Sazuna/UAT_keywords huggingface dataset:
White Dwarfs with Infrared Excess from LAMOST Data Release 5. Infrared (IR) excess is an important probe for substellar companions and/or debris disks around white dwarfs (WDs). Such systems are still rare, so an in-depth understanding of their formation and long-term evolution has yet to be developed. One of the largest spectroscopic surveys, carried out by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), has recently released more than 3000 WDs, a significant fraction of which have not been searched for IR excess. Here, we present a cross-correlation between the LAMOST Data Release 5 WD catalog and Pan-STARRS, the Sloan Digital Sky Survey (SDSS), the UKIRT Infrared Deep Sky Survey, the Two-Micron All Sky Survey (2MASS), and the Wide-field Infrared Survey Explorer (WISE). By performing spectral energy distribution fittings for 846 WDs with WISE detections, we identify 50 candidates with IR excess, including seven candidate WD+M dwarf binaries, 31 candidate WD+brown dwarf (BD) binaries, and 12 candidate WD+dust disk systems. Eight of the dust disk systems are our new identifications. By utilizing a systematic survey with accurate stellar parameters derived from spectral fitting, our work is an important addition to previous searches for IR excess from SDSS and Gaia WDs, and it provides a significant (≳8%) complement to the current database of WDs with candidate BD companions and dust disks. The frequencies of the WD+BD binaries and the WD+dust disk systems are constrained to be ≲3.7% and ~1.4%, respectively. The properties of the candidate dust disk systems are discussed. All of our candidates require follow-up observations for confirmation, owing to the limited spatial resolution of WISE.

Keywords: Brown dwarfs, White dwarf stars, Infrared excess, Circumstellar dust, Debris disks
Synchrotron Firehose Instability. We demonstrate using linear theory and particle-in-cell (PIC) simulations that a synchrotron-cooling collisionless plasma acquires pressure anisotropy and, if the plasma beta is sufficiently high, becomes unstable to the firehose instability, in a process that we dub the synchrotron firehose instability (SFHI). The SFHI channels free energy from the pressure anisotropy of the radiating, relativistic electrons (and/or positrons) into small-amplitude, kinetic-scale, magnetic-field fluctuations, which pitch-angle scatter the particles and bring the plasma to a near-thermal state of marginal instability. The PIC simulations reveal a nonlinear cyclic evolution of firehose bursts interspersed by periods of stable cooling. We compare the SFHI for electron-positron and electron-ion plasmas. As a byproduct of the growing electron-firehose magnetic-field fluctuations, magnetized ions gain a pressure anisotropy opposite to that of the electrons. If these ions are relativistically hot, we find that they also experience cooling due to collisionless thermal coupling with the electrons, which we argue is mediated by a secondary ion-cyclotron instability. We suggest that the SFHI may be activated in a number of astrophysical scenarios, such as within ejecta from black hole accretion flows and relativistic jets, where the redistribution of energetic electrons from low to high pitch angles may cause transient bursts of radiation.

Keywords: Plasma astrophysics
Evolving Morphology of Resolved Stellar Einstein Rings. We consider strong gravitational lensing by nearby stars. Using our wave-optical treatment of lensing phenomena, we study Einstein rings that may form around nearby stellar lenses. It is remarkable that these rings are bright and large enough to be detected and resolved by existing instruments. Such lensing events have durations of hours or days, with peak light amplification lasting for several minutes. Many such events may be predicted using the Gaia astrometric catalog. Serendipitous discoveries are also possible. Fortuitous alignments can be used to confirm or discover and study exoplanets. For lenses that have dense stellar regions in their background, these events may occur several time a year, warranting their continuous or recurrent monitoring. Resolved imaging and spectroscopy of the evolving morphology of an Einstein ring offers knowledge about both the lens and the source. The angular size of the Einstein ring amounts to a direct measurement of the lens mass. The changing orientation of the major and minor images of the source offers astrometric information related to the mutual orientation of the objects. The event duration, when the full ring is present, helps to determine the source's size. The sky position of planetary lensing events constrains the planet's orbit. Spectroscopy of the ring allows for direct investigations of the source. The frequency and predictability of these events and the wealth of information that can be obtained by imaging motivate observational campaigns using existing facilities and/or construction of new instruments dedicated to the search and study of Einstein rings that are forming around nearby stars. As a specific example, we consider a predicted 2028 lensing of a red giant by α Centauri A and discuss the relevant science campaign.

Keywords: Gravitational lensing
Massive Star Formation in the Tarantula Nebula. In this work, we present 299 candidate young stellar objects (YSOs) in 30 Doradus discovered using Spitzer and Herschel point-source catalogs, 276 of which are new. We study the parental giant molecular clouds in which these YSO candidates form using recently published Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 7 observations of 12CO and 13CO. The threshold for star formation in 30 Doradus inferred by the LTE-based mass surface density is 178 M ⊙ pc-2, 40% higher than the threshold for star formation in the Milky Way. This increase in star formation threshold in comparison to the Milky Way and increase in line width seen in clumps 11 pc away in comparison to clumps 45 pc away from the R136 super star cluster could be due to injected turbulent energy, increase in interstellar medium pressure, and/or local magnetic field strength. Of the 299 YSO candidates in this work, 62% are not associated with 12CO molecular gas. This large fraction can be explained by the fact that 75%-97% of the H2 gas is not traced by CO. We fit a Kroupa initial mass function to the YSO candidates and find that the total integrated stellar mass is 18,000 M ⊙ and that the region has a star formation rate (SFR) of 0.18 M ⊙ yr-1. The initial mass function determined here applies to the four 150″ × 150″ (37.5 pc × 37.5 pc) subfields and one 150″ × 75″ (37.5 pc × 18.8 pc) subfield observed with ALMA. The SFR in 30 Doradus has increased in the past few million years.

Keywords: Young stellar objects, Star formation, Interstellar medium
Robust Field-level Inference of Cosmological Parameters with Dark Matter Halos. We train graph neural networks on halo catalogs from Gadget N-body simulations to perform field-level likelihood-free inference of cosmological parameters. The catalogs contain ≲5000 halos with masses ≳1010 h -1 M ⊙ in a periodic volume of ${(25\,{h}^{-1}\,\mathrm{Mpc})}^{3}$ ; every halo in the catalog is characterized by several properties such as position, mass, velocity, concentration, and maximum circular velocity. Our models, built to be permutationally, translationally, and rotationally invariant, do not impose a minimum scale on which to extract information and are able to infer the values of Ωm and σ 8 with a mean relative error of ~6%, when using positions plus velocities and positions plus masses, respectively. More importantly, we find that our models are very robust: they can infer the value of Ωm and σ 8 when tested using halo catalogs from thousands of N-body simulations run with five different N-body codes: Abacus, CUBEP3M, Enzo, PKDGrav3, and Ramses. Surprisingly, the model trained to infer Ωm also works when tested on thousands of state-of-the-art CAMELS hydrodynamic simulations run with four different codes and subgrid physics implementations. Using halo properties such as concentration and maximum circular velocity allow our models to extract more information, at the expense of breaking the robustness of the models. This may happen because the different N-body codes are not converged on the relevant scales corresponding to these parameters.

Keywords: Cosmology, Density parameters, Sigma8, Cosmological parameters from large-scale structure
GRMHD Simulations of Neutron-star Mergers with Weak Interactions: r-process Nucleosynthesis and Electromagnetic Signatures of Dynamical Ejecta. Fast neutron-rich material ejected dynamically over ≲10 ms during the merger of a binary neutron star (BNS) can give rise to distinctive electromagnetic counterparts to the system's gravitational-wave emission that serve as a "smoking gun" to distinguish between a BNS and an NS-black hole merger. We present novel ab initio modeling of the kilonova precursor and kilonova afterglow based on 3D general-relativistic magnetohydrodynamic simulations of BNS mergers with nuclear, tabulated, finite-temperature equations of state (EOSs), weak interactions, and approximate neutrino transport. We analyze dynamical mass ejection from 1.35-1.35 M ⊙ binaries, consistent with properties of the first observed BNS merger GW170817, using three nuclear EOSs that span the range of allowed compactness of 1.35 M ⊙-neutron stars. Nuclear reaction network calculations yield a robust second-to-third-peak r-process. We find few ×10-6 M ⊙ of fast (v &gt; 0.6c) ejecta that give rise to broadband synchrotron emission on ~years timescales, consistent with tentative evidence for excess X-ray/radio emission following GW170817. We find ≈2 × 10-5 M ⊙ of free neutrons that power a kilonova precursor on ≲ hours timescale. A boost in early UV/optical brightness by a factor of a few due to previously neglected relativistic effects, with enhancements up to ≲10 hr post-merger, is promising for future detection with UV/optical telescopes like Swift or ULTRASAT. We find that a recently predicted opacity boost due to highly ionized lanthanides at ≳70,000 K is unlikely to affect the early kilonova based on the obtained ejecta structures. Azimuthal inhomogeneities in dynamical ejecta composition for soft EOSs found here ("lanthanide/actinide pockets") may have observable consequences for both early kilonova and late-time nebular emission.

Keywords: Gravitational wave astronomy, Neutron stars, Compact binary stars, Magnetohydrodynamical simulations
Reverberation Mapping of IC 4329A. We present the results of a new reverberation mapping campaign for the broad-line active galactic nucleus (AGN) in the edge-on spiral IC 4329A. Monitoring of the optical continuum with V-band photometry and broad emission-line flux variability with moderate-resolution spectroscopy allowed emission-line light curves to be measured for Hβ, Hγ, and He II λ4686. We find a time delay of ${16.3}_{-2.3}^{+2.6}$ days for Hβ, a similar time delay of ${16.0}_{-2.6}^{+4.8}$ days for Hγ, and an unresolved time delay of $-{0.6}_{-3.9}^{+3.9}$ days for He II. The time delay for Hβ is consistent with the predicted value from the relationship between AGN luminosity and broad-line region radius, after correction for the ~2.4 mag of intrinsic extinction at 5100 Å. Combining the measured time delay for Hβ with the broad emission-line width and an adopted value of &lt;f&gt; = 4.8, we find a central supermassive black hole mass of ${M}_{\mathrm{BH}}={6.8}_{-1.1}^{+1.2}\times {10}^{7}$ M ⊙. Velocity-resolved time delays were measured across the broad Hβ emission-line profile and may be consistent with an "M"-like shape. Modeling of the full reverberation response of Hβ was able to provide only modest constraints on some parameters, but does exhibit agreement with the black hole mass and average time delay. The models also suggest that the AGN structure is misaligned by a large amount from the edge-on galaxy disk. This is consistent with expectations from the unified model of AGNs, in which broad emission lines are expected to be visible only for AGNs that are viewed at relatively face-on inclinations.

Keywords: Supermassive black holes, Reverberation mapping, Seyfert galaxies
Enhanced Star Formation Efficiency in the Central Regions of Nearby Quasar Hosts. We combine Atacama Large Millimeter/submillimeter Array and Multi Unit Spectroscopic Explorer observations tracing the molecular gas, millimeter continuum, and ionized gas emission in six low-redshift (z ≲ 0.06) Palomar-Green (PG) quasar host galaxies to investigate their ongoing star formation at roughly kiloparsec-scale resolution. The AGN contribution to the cold dust emission and the optical emission-line flux is carefully removed to derive spatial distributions of the star formation rate (SFR), which, complemented with the molecular gas data, enables the mapping of the depletion time (t dep). We report ubiquitous star formation activity within the quasar host galaxies, with the majority of the ongoing star formation occurring in the galactic center. The rise of the SFR surface density (ΣSFR) toward the nucleus is steeper than that observed for the cold molecular gas surface density, reaching values up to ΣSFR ≈ 0.15-0.80 M ☉ yr-1 kpc-2. The gas in the nuclear regions is converted into stars at a shortened depletion time (t dep ≈ 0.2-2.0 Gyr), suggesting that those zones can be deemed as starbursts. At large galactocentric radius, we find that the ongoing star formation takes place within spiral arms or H II region complexes, with an efficiency comparable to that reported for nearby inactive spirals (t dep ≈ 1.8 Gyr). We find no evidence of star formation activity shutoff in the PG quasar host galaxies. On the contrary, these observations shed light on how the central environments of galaxies hosting actively accreting supermassive black holes build up stellar mass.

Keywords: Active galaxies, Star formation, Quasars
Long-term Protoplanetary Disk Evolution from Molecular Cloud Core Collapse and Implications for Planet Formation. I. Weak and Moderate Disk Self-gravities. We construct a one-dimensional protoplanetary disk model to investigate long-term disk evolution from molecular cloud core collapse. To obtain details of disk evolution, instead of solving the traditional diffusion equation for disk surface density, we suggest a set of equations derived from the basic principles of fluid mechanics. Effects of infalling material, magnetorotational instability, and disk self-gravity are taken into account. According to the role of disk self-gravity, we find that disks can be classified into three types. For a type I disk, disk self-gravity is not important. For a type II disk, disk self-gravity has effects on both disk scale height and gas radial motion. In addition, gravitational instability can cause the transport of angular momentum. For a type III disk, disk self-gravity plays a dominant role in disk evolution. In this paper, we focus on the first two types and the investigation of the third one is presented in a companion paper. For each disk, we find that there are three phases during evolution. Phase 1 is the very early phase during which the radial velocity is on the order of 106 cm s-1 and the transport of angular momentum caused by viscosity is not important. Phase 2 begins when a rotationally supported disk is formed. From this phase, viscosity plays a role in the transport of angular momentum. When the infall ends, phase 3 begins. Since angular velocity is calculated directly, we can reveal the non-Keplerian effect, which has important effects on the radial drift of solids and planetesimal formation.

Keywords: Exoplanet formation, Protoplanetary disks, Planet formation
Long-term Protoplanetary Disk Evolution from Molecular Cloud Core Collapse and Implications for Planet Formation. II. Strong Disk Self-gravity. We continue to investigate long-term protoplanetary disk evolution and focus on the situation of strong disk self-gravity (DSG). We call such a disk a type III disk. A large amount of mass is stored in the disk due to large angular momentum. When the disk becomes massive enough, a dense region (DR) is formed due to gravitational instability. This instability is triggered by the combined effect of radial gravitational attraction and a decrease in disk scale height. Viscosity cannot smooth out the DR due to strong DSG. We further investigate the subsequent disk evolution under the assumption of axisymmetry. Besides the viscous process, angular momentum flux caused by the perturbation of DSG also plays a role in the transport of angular momentum. The combination of the two processes results in the efficient transport of angular momentum in the outer disk and prevents the disk from becoming very massive. Due to the interaction between the DR and the inner disk, a gap between them is formed. This gives a nonplanetary origin of the gap. In ~106 yr, a surface density plateau and a very low surface density region are formed in the inner disk. In a type III disk, there are several locations where the radial drift of solids can be stopped. Objects formed in the DR may remember some of the properties of the DR, such as large mass and large angular momentum. In particular, a planetary system with wide-orbit giant planets may be formed in the DR. Finally, it is still difficult to identify what type of disk the solar nebula belongs to.

Keywords: Gravitational instability, Solar system formation, Exoplanet systems, Protoplanetary disks, Planet formation
Far-ultraviolet Dust Extinction and Molecular Hydrogen in the Diffuse Milky Way Interstellar Medium. We aim to compare variations in the full-UV dust extinction curve (912-3000 Å), with the H I/H2/total H content along diffuse Milky Way sightlines, to investigate possible connections between ISM conditions and dust properties. We combine an existing sample of 75 UV extinction curves based on IUE and FUSE data, with atomic and molecular column densities measured through UV absorption. The H2 column density data are based on existing Lyman-Werner absorption band models from earlier work on the extinction curves. Literature values for the H I column density were compiled, and improved for 23 stars by fitting a Lyα profile to archived spectra. We discover a strong correlation between the H2 column and the far-UV extinction, and the underlying cause is a linear relationship between H2 and the strength of the far-UV rise feature. This extinction does not scale with H I, and the total H column scales best with $A\left(V\right)$ instead. The carrier of the far-UV rise therefore coincides with molecular gas, and further connections are shown by comparing the UV extinction features to the molecular fraction. Variations in the gas-to-extinction ratio $N({\rm{H}})/A\left(V\right)$ correlate with the UV-to-optical extinction ratio, and we speculate this could be due to coagulation or shattering effects. Based on the H2 temperature, the strongest far-UV rise strengths are found to appear in colder and denser sightlines.

Keywords: Dust composition, Ultraviolet spectroscopy, Interstellar dust extinction, Neutral hydrogen clouds, Interstellar absorption, Interstellar medium, Diffuse molecular clouds
Critical Metallicity of Cool Supergiant Formation. I. Effects on Stellar-mass Loss and Feedback. This paper systematically studies the relation between metallicity and mass loss of massive stars. We perform one-dimensional stellar evolution simulations and build a grid of ~2000 models with initial masses ranging between 11 and 60 M ⊙ and absolute metallicities Z between 0.00001 and 0.02. Steady-state winds, comprising hot main-sequence winds and cool supergiant winds, are the main drivers of the mass loss of massive stars in our models. We calculate the total mass loss over the stellar lifetime for each model. Our results reveal the existence of a critical metallicity Z c at Z ~ 10-3, where the mass loss exhibits a dramatic jump. If Z &gt; Z c, massive stars tend to evolve into cool supergiants, and a robust cool wind is operational. In contrast, if Z &lt; Z c, massive stars usually remain as blue supergiants, wherein the cool wind is not activated and the mass loss is generally weak. Moreover, we calculate the wind feedback in a 105 M ⊙ star cluster with the Salpeter initial mass function. The kinetic energy released by winds does not exhibit any significant transition at Z c because the wind velocity of a cool supergiant wind is low and contributes little to the kinetic energy. The effects of critical metallicity provide implications for the fates of metal-poor stars in the early universe.

Keywords: Late-type supergiant stars, Massive stars, Metallicity, Stellar mass loss
Massive Molecular Gas Companions Uncovered by Very Large Array CO(1-0) Observations of the z = 5.2 Radio Galaxy TN J0924-2201. We present Karl G. Jansky Very Large Array K-band (19 GHz) observations of the redshifted CO(1-0) line emission toward the radio galaxy TN J0924-2201 at z = 5.2, which is one of the most distant radio galaxies with CO detected. With an angular resolution of ~2″, the CO(1-0) line emission is resolved into three clumps, within ±500 km s-1 relative to its redshift, which is determined by Lyα. We find that the clumps are located off-center and 12-33 kpc away from the center of the host galaxy, which has counterparts in the Hubble Space Telescope i band, Spitzer/IRAC, and the Atacama Large Millimeter/submillimeter Array (ALMA) band 6 (230 GHz; 1.3 mm). With the ALMA detection, we estimate the infrared luminosity L IR and the star formation rate (SFR) of the host galaxy to be (9.3 ± 1.7) × 1011 L ⊙ and 110 ± 20 M ⊙ yr-1, respectively. We also derive the 3σ upper limit of ${M}_{{{\rm{H}}}_{2}}\lt 1.3\times {10}^{10}$ M ⊙ at the host galaxy. The detected CO(1-0) line luminosities of the three clumps, $L{{\prime} }_{\mathrm{CO}(1-0)}$ = (3.2-4.7) × 1010 K km s-1 pc2, indicate the presence of three massive molecular gas reservoirs, with ${M}_{{{\rm{H}}}_{2}}$ = (2.5-3.7) × 1010 M ⊙, assuming a CO-to-H2 conversion factor of α CO = 0.8 ${M}_{\odot }{({\rm{K}}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{pc}}^{2})}^{-1}$ , although the SFR is not elevated due to the nondetection of the ALMA 1.3 mm continuum (SFR &lt; 40 M ⊙ yr-1). From the host galaxy, the nearest molecular gas clump, labeled "clump A," is apparently in alignment with the radio jet axis, showing radio-CO alignment. The origins of these three clumps around TN J0924-2201 can possibly be interpreted as outflows, mergers, or jet-induced metal enrichment.

Keywords: Radio active galactic nuclei, Radio galaxies, High-redshift galaxies, AGN host galaxies
Do Central Compact Objects have Carbon Atmospheres?. Only three of the dozen central compact objects (CCOs) in supernova remnants (SNRs) show thermal X-ray pulsations due to nonuniform surface temperature (hot spots). The absence of X-ray pulsations from several unpulsed CCOs has motivated suggestions that they have uniform-temperature carbon atmospheres (UTCAs), which adequately fit their spectra with appropriate neutron star (NS) surface areas. This is in contrast to the two-temperature blackbody or hydrogen atmospheres that also fit well. Here we investigate the applicability of UTCAs to CCOs. We show the following: (i) The phase-averaged spectra of the three pulsed CCOs can also be fitted with a UTCA of the appropriate NS area, despite pulsed CCOs manifestly having nonuniform surface temperature. A good spectral fit is therefore not strong support for the UTCA model of unpulsed CCOs. (ii) An improved spectrum of one unpulsed CCO, previously analyzed with a UTCA, does not allow an acceptable fit. (iii) For two unpulsed CCOs, the UTCA does not allow a distance compatible with the SNR distance. These results imply that, in general, CCOs must have hot, localized regions on the NS surface. We derive new X-ray pulse modulation upper limits on the unpulsed CCOs, and constrain their hot spot sizes and locations. We develop an alternative model that accounts for both the pulsed and unpulsed CCOs: a range of angles between hot spot and rotation axes consistent with an exponential distribution with scale factor λ ~ 20°. We discuss the physical mechanisms that could produce such small angles and small hot spots.

Keywords: Neutron stars, Supernova remnants, X-ray sources