Sazuna/UAT_keywords huggingface dataset:
Absorption Line Search through Three Local Group Dwarf Galaxy Halos. Dwarf galaxies are missing nearly all of their baryons and metals from the stellar disk, which are presumed to be in a bound halo or expelled beyond the virial radius. The virial temperature for galaxies with M h ~ 109-1010 M ⊙ is similar to the collisional ionization equilibrium temperature for the C IV ion. We search for UV absorption from C IV in six sightlines toward three dwarf galaxies in the anti-M31 direction and at the periphery of the Local Group (D ≈ 1.3 Mpc; Sextans A, Sextans B, and NGC 3109). The C IV doublet is detected in only one of six sightlines, toward Sextans A, with $\mathrm{log}N({\rm{C}}\,{\rm\small{IV}})=13.06\pm 0.08$ . This is consistent with our gaseous halo models, where the halo gas mass is determined by the cooling rate, feedback, and the star formation rate; the inclusion of photoionization is an essential ingredient. This model can also reproduce the higher detection rate of O VI absorption in other dwarf samples (beyond the Local Group), with C IV only detectable within ~0.5R vir.

Keywords: Local Group, Dwarf galaxies, Circumgalactic medium
Mapping the Three-dimensional Lyα Forest Large-scale Structure in Real and Redshift Space. This work presents a new physically motivated supervised machine-learning method, HYDRO-BAM, to reproduce the three-dimensional Lyα forest field in real and redshift space, which learns from a reference hydrodynamic simulation and thereby saves about seven orders of magnitude in computing time. We show that our method is accurate up to k ~ 1 h Mpc-1 in the one- (probability distribution function), two- (power spectra), and three-point (bispectra) statistics of the reconstructed fields. When compared to the reference simulation including redshift-space distortions, our method achieves deviations of ≲2% up to k = 0.6 h Mpc-1 in the monopole and ≲5% up to k = 0.9 h Mpc-1 in the quadrupole. The bispectrum is well reproduced for triangle configurations with sides up to k = 0.8 h Mpc-1. In contrast, the commonly adopted Fluctuating Gunn-Peterson approximation shows significant deviations, already when peculiar motions are not included (real space) at configurations with sides of k = 0.2-0.4 h Mpc-1 in the bispectrum and is also significantly less accurate in the power spectrum (within 5% up to k = 0.7 h Mpc-1). We conclude that an accurate analysis of the Lyα forest requires considering the complex baryonic thermodynamical large-scale structure relations. Our hierarchical domain-specific machine-learning method can efficiently exploit this and is ready to generate accurate Lyα forest mock catalogs covering the large volumes required by surveys such as DESI and WEAVE. * Released on 2022 January 20.

Keywords: Cosmology, Hydrodynamical simulations, Lyman alpha forest, Large-scale structure of the universe, Intergalactic medium
Repeated Mergers, Mass-gap Black Holes, and Formation of Intermediate-mass Black Holes in Dense Massive Star Clusters. Current theoretical models predict a mass gap with a dearth of stellar black holes (BHs) between roughly 50 M ⊙ and 100 M ⊙, while above the range accessible through massive star evolution, intermediate-mass BHs (IMBHs) still remain elusive. Repeated mergers of binary BHs, detectable via gravitational-wave emission with the current LIGO/Virgo/Kagra interferometers and future detectors such as LISA or the Einstein Telescope, can form both mass-gap BHs and IMBHs. Here we explore the possibility that mass-gap BHs and IMBHs are born as a result of successive BH mergers in dense star clusters. In particular, nuclear star clusters at the centers of galaxies have deep enough potential wells to retain most of the BH merger products after they receive significant recoil kicks due to anisotropic emission of gravitational radiation. Using for the first time simulations that include full stellar evolution, we show that a massive stellar BH seed can easily grow to ~103-104 M ⊙ as a result of repeated mergers with other smaller BHs. We find that lowering the cluster metallicity leads to larger final BH masses. We also show that the growing BH spin tends to decrease in magnitude with the number of mergers so that a negative correlation exists between the final mass and spin of the resulting IMBHs. Assumptions about the birth spins of stellar BHs affect our results significantly, with low birth spins leading to the production of a larger population of massive BHs.

Keywords: Intermediate-mass black holes, Gravitational wave detectors, Black holes, Stellar mass black holes, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Astrophysical black holes, Star clusters
GWSkyNet-Multi: A Machine-learning Multiclass Classifier for LIGO-Virgo Public Alerts. Compact object mergers which produce both detectable gravitational waves and electromagnetic (EM) emission can provide valuable insights into the neutron star equation of state, the tension in the Hubble constant, and the origin of the r-process elements. However, EM follow-up of gravitational wave sources is complicated by false-positive detections, and the transient nature of the associated EM emission. GWSkyNet-Multi is a machine learning model that attempts facilitate EM follow-up by providing real-time predictions of the source of a gravitational wave detection. The model uses information from Open Public Alerts (OPAs) released by LIGO-Virgo within minutes of a gravitational wave detection. GWSkyNet was introduced in Cabero et al. as a binary classifier and uses the OPA skymaps to classify sources as either astrophysical or as glitches. In this paper, we introduce GWSkyNet-Multi, an extension of GWSkyNet which further distinguishes sources as binary black hole mergers, mergers involving a neutron star, or non-astrophysical glitches. GWSkyNet-Multi is a sequence of three one-versus-all classifiers trained using a class-balanced and physically motivated source mass distribution. Training on this data set, we obtain test set accuracies of 93.7% for binary black hole-versus-all, 94.4% for neutron star-versus-all, and 95.1% for glitch-versus-all. We obtain an overall accuracy of 93.4% using a hierarchical classification scheme. Furthermore, we correctly identify 36 of the 40 gravitational wave detections from the first half of LIGO-Virgo's third observing run (O3a) and present predictions for O3b sources. As gravitational wave detections increase in number and frequency, GWSkyNet-Multi will be a powerful tool for prioritizing successful EM follow-up.

Keywords: Gravitational wave astronomy, Gravitational wave sources
Measuring the Nonaxially Symmetric Surface Temperature Distribution of the Central Compact Object in Puppis A. The surface temperature distributions of central compact objects (CCOs) are powerful probes of their crustal magnetic field strengths and geometries. Here we model the surface temperature distribution of RX J0822-4300, the CCO in the Puppis A supernova remnant, using 471 ks of XMM-Newton data. We compute the energy-dependent pulse profiles in 16 energy bands, fully including the general relativistic effects of gravitational redshift and light bending, to accurately model the two heated surface regions of different temperatures and areas, in addition to constraining the viewing geometry. This results in precise measurements of the two temperatures: ${{kT}}_{\mathrm{warm}}=(1+z)\times {0.222}_{-0.019}^{+0.018}$ keV and kT hot = (1 + z) × 0.411 ± 0.011 keV. The two heated surface regions are likely located very close to the rotational poles, with the most probable position of the hotter component ≍ 6° from the rotational pole. For the first time, we are able to measure a deviation from a pure antipodal hot-spot geometry, with a longitudinal offset ${\delta }_{\gamma }=11\buildrel{\circ}\over{.} {7}_{-2\buildrel{\circ}\over{.} \,5}^{+2\buildrel{\circ}\over{.} \,6}$ . The discovery of this asymmetry, along with the factor of ≍2 temperature difference between the two emitting regions, may indicate that RX J0822-4300 was born with a strong, tangled crustal magnetic field.

Keywords: Neutron stars, Magnetic fields, X-ray sources
Chandra Observations of Spikey: A Possible Self-lensing Supermassive Black Hole Binary System. This work examines the recent X-ray observations of the active galactic nucleus KIC 11606854 (nicknamed "Spikey") by the Chandra space telescope. Based on previous observations of a symmetric flare in the system's light curve by the Kepler space telescope, Spikey has been proposed to be a self-lensing supermassive black hole binary system in which the more massive black hole gravitationally lenses the accretion flow of its smaller companion. The recent Chandra observations (2020 March-May) correspond to the time when the next pulse was expected to occur and were separated in enough time to observe the apparent relativistic Doppler boosting effect from the high orbital velocities of the black holes. We model the expected self-lensing plus Doppler boosting light curve using our wavelength-dependent extended source self-lensing model combined with our relativistic orbital motion code. This orbital motion code is capable of modeling the expected apsidal precession for Spikey, which can be used to predict future pulses. We show that the expected signal was undetectable in the Chandra data as the intrinsic X-ray variability associated with the system was large relative to the changes expected by self-lensing and Doppler boosting. Expected flux increases in more favorable wavelengths were also calculated using our wavelength-dependent self-lensing model, revealing a relationship between the observing wavelength and measured orbital inclination.

Keywords: Gravitational microlensing, Black hole physics, Supermassive black holes
Significant Molecular Gas Deficiencies in Star-forming Cluster Galaxies at z   1.4. We present the average gas properties derived from Atacama Large Millimeter Array (ALMA) Band 6 dust continuum imaging of 126 massive (log M ⋆/M ⊙ ≳ 10.5), star-forming cluster galaxies across 11 galaxy clusters at z = 1-1.75. Using stacking analysis on the ALMA images, combined with UV-far-infrared data, we quantify the average infrared spectral energy distributions (SEDs) and gas properties (molecular gas masses, M mol;gas depletion timescales, τ depl; and gas fractions, fgas) as functions of cluster-centric radius and properties including stellar mass and distance from the main sequence. We find a significant dearth in the ALMA fluxes relative to that expected in the field-with correspondingly low M mol and fgas, and short τ depl-with weak or no dependence on cluster-centric radius out to twice the virial radius. The Herschel+ALMA SEDs indicate warmer dust temperatures (~36-38 K) than coeval field galaxies (~30 K). We perform a thorough comparison of the cluster galaxy gas properties to field galaxies, finding deficits of 2-3×, 3-4×, and 2-4× in M mol, τ depl, and fgas compared to coeval field stacks, and larger deficits compared to field scaling relations built primarily on detections. The cluster gas properties derived here are comparable with stacking analyses of (proto-)clusters in the literature, and at odds with findings of field-like τ depl and enhanced fgas reported using CO and dust continuum detections. Our analysis suggests that environment has a considerable impact on gas properties out to large radii, in good agreement with cosmological simulations which project that gas depletion begins beyond the virial radius and largely completes by first passage of the cluster core.

Keywords: Galaxy clusters, Molecular gas, High-redshift galaxy clusters, Galactic and extragalactic astronomy, Galaxy quenching
The Physical Properties of Luminous z ≳ 8 Galaxies and Implications for the Cosmic Star Formation Rate Density from 0.35 deg<SUP>2</SUP> of (Pure-)Parallel HST Observations. We present the largest systematic, Hubble Space Telescope (HST)-based search to date for luminous z ≳ 8 galaxy candidates using ~1267 arcmin2 of (pure-)parallel observations from a compilation of 288 random sightlines with Advanced Camera for Surveys and Wide Field Camera 3 observations, derived from the (Super)Brightest of Reionizing Galaxies (SuperBoRG) data set and together representing a factor ~1.12× larger than existing space-based data sets. Using near-infrared (NIR) color cuts and careful photo-z analyses, we find 31 z ≳ 8 galaxy candidates over 29 unique sightlines, and derive global galaxy properties such as UV magnitudes and continuum slopes, sizes, and rest-frame optical properties (e.g., star formation rates (SFRs), stellar masses, A v). Taking advantage of the (pure-)parallel nature of our data set-making it one of the most representative thus far-and derived SFRs, we evaluate the cosmic SFR density for the bright end of the UV luminosity function (LF) at z ~ 8-10 and test the validity of luminosity-function-derived results using a conversion factor. We find that our method yields comparable results to those derived with LFs. Furthermore, we present follow-up observations of five (Super)BoRG targets with the Keck Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) instrument, finding no evidence of Lyα in &gt;3 hr of Y-band observations in either, consistent with a largely neutral medium at z ~ 8. Our results offer a definitive HST legacy on the bright end of the LF and provide a valuable benchmark as well as targets for follow-up with the James Webb Space Telescope. *Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

Keywords: Star formation, Early universe, Reionization, High-redshift galaxies
Rapid Growth of Seed Black Holes during Early Bulge Formation. We study the early growth of massive seed black holes (BHs) via accretion in protogalactic nuclei where the stellar bulge component is assembled, performing axisymmetric two-dimensional radiation hydrodynamical simulations. We find that when a seed BH with M • ~ 105 M ⊙ is embedded in dense metal-poor gas (Z = 0.01 Z ⊙) with a density of ≳ 100 cm-3 and bulge stars with a total mass of M ⋆ ≳ 100 M •, a massive gaseous disk feeds the BH efficiently at rates of ≳ 0.3-1 M ⊙ yr-1, and the BH mass increases nearly tenfold within ~2 Myr. This rapid accretion phase lasts until a good fraction of the gas bounded within the bulge accretes onto the BH, although the feeding rate is regulated owing to strong outflows driven by ionizing radiation emitted from the accreting BH. The transient growing mode can be triggered for seed BHs formed in massive dark-matter halos with masses of ≳ 109 M ⊙ at z ~ 15-20 (the virial temperature is T vir ≃ 105 K). The host halos are heavier and rarer than those of typical first galaxies, but are more likely to end up in quasar hosts by z ≃ 6. This mechanism naturally yields a mass ratio of M •/M ⋆ &gt; 0.01 higher than the value seen in the local universe. The existence of such overmassive BHs provides us with a unique opportunity to detect highly accreting seed BHs at z ~ 15 with AB magnitude of m AB ~ 26-29 mag at 2 μm (rest frame 10 eV) by the upcoming observations by the James Webb Space Telescope and Nancy Grace Roman Space Telescope.

Keywords: Supermassive black holes, High-redshift galaxies, Quasars
Global 3D Simulation of the Upper Atmosphere of HD189733b and Absorption in Metastable He I and Lyα Lines. A 3D fully self-consistent multifluid hydrodynamic aeronomy model is applied to simulate the hydrogen-helium expanding upper atmosphere of the hot Jupiter HD189733b, and related absorption in the Lyα line and the 10830 Å line of metastable helium. We studied the influence of a high-energy stellar flux, a stellar wind, and Lyα cooling to reproduce the available observations. We found that to fit the width of the absorption profile of the 10830 Å line the escaping upper atmosphere of the planet should be close to the energy-limited escape achieved with significantly reduced Lyα cooling at the altitudes with an H I density higher than 3 × 106 cm-3. Based on the performed simulations, we constrain the helium abundance in the upper atmosphere of HD189733b to be a rather low value of He/H ~ 0.005. We show that under the conditions of a moderate stellar wind similar to that of the Sun the absorption of the Lyα line takes place mostly within the Roche lobe due to thermal broadening at a level of about 7%. For an order of magnitude stronger wind, a significant absorption of about 15% at high blueshifted velocities of up to 100 km s-1 is generated in the bowshock region, due to Doppler broadening. These blueshifted velocities are still lower than those (~200 km s-1) detected in one of the observations. We explain the differences between the performed observations, though not in all of the details, by stellar activity and the related fluctuations of the ionizing radiation (in the case of the 10830 Å line), and the stellar wind (in the case of the Lyα line).

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheres
Milliarcsecond Localization of the Repeating FRB 20201124A. Very long baseline interferometric (VLBI) localizations of repeating fast radio bursts (FRBs) have demonstrated a diversity of local environments: from nearby star-forming regions to globular clusters. Here we report the VLBI localization of FRB 20201124A using an ad hoc array of dishes that also participate in the European VLBI Network (EVN). In our campaign, we detected 18 bursts from FRB 20201124A at two separate epochs. By combining the visibilities from both epochs, we were able to localize FRB 20201124A with a 1σ uncertainty of 2.7 mas. We use the relatively large burst sample to investigate astrometric accuracy and find that for ≳20 baselines (≳7 dishes) we can robustly reach milliarcsecond precision even using single-burst data sets. Subarcsecond precision is still possible for single bursts, even when only ~6 baselines (four dishes) are available. In such cases, the limited uv coverage for individual bursts results in very high side-lobe levels. Thus, in addition to the peak position from the dirty map, we also explore smoothing the structure in the dirty map by fitting Gaussian functions to the fringe pattern in order to constrain individual burst positions, which we find to be more reliable. Our VLBI work places FRB 20201124A 710 ± 30 mas (1σ uncertainty) from the optical center of the host galaxy, consistent with originating from within the recently discovered extended radio structure associated with star formation in the host galaxy. Future high-resolution optical observations, e.g., with Hubble Space Telescope, can determine the proximity of FRB 20201124A's position to nearby knots of star formation.

Keywords: Very long baseline interferometry, Radio astrometry, Radio transient sources
Misalignment of Terrestrial Circumbinary Planets as an Indicator of Their Formation Mechanism. Circumbinary gas disks are often observed to be misaligned with the binary orbit, suggesting that planet formation may proceed in a misaligned disk. With n-body simulations, we consider the formation of circumbinary terrestrial planets from a particle disk that is initially misaligned. We find that if terrestrial planets form in this way, in the absence of gas, they can only form close to coplanar or close to polar to the binary orbit. Planets around a circular binary form coplanar while planets around an eccentric binary can form coplanar or polar depending on the initial disk misalignment and the binary eccentricity. The more massive a terrestrial planet is, the more aligned it is (to coplanar or polar) because it has undergone more mergers that lead on average to smaller misalignment angles. Nodal precession of particle disks with very large initial inclinations lead to high mutual inclinations between the particles. This produces high relative velocities between particles that lead to mass ejections that can completely inhibit planet formation. Misaligned terrestrial circumbinary planets may be able to form in the presence of a misaligned circumbinary gas disk that may help to nodally align the particle orbits and maintain the inclination of the planets during their formation.

Keywords: Extrasolar rocky planets, Exoplanet formation, Binary stars, Planet formation
Anomalous Flux in the Cosmic Optical Background Detected with New Horizons Observations. We used New Horizons LORRI images to measure the optical-band (0.4 ≲ λ ≲ 0.9μm) sky brightness within a high-galactic-latitude field selected to have reduced diffuse scattered light from the Milky Way galaxy (DGL), as inferred from the IRIS all-sky 100 μm map. We also selected the field to significantly reduce the scattered light from bright stars (SSL) outside the LORRI field. Suppression of DGL and SSL reduced the large uncertainties in the background flux levels present in our earlier New Horizons cosmic optical background (COB) results. The raw total sky level, measured when New Horizons was 51.3 au from the Sun, is 24.22 ± 0.80 nW m-2 sr-1. Isolating the COB contribution to the raw total required subtracting scattered light from bright stars and galaxies, faint stars below the photometric detection limit within the field, and the hydrogen plus ionized-helium two-photon continua. This yielded a highly significant detection of the COB at 16.37 ± 1.47 nW m-2 sr-1 at the LORRI pivot wavelength of 0.608 μm. This result is in strong tension with the hypothesis that the COB only comprises the integrated light of external galaxies (IGL) presently known from deep HST counts. Subtraction of the estimated IGL flux from the total COB level leaves a flux component of unknown origin at 8.06 ± 1.92 nW m-2 sr-1. Its amplitude is equal to the IGL.

Keywords: Observational cosmology
Early Warnings of Binary Neutron Star Coalescence Using the SPIIR Search. Gravitational waves from binary neutron star mergers can be used as alerts to enable prompt follow-up observations. In particular, capturing prompt electromagnetic and astroparticle emissions from the moment of a binary merger presents unique constraints on the timescale and sky localization for online gravitational-wave detection. Here we present the expected performance of the SPIIR online detection pipeline that is designed for this purpose in the upcoming international LIGO-Virgo's 4th Science Run (O4). Using simulated Gaussian data for the two LIGO observatories with expected O4 sensitivity, we demonstrate that there is a nonnegligible opportunity to deliver premerger warnings at least 10 s before the final plunge. These alerts are expected to be issued at a nominal rate of one binary neutron star coalescence per year and localized within a median searched area of 300 deg2. We envision such detection to be extremely useful for follow-up observatories with a large field of view such as the Murchison Widefield Array radio facility in Western Australia.

Keywords: Gravitational wave astronomy, Neutron stars, Compact binary stars, Gravitational wave sources