Sazuna/UAT_keywords huggingface dataset:
ODIN: Improved Narrowband Lyα Emitter Selection Techniques for z = 2.4, 3.1, and 4.5. Lyman-alpha-emitting galaxies (LAEs) are typically young, low-mass, star-forming galaxies with little extinction from interstellar dust. Their low dust attenuation allows their Lyα emission to shine brightly in spectroscopic and photometric observations, providing an observational window into the high-redshift Universe. Narrowband surveys reveal large, uniform samples of LAEs at specific redshifts that probe large-scale structure and the temporal evolution of galaxy properties. The One-hundred-deg2 DECam Imaging in Narrowbands (ODIN) utilizes three custom-made narrowband filters on the Dark Energy Camera (DECam) to discover LAEs at three equally spaced periods in cosmological history. In this paper, we introduce the hybrid-weighted double-broadband continuum estimation technique, which yields improved estimation of Lyα equivalent widths. Using this method, we discover 6032, 5691, and 4066 LAE candidates at z = 2.4, 3.1, and 4.5 in the extended COSMOS field (∼9 deg2). We find that [O II] emitters are a minimal contaminant in our LAE samples, but that interloping Green Pea–like [O III] emitters are important for our redshift 4.5 sample. We introduce an innovative method for identifying [O II] and [O III] emitters via a combination of narrowband excess and galaxy colors, enabling their study as separate classes of objects. We present scaled median stacked spectral energy distributions for each galaxy sample, revealing the overall success of our selection methods. We also calculate rest-frame Lyα equivalent widths for our LAE samples and find that the EW distributions are best fit by exponential functions with scale lengths of w 0 = 53 ± 1, 65 ± 1, and 59 ± 1 Å, respectively.

Keywords: Cosmology, Galaxy formation, Galaxy evolution, Emission line galaxies
The Effects of Cooling on Boundary Layer Accretion. In many cases accretion proceeds from disks onto planets, stars, white dwarfs, and neutron stars via a boundary layer, a region of intense shear where gas transitions from a near-Keplerian speed to that of the surface. These regions are not susceptible to the common magnetorotational and Kelvin–Helmholtz instabilities, and instead global modes generated by supersonic shear instabilities are a leading candidate to govern transport in these regions. This work investigates the dynamics of these systems under a range of thermodynamic conditions, surveying both disk sound speeds and cooling rates. Very fast and very slow cooling have little effect on wave dynamics: In the fast-cooling limit, waves propagate in an effectively isothermal manner, and in the slow-cooling limit, wave propagation is effectively adiabatic. However, when the cooling timescale is comparable to the wave period, wave damping becomes extreme. In cases with intermediate cooling rates, mass and angular momentum transport can be suppressed by orders of magnitude compared to isothermal and uncooled cases. Cooling in accretion disks leads to a preference for wavenumbers near and below the Mach number of the disk; the corresponding lower frequencies can (in nonisothermal systems) couple to gravity modes within the star, potentially driving low-frequency variability such as dwarf nova and quasi-periodic oscillations in accreting systems.

Keywords: Accretion, Hydrodynamical simulations, Compact binary stars, Hydrodynamics
Galactic-Seismology Substructures and Streams Hunter with LAMOST and Gaia. I. Methodology and Local Halo Results. We present a novel, deep-learning-based method—dubbed Galactic-Seismology Substructures and Streams Hunter, or GS3 Hunter for short—to search for substructures and streams in stellar kinematics data. GS3 Hunter relies on a combined application of Siamese neural networks to transform the phase space information and the K-means algorithm for the clustering. As a validation test, we apply GS3 Hunter to a subset of the Feedback in Realistic Environments (FIRE) cosmological simulations. The stellar streams and substructures thus identified are in good agreement with corresponding results reported earlier by the FIRE team. In the same vein, we apply our method to a subset of local halo stars from the Gaia Early Data Release 3 and GALAH DR3 data sets and recover several previously known dynamical groups, such as Thamnos 1+2, the hot thick disk, ED-1, L-RL3, Helmi 1+2, Gaia-Sausage-Enceladus, Sequoia, Virgo Radial Merger, Cronus, and Nereus. Finally, we apply our method without fine-tuning to a subset of K giant stars located in the inner halo region, obtained from the LAMOST Data Release 5 data set. We recover three previously known structures (Sagittarius, Hercules-Aquila Cloud, and the Virgo Overdensity), but we also discover a number of new substructures. We anticipate that GS3 Hunter will become a useful tool for the community dedicated to the search for stellar streams and structures in the Milky Way (MW) and the Local Group, thus helping advance our understanding of the stellar inner and outer halos and the assembly and tidal stripping history in and around the MW.

Keywords: Local Group, Milky Way disk, Milky Way stellar halo, Milky Way Galaxy
Spectral Properties and the Influence of Coronal Mass Ejections in <SUP>3</SUP>He-rich Solar Energetic Particle Events. We analyze the spectral properties of 3He and 4He as well as the heavy ions (oxygen, neon, magnesium, silicon, and iron) in 80 3He-rich solar energetic particle (SEP) events observed by the Ultra-Low-Energy Ion Spectrometer on board the Advanced Composition Explorer spacecraft since its launch in 1997 until 2024. We split the spectral analysis into two criteria: events with fast and wide coronal mass ejections (CMEs; called "FW events") and events with slow, narrow, or no observed CMEs (called "non-FW events"). Overall, we find that events with fast and wide CMEs exhibit more uniform spectra across all species, and their low-energy spectral indices are strongly correlated, suggesting a CME provides an additional reacceleration mechanism for the 3He-rich SEPs. When comparing each species' low-energy spectral index for events with no associated fast-and-wide CME, we find a primary peak in the spectral hardness of 3He, and a secondary peak in Mg and Si. If we consider a plasma temperature of 1.0–1.3 MK, Mg and Si have a charge-to-mass ratio (Q/M) nearest to one-third (1/3), directly half that of 3He. Thus, our results support the results of Roth &amp; Temerin, which suggest heavy ions resonate with the second harmonic of the same ion cyclotron waves energizing 3He. However, it is unclear why the Fe enhancement is not reflected in its spectral index, and we propose that additional acceleration and/or transport mechanisms are playing a role in the abundance enhancement of Fe and heavier ions.

Keywords: Solar flares, Solar magnetic reconnection, Heliosphere, Solar energetic particles, Active sun
Unveiling the Multifaceted GRB 200613A: Prompt Emission Dynamics, Afterglow Evolution, and the Host Galaxy's Properties. We present our optical observations and multiwavelength analysis of the GRB 200613A detected by the Fermi satellite. Time-resolved spectral analysis of the prompt gamma-ray emission was conducted utilizing the Bayesian block method to determine statistically optimal time bins. Based on the Bayesian Information Criterion, the data generally favor the Band+blackbody (BB) model. We speculate that the main Band component comes from the Blandford–Znajek mechanism, while the additional BB component comes from the neutrino annihilation process. The BB component becomes significant for a low-spin, high-accretion-rate black hole central engine, as evidenced by our model comparison with the data. The afterglow light curve exhibits typical power-law decay, and its behavior can be explained by the collision between the ejecta and the constant interstellar medium. Model fitting yields the following parameters:  EK,iso=(2.04‑1.50+11.8)×1053  erg,  Γ0=354‑217+578 ,  p=2.09‑0.03+0.02 ,  n18=(2.04‑1.87+9.71)×102  cm‑3,  θj=24.0‑5.54+6.50  degree,  ϵe=1.66‑1.39+4.09)×10‑1  and  ϵB=(7.76‑5.9+48.5)×10‑6 . In addition, we employed the public Python package Prospector to perform a spectral energy distribution modeling of the host galaxy. The results suggest that the host galaxy is a massive galaxy ( log(M*/M⊙)=11.75‑0.09+0.10 ) with a moderate star formation rate ( SFR=22.58‑7.22+13.63M⊙  yr‑1). This SFR is consistent with the SFR of ∼34.2M ⊙ yr‑1 derived from the [O II] emission line in the observed spectrum.

Keywords: Gamma-ray bursts, Transient sources, High energy astrophysics
Simulating Brown Dwarf Observations for Various Mass Functions, Birthrates, and Low-mass Cutoffs. After decades of brown dwarf discovery and follow-up, we can now infer the functional form of the mass distribution within 20 pc, which serves as a constraint on star formation theory at the lowest masses. Unlike objects on the main sequence that have a clear luminosity-to-mass correlation, brown dwarfs lack a correlation between an observable parameter (luminosity, spectral type, or color) and mass. A measurement of the brown dwarf mass function must therefore be procured through proxy measurements and theoretical models. We utilize various assumed forms of the mass function, together with a variety of birthrate functions, low-mass cutoffs, and theoretical evolutionary models, to build predicted forms of the effective temperature distribution. We then determine the best fit of the observed effective temperature distribution to these predictions, which in turn reveals the most likely mass function. We find that a simple power law ( dN/dM∝M‑α ) with α ≈ 0.5 is optimal. Additionally, we conclude that the low-mass cutoff for star formation is ≲0.005 M ⊙. We corroborate the findings of Burgasser, which state that the birthrate has a far lesser impact than the mass function on the form of the temperature distribution, but we note that our alternate birthrates tend to favor slightly smaller values of α than the constant birthrate. Our code for simulating these distributions is publicly available. As another use case for this code, we present findings on the width and location of the subdwarf temperature gap by simulating distributions of very old (8–10 Gyr) brown dwarfs.

Keywords: Brown dwarfs, Initial mass function, Solar neighborhood, Stellar mass functions, Star formation
The Imprint of Dark Matter on the Galactic Acceleration Field. Measurements of the accelerations of stars enabled by time-series extreme-precision spectroscopic observations, pulsar timing, and eclipsing binary stars in the solar neighborhood offer insights into the mass distribution of the Milky Way that do not rely on traditional equilibrium modeling. Given the measured accelerations, we can determine a total mass density and infer the amount of dark matter (DM) by accounting for the mass in stars, gas, and dust. Leveraging FIRE-2 simulations of Milky Way–mass galaxies we compare vertical acceleration profiles between cold DM (CDM) and self-interacting DM (SIDM) with a constant cross section of 1 cm2 g‑1 across three halos with diverse assembly histories. Notably, significant asymmetries in vertical acceleration profiles near the midplane at fixed radii are observed in both CDM and SIDM, particularly in halos recently affected by mergers with satellites of Sagittarius/SMC-like masses or greater. These asymmetries offer a unique window into exploring the merger history of a galaxy. We show that SIDM halos manifest a more oblate shape and consistently exhibit higher local stellar and DM densities and steeper vertical acceleration gradients, up to 10%–30% steeper near the solar neighborhood. However, similar magnitude changes can arise from azimuthal variations in the baryonic components at a fixed radius and external influences like mergers, making it difficult to distinguish between CDM and SIDM using acceleration measurements in a single galaxy.

Keywords: Dark matter density, Galaxy dynamics, Dark matter
Galaxy–Absorber Association in the Epoch of Reionization: Galactic Population Luminosity Distribution for Different Absorbers at 10 ≥ z ≥ 5.5. How do galaxies of different luminosities contribute to the metal absorber populations of varying species and strength? We present our analysis of the predicted metal contributions from galaxies as observed in quasar absorption line spectra during the end of the epoch of reionization (10 ≥ z ≥ 5.5). This was done by implementing on-the-fly particle tracking into the latest TECHNICOLOR DAWN simulation and then linking C II, C IV, Si II, Si IV, O I, and Mg II absorbers to host galaxies in postprocessing. We define the host galaxy luminosity distribution (HGLD) as the rest-frame ultraviolet luminosity distribution of galaxies contributing ions to an absorber, weighted by the fractional contribution, and compute its dependence on ion and absorber strength. The HGLD shape is predicted to be indistinguishable from the field luminosity function, indicating that there is no relationship between the absorber strength or ion and the luminosity of the dominant contributing galaxy. Switching from galaxy luminosity to stellar mass, the predicted host galaxy mass distributions (HGMDs) indicate that more-massive galaxies contribute a higher fraction of metal ions to absorbers of each species, with the HGMDs of stronger absorbers extending out to higher masses. We conclude that the fraction of absorbing metal ions contributed by galaxies increases weakly with stellar mass, but the scatter in luminosity at fixed stellar mass obscures this relationship. For the same reason, we predict that observational analyses of the absorber–galaxy relationship will uncover stronger trends with stellar mass than with luminosity.

Keywords: Metal line absorbers, Hydrodynamical simulations, Reionization, Quasar absorption line spectroscopy
Evidence for Intrinsic X-Ray Weakness among Red Quasars at Cosmic Noon. Quasar feedback is a key ingredient in shaping galaxy evolution. A rare population of extremely red quasars (ERQs) at z = 2‑3 are often associated with high-velocity [O III]λ5008 outflows and may represent sites of strong feedback. In this paper, we present an X-ray study of 50 ERQs to investigate the link between the X-ray and outflow properties of these intriguing objects. Using hardness ratio analysis, we confirm that the ERQs are heavily obscured systems with gas column density reaching N H = 1023‑24 cm‑2. We identify 20 X-ray-nondetected ERQs at high mid-infrared (MIR) luminosities of ν L  ν,6 μm ≳ 3 × 1046 erg s‑1. By stacking the X-ray observations, we find that the nondetected ERQs are on average underluminous in X-rays by a factor of ∼10 for their MIR luminosities. We consider such X-ray weakness to be due to both heavy gas absorption and intrinsic factors. Moreover, we find that the X-ray-weak sources also display higher-velocity outflows. One option to explain this trend is that weaker X-rays facilitate more vigorous line-driven winds, which then accelerate the [O III]-emitting gas to kiloparsec scales. Alternatively, super-Eddington accretion could also lead to intrinsic X-ray weakness and more powerful continuum-driven outflow.

Keywords: Supermassive black holes, X-ray quasars, Quasars
Halo Bias in the Peak Model: A First-principles Nonparametric Approach. The Press–Schechter (PS) and excursion set (ES) models of structure formation fail in reproducing the halo bias found in simulations, while the ES-peaks' formalism built in the peak model reproduces it only at high masses and does not address in a fully satisfactory manner peak nesting, and the mass and time of ellipsoidal collapse of triaxial peaks in the Gaussian-smoothed density field. Here, we apply the confluent system of peak trajectories formalism fixing all these issues from first principles and with no free parameters to infer the Lagrangian local peak bias parameters, which adopt very simple analytic expressions similar to those found in the PS and ES models. The predicted Eulerian linear halo bias recovers the results of simulations. More specifically, we show that the only small departure observed at intermediate and low masses can be due to the spurious halo splitting and grouping caused by the spherical overdensity halo-finding algorithm used in simulations.

Keywords: Cosmology, Galaxy dark matter halos, Hierarchical cosmology, Dark matter
Two-process Model and Residual Abundance Analysis of the Milky Way Massive Satellites. The "two-process model" is a promising technique for interpreting stellar chemical abundance data from large-scale surveys (e.g., the Sloan Digital Sky Survey IV/V and the Galactic Archeology with HERMES survey), enabling more quantitative empirical studies of differences in chemical enrichment history between galaxies without relying on detailed yield and evolution models. In this work, we fit two-process model parameters to (1) a luminous giant Milky Way (MW) sample and (2) stars comprising the Sagittarius dwarf galaxy (Sgr). We then use these two sets of model parameters to predict the abundances of 14 elements of stars belonging to the MW and in five of its massive satellite galaxies, analyzing the residuals between the predicted and observed abundances. We find that the model fit to (1) results in large residuals (0.1–0.3 dex) for most metallicity-dependent elements in the metal-rich ([Mg/H] &gt; ‑0.8) stars of the satellite galaxies. However, the model fit to (2) results in small or no residuals for all elements across all satellite galaxies. Therefore, despite the wide variation in [X/Mg]–[Mg/H] abundance patterns of the satellite galaxies, the two-process framework provides an accurate characterization of their abundance patterns across many elements, but these multielement patterns are systematically different between the dwarf galaxy satellites and the MW disks. We consider a variety of scenarios for the origin of this difference, highlighting the possibility that a large inflow of pristine gas to the MW disk diluted the metallicity of star-forming gas without changing abundance ratios.

Keywords: Chemical abundances, Galaxy chemical evolution
The Mean Free Path of 13–64 MeV Protons Derived from Statistical Results of Solar Energetic Particle Events. A recent study by Wang et al. investigated gradual solar proton events with energies &gt;10 MeV, as observed by STEREO-A, STEREO-B, and the Solar and Heliospheric Observatory spacecraft. For each event, the spacecraft with the best magnetic connection to the source region among the three spacecraft was identified, and energetic proton intensities observed by the spacecraft were analyzed through fitting. The fitting process produced two parameters, b and c, for four energy channels (13–16 MeV, 20–25 MeV, 32–40 MeV, and 40–64 MeV) in each event. Parameters b and c govern the rise and decay of particle intensities, respectively. Statistical analysis revealed a power-law correlation between b and c, expressed as c ∼ b ‑γ . In this study, in order to explain the relation between the two parameters, we investigate the model of particle diffusion coefficients in the interplanetary space. In our simulations, the radial mean free path is modeled as a power function of radial distance, successfully reproducing the b–c relation. Consequently, the observations demonstrate that the radial mean free path varies with radial distance in a power law. In future research, the model of diffusion coefficients holds promise in determining the mean free path of energetic protons.

Keywords: Solar energetic particles, Solar wind, Solar flares
Cloud–Cloud Collision: Formation of Hub-filament Systems and Associated Gas Kinematics. Mass-collecting Cone—A New Signature of Cloud–Cloud Collision. Massive star-forming regions (MSFRs) are commonly associated with hub-filament systems (HFSs) and sites of cloud–cloud collision (CCC). Recent observational studies of some MSFRs suggest a possible connection between CCC and the formation of HFSs. To understand this connection, we analyzed the magnetohydrodynamic simulation data from Inoue et al. This simulation involves the collision of a spherical turbulent molecular cloud with a plane-parallel sea of dense molecular gas at a relative velocity of about 10 km s‑1. Following the collision, the turbulent and nonuniform cloud undergoes shock compression, rapidly developing filamentary structures within the compressed layer. We found that CCC can lead to the formation of HFSs, which is the combined effect of turbulence, shock compression, magnetic field, and gravity. The collision between the cloud components shapes the filaments into a cone and drives inward flows among them. These inward flows merge at the vertex of the cone, rapidly accumulating high-density gas, which can lead to the formation of massive star(s). The cone acts as a mass-collecting machine, involving a nongravitational early process of filament formation, followed by gravitational gas attraction to finalize the HFS. The gas distribution in the position–velocity (PV) and position–position spaces highlights the challenges in detecting two cloud components and confirming their complementary distribution if the colliding clouds have a large size difference. However, such CCC events can be confirmed by the PV diagrams presenting gas flow toward the vertex of the cone, which hosts gravitationally collapsing high-density objects, and by the magnetic field morphology curved toward the direction of the collision.

Keywords: Massive stars, Magnetohydrodynamics, Star formation, Interstellar filaments
Gravitational Wave Ringdown Analysis Using the <inline-formula> <mml:math overflow="scroll"><mml:mi class="MJX-tex-calligraphic" mathvariant="script">F</mml:mi></mml:math> </inline-formula>-statistic. After the final stage of the merger of two black holes (BHs), the ringdown signal takes an important role in providing information about the gravitational dynamics in strong field. We introduce a novel time-domain (TD) approach, predicated on the  F -statistic, for ringdown analysis. This method diverges from traditional TD techniques in that its parameter space remains constant irrespective of the number of modes incorporated. This feature is achieved by reconfiguring the likelihood and analytically maximizing over the extrinsic parameters that encompass the amplitudes and reference phases of all modes. Consequently, when performing the ringdown analysis under the assumption that the ringdown signal is detected by the Einstein Telescope, the parameter estimation computation time is shortened by at most 5 orders of magnitude compared to the traditional TD method. We further establish that traditional TD methods become difficult when including multiple overtone modes due to close oscillation frequencies and damping times across different overtone modes. Encouragingly, this issue is effectively addressed by our new TD technique. The accessibility of this new TD method extends to a broad spectrum of research and offers flexibility for various topics within BH spectroscopy applicable to both current and future gravitational wave detectors.

Keywords: Quasinormal modes, Bayesian statistics, Kerr black holes, Stellar mass black holes, Time domain astronomy, Gravitational waves, Astrophysical black holes