Sazuna/UAT_keywords huggingface dataset:
Study of Advective Energy Transport in the Inflow and Outflow of Super-Eddington Accretion Flows. Photon trapping is believed to be an important mechanism in super-Eddington accretion, which greatly reduces the radiative efficiency as photons are swallowed by the central black hole before they can escape from the accretion flow. This effect is interpreted as the radial advection of energy in one-dimensional height-integrated models, such as the slim-disk model. However, when multidimensional effects are considered, the conventional understanding may no longer hold. In this paper, we study the advective energy transport in super-Eddington accretion based on a new two-dimensional inflow-outflow solution with radial self-similarity, in which the advective factor is calculated self-consistently by incorporating the calculation of radiative flux instead of being set as an input parameter. We found that radial advection is actually a heating mechanism in the inflow due to compression, and the energy balance in the inflow is maintained by cooling via radiation and vertical (θ-direction) advection, which transports entropy upward to be radiated closer to the surface or carried away by the outflow. As a result, fewer photons are advected inward, and more photons are released from the surface, so that the mean advective factor is smaller and the emergent flux is higher than the fluxes predicted by the slim-disk model. The radiative efficiency of super-Eddington accretion thus should be higher than that of the slim-disk model, which agrees with the results of some recent numerical simulations.

Keywords: Accretion, High energy astrophysics, Hydrodynamics
A Light Redback Companion of PSR J1622-0315 and Irradiation Power in Spider Systems. We report optical observations of the millisecond pulsar binary system PSR J1622-0315 with the Lulin 1 m telescope in Taiwan and the Lijiang 2.4 m telescope in China between 2019 and 2021. The companion of the pulsar, which is of V ~ 19 mag, showed ellipsoidal-distorted orbital variations in its light curves. The best-fit model to the light curves, with the binary code PHOEBE, gives a companion mass of 0.122 ± 0.006 M ⊙. This places PSR J1622-0315 in the spider-system subclass. We compared the properties of PSR J1622-0315 with other spider pulsar binaries for the scalings between the spin-down luminosity derived for the pulsar, irradiation luminosity of the companion, and X-ray luminosity of the binary. We find that pulsar irradiation in PSR J1622-0315 is insignificant and the irradiation luminosity of the transitional millisecond pulsars PSR J1023+0038 and PSR J1227-4853 are the highest among the redback systems.

Keywords: Low-mass x-ray binary stars, Compact binary stars, Millisecond pulsars
The HERBAL Model: A Hierarchical Errors-in-variables Bayesian Lognormal Hurdle Model for Galactic Globular Cluster Populations. Galaxy stellar mass is known to be monotonically related to the size of the galaxy's globular cluster (GC) population for Milky Way sized and larger galaxies. However, the relation becomes ambiguous for dwarf galaxies, where there is some evidence for a downturn in GC population size at low galaxy masses. Smaller dwarfs are increasingly likely to have no GCs, and these zeros cannot be easily incorporated into linear models. We introduce the Hierarchical Errors-in-variables ERrors-in-variables BAyesian Lognormal hurdle (HERBAL) model to represent the relationship between dwarf galaxies and their GC populations, and apply it to the sample of Local Group galaxies, where the luminosity range coverage is maximal. This bimodal model accurately represents the two populations of dwarf galaxies: those that have GCs and those that do not. Our model thoroughly accounts for all uncertainties, including measurement uncertainty, uncertainty in luminosity to stellar mass conversions, and intrinsic scatter. The hierarchical nature of our Bayesian model also allows us to estimate galaxy masses and individual mass-to-light ratios from luminosity data within the model. We find that 50% of galaxies are expected to host GC populations at a stellar mass of ${\mathrm{log}}_{10}({M}_{* })=6.996$ , and that the expected mass of GC populations remains linear down to the smallest galaxies. Our hierarchical model recovers an accurate estimate of the Milky Way stellar mass. Under our assumed error model, we find a nonzero intrinsic scatter of ${0.59}_{-0.21}^{+0.3}$ (95% credible interval) that should be accounted for in future models.

Keywords: Globular star clusters, Local Group, Bayesian statistics, Dwarf galaxies, Astrostatistics, Galactic and extragalactic astronomy, Interdisciplinary astronomy, Hierarchical models, Galaxies
High-energy Electromagnetic, Neutrino, and Cosmic-Ray Emission by Stellar-mass Black Holes in Disks of Active Galactic Nuclei. Some Seyfert galaxies are detected in high-energy gamma rays, but the mechanism and site of gamma-ray emission are unknown. Also, the origins of the cosmic high-energy neutrino and MeV gamma-ray backgrounds have been veiled in mystery since their discoveries. We propose emission from stellar-mass BHs (sBHs) embedded in disks of active galactic nuclei as their possible sources. These sBHs are predicted to launch jets due to the Blandford-Znajek mechanism, which can produce intense electromagnetic, neutrino, and cosmic-ray emissions. We investigate whether these emissions can be the sources of cosmic high-energy particles. We find that emission from internal shocks in the jets can explain gamma rays from nearby radio-quiet Seyfert galaxies including NGC 1068, if the Lorentz factor of the jets (Γj) is high. On the other hand, for moderate Γj, the emission can significantly contribute to the background gamma-ray and neutrino intensities in the ~MeV and ≲PeV bands, respectively. Furthermore, for moderate Γj with efficient amplification of the magnetic field and cosmic-ray acceleration, the neutrino emission from NGC 1068 and the ultrahigh-energy cosmic rays can be explained. These results suggest that the neutrino flux from NGC 1068 as well as the background intensities of MeV gamma rays, neutrinos, and the ultrahigh-energy cosmic rays can be explained by a unified model. Future MeV gamma-ray satellites will test our scenario for neutrino emission.

Keywords: Jets, High energy astrophysics, Neutrino astronomy, Cosmic ray astronomy, Active galactic nuclei, Gamma-ray astronomy, Astrophysical black holes
A Census of Near-UV M-dwarf Flares Using Archival GALEX Data and the gPHOTON2 Pipeline. M-dwarfs are common stellar hosts of habitable-zone exoplanets. Near-UV (NUV) radiation can severely impact the atmospheric and surface conditions of such planets, making the characterization of NUV flaring activity a key aspect in determining habitability. We use archival data from the Galaxy Evolution Explorer (GALEX) and XMM-Newton telescopes to study the flaring activity of M-dwarfs in the NUV. The GALEX observations form the most extensive data set of M-dwarfs in the NUV to date, with the exploitation of this data possible due to the new gPHOTON2 pipeline. We run a dedicated algorithm to detect flares in the pipeline-produced lightcurves and find some of the most energetic flares observed to date within the NUV bandpass, with energies of ~1034 erg. Using GALEX data, we constrain flare frequency distributions for stars from M0-M6 in the NUV up to 105 s in equivalent duration and 1034 erg in energy, orders of magnitude above any previous study in the UV. We estimate the combined effect of NUV luminosities and flare rates of stars later than M2 to be sufficient for abiogenesis on habitable-zone exoplanets orbiting them. As a counterpoint, we speculate the high frequencies of energetic UV flares and associated coronal mass ejections would inhibit the formation of an ozone layer, possibly preventing the genesis of complex Earth-like life-forms due to sterilizing levels of surface UV radiation. We also provide a framework for future observations of M-dwarfs with ULTRASAT, a wide field-of-view NUV telescope to be launched in 2026.

Keywords: M dwarf stars, Near ultraviolet astronomy, Red dwarf flare stars, Ultraviolet astronomy, Stellar flares, Habitable planets, Pre-biotic astrochemistry
Strongly Lensed Supermassive Black Hole Binaries as Nanohertz Gravitational-wave Sources. Supermassive black hole binary systems (SMBHBs) should be the most powerful sources of gravitational waves (GWs) in the universe. Once pulsar timing arrays (PTAs) detect the stochastic GW background from their cosmic merger history, searching for individually resolvable binaries will take on new importance. Since these individual SMBHBs are expected to be rare, here we explore how strong gravitational lensing can act as a tool for increasing their detection prospects by magnifying fainter sources and bringing them into view. Unlike for electromagnetic waves, when the geometric optics limit is nearly always valid, for GWs the wave-diffraction-interference effects can become important when the wavelength of the GWs is larger than the Schwarzchild radius of the lens, i.e., ${M}_{\mathrm{lens}}\sim {10}^{8}{\left(\tfrac{f}{\mathrm{mHz}}\right)}^{-1}\,{M}_{\odot }$ . For the GW frequency range explored in this work, the geometric optics limit holds. We investigate GW signals from SMBHBs that might be detectable with current and future PTAs under the assumption that quasars serve as bright beacons that signal a recent merger. Using the black hole mass function derived from quasars and a physically motivated magnification distribution, we expect to detect a few strongly lensed binary systems out to z ≈ 2. Additionally, for a range of fixed magnifications 2 ≤ μ ≤ 100, strong lensing adds up to ~30 more detectable binaries for PTAs. Finally, we investigate the possibility of observing both time-delayed electromagnetic signals and GW signals from these strongly lensed binary systems-that will provide us with unprecedented multi-messenger insights into their orbital evolution.

Keywords: Gravitational wave detectors, Pulsar timing method, Quasars, Gravitational wave sources, Gravitational wave astronomy, Gravitational lensing
Constraining Cosmological Parameters Using the Cluster Mass-Richness Relation. The cluster mass-richness relation (MRR) is an observationally efficient and potentially powerful cosmological tool for constraining the matter density Ωm and the amplitude of fluctuations σ 8 using the cluster abundance technique. We derive the MRR relation using GalWCat19, a publicly available galaxy cluster catalog we created from the Sloan Digital Sky Survey-DR13 spectroscopic data set. In the MRR, cluster mass scales with richness as $\mathrm{log}{M}_{200}=\alpha +\beta \mathrm{log}{N}_{200}$ . We find that the MRR we derive is consistent with both the IllustrisTNG and mini-Uchuu cosmological numerical simulations, with a slope of β ≈ 1. We use the MRR we derived to estimate cluster masses from the GalWCat19 catalog, which we then use to set constraints on Ωm and σ 8. Utilizing the all-member MRR, we obtain constraints of Ωm = ${0.31}_{-0.03}^{+0.04}$ and σ 8 = ${0.82}_{-0.04}^{+0.05}$ , and utilizing the red member MRR only, we obtain Ωm = ${0.31}_{-0.03}^{+0.04}$ and σ 8 = ${0.81}_{-0.04}^{+0.05}$ . Our constraints on Ωm and σ 8 are consistent and very competitive with the Planck 2018 results.

Keywords: Galaxy clusters, Galaxy cluster counts, Cosmological parameters
Molecular Abundance of the Circumnuclear Region Surrounding an Active Galactic Nucleus in NGC 1068 Based on an Imaging Line Survey in the 3 mm Band with ALMA. We present an imaging molecular line survey in the 3 mm band (85-114 GHz) focused on one of the nearest galaxies with an active galactic nucleus (AGN), NGC 1068, based on observations taken with the Atacama Large Millimeter/submillimeter Array. Distributions of 23 molecular transitions are obtained in the central ~3 kpc region, including both the circumnuclear disk (CND) and starburst ring (SBR) with 60 and 350 pc resolution. The column densities and relative abundances of all the detected molecules are estimated under the assumption of local thermodynamic equilibrium in the CND and SBR. Then, we discuss the physical and chemical effects of the AGN on molecular abundance corresponding to the observation scale. We found that H13CN, SiO, HCN, and H13CO+ are abundant in the CND relative to the SBR. In contrast, 13CO is more abundant in the SBR. Based on the calculated column density ratios of N(HCN)/N(HCO+), N(HCN)/N(CN), and other molecular distributions, we conclude that the enhancement of HCN in the CND may be due to high-temperature environments resulting from strong shocks, which are traced by the SiO emission. Moreover, the abundance of CN in the CND is significantly lower than the expected value of the model calculations in the region affected by strong radiation. The expected strong X-ray irradiation from the AGN has a relatively lower impact on the molecular abundance in the CND than mechanical feedback.

Keywords: AGN host galaxies, Active galactic nuclei, Interstellar molecules, Chemical abundances
Unique Chemical Composition of the Very Metal-poor Star LAMOST J1645+4357. We report on the chemical composition of the very metal-poor (VMP; [Fe/H] = -2.9) star LAMOST J1645+4357, which was identified as a red giant having peculiar abundance ratios by Li et al. The standard abundance analysis is carried out for this object and the well-studied metal-poor star HD 122563, which has similar atmospheric parameters. LAMOST J1645+4357 has a remarkable abundance set, highlighted by these features: (1) nitrogen is significantly enhanced ([N/Fe] = +1.4), and the total abundance of C and N is also very high ([(C+N)/Fe] = +0.9); (2) α-elements are overabundant with respect to iron, as generally found in VMP stars; (3) Ti, Sc, Co, and Zn are significantly deficient; (4) Cr and Mn are enhanced compared to most of VMP stars; and (5) Sr and Ba are deficient, and the Sr/Ba ratio ([Sr/Ba] = -1.0) is significantly lower than the value expected for the r-process. The overall abundance pattern of this object from C to Zn is well reproduced by a faint supernova model assuming spherical explosion, except for the excess of Cr and Mn, which requires enhancement of incomplete Si burning or small contributions from a Type Ia or pair-instability supernova. There remains, however, a question as to why the abundance pattern of this star is so unique among VMP stars.

Keywords: Stellar abundances, Population II stars, Nucleosynthesis
A Multiwavelength Investigation of Dust and Stellar Mass Distributions in Galaxies: Insights from High-resolution JWST Imaging. We study the morphological properties of mid-infrared selected galaxies at 1.0 &lt; z &lt; 1.7 in the SMACS J0723.3-7327 cluster field to investigate the mechanisms of galaxy mass assembly and structural formation at cosmic noon. We develop a new algorithm to decompose the dust and stellar components of individual galaxies by using high-resolution images in the MIRI F770W and NIRCam F200W bands. Our analysis reveals that a significant number of galaxies with stellar masses between 109.5 &lt; M */M ⊙ &lt; 1010.5 exhibit dust cores that are relatively more compact than their stellar cores. Specifically, within this mass range, the nonparametric method indicates that the dust cores are 1.23 (±0.05) times more compact than the stellar cores on average when evaluated with flux concentration of the two components within a fixed radius. Similarly, the parametric method yields an average compactness ratio of 1.27 (±0.06). Notably, the most massive galaxy (M * ~ 1010.9 M ⊙) in our sample demonstrates a comparable level of compactness between its stellar core and dust, with a dust-to-stellar ratio of 0.86 (0.89) as derived from nonparametric (parametric) method. The observed compactness of the dust component is potentially attributed to the presence of a (rapidly growing) massive bulge that in some cases is associated with elevated star formation. Expanding the sample size through a joint analysis of multiple Cycle 1 deep-imaging programs can help to confirm the inferred picture. Our pilot study highlights that MIRI offers an efficient approach to studying the structural formation of galaxies from cosmic noon to the modern Universe.

Keywords: Galaxy structure, Galaxy bulges, Galaxy evolution, Interstellar medium
Stellar Collisions in the Galactic Center: Massive Stars, Collision Remnants, and Missing Red Giants. Like most galaxies, the Milky Way harbors a supermassive black hole (SMBH) at its center, surrounded by a nuclear star cluster. In this dense star cluster, direct collisions can occur between stars before they evolve off the main sequence. Using a statistical approach, we characterize the outcomes of these stellar collisions within the inner parsec of the Galactic center (GC). Close to the SMBH, where the velocity dispersion is larger than the escape speed from a Sun-like star, collisions lead to mass loss. We find that the stellar population within 0.01 pc is halved within about a billion years because of destructive collisions. Additionally, we predict a diffuse population of peculiar low-mass stars in the GC. These stars have been divested of their outer layers in the inner 0.01 pc before migrating to larger distances from the SMBH. Between 0.01 and 0.1 pc from the SMBH, collisions can result in mergers. Our results suggest that repeated collisions between lower-mass stars can produce massive (≳10 M ⊙) stars, and that there may be ~100 of them residing in this region. We provide predictions on the number of so-called G objects, dust- and gas-enshrouded stellar objects, that may result from main-sequence stellar collisions. Lastly, we comment on uncertainties in our model and possible connections between stellar collisions and the missing red giants in the GC.

Keywords: Galactic center, Stellar dynamics, Stellar mergers, Star clusters
Identifying Acoustic Wave Sources on the Sun. II. Improved Filter Techniques for Source Wavefield Seismology. In this paper, we refine a previously developed acoustic source filter, improving its reliability and extending its capabilities. We demonstrate how to fine-tune the filter to meet observational constraints and focus on specific wave-front speeds. This refinement enables discrimination of acoustic source depths and tracking of local source wave fronts, thereby facilitating ultralocal helioseismology. By utilizing the photospheric Doppler signal from a subsurface source in a MURaM simulation, we demonstrate that robust ultralocal three-dimensional helioseismic inversions for the granular flows and the local sound speed to depths of at least 80 km below the photosphere are possible. The capabilities of the National Science Foundation's new Daniel K. Inouye Solar Telescope will enable such measurements of the real Sun.

Keywords: Solar photosphere, Helioseismology, The Sun, Solar physics, Solar granulation, Solar oscillations
A Gradual Decline of Star Formation since Cluster Infall: New Kinematic Insights into Environmental Quenching at 0.3 &lt; z &lt; 1.1. The environments where galaxies reside crucially shape their star formation histories. We investigate a large sample of 1626 cluster galaxies located within 105 galaxy clusters spanning a large range in redshift (0.26 &lt; z &lt; 1.13). The galaxy clusters are massive (M 500 ≳ 2 × 1014 M ☉) and uniformly selected from the SPT and ACT Sunyaev-Zel'dovich surveys. With spectra in hand for thousands of cluster members, we use the galaxies' position in projected phase space as a proxy for their infall times, which provides a more robust measurement of environment than quantities such as projected clustercentric radius. We find clear evidence for a gradual age increase of the galaxy's mean stellar populations (~0.71 ± 0.4 Gyr based on a 4000 Å break, Dn4000) with the time spent in the cluster environment. This environmental quenching effect is found regardless of galaxy luminosity (faint or bright) and redshift (low or high-z), although the exact stellar age of galaxies depends on both parameters at fixed environmental effects. Such a systematic increase of Dn4000 with infall proxy would suggest that galaxies that were accreted into hosts earlier were quenched earlier due to longer exposure to environmental effects such as ram pressure stripping and starvation. Compared to the typical dynamical timescales of 1-3 Gyr of cluster galaxies, the relatively small age increase (~0.71 ± 0.4 Gyr) found in our sample galaxies seems to suggest that a slow environmental process such as starvation is the dominant quenching pathway. Our results provide new insights into environmental quenching effects spanning a large range in cosmic time (~5.2 Gyr, z = 0.26-1.13) and demonstrate the power of using a kinematically derived infall time proxy.

Keywords: Galaxy clusters, Galaxy environments, High-redshift galaxy clusters, Galaxy evolution, Galaxy quenching, Galaxies
Using Giant Pulses to Measure the Impulse Response of the Interstellar Medium. Giant pulses emitted by PSR B1937+21 are bright, intrinsically impulsive bursts. Thus, the observed signal from a giant pulse is a noisy but direct measurement of the impulse response from the ionized interstellar medium. We use this fact to detect 13,025 giant pulses directly in the baseband data of two observations of PSR B1937+21. Using the giant pulse signals, we model the time-varying impulse response with a sparse approximation method, in which the time dependence at each delay is decomposed in Fourier components, thus constructing a wavefield as a function of delay and differential Doppler shift. We find that the resulting wavefield has the expected parabolic shape with several diffuse structures within it, suggesting the presence of multiple scattering locations along the line of sight. We also detect an echo at a delay of about 2.4 ms, over 1.5 times the rotation period of the pulsar, which moves along the trajectory expected from geometry between the two observations. The structures in the wavefield are insufficiently sparse to produce a complete model of the system; hence, the model is not predictive across gaps larger than about the scintillation time. Nevertheless, within its range, it reproduces about 75% of the power of the impulse response, a fraction limited mostly by the signal-to-noise ratio of the observations. Furthermore, we show that by deconvolution, using the model impulse response, we can successfully recover the intrinsic pulsar emission from the observed signal.

Keywords: Radio bursts, Deconvolution, Interstellar scintillation, Pulsars