Sazuna/UAT_keywords huggingface dataset:
Forward Modeling Helioseismic Signatures of One- and Two-cell Meridional Circulation. Using a 3D global solver of the linearized Euler equations, we model acoustic oscillations over background velocity flow fields of single-cell meridional circulation with deep and shallow return flows as well as double-cell meridional circulation with strong and weak reversals. The velocities are generated using a mean-field hydrodynamic and dynamo model—moving through the regimes with minimal parameter changes, counterrotation near the base of the tachocline is induced by sign inversion of the nondiffusive action of turbulent Reynolds stresses (Λ-effect) due to the radial inhomogeneity of the Coriolis number. By mimicking the stochastic excitation of resonant modes in the convective interior, we simulate realization noise present in solar observations. Using deep-focusing to analyze differences in travel-time signatures between the four regimes, as well as comparing to solar observations, we show that current helioseismology techniques may offer important insights about the location and strength of the return flow; however, it may not currently be possible to definitively distinguish between profiles of single-cell or double-cell meridional circulation.

Keywords: Helioseismology, Computational methods, Solar meridional circulation
Assessing the Stellar Population and the Environment of an H II Region on the Far Side of the Galaxy. We have investigated the stellar and interstellar content of the distant star formation region IRAS 17591-2228 (WISE H II region GAL 007.47+0.06). It is associated with a water maser, whose parallax distance is $d={20.4}_{-2.2}^{+2.8}$ kpc, supported by independent measurements of proper motion and radial velocity. It is projected in the same direction as an extremely red (J-KS ∼ 6 mag) group of stars, and a shell of mid-infrared emission. We qualify the group of stars as a cluster candidate, VVV CL177. Its radius spans between 0'45 and 1' and contains at least two young stellar objects with an extreme extinction near ${A}_{{\rm{V}}}\sim 40$ mag. Yet more analysis will be required to determine if it is a real single cluster associated with the water maser. The 13CO emissions at the radial velocity of the maser corresponds to the mid-infrared emission. * Refers As VVV CL177.

Keywords: Open star clusters, Young massive clusters, Young stellar objects, Star clusters
Revealing a New Black Widow Binary 4FGL J0336.0+7502. We report on the discovery of a promising candidate for a black widow (BW) millisecond pulsar binary, 4FGL J0336.0+7502, which shows many pulsar-like properties in the 4FGL-DR2 catalog. Within the 95% error region of the LAT source, we identified an optical counterpart with a clear periodicity at Porb = 3.718178(9) hr using the Bohyunsan 1.8 m Telescope, the Lulin One-meter Telescope, the Canada-France-Hawaii Telescope, and Gemini-North. At the optical position, an X-ray source was marginally detected in the Swift/X-Ray Telescope archival data, and the detection was confirmed by our Chandra/ACIS DDT observation. The spectrum of the X-ray source can be described by a power-law model of Γx = 1.6 ± 0.7 and ${F}_{0.3\mbox{--}7\mathrm{keV}}={3.5}_{-1.0}^{+1.2}\times {10}^{-14}$ erg cm-2 s-1. The X-ray photon index and the low X-ray-to-γ-ray flux ratio (i.e., &lt;1%) are both consistent with that of many known BW pulsars. There is also a hint of an X-ray orbital modulation in the Chandra data, although the significance is very low (1.3σ). If the pulsar identity and the X-ray modulation are confirmed, it would be the fifth BW millisecond pulsar binary that showed an orbitally modulated emission in X-rays.

Keywords: High energy astrophysics, Millisecond pulsars, Gamma-ray sources, Compact binary stars, X-ray sources
Investigation of Important Weak Interaction Nuclei in Presupernova Evolution. This project aims to investigate the most important weak interaction nuclei in the presupernova evolution of massive stars. To achieve this goal, an ensemble containing 728 nuclei in the mass range of A = 1-100 was considered. We computed the mass fractions of these nuclei using Saha's equation for predetermined values of T, ρ, and Ye and assuming nuclear statistical equilibrium. The nuclear partition functions were obtained using a newly introduced recipe where excited states, up to 10 MeV, were treated as discrete. The weak interaction rates (electron capture (ec) and β-decay (bd)) were calculated in a totally microscopic fashion using the proton-neutron quasiparticle random phase approximation model and without assuming the Brink-Axel hypothesis. The calculated rates were coupled with the computed mass fractions to investigate the time rate of change of lepton to baryon fraction of the stellar matter. We compare our results with the previous calculations reported in the literature. Noticeable differences up to orders of magnitude are reported with previous calculations. These differences may influence the evolution of the star in the later stages of presupernova. We present a list of the top 50 ec and bd nuclei, which have the largest effect on Ye for conditions after silicon core burning. The competition between the ec and bd rates in the stellar core was investigated and it was found that Ye = 0.424-0.455 is the interval where the bd results are bigger than the ec rates.

Keywords: Isotopic abundances, Nucleosynthesis, Stellar abundances, Stellar dynamics, Stellar physics, Nuclear astrophysics, Stellar evolution
The Diverse Morphology, Stellar Population, and Black Hole Scaling Relations of the Host Galaxies of Nearby Quasars. We present rest-frame B and I imaging of 35 low-redshift ( $z\lt 0.5$ ) Palomar-Green quasars using the Hubble Space Telescope Wide Field Camera 3. We perform multicomponent two-dimensional image decomposition to separate the host galaxy from its bright active nucleus, characterize its morphology, and measure its photometric properties. Special care is devoted to quantifying the structural parameters of the galaxy bulge, determining its B - I color, and estimating its stellar mass. Roughly half of the sample, comprising the less luminous ( ${L}_{5100}\lesssim {10}^{45}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ ) but most high Eddington ratio quasars, reside in disk galaxies that are often barred and possess pseudo bulges. The large stellar masses, large effective radii, and faint surface brightnesses suggest that the host galaxies of the most luminous quasars are mostly ellipticals. Major mergers constitute only a small percentage (≲20%) of our sample. Our quasar sample roughly obeys the scaling relations between black hole mass and host galaxy (bulge, core, total) stellar mass. Hosts with black holes more massive than $\sim {10}^{8}\,{M}_{\odot }$ behave similarly to classical bulges and early-type galaxies, while those with less massive black holes, particularly the narrow-line Seyfert 1s, are consistent with pseudo bulges in late-type galaxies. The host galaxy bulges, irrespective of whether they are classical or pseudo, follow a relatively tight inverse relation between the effective radius and the mean effective surface brightness of inactive classical bulges and ellipticals. We argue that pseudo bulges experience recent or ongoing nuclear star formation.

Keywords: Galaxy bulges, Galaxy structure, Active galactic nuclei, Quasars
Probabilistic Association of Transients to their Hosts (PATH). We introduce a new method to estimate the probability that an extragalactic transient source is associated with a candidate host galaxy. This approach relies solely on simple observables: sky coordinates and their uncertainties, galaxy fluxes, and angular sizes. The formalism invokes Bayes' rule to calculate the posterior probability $P\left({O}_{i}| x\right)$ from the galaxy prior P(O), observables x, and an assumed model for the true distribution of transients in/around their host galaxies. Using simulated transients placed in the well-studied Cosmic Evolution Survey field, we consider several agnostic and physically motivated priors and offset distributions to explore the method sensitivity. We then apply the methodology to the set of 13 fast radio bursts (FRBs) localized with an uncertainty of several arcseconds. Our methodology finds nine of these are securely associated to a single host galaxy, $P\left({O}_{i}| x\right)\gt 0.95$ . We examine the observed and intrinsic properties of these secure FRB hosts, recovering distributions similar to those found in previous works. Furthermore, we find a strong correlation between the apparent magnitude of the securely identified host galaxies and the estimated cosmic dispersion measures of the corresponding FRBs, which results from the Macquart relation. Future work with FRBs will leverage this relation and other measures from the secure hosts as priors for future associations. The methodology is generic to transient type, localization error, and image quality. We encourage its application to other transients where host galaxy associations are critical to the science, e.g., gravitational wave events, gamma-ray bursts, and supernovae. We have encoded the technique in Python on GitHub: https://github.com/FRBs/astropath.

Keywords: Bayes' Theorem, Radio transient sources
Understanding Type Ia Supernova Distance Biases by Simulating Spectral Variations. In the next decade, transient searches from the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope will increase the sample of known Type Ia supernovae (SNe Ia) from ∼103 to 105. With this reduction of statistical uncertainties on cosmological measurements, new methods are needed to reduce systematic uncertainties. Characterizing the underlying spectroscopic evolution of SN Ia remains a major systematic uncertainty in current cosmological analyses, motivating a new simulation tool for the next era of SN Ia cosmology: Build Your Own Spectral Energy Distribution (BYOSED). BYOSED is used within the SNANA framework to simulate light curves by applying spectral variations to model SEDs, enabling flexible testing of possible systematic shifts in SN Ia distance measurements. We test the framework by comparing a nominal Roman SN Ia survey simulation using a baseline SED model to simulations using SEDs perturbed with BYOSED, and investigating the impact of ignoring specific SED features in the analysis. These features include semiempirical models of two possible, predicted relationships: between SN ejecta velocity and light-curve observables, and a redshift-dependent relationship between SN Hubble residuals and host-galaxy mass. We analyze each BYOSED simulation using the SALT2 and BEAMS with Bias Corrections framework, and estimate changes in the measured value of the dark-energy equation-of-state parameter, w. We find a difference of Δw = -0.023 for SN velocity and Δw = 0.021 for redshift-evolving host mass when compared to simulations without these features. By using BYOSED for SN Ia cosmology simulations, future analyses (e.g., the Rubin and Roman SN Ia samples) will have greater flexibility to constrain or reduce such SN Ia modeling uncertainties.

Keywords: Cosmology, Type Ia supernovae, Astronomical simulations
A Possible Kilonova Powered by Magnetic Wind from a Newborn Black Hole. The merger of binary neutron stars (NS-NS) as the progenitor of short gamma-ray bursts (GRBs) has been confirmed by the discovery of the association of the gravitational-wave (GW) event GW170817 with GRB 170817A. However, the merger product of binary NS remains an open question. An X-ray plateau followed by a steep decay ("internal plateau") has been found in some short GRBs, implying that a supramassive magnetar operates as the merger remnant and then collapses into a newborn black hole (BH) at the end of the plateau. X-ray bump or second plateau following the "internal plateau" are considered as the expected signature from the fallback accretion onto this newborn BH through the Blandford-Znajek mechanism (BZ). At the same time, a nearly isotropic wind driven by the Blandford-Payne mechanism (BP) from the newborn BH's disk can produce a bright kilonova. Therefore, the bright kilonova observation for a short GRB with "internal plateau" (and followed by X-ray bump or second plateau) provides further evidence for this scenario. In this paper, we find that GRB 160821B is a candidate of such a case, and the kilonova emission of GRB 160821B is possibly powered by the BP wind from a newborn BH. Future GW detection of GRB 160821B-like events may provide further support to this scenario, enable us to investigate the properties of the magnetar and the newborn BH, and constrain the equation of state of neutron stars.

Keywords: Accretion, Black hole physics, Gamma-ray bursts, Neutron stars
Connection between Galaxies and H I in Circumgalactic and Intergalactic Media: Variation according to Galaxy Stellar Mass and Star Formation Activity. This paper systematically investigates the comoving megaparsec-scale intergalactic medium (IGM) environment around galaxies traced by the Lyα forest. Using our cosmological hydrodynamic simulations, we investigate the IGM-galaxy connection at z = 2 by two methods: (i) cross-correlation analysis between galaxies and the fluctuation of Lyα forest transmission (δF) and (ii) comparison of the overdensity of neutral hydrogen (H I) and galaxies. Our simulations reproduce observed cross-correlation functions (CCFs) between Lyα forest and Lyman-break galaxies. We further investigate the variation of the CCF using subsamples divided by dark matter halo mass (MDH), galaxy stellar mass (M⋆), and star formation rate (SFR) and find that the CCF signal becomes stronger with increasing MDH, M⋆, and SFR. The CCFs between galaxies and gas density fluctuation are also found to have similar trends. Therefore, the variation of δF-CCF depending on MDH, M⋆, and SFR is due to varying gas densities around galaxies. We find that the correlation between galaxies and the IGM H I distribution strongly depends on MDH as expected from linear theory. Our results support the ΛCDM paradigm, confirming a spatial correlation between galaxies and IGM H I, with more massive galaxies being clustered in higher-density regions.

Keywords: Hydrodynamical simulations, Galaxy formation, Lyman alpha forest, Large-scale structure of the universe, Circumgalactic medium, Galaxy evolution, Intergalactic medium
ALMA Lensing Cluster Survey: Bright [C II] 158 μm Lines from a Multiply Imaged Sub-L<SUP>⋆</SUP> Galaxy at z = 6.0719. We present bright [C II] 158 μm line detections from a strongly magnified and multiply imaged (μ ∼ 20-160) sub-L* ( ${M}_{\mathrm{UV}}=-{19.75}_{-0.44}^{+0.55}$ ) Lyman-break galaxy (LBG) at z = 6.0719 ± 0.0004, drawn from the ALMA Lensing Cluster Survey (ALCS). Emission lines are identified at 268.7 GHz at ≥8σ exactly at the positions of two multiple images of the LBG, behind the massive galaxy cluster RXCJ0600-2007. Our lens models, updated with the latest spectroscopy from VLT/MUSE, indicate that a sub region of the LBG crosses the caustic, and is lensed into a long (∼6″) arc with a local magnification of μ ∼ 160, for which the [C II] line is also significantly detected. The source plane reconstruction resolves the interstellar medium (ISM) structure, showing that the [C II] line is co-spatial with the rest-frame UV continuum at a scale of ∼300 pc. The [C II] line properties suggest that the LBG is a rotation-dominated system, whose velocity gradient explains a slight difference in redshifts between the whole LBG and its sub-region. The star formation rate (SFR)-L[CII] relations, for whole and sub-regions of the LBG, are consistent with those of local galaxies. We evaluate the lower limit of the faint-end of the [C II] luminosity function at z = 6, finding it to be consistent with predictions from semi-analytical models and from the local SFR-L[CII] relation with a SFR function at z = 6. These results imply that the local SFR-L[CII] relation is universal for a wide range of scales, including the spatially resolved ISM, the whole region of the galaxy, and the cosmic scale, even in the epoch of reionization.

Keywords: Luminosity function, Galaxy formation, Strong gravitational lensing, Galaxy kinematics, Galaxy evolution, Interstellar medium, High-redshift galaxies
The Complex Gaseous and Stellar Environments of the Nearby Dual Active Galactic Nucleus Mrk 739. We present integral field spectroscopic observations of the nearby (z ∼ 0.03) dual active galactic nuclei (AGNs) Mrk 739, whose projected nuclear separation is ∼3.4 kpc, obtained with the Multi Unit Spectroscopic Explorer at the Very Large Telescope. We find that the galaxy has an extended AGN-ionized emission-line region extending up to ∼20 kpc away from the nuclei, while star-forming regions are more centrally concentrated within 2-3 kpc. We model the kinematics of the ionized gas surrounding the eastern nucleus using a circular disk profile, resulting in a peak velocity of ${237}_{-28}^{+26}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ at a distance of ∼1.2 kpc. The enclosed dynamical mass within 1.2 kpc is $\mathrm{log}M({M}_{\odot })=10.20\pm 0.06$ , ∼1000 times larger than the estimated supermassive black hole (SMBH) mass of Mrk 739E. The morphology and dynamics of the system are consistent with an early stage of the collision, where the foreground galaxy (Mrk 739W) is a young star-forming galaxy in an ongoing first passage with its background companion (Mrk 739E). Since the SMBH in Mrk 739W does not show evidence of being rapidly accreting, we claim that the northern spiral arms of Mrk 739W are ionized by the nuclear activity of Mrk 739E.

Keywords: AGN host galaxies, Markarian galaxies, Active galaxies, Galaxy interactions, Emission line galaxies, Galaxy mergers, Spectroscopy, Interacting galaxies
Prospects for Multimessenger Observations of Thorne-Żytkow Objects. Thorne-Żytkow objects (TŻOs) are a class of stellar object comprised of a neutron star core surrounded by a large and diffuse envelope. Their exterior appearance is identical to red supergiants; the distinctive electromagnetic signature of a TŻO is a suite of unusual chemical abundance patterns, including excesses of Li, Rb, Mo, and Ca. However, electromagnetic observations cannot unambiguously identify the presence of a neutron star core. Detection of continuous gravitational wave emission from a rotating neutron star core would provide strong supporting evidence for the existence of TŻOs. We present a model for gravitational wave detector confirmation of TŻOs and demonstrate that these objects should be detectable with Advanced LIGO. We also investigate possible targets for joint optical and gravitational searches, and comment on prospects for detectability in both current and future gravitational wave detector networks.

Keywords: Neutron stars, Red supergiant stars, Stellar mergers, Gravitational wave sources, Gravitational wave astronomy
Constraining Galaxy Halos from the Dispersion and Scattering of Fast Radio Bursts and Pulsars. Fast radio bursts (FRBs) can be scattered by ionized gas in their local environments, host galaxies, intervening galaxies along their lines of sight (LOS), the intergalactic medium, and the Milky Way. The relative contributions of these different media depend on their geometric configuration and the internal properties of the gas. When these relative contributions are well understood, FRB scattering is a powerful probe of density fluctuations along the LOS. The precise scattering measurements for FRB 121102 and FRB 180916 allow us to place an upper limit on the amount of scattering contributed by the Milky Way halo to these FRBs. The scattering time $\tau \propto (\widetilde{F}\times {\mathrm{DM}}^{2}){A}_{\tau }$ , where DM is the dispersion measure, $\widetilde{F}$ quantifies electron density variations with $\widetilde{F}=0$ for a smooth medium, and the dimensionless constant Aτ quantifies the difference between the mean scattering delay and the 1/e scattering time typically measured. A likelihood analysis of the observed scattering and halo DM constraints finds that $\widetilde{F}$ is at least an order of magnitude smaller in the halo than in the Galactic disk. The maximum pulse broadening from the halo is τ ≲ 12 μs at 1 GHz. We compare our analysis of the Milky Way halo with other galaxy halos by placing limits on the scattering contributions from halos intersecting the LOS to FRB 181112 and FRB 191108. Our results are consistent with halos making negligible or very small contributions to the scattering times of these FRBs.

Keywords: Galaxy stellar halos, Milky Way stellar halo, Interstellar medium, Circumgalactic medium, Radio transient sources
R Coronae Borealis Star Evolution: Simulating 3D Merger Events to 1D Stellar Evolution Including Large-scale Nucleosynthesis. R Coronae Borealis (RCB) stars are rare hydrogen-deficient carbon-rich variable supergiants thought to be the result of dynamically unstable white dwarf mergers. We attempt to model RCB stars through all the relevant timescales by simulating a merger event in Octo-tiger, a 3D adaptive mesh refinement (AMR) hydrodynamics code, and mapping the post-merger object into MESA, a 1D stellar evolution code. We then post-process the nucleosynthesis on a much larger nuclear reaction network to study the enhancement of s-process elements. We present models that match observations or previous studies in most surface abundances, isotopic ratios, early evolution, and lifetimes. We also observe similar mixing behavior to previous modeling attempts that result in the partial He-burning products visible on the surface in observations. However, we do note that our subsolar models lack any enhancement in s-process elements, which we attribute to a lack of hydrogen in the envelope. We also find that the 16O/18O isotopic ratio is very sensitive to initial hydrogen abundance and increases outside of the acceptable range with a hydrogen mass fraction greater than 10-4.

Keywords: Hydrodynamics, Stellar mergers, Close binary stars, Abundance ratios, White dwarf stars, Stellar evolutionary models, R Coronae Borealis variable stars, Stellar nucleosynthesis
Fast Optical Transients from Stellar-mass Black Hole Tidal Disruption Events in Young Star Clusters. Observational evidence suggests that the majority of stars may have been born in stellar clusters or associations. Within these dense environments, dynamical interactions lead to high rates of close stellar encounters. A variety of recent observational and theoretical indications suggest stellar-mass black holes may be present and play an active dynamical role in stellar clusters of all masses. In this study, we explore the tidal disruption of main-sequence stars by stellar-mass black holes in young star clusters. We compute a suite of over 3000 independent N-body simulations that cover a range of cluster mass, metallicity, and half-mass radii. We find stellar-mass black hole tidal disruption events (TDEs) occur at an overall rate of up to roughly 200 Gpc-3 yr-1 in young stellar clusters in the local universe. These TDEs are expected to have several characteristic features, namely, fast rise times of order a day, peak X-ray luminosities of at least 1044 erg s-1, and bright optical luminosities (roughly 1041-1044 erg s-1) associated with reprocessing by a disk wind. In particular, we show these events share many features in common with the emerging class of Fast Blue Optical Transients.

Keywords: Tidal disruption, Young star clusters, Transient sources, X-ray transient sources, N-body simulations, Astrophysical black holes