Sazuna/UAT_keywords huggingface dataset:
Charting the Galactic Acceleration Field. I. A Search for Stellar Streams with Gaia DR2 and EDR3 with Follow-up from ESPaDOnS and UVES. We present maps of the stellar streams detected in the Gaia Data Release 2 (DR2) and Early Data Release 3 (EDR3) catalogs using the STREAMFINDER algorithm. We also report the spectroscopic follow-up of the brighter DR2 stream members obtained with the high-resolution CFHT/ESPaDOnS and VLT/UVES spectrographs as well as with the medium-resolution NTT/EFOSC2 spectrograph. Two new stellar streams that do not have a clear progenitor are detected in DR2 (named Hríd and Gunnthrá), and seven are detected in EDR3 (named Gaia-6 to Gaia-12). Several candidate streams are also identified. The software also finds very long tidal tails associated with the 15 globular clusters: NGC 288, NGC 1261, NGC 1851, NGC 2298, NGC 2808, NGC 3201, M68, ωCen, NGC 5466, Palomar 5, M5, NGC 6101, M92, NGC 6397, and NGC 7089. These stellar streams will be used in subsequent contributions in this series to chart the properties of the Galactic acceleration field on ~100 pc to ~100 kpc scales.

Keywords: Dark matter, Milky Way Galaxy
Cloud Properties of Brown Dwarf Binaries across the L/T Transition. We present a new suite of atmosphere models with flexible cloud parameters to investigate the effects of clouds on brown dwarfs across the L/T transition. We fit these models to a sample of 13 objects with well-known masses, distances, and spectral types spanning L3-T5. Our modeling is guided by spatially resolved photometry from the Hubble Space Telescope and the W. M. Keck Telescopes covering visible to near-infrared wavelengths. We find that, with appropriate cloud parameters, the data can be fit well by atmospheric models with temperature and surface gravity in agreement with the predictions of evolutionary models. We see a clear trend in the cloud parameters with spectral type, with earlier-type objects exhibiting higher-altitude clouds with smaller grains (0.25-0.50 μm) and later-type objects being better fit with deeper clouds and larger grains (≥1 μm). Our results confirm previous work that suggests L dwarfs are dominated by submicron particles, whereas T dwarfs have larger particle sizes.

Keywords: Brown dwarfs, Atmospheric clouds, Infrared photometry, Stellar evolutionary models, L dwarfs, HST photometry, Stellar atmospheres, T dwarfs
The Study of Dust Formation of Four Type Ibn Supernovae. In this paper, we investigate the early-time optical-near-infrared (NIR) spectral energy distributions (SEDs) of four Type Ibn supernovae (SNe). We find that the SEDs of SN 2010al, LSQ13ddu, and SN 2015G can be well explained by the single-component blackbody model, while the SEDs of OGLE-2012-SN-006 cannot. We invoke the double-component model assuming that the SEDs were produced by the SN photosphere and the heated dust to fit the optical-NIR SEDs of the four SNe Ibn, finding that the derived temperatures of the dust associated with OGLE-2012-SN-006 favor the scenario that the dust consists of the graphite grains, and the mass and temperature of dust are ~0.5-2.0 × 10-3 M⊙ and ~1200-1300 K, respectively. Moreover, our fits for SN 2010al, LSQ13ddu, and SN 2015G show that the upper limits of the masses of the dust associated with the three SNe Ibn are respectively 1.45 × 10-5 M⊙, 5.9 × 10-7 M⊙, and 2.4 × 10-7 M⊙. A further analysis demonstrates that the inferred radius of the dust shell surrounding OGLE-2012-SN-006 is significantly larger than that of the SN ejecta at early epochs, indicating that the NIR excesses of the SEDs of OGLE-2012-SN-006 were produced by a preexisting dust shell. Our study for the early-time SEDs of four SNe Ibn, together with the previous studies and the fact that some SNe showed evidence of dust formation at the late-time SEDs, indicates that at least ~1/3 of SNe Ibn show evidence for dust formation.

Keywords: Circumstellar matter, Supernovae
Cosmic Star Formation History Measured at 1.4 GHz. We matched the 1.4 GHz local luminosity functions of star-forming galaxies (SFGs) and active galactic nuclei to the 1.4 GHz differential source counts from 0.25 μJy to 25 Jy using combinations of luminosity and density evolution. We present the most robust and complete local far-infrared (FIR)/radio luminosity correlation to date in a volume-limited sample of ≈4.3 × 103 nearby SFGs, finding that it is very tight but distinctly sublinear: ${L}_{\mathrm{FIR}}\propto {L}_{1.4\,\mathrm{GHz}}^{0.85}$ . If the local FIR/radio correlation does not evolve, the evolving 1.4 GHz luminosity function of SFGs yields the evolving star formation rate density (SFRD) ψ(M⊙ yr-1 Mpc-3) as a function of time since the Big Bang. The SFRD measured at 1.4 GHz grows rapidly at early times, peaks at "cosmic noon" when t ≈ 3 Gyr and z ≈ 2, and subsequently decays with an e-folding timescale τ = 3.2 Gyr. This evolution is similar to, but somewhat stronger than, SFRD evolution estimated from UV and FIR data.

Keywords: Cosmological evolution, Radio galaxies, Star formation, Galaxy evolution, Galaxy counts
The Gaia-ASAS-SN Classical Cepheid Sample. I. Sample Selection. We present a well-defined and characterized all-sky sample of classical Cepheids in the Milky Way, obtained by combining two time-domain all-sky surveys: Gaia DR2 (Gaia Collaboration et al. 2018) and All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014). We first use parallax and variability information from Gaia to select ~30,000 bright (G &lt; 17) Cepheid candidates with MK &lt; - 1. We then analyze their ASAS-SN V-band light curves, determining periods and classifying the light curves using their Fourier parameters. This results in ~1900 likely Galactic Cepheids, which we estimate to be ≳90% complete and pure within our adopted selection criteria. This is the largest all-sky sample of Milky Way Cepheids that has such a well-characterized selection function, needed for population modeling and for systematic spectroscopic follow-up foreseen with Sloan Digital Sky Survey-V. About 130 of these potential Cepheids have not been documented in the literature even as possible candidates.

Keywords: Cepheid variable stars, Milky Way Galaxy
An Ultralong-wavelength Sky Model with Absorption Effect. The radio sky at frequencies below ~10 MHz is still largely unknown; this remains the last unexplored part of the electromagnetic spectrum in astronomy. The upcoming space experiments aiming at such low frequencies (ultralong wavelengths or ultralow frequencies) would benefit from reasonable expectations of the sky brightness distribution at relevant frequencies. In this work, we develop a radio sky model that is valid down to ~1 MHz. In addition to discrete H II objects, we take into account the free-free absorption by thermal electrons in the Milky Way's warm ionized medium. This absorption effect becomes obvious at ≲10 MHz, and could make the global radio spectrum turn over at ~3 MHz. Our sky map shows unique features at the ultralong wavelengths, including a darker Galactic plane in contrast to the sky at higher frequencies, and huge shadows of the spiral arms on the sky map. It will be a useful guide for designing future ultralong-wavelength observations. Our Ultralong-wavelength Sky Model with Absorption (ULSA) model can be downloaded at doi:10.5281/zenodo.4454153.

Keywords: Extragalactic radio sources, Galaxy structure, Interstellar emissions, Radio continuum emission, H II regions
Between Local Interstellar Magnetic and Dynamic Pressure Balance of Heliospheric Boundaries Measured with the IBEX Ribbon-A New Paradigm. The Interstellar Boundary Explorer (IBEX) mission discovered a global structure observed in energetic neutral atoms (ENA) emissions-the IBEX "ribbon." We study the ribbon spatially retained by Alfvén waves. The IBEX ribbon width is used to derive Alfvén speeds in the modified local interstellar medium (LISM), which, averaged across the ribbon, is vA = 42.7 ± 3.0 km s-1. The increase of Alfvén speeds from polar regions to near the nose yields the compression ratio from the pristine LISM into the modified LISM as a function of angle from the ENA pressure maximum in the globally distributed flux. Averaged across the ribbon, the average compression ratio is rc = 1.63 ± 0.22. The compression ratios and Alfvén speeds across the ribbon provide for extrapolations into the pristine LISM, resulting in an average LISM Alfvén speed, vA-LISM = 31.7 ± 3.3 km s-1. With the LISM flow speed of uLISM = 25.82 ± 0.33 km s-1 derived from previous IBEX studies, we find that the ratio of the ram flow energy density to the magnetic energy density in the LISM is ${u}_{\mathrm{LISM}}^{2}/{v}_{{\rm{A}}-\mathrm{LISM}}^{2}=0.66\pm 0.14$ . This indicates that the heliosphere is between the extremes of dynamic and magnetic pressure balance. The complex and time-varying structure of the heliosphere is strongly influenced both by interactions with the interstellar magnetic field and the interstellar flow, representing a new paradigm that will be explored as we connect IBEX observations with those made in the future by the Interstellar Mapping and Acceleration Probe (IMAP).

Keywords: Interstellar medium, Heliosphere
Discovery of Candidate X-Ray Jets in High-redshift Quasars. We present Chandra X-ray observations of 14 radio-loud quasars at redshifts 3 &lt; z &lt; 4, selected from a well-defined sample. All quasars are detected in the 0.5-7.0 keV energy band, and resolved X-ray features are detected in five of the objects at distances of 1″-12″ from the quasar core. The X-ray features are spatially coincident with known radio features for four of the five quasars. This indicates that these systems contain X-ray jets. X-ray fluxes and luminosities are measured, and jet-to-core X-ray flux ratios are estimated. The flux ratios are consistent with those observed for nearby jet systems, suggesting that the observed X-ray emission mechanism is independent of redshift. For quasars with undetected jets, an upper limit on the average X-ray jet intensity is estimated using a stacked image analysis. Emission spectra of the quasar cores are extracted and modeled to obtain best-fit photon indices, and an Fe K emission line is detected from one quasar in our sample. We compare X-ray spectral properties with optical and radio emission in the context of both our sample and other quasar surveys.

Keywords: Jets, High energy astrophysics, X-ray active galactic nuclei, Active galactic nuclei, High-redshift galaxies
Effects of Dust Evolution on the Vertical Shear Instability in the Outer Regions of Protoplanetary Disks. Vertical shear instability (VSI) is a hydrodynamical instability that requires rapid gas cooling and has been suggested to operate in outer regions of protoplanetary disks. VSI drives turbulence with strong vertical motions, which could regulate dust growth and settling. However, dust growth and settling can regulate the VSI because dust depletion makes gas cooling inefficient in outer disk regions that are optically thin to their own thermal emission. In this study, we quantify these potentially stabilizing effects of dust evolution on the VSI based on linear analysis. We construct a model for calculating the cooling timescale, taking into account dust growth beyond micron sizes and size-dependent settling. Combining the model with linear stability analysis, we map the region where the VSI operates, which we call the VSI zone, and estimate the maximum growth rate at each radial position. We find that dust growth, as well as settling, makes the VSI zone more confined around the midplane. This causes a decrease in the growth rate because the vertical shear of the rotation velocity, which is the source of the instability, is weaker at lower altitudes. In our default disk model with 0.01 solar masses, dust growth from 10 μm to 1 mm causes a decrease in the growth rate by a factor of more than 10. The suppression of VSI-driven turbulence by dust evolution may promote further dust evolution in the outer regions and also explain the high degree of dust settling observed in the disk around HL Tau.

Keywords: Protoplanetary disks, Planetesimals
A Chandra and HST View of WISE-selected AGN Candidates in Dwarf Galaxies. Reliably identifying active galactic nuclei (AGNs) in dwarf galaxies is key to understanding black hole (BH) demographics at low masses and constraining models for BH seed formation. Here we present Chandra X-ray Observatory observations of 11 dwarf galaxies that were chosen as AGN candidates using Wide-field Infrared Survey Explorer (WISE) mid-infrared (mid-IR) color-color selection. Hubble Space Telescope images are also presented for 10 of the galaxies. Based on Sloan Digital Sky Survey spectroscopy, six galaxies in our sample have optical evidence for hosting AGNs and five are classified as star-forming. We detect X-ray point sources with luminosities above that expected from X-ray binaries in the nuclei of five of the six galaxies with optical evidence of AGNs. However, the X-ray emission from these AGNs is generally much lower than expected based on AGN scaling relations with infrared and optical tracers. We do not find compelling evidence for AGNs in the five optically-selected star-forming galaxies despite having red mid-IR colors. Only two are detected in X-rays and their properties are consistent with stellar-mass X-ray binaries. Based on this multiwavelength study, we conclude that two-color mid-IR AGN diagnostics at the resolution of WISE cannot be used to reliably select AGNs in optically-star-forming dwarf galaxies. Future observations in the infrared with the James Webb Space Telescope offer a promising path forward.

Keywords: Dwarf galaxies, Active galaxies, X-ray active galactic nuclei, Active galactic nuclei, Infrared sources
On the Polarized Absorption Lines in Gamma-Ray Burst Optical Afterglows. Spectropolarimetric measurements of gamma-ray burst (GRB) optical afterglows contain polarization information for both continuum and absorption lines. Based on the Zeeman effect, an absorption line in a strong magnetic field is polarized and split into a triplet. In this paper, we solve the polarization radiative transfer equations of the absorption lines, and obtain the degree of linear polarization of the absorption lines as a function of the optical depth. In order to effectively measure the degree of linear polarization for the absorption lines, a magnetic field strength of at least 103 G is required. The metal elements that produce the polarized absorption lines should be sufficiently abundant and have large oscillation strengths or Einstein absorption coefficients. We encourage both polarization measurements and high-dispersion observations of the absorption lines in order to detect the triplet structure in early GRB optical afterglows.

Keywords: Gamma-ray bursts
Giant Cosmic-Ray Halos around M31 and the Milky Way. Recently, a diffuse emission of 1-100 GeV γ-rays has been detected from the direction of M31, extending up to 200 kpc from its center. The interpretation of the extended γ-ray emission by the escape of cosmic rays produced in the galactic disk or in the galactic center is problematic. In this paper, we argue that a cosmic-ray origin (either leptonic or hadronic) of the γ-ray emission is possible in the framework of nonstandard cosmic-ray propagation scenarios or is caused by in situ particle acceleration in the galaxy's halo. Correspondingly, the halo is powered by the galaxy's nuclear activity or by the accretion of intergalactic gas. If the formation of cosmic-ray halos around galaxies is a common phenomenon, the interactions of cosmic-ray protons and nuclei with the circumgalactic gas surrounding the Milky Way could be responsible for the isotropic diffuse flux of neutrinos observed by IceCube.

Keywords: Neutrino astronomy, Circumgalactic medium, Andromeda Galaxy, Gamma-rays, Milky Way Galaxy, Cosmic rays
Can Cytosine, Uracil, and Thymine Be Formed from HC<SUB>3</SUB>N and H<SUB>2</SUB>NCO<SUP>+</SUP> in Interstellar Space?. Syntheses of cytosine, uracil, and thymine starting from interstellar molecules were examined theoretically. Potential energy surfaces for the formation of protonated cytosine (CyH+), uracil (UrH+), and thymine (ThH+) from cyanoacetylene (HC3N), protonated isocyanic acid (H2NCO+), and one of NH3, H2O, and CH3OH, respectively, were determined by quantum chemical calculation using the CBS-QB3 method. Barrierless pathways were found for all the three reactions. Investigation of the energetics and kinetics of further possible reactions of CyH+, UrH+, and ThH+ led to the conclusion that cytosine, uracil, and thymine could not be formed along the proposed pathways in the interstellar gas phase, whereas their formation might be possible on interstellar icy grain mantles.

Keywords: Interstellar molecules, Astrobiology, Interstellar medium, Astrochemistry
Turbulent Proton Heating Rate in the Solar Wind from 5-45 R<SUB>⊙</SUB>. Various remote sensing observations have been used so far to probe the turbulent properties of the solar wind. Using the recently reported density modulation indices that are derived using angular broadening observations of Crab Nebula during 1952-2013, we measured the solar wind proton heating using the kinetic Alfvén wave dispersion equation. The estimated heating rates vary from ≈1.58 × 10-14 to 1.01 × 10-8 erg cm-3 s-1 in the heliocentric distance range of 5-45 R⊙. Further, we found that heating rates vary with the solar cycle in correlation with density modulation indices. The models derived using in situ measurements (for example, electron/proton density, temperature, and magnetic field) that the recently launched Parker Solar Probe observations (planned closest perihelia 9.86 R⊙ from the center of the Sun) are useful in the estimation of the turbulent heating rate precisely. Further, we compared our heating rate estimates with the one derived using previously reported remote sensing and in situ observations.

Keywords: Solar wind, Radio occultation
Delayed Detonation Thermonuclear Supernovae with an Extended Dark Matter Component. We present spherically symmetric simulations of the thermonuclear explosion of a white dwarf admixed with an extended component of fermionic dark matter, using the deflagration model with the deflagration-detonation transition. In all the dark matter admixed models we have considered, the dark matter is left behind after the explosion as a compact dark star. The presence of dark matter lengthens the deflagration phase to produce a similar amount of iron-group elements and more thermoneutrinos. Dark matter admixed models also give dimmer but slowly declining light curves, consistent with some observed peculiar supernovae. Our results suggest a formation path for dark compact objects that mimic sub-solar-mass black holes as dark gravitational sources.

Keywords: Hydrodynamical simulations, Supernova neutrinos, Light curves, Type Ia supernovae, Dark matter
Analyses of Laser Propagation Noises for TianQin Gravitational Wave Observatory Based on the Global Magnetosphere MHD Simulations. TianQin is a proposed space-borne gravitational-wave (GW) observatory composed of three identical satellites orbiting around the geocenter with a radius of 105 km. It aims at detecting GWs in the frequency range of 0.1 mHz-1 Hz. The detection of GW relies on the high-precision measurement of optical path length at the 10-12 m level. The dispersion of space plasma can lead to the optical path difference (OPD, Δl) along the propagation of laser beams between any pair of satellites. Here, we study the OPD noises for TianQin. The Space Weather Modeling Framework is used to simulate the interaction between the Earth magnetosphere and solar wind. From the simulations, we extract the magnetic field and plasma parameters on the orbits of TianQin at four relative positions of the satellite constellation in the Earth magnetosphere. We calculate the OPD noise for single link, Michelson combination, and Time-Delay Interferometry (TDI) combinations (α and X). For single link and Michelson interferometer, the maxima of ∣Δl∣ are on the order of 1 pm. For the TDI combinations, these can be suppressed to about 0.004 and 0.008 pm for α and X. The OPD noise of the Michelson combination is colored in the concerned frequency range; while the ones for the TDI combinations are approximately white. Furthermore, we calculate the ratio of the equivalent strain of the OPD noise to that of TQ, and find that the OPD noises for the TDI combinations can be neglected in the most sensitive frequency range of TQ.

Keywords: Space plasmas, Solar wind, Gravitational wave detectors
Stellar Mass Black Hole Formation and Multimessenger Signals from Three-dimensional Rotating Core-collapse Supernova Simulations. We present self-consistent 3D core-collapse supernova simulations of a 40 ${M}_{\odot }$ progenitor model using the isotropic diffusion source approximation for neutrino transport and an effective general relativistic potential up to ~0.9 s postbounce. We consider three different rotational speeds with initial angular velocities of ${{\rm{\Omega }}}_{0}=0$ , 0.5, and 1 rad s-1 and investigate the impact of rotation on shock dynamics, black hole (BH) formation, and gravitational wave (GW) signals. The rapidly rotating model undergoes an early explosion at ~250 ms postbounce and shows signs of the low $T/| W| $ instability. We do not find BH formation in this model within ~460 ms postbounce. In contrast, we find BH formation at 776 ms postbounce and 936 ms postbounce for the nonrotating and slowly rotating models, respectively. The slowly rotating model explodes at ~650 ms postbounce, and the subsequent fallback accretion onto the proto-neutron star (PNS) results in BH formation. In addition, the standing accretion shock instability induces rotation of the PNS in the model that started with a nonrotating progenitor. Assuming conservation of specific angular momentum during BH formation, this corresponds to a BH spin parameter of a = J/M = 0.046. However, if no explosion sets in, all the angular momentum will eventually be accreted by the BH, resulting in a nonspinning BH. The successful explosion of the slowly rotating model drastically slows down the accretion onto the PNS, allowing continued cooling and contraction that results in an extremely high GW frequency (f ~ 3000 Hz) at BH formation, while the nonrotating model generates GW signals similar to our corresponding 2D simulations.

Keywords: Neutron stars, Hydrodynamical simulations, Black holes, Core-collapse supernovae, Gravitational wave astronomy
Culminating the Peak Cusp to Descry the Dark Side of Halos. The ConflUent System of Peak trajectories (CUSP) is a rigorous formalism in the framework of the peak theory that allows one to derive from first principles and no free parameters the typical halo properties from the statistics of peaks in the filtered Gaussian random field of density perturbations. The predicted halo mass function, spherically averaged density, velocity dispersion, velocity anisotropy, ellipticity, prolateness, and potential profiles, as well as the abundance and number density profiles of accreted and stripped subhalos and diffuse dark matter, accurately recover the results of cosmological N-body simulations. CUSP is thus a powerful tool for the calculation, in any desired hierarchical cosmology with Gaussian perturbations, of halo properties beyond the mass, redshift, and radial ranges covered by simulations. More importantly, CUSP unravels the origin of the characteristic features of those properties. In this paper, we culminate its construction. We show that all halo properties but those related to subhalo stripping are independent of the assembly history of those objects, and that the Gaussian is the only smoothing window able to find the finite collapsing patches while properly accounting for the entropy increase produced in major mergers.

Keywords: Hierarchical cosmology, Galaxy dark matter halos