Sazuna/UAT_keywords huggingface dataset:
Contribution of Neutrino-dominated Accretion Flows to the Cosmic MeV Neutrino Background. Neutrino-dominated accretion flows (NDAFs) are one of the important MeV neutrino sources and significantly contribute to the cosmic diffuse neutrino background. In this paper, we investigate the spectrum of the diffuse NDAF neutrino background (DNNB) by fully considering the effects of the progenitor properties and initial explosion energies based on core-collapse supernova (CCSN) simulations, and estimate the detectable event rate by the Super-Kamiokande detector. We find that the predicted background neutrino flux is mainly determined by the typical CCSN initial explosion energy and progenitor metallicity. For the optimistic cases, in which the typical initial explosion energy is low, the diffuse flux of the DNNB is comparable to the diffuse supernova neutrino background, which might be detected by upcoming larger neutrino detectors, such as Hyper-Kamiokande, the Jiangmen Underground Neutrino Observatory, and the Deep Underground Neutrino Experiment. Moreover, the strong outflows from NDAFs could dramatically decrease their contribution to the neutrino background.

Keywords: Accretion, Black holes, Core-collapse supernovae, Neutrino astronomy, Massive stars
The Temperature and Density of a Solar Flare Kernel Measured from Extreme-ultraviolet Lines of O IV. Previously unexplored diagnostics of O IV in the extreme-ultraviolet region 260–280 Å are used to derive a temperature and density for a solar flare kernel observed on 2012 March 9 with the Extreme-ultraviolet Imaging Spectrometer on the Hinode satellite. Seven lines from the 2s2p 2–2s2p3s transition array between 271.99 and 272.31 Å are both temperature- and density-sensitive relative to the line at 279.93 Å. The temperature, T, is constrained with the λ268.02/λ279.93 ratio, giving a value of   $\mathrm{log}(T/{\rm{K}})=5.10\pm 0.03$  . The ratio λ272.13/λ279.93 then yields an electron number density, N e, of   $\mathrm{log}({N}_{{\rm{e}}}/{\mathrm{cm}}^{-3})=12.52$   with a lower limit of 11.90 and an upper limit of 14.40. The O IV emitting volume is estimated to be 0.″4 (300 km) across. Additional O IV lines at 196, 207, and 260 Å are consistent with the derived temperature and density but have larger uncertainties from the radiometric calibration and blending. Density diagnostics of O V and Mg VII from the same spectrum are consistent with a constant pressure of 1017.0 K cm‑3 through the transition region. The temperature derived from O IV supports recent results that O IV is formed around 0.10 dex lower at high densities compared to standard zero-density ionization balance calculations.

Keywords: Solar flares, Atomic data, Solar flare spectra, Ultraviolet spectroscopy, Solar transition region
Morphology and Mach Number Dependence of Subsonic Bondi–Hoyle Accretion. We carry out three-dimensional computations of the accretion rate onto an object (of size R sink and mass m) as it moves through a uniform medium at a subsonic speed v ∞. The object is treated as a fully absorbing boundary (e.g., a black hole). In contrast to early conjectures, we show that for an accretor with   ${R}_{\mathrm{sink}}\ll {R}_{A}=2{Gm}/{v}_{\infty }^{2}$   in a gaseous medium with adiabatic index γ = 5/3, the accretion rate is independent of Mach number and is determined only by m and the gas entropy. Our numerical simulations are conducted using two different numerical schemes via the Athena++ and Arepo hydrodynamics solvers, which reach nearly identical steady-state solutions. We find that pressure gradients generated by the isentropic compression of the flow near the accretor are sufficient to suspend much of the surrounding gas in a near-hydrostatic equilibrium, just as predicted from the spherical Bondi–Hoyle calculation. Indeed, the accretion rates for steady flow match the Bondi–Hoyle rate, and are indicative of isentropic flow for subsonic motion where no shocks occur. We also find that the accretion drag may be predicted using the Safronov number, Θ = R  A /R sink, and is much less than the dynamical friction for sufficiently small accretors (R sink ≪ R  A ).

Keywords: Hydrodynamics, Bondi accretion, Galaxy accretion, Stellar accretion, Exoplanet formation, Astrophysical black holes
NuSTAR Observations of Candidate Subparsec Binary Supermassive Black Holes. We present an analysis of NuSTAR X-ray observations of three active galactic nuclei (AGN) that were identified as candidate subparsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey based on apparent periodicity in their optical light curves. Simulations predict that close-separation accreting SMBH binaries will have different X-ray spectra than single accreting SMBHs. We previously observed these AGN with Chandra and found no differences between their low-energy X-ray properties and the larger AGN population. However, some models predict differences to be more prominent at energies higher than probed by Chandra. We find that even at the higher energies probed by NuSTAR, the spectra of these AGN are indistinguishable from the larger AGN population. This could rule out models predicting large differences in the X-ray spectra in the NuSTAR bands. Alternatively, it might mean that these three AGN are not binary SMBHs.

Keywords: Supermassive black holes, Seyfert galaxies, X-ray active galactic nuclei, Quasars
Comparing Recent Pulsar Timing Array Results on the Nanohertz Stochastic Gravitational-wave Background. The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational-wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within 1σ. The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we "extended" each PTA's data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the Hellings–Downs correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA's Data Release 3, which will involve not just adding in additional pulsars but also including data from all three PTAs where any given pulsar is timed by more than a single PTA.

Keywords: Gravitational waves, Pulsars
Empirical Models of the Hβ Broad Emission Line Gas Density Field. We present the second iteration of the CARAMEL-GAS code, an empirical model of the broad-line region (BLR) gas density field. Building on the initial development and testing of CARAMEL-GAS, we expand the meaning of the model parameter α, which initially represented only the power-law index of the dependency of emissivity on radial distance. In this work, we test a more generalized radial power-law index, α, that also includes a description of the effective emitting size(s) of the BLR structure as a function of radial distance. We select a sample of 10 active galactic nuclei (AGN) from three different Lick AGN Monitoring Project campaigns to further validate the CARAMEL-GAS code and test the generalized radial power-law index, α. Our results confirm that the CARAMEL-GAS results are in general agreement with the published results determined using the original CARAMEL code, further demonstrating that our forward modeling method is robust. We find that a positive radial power-law index is generally favored and propose three possible scenarios: (i) the BLR structure has increasing effective emitting size(s) at larger radial distances from the central source, (ii) emission is concentrated at the outer edges of the BLR, and (iii) stronger theoretical assumptions are needed to break the degeneracies inherent to the interpretation of reverberation mapping data in terms of underlying gas properties.

Keywords: Supermassive black holes, Active galaxies, Active galactic nuclei
Inferring Properties of Dark Galactic Halos Using Strongly Lensed Gravitational Waves. Gravitational waves (GWs) can be deflected, similarly to electromagnetic (EM) waves, by massive objects through the phenomenon of gravitational lensing. The importance of GW lensing for GW astronomy is becoming increasingly apparent in the GW detection era, in which nearly 100 events have already been detected. As current ground-based interferometers reach their design sensitivities, it is anticipated that these detectors may observe a few GW signals that are strongly lensed by the dark halos of intervening galaxies or galaxy clusters. Analyzing the strong lensing effects on GW signals is, thus, becoming important to understand the lens' properties and correctly infer the intrinsic GW source parameters. However, one cannot accurately infer lens parameters for complex lens models with only GW observations because there are strong degeneracies between the parameters of lensed waveforms. In this paper, we discuss how to conduct parameter estimation of strongly lensed GW signals and infer the lens parameters using additional EM information, including the lens galaxy's axis ratio and the GW source-hosting galaxy's lensed images. We find that for simple spherically symmetric lens models, the lens parameters can be well recovered using only GW information. On the other hand, recovering the lens parameters requires systems in which four or more GW images are detected with additional EM observations for nonaxially symmetric lens models. Combinations of GW and EM observations can further improve the inference of the lens parameters.

Keywords: Galaxy dark matter halos, Strong gravitational lensing, Computational methods, Gravitational lensing, Gravitational waves
Synthetic Gaia DR3 Surveys from the FIRE Cosmological Simulations of Milky Way-mass Galaxies. The third data release (DR3) of Gaia has provided a fivefold increase in the number of radial velocity measurements of stars, as well as a stark improvement in parallax and proper motion measurements. To help with studies that seek to test models and interpret Gaia DR3, we present nine Gaia synthetic surveys, based on three solar positions in three Milky Way-mass galaxies of the Latte suite of the FIRE-2 cosmological simulations. These synthetic surveys match the selection function, radial velocity measurements, and photometry of Gaia DR3, adapting the code base Ananke, previously used to match the Gaia DR2 release by Sanderson et al. The synthetic surveys are publicly available and can be found at http://ananke.hub.yt/. Similarly to the previous release of Ananke, these surveys are based on cosmological simulations and thus are able to model nonequilibrium dynamical effects, making them a useful tool in testing and interpreting Gaia DR3.

Keywords: Hydrodynamical simulations, Gaia, Milky Way Galaxy, Milky Way dynamics
Mining the GALAH Data. I. Study of Five Super Lithium-rich Metal-poor Giants. The presence of a large amount of Li in giants is still a mystery. Most of the super Li-rich (SLR) giants reported in recent studies are in the solar metallicity regime. Here, we study the five metal-poor SLRs from the Galactic Archeology with HERMES Data Release 3, with their [Fe/H] ranging from ‑1.35 to ‑2.38 with lithium abundance of A(Li) ≥ 3.4 dex. The asteroseismic analysis reveals that none are on the red giant branch. The average period spacing (ΔP ) values indicate giants are in the core He-burning phase. All of them are low-mass giants (M &lt; 1.5 M ⊙). Their location in the Hertzsprung–Russell diagram suggests one of them is in the red clump (RC) phase, and interestingly, the other four are much brighter and coincide with the early asymptotic giant branch phase. The analysis of the abundance reveals that C, O, Na, Ba, and Eu are normal in giants of respective metallicities and evolutionary phases. Further, we did not find any strong evidence of the presence of dust in the form of infrared excess or binarity from the available radial velocity data. We discuss a few scenarios for the existence of SLRs at higher luminosity, including past merger events. Our findings will help in understanding the production and evolution of Li among giants, in particular, during the RC phase and the post-RC phase.

Keywords: Lithium stars, Chemically peculiar stars, Giant stars
Morphology and Kinematics of the Gas in M51: How Interaction with NGC 5195 Has Molded the Structure of Its Arms. The Whirlpool Galaxy is a well-studied grand design galaxy with two major spiral arms, and a large satellite NGC 5195. The arms both show long uniform sections with perturbations ("kinks" or sharp turns) in specific regions. Comparing the two arms shows a small radial offset between the main kinked regions. We analyzed the morphology and also the velocity field in the disk of M51 using kinematic maps based on Hα and CO line emission. These sample complementary radial ranges, with the CO map covering the central zone and the Hα map extending to cover the outer zone. We looked for indicators of density wave resonance, zones where radial flows of gas in the disk plane reverse their sign. These were present in both velocity maps; their 2D localization placed them along or closely parallel to the spiral arms, at a set of well-defined galactocentric radii, and notably more concentrated along the southern, stronger arm. The results can be well interpreted quantitatively, using a numerical model of the interaction of M51 and NGC 5195 in which the satellite has made two relatively recent passes through the disk plane of M51. During the first pass the pair of dominant spiral arms was stimulated, and during the second pass the strong kinks in both arms were formed at about the same time. The second interaction is particularly well characterized, because the timescale corresponding to the production of the kinks and the recovery of the original pitch angle is identical for the two arms.

Keywords: Galaxy dynamics, Galaxy interactions, Spiral arms, Galaxy kinematics, Spiral pitch angle, Galaxy spectroscopy
Impact of Helium II Resonant Absorption on the Ultraviolet Background Modeled in Three Dimensions. We implement a treatment of helium II absorption and reemission into the TECHNICOLOR DAWN cosmological simulations to study its impact on the metagalactic ultraviolet background (UVB) in three dimensions. By comparing simulations with and without He II reprocessing, we show that it weakens the mean UVB by ∼3 dex from z = 10–5 between 3.5 and 4 Ryd, where the He II Lyman series resonance occurs. In overdense regions, the overall UVB amplitude is higher, and the impact of He II reprocessing is weaker, qualitatively indicating an early start to He II reionization near galaxies. Comparing our simulations to two popular one-dimensional UV models, we find good agreement up to 3 Ryd at z = 5. At higher energies, our simulation shows significantly greater He II absorption because it accounts for He II arising both in diffuse regions and in Lyman limit systems. By contrast, the comparison models account only for He II in Lyman limit systems, which are subdominant prior to the completion of He II reionization. The H I and He II reionization histories are nearly unaffected by He II reprocessing, although the cosmic star formation rate density is altered by up to 4%. The cosmic mass density of C IV is reduced by ∼2 dex when He II is accounted for, while Si IV, C II, Mg II, Si II, and O I are unaffected.

Keywords: Radiative transfer simulations, Galaxy evolution
Analysis of BMR Tilt from AutoTAB Catalog: Hinting toward the Thin Flux Tube Model?. One of the intriguing mechanisms of the Sun is the formation of bipolar magnetic regions (BMRs) in the solar convection zone (CZ), which are observed as regions of concentrated magnetic fields of opposite polarity on the photosphere. These BMRs are tilted with respect to the equatorial line, which statistically increases with latitude. The thin flux tube model, employing the rise of magnetically buoyant flux loops and their twist by Coriolis force, is a popular paradigm for explaining the formation of tilted BMRs. In this study, we assess the validity of the thin flux tube model by analyzing the tracked BMR data obtained through the Automatic Tracking Algorithm for BMRs. Our observations reveal that the tracked BMRs exhibit the expected collective behaviors. We find that the polarity separation of BMRs increases over their normalized lifetime, supporting the assumption of a rising flux tube from the CZ. Moreover, we observe an increasing trend of the tilt with the flux of the BMR, suggesting that rising flux tubes associated with lower flux regions are primarily influenced by drag force and Coriolis force, while in higher flux regions, magnetic buoyancy dominates. Furthermore, we observe Joy's law dependence for emerging BMRs from their first detection, indicating that at least a portion of the tilt observed in BMRs can be attributed to the Coriolis force. Notably, lower flux regions exhibit a higher amount of fluctuations associated with their tilt measurement compared to stronger flux regions, suggesting that lower flux regions are more susceptible to turbulent convection.

Keywords: Solar active region magnetic fields, Bipolar sunspot groups, Solar physics, Solar magnetic fields, Solar activity
Morphology of Galaxies in JWST Fields: Initial Distribution and Evolution of Galaxy Morphology. A recent study from the Horizon Run 5 (HR5) cosmological simulation has predicted that galaxies with   $\mathrm{log}\,{M}_{* }/{M}_{\odot }\lesssim 10$   in the cosmic morning (10 ≳ z ≳ 4) dominantly have disk-like morphology in the ΛCDM universe, which is driven by the tidal torque in the initial fluctuations of matter. For a direct comparison with observation we identify a total of about 19,000 James Webb Space Telescope (JWST) galaxies with   $\mathrm{log}\,{M}_{* }/{M}_{\odot }\gt 9$   at z = 0.6–8.0 utilizing deep JWST/NIRCam images of publicly released fields, including North Ecliptic Pole Time-Domain Fields, Next Generation Deep Extragalactic Exploratory Public survey, Cosmic Evolution Early Release Science Survey, Cosmic Evolution Survey, UltraDeep Survey, and SMACS J0723-7327. We estimate their stellar masses and photometric redshifts with the redshift dispersion of σ NMAD = 0.009 and an outlier fraction of only about 6%. We classify galaxies into three morphological types, disks, spheroids, and irregulars, applying the same criteria used in the HR5 study. The morphological distribution of the JWST galaxies shows that disk galaxies account for 60%–70% at all redshift ranges. However, in the high-mass regime (  $\mathrm{log}\,{M}_{* }/{M}_{\odot }\gtrsim 11$  ), spheroidal morphology becomes the dominant type. This implies that the mass growth of galaxies is accompanied by a morphological transition from disks to spheroids. The fraction of irregulars is about 20% or less at all masses and redshifts. All the trends in the morphology distribution are consistently found in the six JWST fields. These results are in close agreement with the results from the HR5 simulation, particularly confirming the prevalence of disk galaxies at small masses in the cosmic morning and noon.

Keywords: Galaxy evolution, Galaxy classification systems
GRB 221009A: Spectral Signatures Based on ALPs Candidates. GRB 221009A has posed a significant challenge to our current understanding of the mechanisms that produce TeV photons in gamma-ray bursts (GRBs). On one hand, the Klein–Nishina (KN) effect of the inverse Compton scattering leads to less efficient energy losses of high-energy electrons. On the other hand, at a redshift of 0.151, the TeV spectrum of GRB 221009A undergoes significant absorption by the extragalactic background light (EBL). Therefore, the observation of a 13 TeV photon in this event implies the presence of enormous photon fluxes at the source, which the synchrotron self-Compton mechanism in external shocks cannot easily generate. As an alternative, some authors have suggested the possibility of converting the TeV photons into axion-like particles (ALPs) at the host galaxy, in order to avoid the effects of EBL absorption, and then reconverting them into photons within the Milky Way. While this solution relaxes the requirement of very high photon fluxes, the KN effect still poses a challenge. Previously, we have shown that the injections of ALPs could explain the observation of 13 TeV photons. Here, we include the energy dependence of the probability of survival and the amount of energy carried to determine the ALP candidates, which could potentially explain the TeV photons observed by the Large High Altitude Air Shower Observatory and their hard spectrum. We found that the allowed candidates are generally clustered around masses of 10‑7 eV. We also considered different EBL models, for the one predicting larger attenuation tends to reject ALP candidates with the lowest coupling factor. For some hypotheses of the EBL model, these candidates are found below a region of the parameter space in which, if detected, ALPs could account for all of the cold dark matter in the Universe.

Keywords: Gamma-ray bursts, Dark matter, High energy astrophysics
Narrowly Banded Spectra with Peak Frequency around 1 GHz of FRB 20201124A: Implications for Energy Function and Radiation Physics. The radiation physics of fast radio bursts (FRBs) remains an open question. Current observations have discovered that narrowly banded bursts of FRB 20201124A are active in 0.4–2 GHz, and their spectral peak frequency (  ${\nu }_{p}^{\mathrm{obs}}$  ) is mostly toward ∼1 GHz. Utilizing a sample of 1268 bursts of FRB 20201124A detected with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we show that the 1σ spectral regime of 71.4% of the events (in-band bursts) is within the FAST bandpass. The intrinsic burst energies (  ${E}_{\mathrm{BWe}}^{\mathrm{obs}}$  ) and spectral widths (  ${\sigma }_{s}^{\mathrm{obs}}$  ) are well measured by fitting the spectral profile with a Gaussian function. The derived   ${E}_{\mathrm{BWe}}^{\mathrm{obs}}$   and   ${\sigma }_{s}^{\mathrm{obs}}$   distributions are lognormal and centered at   $\mathrm{log}{E}_{\mathrm{BWe}}^{\mathrm{obs}}/\mathrm{erg}=37.2\,(\sigma =0.76)$   and   $\mathrm{log}{\sigma }_{s}^{\mathrm{obs}}/\mathrm{GHz}=-1.16\,(\sigma =0.17)$  . Our Monte Carlo simulation analysis infers its intrinsic ν  p  distribution as a normal function centered at ν  p,c  = 1.16 GHz (σ = 0.22) and its intrinsic energy function as   ${\rm{\Phi }}(E)\propto {E}^{-0.60}{e}^{-E/{E}_{c}}$   with E  c  = 9.49 × 1037 erg. We compare these results with that of typical repeating FRBs 20121102A and 20190520B, which are active over a broad frequency range at several specific frequencies, and discuss possible observational biases on the estimation of the event rate and energy function. Based on these results, we argue that FRB 20201124A likely occurs in a fine-tuned plasma for maser radiation at a narrow frequency range, while FRB 20121102A and FRB 20190520B could involve clumpy plasma conditions that make maser emission around several specific frequencies in a broad range.

Keywords: Radio bursts, Radio transient sources