}_{-0.07}^{+0.07}\ {m}_{\odot }$ (68.3% credibility) determined by the relativistic shapiro time delay. for the first time, we measure secular variation in the orbital period and argue that this effect arises from apparent acceleration due to significant transverse motion. after incorporating contributions from galactic differential rotation and off-plane acceleration in the galactic potential, we obtain a model-dependent distance of $d\,=\,{1.14}_{-0.15}^{+0.17}$ kpc (68.3% credibility). this improved distance confirms the ultracool nature of the white dwarf companion determined from recent optical observations. we discuss the prospects for future observations with next-generation facilities, which will likely improve the precision on mp for j0740+6620 by an order of magnitude within the next few years.

refined mass and geometric measurements of the high-mass psr j0740+6620

the apache point observatory galactic evolution experiment (apogee), one of the programs in the sloan digital sky survey iii (sdss-iii), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the milky way. after a three-year observing campaign on the sloan 2.5 m telescope, apogee has collected a half million high-resolution (r ∼ 22,500), high signal-to-noise ratio (>100), infrared (1.51-1.70 μm) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. this paper describes the motivations for the survey and its overall design—hardware, field placement, target selection, operations—and gives an overview of these aspects as well as the data reduction, analysis, and products. an index is also given to the complement of technical papers that describe various critical survey components in detail. finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. as part of sdss-iii data release 12 and later releases, all of the apogee data products are publicly available.

the apache point observatory galactic evolution experiment (apogee)

hydrodynamical simulations of galaxy formation have now reached sufficient volume to make precision predictions for clustering on cosmologically relevant scales. here, we use our new illustristng simulations to study the non-linear correlation functions and power spectra of baryons, dark matter, galaxies, and haloes over an exceptionally large range of scales. we find that baryonic effects increase the clustering of dark matter on small scales and damp the total matter power spectrum on scales up to k ∼ 10 h mpc-1 by 20 per cent. the non-linear two-point correlation function of the stellar mass is close to a power-law over a wide range of scales and approximately invariant in time from very high redshift to the present. the two-point correlation function of the simulated galaxies agrees well with sloan digital sky survey at its mean redshift z ≃ 0.1, both as a function of stellar mass and when split according to galaxy colour, apart from a mild excess in the clustering of red galaxies in the stellar mass range of109-1010 h-2 m⊙. given this agreement, the tng simulations can make valuable theoretical predictions for the clustering bias of different galaxy samples. we find that the clustering length of the galaxy autocorrelation function depends strongly on stellar mass and redshift. its power-law slope γ is nearly invariant with stellar mass, but declines from γ ∼ 1.8 at redshift z = 0 to γ ∼ 1.6 at redshift z ∼ 1, beyond which the slope steepens again. we detect significant scale dependences in the bias of different observational tracers of large-scale structure, extending well into the range of the baryonic acoustic oscillations and causing nominal (yet fortunately correctable) shifts of the acoustic peaks of around ∼ 5 per cent.

first results from the illustristng simulations: matter and galaxy clustering

the illustristng project is a new suite of cosmological magnetohydrodynamical simulations of galaxy formation performed with the arepo code and updated models for feedback physics. here, we introduce the first two simulations of the series, tng100 and tng300, and quantify the stellar mass content of about 4000 massive galaxy groups and clusters (1013 ≤ m200c/m⊙ ≤ 1015) at recent times (z ≤ 1). the richest clusters have half of their total stellar mass bound to satellite galaxies, with the other half being associated with the central galaxy and the diffuse intracluster light. haloes more massive than about 5 × 1014 m⊙ have more diffuse stellar mass outside 100 kpc than within 100 kpc, with power-law slopes of the radial mass density distribution as shallow as the dark matter's ( - 3.5 ≲ α3d ≲ -3). total halo mass is a very good predictor of stellar mass, and vice versa: at z = 0, the 3d stellar mass measured within 30 kpc scales as ∝(m500c)0.49 with a ∼0.12 dex scatter. this is possibly too steep in comparison to the available observational constraints, even though the abundance of the next generation less-massive galaxies ( ≲ 1011 m⊙ in stars) is in good agreement with the measured galaxy stellar mass functions at recent epochs. the 3d sizes of massive galaxies fall too on a tight (∼0.16 dex scatter) power-law relation with halo mass, with r^stars_0.5 ∝ (m_200c)^{0.53}. even more fundamentally, halo mass alone is a good predictor for the whole stellar mass profiles beyond the inner few kiloparsecs, and we show how on average these can be precisely recovered given a single-mass measurement of the galaxy or its halo.

first results from the illustristng simulations: the stellar mass content of groups and clusters of galaxies

we describe the sloan digital sky survey iv (sdss-iv), a project encompassing three major spectroscopic programs. the apache point observatory galactic evolution experiment 2 (apogee-2) is observing hundreds of thousands of milky way stars at high resolution and high signal-to-noise ratios in the near-infrared. the mapping nearby galaxies at apache point observatory (manga) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median z∼ 0.03). the extended baryon oscillation spectroscopic survey (eboss) is mapping the galaxy, quasar, and neutral gas distributions between z∼ 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. within eboss, we are conducting two major subprograms: the spectroscopic identification of erosita sources (spiders), investigating x-ray agns and galaxies in x-ray clusters, and the time domain spectroscopic survey (tdss), obtaining spectra of variable sources. all programs use the 2.5 m sloan foundation telescope at the apache point observatory; observations there began in summer 2014. apogee-2 also operates a second near-infrared spectrograph at the 2.5 m du pont telescope at las campanas observatory, with observations beginning in early 2017. observations at both facilities are scheduled to continue through 2020. in keeping with previous sdss policy, sdss-iv provides regularly scheduled public data releases; the first one, data release 13, was made available in 2016 july.

sloan digital sky survey iv: mapping the milky way, nearby galaxies, and the distant universe

we present a new three-dimensional map of dust reddening, based on gaia parallaxes and stellar photometry from pan-starrs 1 and 2mass. this map covers the sky north of a decl. of -30°, out to a distance of a few kiloparsecs. this new map contains three major improvements over our previous work. first, the inclusion of gaia parallaxes dramatically improves distance estimates to nearby stars. second, we incorporate a spatial prior that correlates the dust density across nearby sightlines. this produces a smoother map, with more isotropic clouds and smaller distance uncertainties, particularly to clouds within the nearest kiloparsec. third, we infer the dust density with a distance resolution that is four times finer than in our previous work, to accommodate the improvements in signal-to-noise enabled by the other improvements. as part of this work, we infer the distances, reddenings, and types of 799 million stars. (our 3d dust map can be accessed at doi:10.7910/dvn/2ej9tx or through the python package dustmaps, while our catalog of stellar parameters can be accessed at doi:10.7910/dvn/av9gxo. more information about the map, as well as an interactive viewer, can be found at argonaut.skymaps.info.) we obtain typical reddening uncertainties that are ∼30% smaller than those reported in the gaia dr2 catalog, reflecting the greater number of photometric passbands that enter into our analysis.

a 3d dust map based on gaia, pan-starrs 1, and 2mass

many aspects of the large-scale structure of the universe can be described successfully using cosmological models in which 27 ±1 % of the critical mass-energy density consists of cold dark matter (cdm). however, few—if any—of the predictions of cdm models have been successful on scales of ∼10 kpc or less. this lack of success is usually explained by the difficulty of modeling baryonic physics (star formation, supernova and black-hole feedback, etc.). an intriguing alternative to cdm is that the dark matter is an extremely light (m ∼10-22 ev ) boson having a de broglie wavelength λ ∼1 kpc , often called fuzzy dark matter (fdm). we describe the arguments from particle physics that motivate fdm, review previous work on its astrophysical signatures, and analyze several unexplored aspects of its behavior. in particular, (i) fdm halos or subhalos smaller than about 1 07(m /10-22 ev )-3 /2 m⊙ do not form, and the abundance of halos smaller than a few times 1 010(m /10-22 ev )-4 /3 m⊙ is substantially smaller in fdm than in cdm. (ii) fdm halos are comprised of a central core that is a stationary, minimum-energy solution of the schrödinger-poisson equation, sometimes called a "soliton," surrounded by an envelope that resembles a cdm halo. the soliton can produce a distinct signature in the rotation curves of fdm-dominated systems. (iii) the transition between soliton and envelope is determined by a relaxation process analogous to two-body relaxation in gravitating n-body systems, which proceeds as if the halo were composed of particles with mass ∼ρ λ3 where ρ is the halo density. (iv) relaxation may have substantial effects on the stellar disk and bulge in the inner parts of disk galaxies, but has negligible effect on disk thickening or globular cluster disruption near the solar radius. (v) relaxation can produce fdm disks but a fdm disk in the solar neighborhood must have a half-thickness of at least ∼300 (m /10-22 ev )-2/3 pc and a midplane density less than 0.2 (m /10-22 ev )2/3 times the baryonic disk density. (vi) solitonic fdm subhalos evaporate by tunneling through the tidal radius and this limits the minimum subhalo mass inside ∼30 kpc of the milky way to a few times 1 08(m /10-22 ev )-3 /2 m⊙ . (vii) if the dark matter in the fornax dwarf galaxy is composed of cdm, most of the globular clusters observed in that galaxy should have long ago spiraled to its center, and this problem is resolved if the dark matter is fdm. (viii) fdm delays galaxy formation relative to cdm but its galaxy-formation history is consistent with current observations of high-redshift galaxies and the late reionization observed by planck. if the dark matter is composed of fdm, most observations favor a particle mass ≳10-22 ev and the most significant observational consequences occur if the mass is in the range 1 - 10 ×10-22 ev . there is tension with observations of the lyman-α forest, which favor m ≳10 - 20 ×10-22 ev and we discuss whether more sophisticated models of reionization may resolve this tension.

ultralight scalars as cosmological dark matter

in the last few years, graph neural networks (gnns) have become the standard toolkit for analyzing and learning from data on graphs. this emerging field has witnessed an extensive growth of promising techniques that have been applied with success to computer science, mathematics, biology, physics and chemistry. but for any successful field to become mainstream and reliable, benchmarks must be developed to quantify progress. this led us in march 2020 to release a benchmark framework that i) comprises of a diverse collection of mathematical and real-world graphs, ii) enables fair model comparison with the same parameter budget to identify key architectures, iii) has an open-source, easy-to-use and reproducible code infrastructure, and iv) is flexible for researchers to experiment with new theoretical ideas. as of december 2022, the github repository has reached 2,000 stars and 380 forks, which demonstrates the utility of the proposed open-source framework through the wide usage by the gnn community. in this paper, we present an updated version of our benchmark with a concise presentation of the aforementioned framework characteristics, an additional medium-sized molecular dataset aqsol, similar to the popular zinc, but with a real-world measured chemical target, and discuss how this framework can be leveraged to explore new gnn designs and insights. as a proof of value of our benchmark, we study the case of graph positional encoding (pe) in gnns, which was introduced with this benchmark and has since spurred interest of exploring more powerful pe for transformers and gnns in a robust experimental setting.

benchmarking graph neural networks

we present the full public release of all data from the tng100 and tng300 simulations of the illustristng project. illustristng is a suite of large volume, cosmological, gravo-magnetohydrodynamical simulations run with the moving-mesh code arepo. tng includes a comprehensive model for galaxy formation physics, and each tng simulation self-consistently solves for the coupled evolution of dark matter, cosmic gas, luminous stars, and supermassive black holes from early time to the present day, z=0. each of the flagship runs—tng50, tng100, and tng300—are accompanied by halo/subhalo catalogs, merger trees, lower-resolution and dark-matter only counterparts, all available with 100 snapshots. we discuss scientific and numerical cautions and caveats relevant when using tng. the data volume now directly accessible online is ∼750 tb, including 1200 full volume snapshots and ∼80,000 high time-resolution subbox snapshots. this will increase to ∼1.1 pb with the future release of tng50. data access and analysis examples are available in idl, python, and matlab. we describe improvements and new functionality in the web-based api, including on-demand visualization and analysis of galaxies and halos, exploratory plotting of scaling relations and other relationships between galactic and halo properties, and a new jupyterlab interface. this provides an online, browser-based, near-native data analysis platform enabling user computation with local access to tng data, alleviating the need to download large datasets.

the illustristng simulations: public data release

we present a method to flexibly and self-consistently determine individual galaxies' star formation rates (sfrs) from their host haloes' potential well depths, assembly histories, and redshifts. the method is constrained by galaxies' observed stellar mass functions, sfrs (specific and cosmic), quenched fractions, ultraviolet (uv) luminosity functions, uv-stellar mass relations, irx-uv relations, auto- and cross-correlation functions (including quenched and star-forming subsamples), and quenching dependence on environment; each observable is reproduced over the full redshift range available, up to 0 < z < 10. key findings include the following: galaxy assembly correlates strongly with halo assembly; quenching correlates strongly with halo mass; quenched fractions at fixed halo mass decrease with increasing redshift; massive quenched galaxies reside in higher-mass haloes than star-forming galaxies at fixed galaxy mass; star-forming and quenched galaxies' star formation histories at fixed mass differ most at z < 0.5; satellites have large scatter in quenching time-scales after infall, and have modestly higher quenched fractions than central galaxies; planck cosmologies result in up to 0.3 dex lower stellar - halo mass ratios at early times; and, none the less, stellar mass-halo mass ratios rise at z > 5. also presented are revised stellar mass - halo mass relations for all, quenched, star-forming, central, and satellite galaxies; the dependence of star formation histories on halo mass, stellar mass, and galaxy ssfr; quenched fractions and quenching time-scale distributions for satellites; and predictions for higher-redshift galaxy correlation functions and weak lensing surface densities. the public data release (dr1) includes the massively parallel (>105 cores) implementation (the universemachine), the newly compiled and remeasured observational data, derived galaxy formation constraints, and mock catalogues including lightcones.

universemachine: the correlation between galaxy growth and dark matter halo assembly from z = 0-10

the dark energy spectroscopic instrument (desi) completed its five-month survey validation in may 2021. spectra of stellar and extragalactic targets from survey validation constitute the first major data sample from the desi survey. this paper describes the public release of those spectra, the catalogs of derived properties, and the intermediate data products. in total, the public release includes good-quality spectral information from 466,447 objects targeted as part of the milky way survey, 428,758 as part of the bright galaxy survey, 227,318 as part of the luminous red galaxy sample, 437,664 as part of the emission line galaxy sample, and 76,079 as part of the quasar sample. in addition, the release includes spectral information from 137,148 objects that expand the scope beyond the primary samples as part of a series of secondary programs. here, we describe the spectral data, data quality, data products, large-scale structure science catalogs, access to the data, and references that provide relevant background to using these spectra.

the early data release of the dark energy spectroscopic instrument

on 2017 june 8 at 02:01:16.49 utc, a gravitational-wave (gw) signal from the merger of two stellar-mass black holes was observed by the two advanced laser interferometer gravitational-wave observatory detectors with a network signal-to-noise ratio of 13. this system is the lightest black hole binary so far observed, with component masses of {12}-2+7 {m}⊙and {7}-2+2 {m}⊙(90% credible intervals). these lie in the range of measured black hole masses in low-mass x-ray binaries, thus allowing us to compare black holes detected through gws with electromagnetic observations. the source’s luminosity distance is {340}-140+140 {mpc}, corresponding to redshift {0.07}-0.03+0.03. we verify that the signal waveform is consistent with the predictions of general relativity.

gw170608: observation of a 19 solar-mass binary black hole coalescence

we present results on the mass, spin, and redshift distributions with phenomenological population models using the 10 binary black hole (bbh) mergers detected in the first and second observing runs completed by advanced ligo and advanced virgo. we constrain properties of the bbh mass spectrum using models with a range of parameterizations of the bbh mass and spin distributions. we find that the mass distribution of the more massive bh in such binaries is well approximated by models with no more than 1% of bhs more massive than 45 {m}⊙and a power-law index of α = {1.3}-1.7+1.4 (90% credibility). we also show that bbhs are unlikely to be composed of bhs with large spins aligned to the orbital angular momentum. modeling the evolution of the bbh merger rate with redshift, we show that it is flat or increasing with redshift with 93% probability. marginalizing over uncertainties in the bbh population, we find robust estimates of the bbh merger rate density of r = {53.2}-28.2+55.8 gpc-3 yr-1 (90% credibility). as the bbh catalog grows in future observing runs, we expect that uncertainties in the population model parameters will shrink, potentially providing insights into the formation of bhs via supernovae, binary interactions of massive stars, stellar cluster dynamics, and the formation history of bhs across cosmic time.

binary black hole population properties inferred from the first and second observing runs of advanced ligo and advanced virgo

kagome metals a v3sb5 (a =k , rb, and cs) exhibit intriguing superconductivity below 0.9 ∼2.5 k , a charge density wave (cdw) transition around 80 ∼100 k , and z2 topological surface states. the nature of the cdw phase and its relation to superconductivity remains elusive. in this work, we investigate the electronic and structural properties of cdw by first-principles calculations. we reveal an inverse star of david deformation as the 2 ×2 ×2 cdw ground state of the kagome lattice. the kagome lattice shows softening breathing-phonon modes, indicating the structural instability. however, electrons play an essential role in the cdw transition via fermi surface nesting and van hove singularity. the inverse star of david structure agrees with recent experiments by scanning tunneling microscopy (stm). the cdw phase inherits the nontrivial z2-type topological band structure. further, we find that the electron-phonon coupling is too weak to account for the superconductivity tc in all three materials. it implies the existence of unconventional pairing of these kagome metals. our results provide essential knowledge toward understanding the superconductivity and topology in kagome metals.

charge density waves and electronic properties of superconducting kagome metals

erosita (extended roentgen survey with an imaging telescope array) is the primary instrument on the spectrum-roentgen-gamma (srg) mission, which was successfully launched on july 13, 2019, from the baikonour cosmodrome. after the commissioning of the instrument and a subsequent calibration and performance verification phase, erosita started a survey of the entire sky on december 13, 2019. by the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. at the end of this program, the erosita all-sky survey in the soft x-ray band (0.2-2.3 kev) will be about 25 times more sensitive than the rosat all-sky survey, while in the hard band (2.3-8 kev) it will provide the first ever true imaging survey of the sky. the erosita design driving science is the detection of large samples of galaxy clusters up to redshifts z > 1 in order to study the large-scale structure of the universe and test cosmological models including dark energy. in addition, erosita is expected to yield a sample of a few million agns, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. the survey will also provide new insights into a wide range of astrophysical phenomena, including x-ray binaries, active stars, and diffuse emission within the galaxy. results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. with this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements.

the erosita x-ray telescope on srg

we introduce the first two simulations of the illustristng project, a next generation of cosmological magnetohydrodynamical simulations, focusing on the optical colours of galaxies. we explore tng100, a rerun of the original illustris box, and tng300, which includes 2 × 25003 resolution elements in a volume 20 times larger. here, we present first results on the galaxy colour bimodality at low redshift. accounting for the attenuation of stellar light by dust, we compare the simulated (g - r) colours of 109 < m⋆/m⊙ < 1012.5 galaxies to the observed distribution from the sloan digital sky survey. we find a striking improvement with respect to the original illustris simulation, as well as excellent quantitative agreement with the observations, with a sharp transition in median colour from blue to red at a characteristic m⋆ ∼ 1010.5 m⊙. investigating the build-up of the colour-mass plane and the formation of the red sequence, we demonstrate that the primary driver of galaxy colour transition is supermassive black hole feedback in its low accretion state. across the entire population the median colour transition time-scale δtgreen is ∼1.6 gyr, a value which drops for increasingly massive galaxies. we find signatures of the physical process of quenching: at fixed stellar mass, redder galaxies have lower star formation rates, gas fractions, and gas metallicities; their stellar populations are also older and their large-scale interstellar magnetic fields weaker than in bluer galaxies. finally, we measure the amount of stellar mass growth on the red sequence. galaxies with m⋆ > 1011 m⊙ which redden at z < 1 accumulate on average ∼25 per cent of their final z = 0 mass post-reddening; at the same time, ∼18 per cent of such massive galaxies acquire half or more of their final stellar mass while on the red sequence.

first results from the illustristng simulations: the galaxy colour bimodality

we present an investigation into the first 500 myr of galaxy evolution from the cosmic evolution early release science (ceers) survey. ceers, one of 13 jwst ers programs, targets galaxy formation from z ~ 0.5 to >10 using several imaging and spectroscopic modes. we make use of the first epoch of ceers nircam imaging, spanning 35.5 arcmin2, to search for candidate galaxies at z > 9. following a detailed data reduction process implementing several custom steps to produce high-quality reduced images, we perform multiband photometry across seven nircam broad- and medium-band (and six hubble broadband) filters focusing on robust colors and accurate total fluxes. we measure photometric redshifts and devise a robust set of selection criteria to identify a sample of 26 galaxy candidates at z ~ 9-16. these objects are compact with a median half-light radius of ~0.5 kpc. we present an early estimate of the z ~ 11 rest-frame ultraviolet (uv) luminosity function, finding that the number density of galaxies at m uv ~ -20 appears to evolve very little from z ~ 9 to 11. we also find that the abundance (surface density [arcmin-2]) of our candidates exceeds nearly all theoretical predictions. we explore potential implications, including that at z > 10, star formation may be dominated by top-heavy initial mass functions, which would result in an increased ratio of uv light per unit halo mass, though a complete lack of dust attenuation and/or changing star formation physics may also play a role. while spectroscopic confirmation of these sources is urgently required, our results suggest that the deeper views to come with jwst should yield prolific samples of ultrahigh-redshift galaxies with which to further explore these conclusions.

ceers key paper. i. an early look into the first 500 myr of galaxy formation with jwst

casa, the common astronomy software applications, is the primary data processing software for the atacama large millimeter/submillimeter array (alma) and the karl g. jansky very large array (vla), and is frequently used also for other radio telescopes. the casa software can handle data from single-dish, aperture-synthesis, and very long baseline interferometery (vlbi) telescopes. one of its core functionalities is to support the calibration and imaging pipelines for alma, vla, vla sky survey, and the nobeyama 45 m telescope. this paper presents a high-level overview of the basic structure of the casa software, as well as procedures for calibrating and imaging astronomical radio data in casa. casa is being developed by an international consortium of scientists and software engineers based at the national radio astronomy observatory (nrao), the european southern observatory, the national astronomical observatory of japan, and the joint institute for vlbi european research infrastructure consortium (jiv-eric), under the guidance of nrao.

casa, the common astronomy software applications for radio astronomy

one aim of modern astronomy is to detect temperate, earth-like exoplanets that are well suited for atmospheric characterization. recently, three earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the sun, located 12 parsecs away. the transiting configuration of these planets, combined with the jupiter-like size of their host star—named trappist-1—makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities. here we report the results of a photometric monitoring campaign of that star from the ground and space. our observations reveal that at least seven planets with sizes and masses similar to those of earth revolve around trappist-1. the six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. this architecture suggests that the planets formed farther from the star and migrated inwards. moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces.

seven temperate terrestrial planets around the nearby ultracool dwarf star trappist-1

jwst is revealing a new population of dust-reddened broad-line active galactic nuclei (agn) at redshifts $z\gtrsim5$. here we present deep nirspec/prism spectroscopy from the cycle 1 treasury program uncover of 15 agn candidates selected to be compact, with red continua in the rest-frame optical but with blue slopes in the uv. from nircam photometry alone, they could have been dominated by dusty star formation or agn. here we show that the majority of the compact red sources in uncover are dust-reddened agn: $60\%$ show definitive evidence for broad-line h$\alpha$ with fwhm$\, >2000$ km/s, for $20\%$ current data are inconclusive, and $20\%$ are brown dwarf stars. we propose an updated photometric criterion to select red $z>5$ agn that excludes brown dwarfs and is expected to yield $>80\%$ agn. remarkably, among all $z_{\rm phot}>5$ galaxies with f277w$-$f444w$>1$ in uncover at least $33\%$ are agn regardless of compactness, climbing to at least $80\%$ agn for sources with f277w$-$f444w$>1.6$. the confirmed agn have black hole masses of $10^7-10^9$ m$_{\odot}$. while their uv-luminosities ($-16>m_{\rm uv}>-20$ ab mag) are low compared to uv-selected agn at these epochs, consistent with percent-level scattered agn light or low levels of unobscured star formation, the inferred bolometric luminosities are typical of $10^7-10^9$ m$_{\odot}$ black holes radiating at $\sim 10-40\%$ of eddington. the number densities are surprisingly high at $\sim10^{-5}$ mpc$^{-3}$ mag$^{-1}$, 100 times more common than the faintest uv-selected quasars, while accounting for $\sim1\%$ of the uv-selected galaxies. while their uv-faintness suggest they may not contribute strongly to reionization, their ubiquity poses challenges to models of black hole growth.

uncover spectroscopy confirms a surprising ubiquity of agn in red galaxies at $z>5$

we report results from searches for new physics with low-energy electronic recoil data recorded with the xenon1t detector. with an exposure of 0.65 tonne-years and an unprecedentedly low background rate of 76 ±2stat events /(tonne ×year ×kev ) between 1 and 30 kev, the data enable one of the most sensitive searches for solar axions, an enhanced neutrino magnetic moment using solar neutrinos, and bosonic dark matter. an excess over known backgrounds is observed at low energies and most prominent between 2 and 3 kev. the solar axion model has a 3.4 σ significance, and a three-dimensional 90% confidence surface is reported for axion couplings to electrons, photons, and nucleons. this surface is inscribed in the cuboid defined by gae<3.8 ×10-12 , gaeganeff<4.8 ×10-18 , and gaega γ<7.7 ×10-22 gev-1 , and excludes either gae=0 or gaega γ=gaeganeff=0 . the neutrino magnetic moment signal is similarly favored over background at 3.2 σ , and a confidence interval of μν∈(1.4 ,2.9 )×10-11 μb (90% c.l.) is reported. both results are in strong tension with stellar constraints. the excess can also be explained by β decays of tritium at 3.2 σ significance with a corresponding tritium concentration in xenon of (6.2 ±2.0 )×10-25 mol /mol . such a trace amount can neither be confirmed nor excluded with current knowledge of its production and reduction mechanisms. the significances of the solar axion and neutrino magnetic moment hypotheses are decreased to 2.0 σ and 0.9 σ , respectively, if an unconstrained tritium component is included in the fitting. with respect to bosonic dark matter, the excess favors a monoenergetic peak at (2.3 ±0.2 ) kev (68% c.l.) with a 3.0 σ global (4.0 σ local) significance over background. this analysis sets the most restrictive direct constraints to date on pseudoscalar and vector bosonic dark matter for most masses between 1 and 210 kev /c2 . we also consider the possibility that 37ar may be present in the detector, yielding a 2.82 kev peak from electron capture. contrary to tritium, the 37ar concentration can be tightly constrained and is found to be negligible.

excess electronic recoil events in xenon1t

at present, we have almost as many theories to explain fast radio bursts as we have fast radio bursts observed. this landscape will be changing rapidly with chime/frb, recently commissioned in canada, and hirax, under construction in south africa. this is an opportune time to review existing theories and their observational consequences, allowing us to efficiently curtail viable astrophysical models as more data becomes available. in this article we provide a currently up to date catalogue of the numerous and varied theories proposed for fast radio bursts so far. we also launched an online evolving repository for the use and benefit of the community to dynamically update our theoretical knowledge and discuss constraints and uses of fast radio bursts.

a living theory catalogue for fast radio bursts

magnetars are highly magnetized young neutron stars that occasionally produce enormous bursts and flares of x-rays and γ-rays1. of the approximately thirty magnetars currently known in our galaxy and the magellanic clouds, five have exhibited transient radio pulsations2,3. fast radio bursts (frbs) are millisecond-duration bursts of radio waves arriving from cosmological distances4, some of which have been seen to repeat5-8. a leading model for repeating frbs is that they are extragalactic magnetars, powered by their intense magnetic fields9-11. however, a challenge to this model is that frbs must have radio luminosities many orders of magnitude larger than those seen from known galactic magnetars. here we report the detection of an extremely intense radio burst from the galactic magnetar sgr 1935+2154 using the canadian hydrogen intensity mapping experiment (chime) frb project. the fluence of this two-component bright radio burst and the estimated distance to sgr 1935+2154 together imply a burst energy at 400 to 800 megahertz of approximately 3 × 1034 erg, which is three orders of magnitude higher than the burst energy of any radio-emitting magnetar detected thus far. such a burst coming from a nearby galaxy (at a distance of less than approximately 12 megaparsecs) would be indistinguishable from a typical frb. however, given the large gaps in observed energies and activity between the brightest and most active frb sources and what is observed for sgr 1935+2154-like magnetars, more energetic and active sources—perhaps younger magnetars—are needed to explain all observations.

a bright millisecond-duration radio burst from a galactic magnetar

the assembly of our galaxy can be reconstructed using the motions and chemistry of individual stars1,2. chemo-dynamical studies of the stellar halo near the sun have indicated the presence of multiple components3, such as streams4 and clumps5, as well as correlations between the stars' chemical abundances and orbital parameters6-8. recently, analyses of two large stellar surveys9,10 revealed the presence of a well populated elemental abundance sequence7,11, two distinct sequences in the colour-magnitude diagram12 and a prominent, slightly retrograde kinematic structure13,14 in the halo near the sun, which may trace an important accretion event experienced by the galaxy15. however, the link between these observations and their implications for galactic history is not well understood. here we report an analysis of the kinematics, chemistry, age and spatial distribution of stars that are mainly linked to two major galactic components: the thick disk and the stellar halo. we demonstrate that the inner halo is dominated by debris from an object that at infall was slightly more massive than the small magellanic cloud, and which we refer to as gaia-enceladus. the stars that originate in gaia-enceladus cover nearly the full sky, and their motions reveal the presence of streams and slightly retrograde and elongated trajectories. with an estimated mass ratio of four to one, the merger of the milky way with gaia-enceladus must have led to the dynamical heating of the precursor of the galactic thick disk, thus contributing to the formation of this component approximately ten billion years ago. these findings are in line with the results of galaxy formation simulations, which predict that the inner stellar halo should be dominated by debris from only a few massive progenitors2,16.

the merger that led to the formation of the milky way's inner stellar halo and thick disk

since their discovery in 20071, much effort has been devoted to uncovering the sources of the extragalactic, millisecond-duration fast radio bursts (frbs)2. a class of neutron stars known as magnetars is a leading candidate source of frbs3,4. magnetars have surface magnetic fields in excess of 1014 gauss, the decay of which powers a range of high-energy phenomena5. here we report observations of a millisecond-duration radio burst from the galactic magnetar sgr 1935+2154, with a fluence of 1.5 ± 0.3 megajansky milliseconds. this event, frb 200428 (st 200428a), was detected on 28 april 2020 by the stare2 radio array6 in the 1,281-1,468 megahertz band. the isotropic-equivalent energy released in frb 200428 is 4 × 103 times greater than that of any radio pulse from the crab pulsar—previously the source of the brightest galactic radio bursts observed on similar timescales7. frb 200428 is just 30 times less energetic than the weakest extragalactic frb observed so far8, and is drawn from the same population as the observed frb sample. the coincidence of frb 200428 with an x-ray burst9-11 favours emission models that describe synchrotron masers or electromagnetic pulses powered by magnetar bursts and giant flares3,4,12,13. the discovery of frb 200428 implies that active magnetars such as sgr 1935+2154 can produce frbs at extragalactic distances.

a fast radio burst associated with a galactic magnetar

multi-epoch radial velocity measurements of stars can be used to identify stellar, substellar, and planetary-mass companions. even a small number of observation epochs can be informative about companions, though there can be multiple qualitatively different orbital solutions that fit the data. we have custom-built a monte carlo sampler (the joker) that delivers reliable (and often highly multimodal) posterior samplings for companion orbital parameters given sparse radial velocity data. here we use the joker to perform a search for companions to 96,231 red giant stars observed in the apogee survey (dr14) with ≥3 spectroscopic epochs. we select stars with probable companions by making a cut on our posterior belief about the amplitude of the variation in stellar radial velocity induced by the orbit. we provide (1) a catalog of 320 companions for which the stellar companion’s properties can be confidently determined, (2) a catalog of 4898 stars that likely have companions, but would require more observations to uniquely determine the orbital properties, and (3) posterior samplings for the full orbital parameters for all stars in the parent sample. we show the characteristics of systems with confidently determined companion properties and highlight interesting systems with candidate compact object companions.

binary companions of evolved stars in apogee dr14: search method and catalog of ∼5000 companions

we conduct a comprehensive study on dropout galaxy candidates at z ~ 9-16 using the first 90 arcmin2 james webb space telescope (jwst) near infrared camera images taken by the early release observations (ero) and early release science programs. with the jwst simulation images, we find that a number of foreground interlopers are selected with a weak photo-z determination (δχ 2 > 4). we thus carefully apply a secure photo-z selection criterion (δχ 2 > 9) and conventional color criteria with confirmations of the ero near infrared spectrograph spectroscopic redshifts, and obtain a total of 23 dropout galaxies at z ~ 9-16, including two candidates at ${z}_{\mathrm{phot}}={16.25}_{-0.46}^{+0.24}$ and ${16.41}_{-0.55}^{+0.66}$ . we perform thorough comparisons of dropout galaxies found in our work with recent jwst studies, and conclude that our galaxy sample is reliable enough for statistical analyses. we derive the uv luminosity functions at z ~ 9-16, and confirm that our uv luminosity functions at z ~ 9 and 12 agree with those determined by other hubble space telescope and jwst studies. the cosmic star formation rate (sfr) density decreases from z ~ 9 to 12, and perhaps to 16, but the densities at z ~ 12-16 are higher than the constant star formation efficiency model. interestingly, there are six bright galaxy candidates at z ~ 10-16 with m uv < -19.5 mag and m * ~ 108-9 m ⊙. because a majority (~80%) of these galaxies show no signatures of active galactic nuclei in their morphologies, the high cosmic sfr densities and the existence of these uv-luminous galaxies are explained by the lack of suppression of star formation by the uv background radiation at the pre-reionization epoch and/or an efficient uv radiation production by a top-heavy initial mass function with population iii-like star formation.

a comprehensive study of galaxies at z 9-16 found in the early jwst data: ultraviolet luminosity functions and cosmic star formation history at the pre-reionization epoch

our galaxy, the milky way, is a benchmark for understanding disk galaxies. it is the only galaxy whose formation history can be studied using the full distribution of stars from faint dwarfs to supergiants. the oldest components provide us with unique insight into how galaxies form and evolve over billions of years. the galaxy is a luminous (l⋆) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo. based on global properties, it falls in the sparsely populated “green valley” region of the galaxy color-magnitude diagram. here we review the key integrated, structural and kinematic parameters of the galaxy, and point to uncertainties as well as directions for future progress. galactic studies will continue to play a fundamental role far into the future because there are measurements that can only be made in the near field and much of contemporary astrophysics depends on such observations.

the galaxy in context: structural, kinematic, and integrated properties

the fourth generation of the sloan digital sky survey (sdss-iv) has been in operation since 2014 july. this paper describes the second data release from this phase, and the 14th from sdss overall (making this data release fourteen or dr14). this release makes the data taken by sdss-iv in its first two years of operation (2014-2016 july) public. like all previous sdss releases, dr14 is cumulative, including the most recent reductions and calibrations of all data taken by sdss since the first phase began operations in 2000. new in dr14 is the first public release of data from the extended baryon oscillation spectroscopic survey; the first data from the second phase of the apache point observatory (apo) galactic evolution experiment (apogee-2), including stellar parameter estimates from an innovative data-driven machine-learning algorithm known as “the cannon” and almost twice as many data cubes from the mapping nearby galaxies at apo (manga) survey as were in the previous release (n = 2812 in total). this paper describes the location and format of the publicly available data from the sdss-iv surveys. we provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. the sdss web site (www.sdss.org) has been updated for this release and provides links to data downloads, as well as tutorials and examples of data use. sdss-iv is planning to continue to collect astronomical data until 2020 and will be followed by sdss-v.

the fourteenth data release of the sloan digital sky survey: first spectroscopic data from the extended baryon oscillation spectroscopic survey and from the second phase of the apache point observatory galactic evolution experiment

the first observational run of the advanced ligo detectors, from september 12, 2015 to january 19, 2016, saw the first detections of gravitational waves from binary black hole mergers. in this paper, we present full results from a search for binary black hole merger signals with total masses up to 100 m⊙ and detailed implications from our observations of these systems. our search, based on general-relativistic models of gravitational-wave signals from binary black hole systems, unambiguously identified two signals, gw150914 and gw151226, with a significance of greater than 5 σ over the observing period. it also identified a third possible signal, lvt151012, with substantially lower significance and with an 87% probability of being of astrophysical origin. we provide detailed estimates of the parameters of the observed systems. both gw150914 and gw151226 provide an unprecedented opportunity to study the two-body motion of a compact-object binary in the large velocity, highly nonlinear regime. we do not observe any deviations from general relativity, and we place improved empirical bounds on several high-order post-newtonian coefficients. from our observations, we infer stellar-mass binary black hole merger rates lying in the range 9 - 240 gpc-3 yr-1 . these observations are beginning to inform astrophysical predictions of binary black hole formation rates and indicate that future observing runs of the advanced detector network will yield many more gravitational-wave detections.

binary black hole mergers in the first advanced ligo observing run

aims: solar orbiter, the first mission of esa's cosmic vision 2015-2025 programme and a mission of international collaboration between esa and nasa, will explore the sun and heliosphere from close up and out of the ecliptic plane. it was launched on 10 february 2020 04:03 utc from cape canaveral and aims to address key questions of solar and heliospheric physics pertaining to how the sun creates and controls the heliosphere, and why solar activity changes with time. to answer these, the mission carries six remote-sensing instruments to observe the sun and the solar corona, and four in-situ instruments to measure the solar wind, energetic particles, and electromagnetic fields. in this paper, we describe the science objectives of the mission, and how these will be addressed by the joint observations of the instruments onboard.methods: the paper first summarises the mission-level science objectives, followed by an overview of the spacecraft and payload. we report the observables and performance figures of each instrument, as well as the trajectory design. this is followed by a summary of the science operations concept. the paper concludes with a more detailed description of the science objectives.results: solar orbiter will combine in-situ measurements in the heliosphere with high-resolution remote-sensing observations of the sun to address fundamental questions of solar and heliospheric physics. the performance of the solar orbiter payload meets the requirements derived from the mission's science objectives. its science return will be augmented further by coordinated observations with other space missions and ground-based observatories. array(0x207ce98)

the solar orbiter mission. science overview

we report the observation of gravitational waves from a binary-black-hole coalescence during the first two weeks of ligo's and virgo's third observing run. the signal was recorded on april 12, 2019 at 05∶30∶44 utc with a network signal-to-noise ratio of 19. the binary is different from observations during the first two observing runs most notably due to its asymmetric masses: a ∼30 m⊙ black hole merged with a ∼8 m⊙ black hole companion. the more massive black hole rotated with a dimensionless spin magnitude between 0.22 and 0.60 (90% probability). asymmetric systems are predicted to emit gravitational waves with stronger contributions from higher multipoles, and indeed we find strong evidence for gravitational radiation beyond the leading quadrupolar order in the observed signal. a suite of tests performed on gw190412 indicates consistency with einstein's general theory of relativity. while the mass ratio of this system differs from all previous detections, we show that it is consistent with the population model of stellar binary black holes inferred from the first two observing runs.

gw190412: observation of a binary-black-hole coalescence with asymmetric masses

we present jades jwst/nirspec spectroscopy of gn-z11, the most luminous candidate z > 10 lyman break galaxy in the goods-north field with muv = −21.5. we derive a redshift of z = 10.603 (lower than previous determinations) based on multiple emission lines in our low and medium resolution spectra over 0.7 − 5.3 μm. we significantly detect the continuum and measure a blue rest-uv spectral slope of β = −2.4. remarkably, we see spatially extended lyman-α in emission (despite the highly neutral intergalactic medium expected at this early epoch), offset 555 km s−1 redwards of the systemic redshift. from our measurements of collisionally excited lines of both low and high ionisation (including [o ii] λ3727, [ne iii] λ3869, and c iii] λ1909), we infer a high ionisation parameter (log u ∼ −2). we detect the rarely seen n iv] λ1486 and n iii] λ1748 lines in both our low and medium resolution spectra, with other high ionisation lines seen in the low resolution spectrum, such as he ii (blended with o iii]) and c iv (with a possible p-cygni profile). based on the observed rest-uv line ratios, we cannot conclusively rule out photoionisation from an active galactic nucleus (agn), although the high c iii]/he ii and n iii]/he ii ratios are compatible with a star formation explanation. if the observed emission lines are powered by star formation, then the strong n iii] λ1748 observed may imply an unusually high n/o abundance. balmer emission lines (hγ, hδ) are also detected, and if powered by star formation rather than an agn, we infer a star formation rate of ∼20 − 30 m⊙ yr−1 (depending on the initial mass function) and low dust attenuation. our nirspec spectroscopy confirms that gn-z11 is a remarkable galaxy with extreme properties seen 430 myr after the big bang.

jades nirspec spectroscopy of gn-z11: lyman-α emission and possible enhanced nitrogen abundance in a z = 10.60 luminous galaxy

after stars formed in the early universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. this alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz. here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0.5 kelvin. the profile is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions. this discrepancy suggests that either the primordial gas was much colder than expected or the background radiation temperature was hotter than expected. astrophysical phenomena (such as radiation from stars and stellar remnants) are unlikely to account for this discrepancy; of the proposed extensions to the standard model of cosmology and particle physics, only cooling of the gas as a result of interactions between dark matter and baryons seems to explain the observed amplitude. the low-frequency edge of the observed profile indicates that stars existed and had produced a background of lyman-α photons by 180 million years after the big bang. the high-frequency edge indicates that the gas was heated to above the radiation temperature less than 100 million years later.

an absorption profile centred at 78 megahertz in the sky-averaged spectrum

i describe a method to transform a set of stellar evolution tracks onto a uniform basis and then interpolate within that basis to construct stellar isochrones. this method accommodates a broad range of stellar types, from substellar objects to high-mass stars, and phases of evolution, from the pre-main sequence to the white dwarf cooling sequence. i discuss situations in which stellar physics leads to departures from the otherwise monotonic relation between initial stellar mass and lifetime, and how these may be dealt with in isochrone construction. i close with convergence tests and recommendations for the number of points in the uniform basis and the mass between tracks in the original grid required to achieve a certain level accuracy in the resulting isochrones. the programs that implement these methods are free and open-source; they may be obtained from the project webpage.1

mesa isochrones and stellar tracks (mist) 0: methods for the construction of stellar isochrones

astrophysical black holes are expected to be described by the kerr metric. this is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies einstein's equations and does not have pathologies outside of the event horizon. we present new constraints on potential deviations from the kerr prediction based on 2017 eht observations of sagittarius a* (sgr a*). we calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both kerr and non-kerr simulations. we use the exquisite prior constraints on the mass-to-distance ratio for sgr a* to show that the observed image size is within ~10% of the kerr predictions. we use these bounds to constrain metrics that are parametrically different from kerr, as well as the charges of several known spacetimes. to consider alternatives to the presence of an event horizon, we explore the possibility that sgr a* is a compact object with a surface that either absorbs and thermally reemits incident radiation or partially reflects it. using the observed image size and the broadband spectrum of sgr a*, we conclude that a thermal surface can be ruled out and a fully reflective one is unlikely. we compare our results to the broader landscape of gravitational tests. together with the bounds found for stellar-mass black holes and the m87 black hole, our observations provide further support that the external spacetimes of all black holes are described by the kerr metric, independent of their mass.

first sagittarius a* event horizon telescope results. vi. testing the black hole metric

we introduce the disk substructures at high angular resolution project (dsharp), one of the initial large programs conducted with the atacama large millimeter/submillimeter array (alma). the primary goal of dsharp is to find and characterize substructures in the spatial distributions of solid particles for a sample of 20 nearby protoplanetary disks, using very high resolution (∼0.″035, or 5 au, fwhm) observations of their 240 ghz (1.25 mm) continuum emission. these data provide a first homogeneous look at the small-scale features in disks that are directly relevant to the planet formation process, quantifying their prevalence, morphologies, spatial scales, spacings, symmetry, and amplitudes, for targets with a variety of disk and stellar host properties. we find that these substructures are ubiquitous in this sample of large, bright disks. they are most frequently manifested as concentric, narrow emission rings and depleted gaps, although large-scale spiral patterns and small arc-shaped azimuthal asymmetries are also present in some cases. these substructures are found at a wide range of disk radii (from a few astronomical units to more than 100 au), are usually compact (≲10 au), and show a wide range of amplitudes (brightness contrasts). here we discuss the motivation for the project, describe the survey design and the sample properties, detail the observations and data calibration, highlight some basic results, and provide a general overview of the key conclusions that are presented in more detail in a series of accompanying articles. the dsharp data—including visibilities, images, calibration scripts, and more—are released for community use at https://almascience.org/alma-data/lp/dsharp.

the disk substructures at high angular resolution project (dsharp). i. motivation, sample, calibration, and overview

we identify a class of scalar-tensor theories with coupling between the scalar and the gauss-bonnet invariant that exhibit spontaneous scalarization for both black holes and compact stars. in particular, these theories formally admit all of the stationary solutions of general relativity, but these are not dynamically preferred if certain conditions are satisfied. remarkably, black holes exhibit scalarization if their mass lies within one of many narrow bands. we find evidence that scalarization can occur in neutron stars as well.

spontaneous scalarization of black holes and compact stars from a gauss-bonnet coupling

we describe the catalogs assembled and the algorithms used to populate the revised tess input catalog (tic), based on the incorporation of the gaia second data release. we also describe a revised ranking system for prioritizing stars for 2 minute cadence observations, and we assemble a revised candidate target list (ctl) using that ranking. the tic is available on the mikulski archive for space telescopes server, and an enhanced ctl is available through the filtergraph data visualization portal system at http://filtergraph.vanderbilt.edu/tess_ctl.

the revised tess input catalog and candidate target list

the feedback in realistic environments (fire) project explores feedback in cosmological galaxy formation simulations. previous fire simulations used an identical source code (`fire-1') for consistency. motivated by the development of more accurate numerics - including hydrodynamic solvers, gravitational softening, and supernova coupling algorithms - and exploration of new physics (e.g. magnetic fields), we introduce `fire-2', an updated numerical implementation of fire physics for the gizmo code. we run a suite of simulations and compare against fire-1: overall, fire-2 improvements do not qualitatively change galaxy-scale properties. we pursue an extensive study of numerics versus physics. details of the star formation algorithm, cooling physics, and chemistry have weak effects provided that we include metal-line cooling and star formation occurs at higher-than-mean densities. we present new resolution criteria for high-resolution galaxy simulations. most galaxy-scale properties are robust to numerics we test, provided: (1) toomre masses are resolved; (2) feedback coupling ensures conservation, and (3) individual supernovae are time-resolved. stellar masses and profiles are most robust to resolution, followed by metal abundances and morphologies, followed by properties of winds and circum-galactic media. central (∼kpc) mass concentrations in massive (>l*) galaxies are sensitive to numerics (via trapping/recycling of winds in hot haloes). multiple feedback mechanisms play key roles: supernovae regulate stellar masses/winds; stellar mass-loss fuels late star formation; radiative feedback suppresses accretion on to dwarfs and instantaneous star formation in discs. we provide all initial conditions and numerical algorithms used.

fire-2 simulations: physics versus numerics in galaxy formation

the distribution of elements in galaxies provides a wealth of information about their production sites and their subsequent mixing into the interstellar medium. here we investigate the elemental distributions of stars in the illustristng simulations. we analyse the abundance ratios of magnesium and europium in milky way-like galaxies from the tng100 simulation (stellar masses log (m⋆/m⊙) ∼ 9.7-11.2). comparison of observed magnesium and europium for individual stars in the milky way with the stellar abundances in our more than 850 milky way-like galaxies provides stringent constraints on our chemical evolutionary methods. here, we use the magnesium-to-iron ratio as a proxy for the effects of our snii (core-collapse supernovae) and snia (type ia supernovae) metal return prescription and as a comparison to a variety of galactic observations. the europium-to-iron ratio tracks the rare ejecta from neutron star-neutron star mergers, the assumed primary site of europium production in our models, and is a sensitive probe of the effects of metal diffusion within the gas in our simulations. we find that europium abundances in milky way-like galaxies show no correlation with assembly history, present-day galactic properties, and average galactic stellar population age. we reproduce the europium-to-iron spread at low metallicities observed in the milky way, and find it is sensitive to gas properties during redshifts z ≈ 2-4. we show that while the overall normalization of [eu/fe] is susceptible to resolution and post-processing assumptions, the relatively large spread of [eu/fe] at low [fe/h] when compared to that at high [fe/h] is quite robust.

first results from the illustristng simulations: a tale of two elements - chemical evolution of magnesium and europium

on 17 august 2017, the advanced ligo and virgo detectors observed the gravitational-wave event gw170817—a strong signal from the merger of a binary neutron-star system. less than two seconds after the merger, a γ-ray burst (grb 170817a) was detected within a region of the sky consistent with the ligo-virgo-derived location of the gravitational-wave source. this sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy ngc 4993. this detection of gw170817 in both gravitational waves and electromagnetic waves represents the first ‘multi-messenger’ astronomical observation. such observations enable gw170817 to be used as a ‘standard siren’ (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the hubble constant. this quantity represents the local expansion rate of the universe, sets the overall scale of the universe and is of fundamental importance to cosmology. here we report a measurement of the hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. in contrast to previous measurements, ours does not require the use of a cosmic ‘distance ladder’: the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. we determine the hubble constant to be about 70 kilometres per second per megaparsec. this value is consistent with existing measurements, while being completely independent of them. additional standard siren measurements from future gravitational-wave sources will enable the hubble constant to be constrained to high precision.

a gravitational-wave standard siren measurement of the hubble constant

we present a new and independent determination of the local value of the hubble constant based on a calibration of the tip of the red giant branch (trgb) applied to type ia supernovae (sne ia). we find a value of h 0 = 69.8 ± 0.8 (±1.1% stat) ± 1.7 (±2.4% sys) km s-1 mpc-1. the trgb method is both precise and accurate and is parallel to but independent of the cepheid distance scale. our value sits midway in the range defined by the current hubble tension. it agrees at the 1.2σ level with that of the planck collaboration et al. estimate and at the 1.7σ level with the hubble space telescope (hst) shoes measurement of h 0 based on the cepheid distance scale. the trgb distances have been measured using deep hst advanced camera for surveys imaging of galaxy halos. the zero-point of the trgb calibration is set with a distance modulus to the large magellanic cloud of 18.477 ± 0.004 (stat) ± 0.020 (sys) mag, based on measurement of 20 late-type detached eclipsing binary stars, combined with an hst parallax calibration of a 3.6 μm cepheid leavitt law based on spitzer observations. we anchor the trgb distances to galaxies that extend our measurement into the hubble flow using the recently completed carnegie supernova project i ( csp-i ) sample containing about 100 well-observed sne ia . there are several advantages of halo trgb distance measurements relative to cepheid variables; these include low halo reddening, minimal effects of crowding or blending of the photometry, only a shallow (calibrated) sensitivity to metallicity in the i band, and no need for multiple epochs of observations or concerns of different slopes with period. in addition, the host masses of our trgb host-galaxy sample are higher, on average, than those of the cepheid sample, better matching the range of host-galaxy masses in the csp-i distant sample and reducing potential systematic effects in the sne ia measurements. based on observations made with the nasa/esa hubble space telescope, obtained at the space telescope science institute, which is operated by the association of universities for research in astronomy, inc., under nasa contract nas 5-26555. these observations are associated with program nos. 13472 and 13691.

the carnegie-chicago hubble program. viii. an independent determination of the hubble constant based on the tip of the red giant branch

the first few 100 myr at z > 10 mark the last major uncharted epoch in the history of the universe, where only a single galaxy (gn-z11 at z ≈ 11) is currently spectroscopically confirmed. here we present a search for luminous z > 10 galaxies with jwst/nircam photometry spanning ≈1-5 μm and covering 49 arcmin2 from the public jwst early release science programs (ceers and glass). our most secure candidates are two m uv ≈ -21 systems: glass-z12 and glass-z10. these galaxies display abrupt ≳1.8 mag breaks in their spectral energy distributions (seds), consistent with complete absorption of flux bluewards of lyα that is redshifted to $z={12.4}_{-0.3}^{+0.1}$ and $z={10.4}_{-0.5}^{+0.4}$ . lower redshift interlopers such as quiescent galaxies with strong balmer breaks would be comfortably detected at >5σ in multiple bands where instead we find no flux. from sed modeling we infer that these galaxies have already built up ~109 solar masses in stars over the ≲300-400 myr after the big bang. the brightness of these sources enable morphological constraints. tantalizingly, glass-z10 shows a clearly extended exponential light profile, potentially consistent with a disk galaxy of r 50 ≈ 0.7 kpc. these sources, if confirmed, join gn-z11 in defying number density forecasts for luminous galaxies based on schechter uv luminosity functions, which require a survey area >10× larger than we have studied here to find such luminous sources at such high redshifts. they extend evidence from lower redshifts for little or no evolution in the bright end of the uv luminosity function into the cosmic dawn epoch, with implications for just how early these galaxies began forming. this, in turn, suggests that future deep jwst observations may identify relatively bright galaxies to much earlier epochs than might have been anticipated.

two remarkably luminous galaxy candidates at z ≈ 10-12 revealed by jwst

on 17 august 2017, the laser interferometer gravitational-wave observatory (ligo) and the virgo interferometer detected gravitational waves (gws) emanating from a binary neutron star merger, gw170817. nearly simultaneously, the fermi and integral (international gamma-ray astrophysics laboratory) telescopes detected a gamma-ray transient, grb 170817a. at 10.9 hours after the gw trigger, we discovered a transient and fading optical source, swope supernova survey 2017a (sss17a), coincident with gw170817. sss17a is located in ngc 4993, an s0 galaxy at a distance of 40 megaparsecs. the precise location of gw170817 provides an opportunity to probe the nature of these cataclysmic events by combining electromagnetic and gw observations.

swope supernova survey 2017a (sss17a), the optical counterpart to a gravitational wave source