Sazuna/UAT_keywords huggingface dataset:
Radiation and Magnetic Pressure Support in Accretion Disks Around Supermassive Black Holes and the Physical Origin of the Extreme-ultraviolet to Soft X-Ray Spectrum. We present the results of four 3D radiation magnetohydrodynamic simulations of accretion disks around a 108 solar mass black hole, which produce the far-ultraviolet spectrum peak and demonstrate a robust physical mechanism for producing the extreme-ultraviolet to soft X-ray power-law continuum component. The disks are fed from rotating tori and reach accretion rates ranging from 0.03 to 4 times the Eddington value. The disks become radiation pressure or magnetic pressure dominated, depending on the relative timescales of radiative cooling and gas inflow. Magnetic pressure supported disks can form with or without net poloidal magnetic fields, as long as the inflowing gas can cool quickly enough, which can typically happen when the accretion rate is low. We calculate the emerging spectra from these disks using multigroup radiation transport with realistic opacities and find that they typically peak around 10 eV. At accretion rates close to or above the Eddington limit, a power-law component can appear for photon energies between 10 eV and 1 keV, with a spectral slope varying between Lν ∝ ν−1 and ν−2, comparable to what is observed in radio-quiet quasars. A disk with a 3% Eddington accretion rate does not exhibit this component. These high-energy photons are produced in an optically thick region ≍30∘─45∘ from the disk midplane, by compressible bulk Comptonization within the converging accretion flow. Strongly magnetized disks that have a very small surface density will produce a spectrum that is very different from what is observed.

Keywords: Accretion, Radiative magnetohydrodynamics, Black holes, Quasars, Active galactic nuclei, Radiative transfer
Spatially Resolved Modeling of Galactic Hα Emission for Galaxy Clustering. Near-infrared spectroscopic surveys target high-redshift emission-line galaxies (ELGs) to probe cosmological scenarios. Understanding the clustering properties of ELGs is essential to derive optimal constraints. We present a simple radiative transfer model for spatially resolved galactic Hα emission, which includes emission from the warm-hot diffuse interstellar medium. The atomic-level populations are in steady state and computed in the coronal approximation. The model is applied to multiple IllustrisTNG simulations in the redshift range 1 ≤ z ≤ 2 to produce the luminosity function (LF) and the halo occupation distribution (HOD). Collisional processes account for a significant fraction (≍40%) of the total Hα luminosity (LHα). Our LFs are in reasonable agreement with measurements from Hα surveys if a uniform extinction of 0.3 &lt; AHα &lt; 0.85 mag is assumed. Our HOD is consistent with that of the Euclid Flagship galaxy mock up to differences that can be attributed to baryonic feedback, which is absent from the latter. When Hα luminosities are computed from an empirical relation between LHα and the total star formation rate, the resulting LFs are in tension with previous observations. Our approach can be extended to other atomic lines, which should be helpful for the mining of high-redshift galaxy spectra in forthcoming surveys.

Keywords: Galaxies, Emission line galaxies
Inferring the Density and Membership of Stellar Streams with Flexible Models: The GD-1 Stream in Gaia Data Release 3. Stellar streams provide one of the most promising avenues for constraining the global mass distribution of the Milky Way and the nature of dark matter (DM). The stream stars' kinematic "track" enables inference of large-scale properties of the DM distribution, while density variations and anomalies provide information about local DM clumps (e.g., from DM subhalos). A full accounting of the density tracks and substructures within all &gt;100 Milky Way stellar streams will therefore enable powerful new constraints on DM. Here, we present a new, flexible framework for modeling stellar stream density and membership. With it, one can empirically model a given stream in a variety of coordinate spaces (e.g., on-sky position and velocity) using probability distributions, thereby generating membership probabilities. The most significant improvement over previous methods is the inclusion of off-track or non-Gaussian components to the stream density, meaning we can capture anomalous features (such as the GD-1 steam's spur). We test our model on GD-1, where we characterize previously known features and provide the largest catalog of probable member stars to date (1689 stars). We then use the derived model to provide measurements of GD-1's density and kinematic tracks, velocity dispersion, as well as its initial and current mass. Our framework (built on JAX and numpyro) provides a path toward uniform analysis of all Milky Way streams, enabling tight constraints on the Galactic mass distribution and its dark matter.

Keywords: Mixture model, Astronomy data modeling, Dark matter, Stellar streams
Probing Chemical Enrichment in Extremely Metal-poor Galaxies. The chemical composition of galaxies offers vital insights into their formation and evolution. In particular, the relationship between helium abundance (He/H) and metallicity serves as a key diagnostic for estimating the primordial helium yield from Big Bang nucleosynthesis. We investigate the chemical enrichment history of low-metallicity galaxies, focusing especially on extremely metal-poor galaxies (EMPGs), using one-zone chemical evolution models. Adopting elemental yields from M. Limongi &amp; A. Chieffi, our models reach He/H ∼ 0.089 at (O/H) × 105 &lt; 20, yet they fall short of reproducing the elevated He/H values observed in low-redshift dwarf galaxies. In contrast, the observed Fe/O ratios in EMPGs are successfully reproduced using both the K. Nomoto et al. and M. Limongi &amp; A. Chieffi yield sets. To address the helium discrepancy, we incorporate supermassive stars (SMSs) as Population III stars in our models. We find that SMSs can significantly enhance He/H, depending on the mass-loss prescription. When only 10% of the SMS mass is ejected, the model yields the steepest slope in the (O/H) × 105–He/H relation. Alternatively, if the entire outer envelope up to the CO core is expelled, the model can reproduce the high He/H ratios observed in high-redshift galaxies (He/H &gt; 0.1). Additionally, these SMS-enriched models also predict elevated N/O ratios, in agreement with recent JWST observations of the early Universe.

Keywords: Dwarf galaxies, Chemical abundances, Galaxy evolution, Galactic abundances, High-redshift galaxies
LATIS: A Sample of IGM-selected Protoclusters and Protogroups at z ∼ 2.5. The Lyα Tomography IMACS Survey (LATIS) has produced large 3D maps of the intergalactic medium (IGM), providing a new window on the cosmic web at z ∼ 2.5. A key advantage of Lyα tomography is that it enables the discovery of overdense regions without the need to detect their galaxy members in spectroscopic surveys, circumventing possible selection biases. We use these maps to identify 37 IGM-selected overdensities as regions of strong and spatially coherent Lyα absorption. Simulations indicate that 85% of these are protoclusters, defined as the progenitors of z = 0 halos with mass Mdesc &gt; 1014M⊙, and that nearly all of the rest are protogroups (1013.5 &lt; Mdesc/M⊙ &lt; 1014). We estimate the masses and space densities of the IGM-selected overdensities and show they are in accordance with mock surveys. We investigate the LATIS counterparts of some previously reported protoclusters, including the proto-supercluster Hyperion. We identify a new component of Hyperion beyond its previously known extent. We show that the Lyα transmission of the galaxy density peaks within Hyperion is consistent with a simple physical model (the fluctuating Gunn–Peterson approximation), suggesting that active galactic nucleus feedback or other processes have not affected the large-scale gas ionization within this structure as a whole. The LATIS catalog represents an order-of-magnitude increase in the number of IGM-selected protogroups and protoclusters and will enable new investigations of the connections between galaxies and their large-scale environments at cosmic noon.

Keywords: Protoclusters, Lyman alpha forest, Galaxy environments
LATIS: Comparing Galaxy and IGM Tomography Maps as Tracers of Large-scale Structure and Protoclusters at z ∼ 2.5. We investigate the consistency of intergalactic medium (IGM) tomography and galaxy surveys as tracers of the cosmic web and protoclusters at z ∼ 2.5. We use maps from the Lyα Tomography IMACS Survey (LATIS), which trace the distributions of Lyman-break galaxies (LBGs) and IGM Lyα absorption on ≃4 h‑1 cMpc scales within the same large volume. Overall, the joint distribution of IGM absorption and LBG density is well constrained and accurately described by a simple physical model. However, we identify several exceptional locations exhibiting strong IGM absorption indicative of a massive protocluster, yet no coincident overdensity of LBGs. As discussed by Newman et al., whose results we revise using the complete LATIS survey data, these are candidate ultraviolet (UV)-dim protoclusters that may harbor distinct galaxy populations missed by rest-UV spectroscopic surveys. We present follow-up observations targeting one such candidate embedded within Antu, an extended region of IGM absorption at z = 2.685 that contains five IGM-selected protoclusters and has a total mass of 3 × 1015M⊙. Lyα emitters trace the overall structure of Antu but avoid the center of the candidate UV-dim protocluster, which also appears to contain no submillimeter-selected sources. A near-infrared spectroscopic galaxy census is needed to determine whether this large region is dominated by galaxies with reduced or absent star formation activity. This work adds to a growing and puzzling literature on discrepancies among different galaxy and IGM tracers, whose resolution promises to shed light on the early stages of environment-dependent galaxy evolution.

Keywords: Protoclusters, Lyman alpha forest, Galaxy environments
Switchbacks near Boundaries of Small-scale Magnetic Flux Ropes in the Young Solar Wind from Parker Solar Probe Observations. The Parker Solar Probe (PSP) mission has revealed frequent occurrences of switchbacks (SBs) and small-scale magnetic flux ropes (SMFRs) as prominent structures within the solar wind. These mesoscale features are observed across all heliocentric distances, with heightened activity in the young solar wind, such as successive SMFRs, blobs, and SBs using PSP in situ observations. One study, in particular, focuses on SMFRs observed during the intervals of PSP corotating with the Sun, which suggests a similar source of the observed solar wind. In this paper, we identified SBs at the boundaries of SMFRs as a regularly observed phenomenon and found instances where SBs and SMFRs co-occur, with the significance level α &lt; 0.05. The SMFR-related SBs—observed at the leading and trailing edges of an SMFR—exhibit well-organized axial co-orientations, with their polarity flipping, meaning the radial direction remains constrained while the transversal field reverses. Furthermore, the axial field directions of SMFR-related SBs appear to be more closely connected than to another SB that is spatially closer and are linked to the SMFR orientation. Our analysis of their relative geometry, which examines the alignment between SBs and the SMFR axis, reveals a distinct tendency emphasizing their correlation, further supporting the idea that the axes of SMFR-related SBs are presumably determined by the SMFR orientation. Observations suggest that a fraction of SBs are spatially and temporally associated with SMFRs, implying that processes related to SMFR boundaries may contribute to SB formation or that SBs tend to develop in magnetic environments shaped by SMFRs.

Keywords: Solar wind, Interplanetary magnetic fields
Driven Phase-mixed Alfvén Waves in a Partially Ionized Solar Plasma. Phase mixing has long been understood to be a viable mechanism for expediting the dissipation of Alfvén wave energy resulting in the subsequent heating of the solar atmosphere. To fulfill the conditions necessary for phase mixing to occur, we consider the cross-field gradient in the Alfvén speed as a free parameter in our model. Using a single-fluid description of a partially ionized chromospheric plasma, we explore the efficiency of damping of shear Alfvén waves subject to phase mixing when a pulse wave driver is employed. Our results demonstrate a strong dependence of the dissipation length of shear Alfvén waves on both the ionization degree of the plasma and the gradient of the Alfvén speed. When assessing the efficiency of phase mixing across various inhomogeneities, our findings indicate that waves originating from a pulse driver initially exhibit heating rates identical to those generated by a continuous wave driver. One key difference observed was that Alfvén pulses possess a lower overall decay rate, due to a change in damping profile from exponential to algebraic. This discrepancy arises from the absence of a consistent injection of energy into the base of the domain, which preserves longitudinal gradients of the magnetic field perturbations more effectively. These findings demonstrate the importance of understanding the relations between the wave driver, damping mechanisms, and propagation dynamics in resolving the atmospheric heating problem.

Keywords: Magnetohydrodynamics, Solar chromosphere, Alfven waves
Finding White Dwarfs' Hidden Companions Using an Unsupervised Machine Learning Technique. White dwarfs (WD) with main-sequence (MS) companions are crucial probes of stellar evolution. However, due to the significant difference in their luminosities, the WD is often outshined by the MS star. The aim of this work is to find hidden companions in Gaia's sample of WD candidates. Our methodology involves applying an unsupervised machine learning algorithm for dimensionality reduction and clustering, known as a self-organizing map (SOM), to Gaia BP/RP (XP) spectra. This strategy allows us to naturally separate WDMS binaries from single WDs from the detection of subtle red flux excesses in the XP spectra that are indicative of low-mass MS companions. We validate our approach using confirmed WDMS binaries from the Sloan Digital Sky Survey and LAMOST surveys, achieving a precision of ∼90%. We demonstrated that the luminosity of the faint companions in the missed systems is ∼50 times lower than that of their WD primaries. Applying our SOM to 90,667 sources, we identify 993 WDMS candidates, 506 of which have not been previously reported in the literature. If confirmed, our sample will increase the known WDMS binaries by 20%. Additionally, we use the Virtual Observatory Spectral Energy Distribution Analyzer tool to refine and parameterize a "golden sample" of 136 WDMS binaries through multiwavelength photometry and a two-body spectral energy distribution fitting. These high-confidence WDMS binaries are composed of low-mass WDs (∼0.42M⊙), with cool MS companions (∼2800 K). Finally, 13 systems exhibit periodic variability consistent with eclipsing binaries, making them prime targets for further follow-up observations.

Keywords: Binary stars, Classification, Neural networks, White dwarf stars, Astronomy data analysis
Identification of New Candidate Be/X-Ray Binary Systems in the Small Magellanic Cloud via Analysis of the S-CUBED Source Catalog. It has long been known that a large population of Be/X-ray binaries (BeXRBs) exists in the Milky Way's neighboring dwarf galaxy, the Small Magellanic Cloud (SMC), due to a recent period of intense star formation. Since 2016, efforts have been made to monitor this population and identify new BeXRBs through the Swift SMC Survey (S-CUBED). S-CUBED's weekly observation cadence has identified many new BeXRBs that exist within the SMC, but evidence suggests that more systems exist that have thus far escaped detection. A major challenge in identifying new BeXRBs is their transient nature at high-energy wavelengths, which prevents them from being detected via their X-ray emission characteristics when not in outburst. In order to identify sources that may have been missed owing to a long period of quiescence, it becomes necessary to devise methods of detection that rely on wavelengths at which BeXRBs are more persistent emitters. In this work, we attempt to use archival analysis of infrared, optical, and ultraviolet observations to identify new candidate BeXRBs that have been overlooked within the S-CUBED source catalog. Using X-ray/optical selection of source properties, unsupervised clustering, spectral energy distribution fitting to VizieR archival measurements, and ultraviolet light-curve analysis, we are able to identify six new candidate BeXRB systems that otherwise would have been missed by automated analysis pipelines. Using these results, we demonstrate the use of ultraviolet through near-infrared observational data in identifying candidate BeXRBs when they cannot be identified using their X-ray emission.

Keywords: X-ray photometry, High energy astrophysics, High mass x-ray binary stars, Small Magellanic Cloud, X-ray surveys, Ultraviolet photometry
Atmospheric Retrieval of Subaru/IRD High-resolution Spectrum of the Archetype T-type Brown Dwarf Gl 229 B. Brown dwarfs provide a unique opportunity to study atmospheres and their physical and chemical processes with high precision, especially in temperature ranges relevant to exoplanets. In this study, we performed high-resolution (R ∼ 70,000) spectroscopy using Subaru/IRD (Y, J, H bands) of the T7.0p-type object Gl 229 B, the first discovered T-type brown dwarf, which orbits an M1V host star at a separation of 33 au. We conducted atmospheric retrieval on the reduced H-band spectrum using the high-resolution spectrum model compatible with automatic differentiation and GPU, ExoJAX. In contrast to previous retrieval studies on medium-resolution spectra, we obtained a C/O ratio consistent with that of the host star, aligning with the expected formation process for such a massive brown dwarf. Additionally, based on the strong constraint on temperature from the high-resolution spectrum and previously measured photometric magnitude, our analysis indicates that Gl 229 B is a binary, which was also proposed by G. M. Brandt et al. and recently confirmed by J. W. Xuan et al. Finally, we validated current molecular line lists by leveraging the obtained high-resolution, high signal-to-noise ratio spectrum of this warm (∼900 K) atmosphere. This study highlights the importance of observing companion brown dwarfs as benchmark objects for establishing characterization techniques for low-mass objects and enhancing our understanding of their atmospheres, given the wealth of available information and the relative ease of observation. *This research is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We are honored and grateful for the opportunity to observe the Universe from Maunakea, which has cultural, historical, and natural significance in Hawaii.

Keywords: High resolution spectroscopy, Brown dwarfs, Molecular spectroscopy, Exoplanet atmospheres, T dwarfs
On the Effects of Parameters on Galaxy Properties in CAMELS and the Predictability of Ω<SUB>m</SUB>. Recent analyses of cosmological hydrodynamic simulations from CAMELS have shown that machine learning models can predict the parameter describing the total matter content of the universe, Ωm, from the features of a single galaxy. We investigate the statistical properties of two of these simulation suites, IllustrisTNG and ASTRID, confirming that Ωm induces a strong displacement on the distribution of galaxy features. We also observe that most other parameters have little to no effect on the distribution, except for the stellar-feedback parameter ASN1, which introduces some near-degeneracies that can be broken with specific features. These two properties explain the predictability of Ωm. We use optimal transport to further measure the effect of parameters on the distribution of galaxy properties, which is found to be consistent with physical expectations. However, we observe discrepancies between the two simulation suites, both in the effect of Ωm on the galaxy properties and in the distributions themselves at identical parameter values. Thus, although Ωm's signature can be easily detected within a given simulation suite using just a single galaxy, applying this result to real observational data may prove significantly more challenging.

Keywords: Astrostatistics, Galaxy properties, Cosmological parameters
PHIBSS: Searching for Molecular Gas Outflows in Star-forming Galaxies at z = 0.5─2.6. We present an analysis of millimeter CO observations to search for and quantify signatures of molecular gas outflows. We exploit the large sample of 0.5 &lt; z &lt; 2.6 galaxies observed as part of the PHIBSS1/2 surveys with the IRAM Plateau de Bure interferometer, focusing on the 154 typical massive star-forming galaxies with CO detections (mainly CO(3─2), but including also CO(2─1) and CO(6─5)) at signal-to-noise ratio (SNR) &gt; 1.5 and available properties (stellar mass, star formation rate or SFR, size) from ancillary data. None of the individual spectra exhibit a compelling signature of CO outflow emission, even at high SNR &gt; 7. To search for fainter outflow signatures, we carry out an analysis of stacked spectra, including the full sample, as well as subsets, split in terms of stellar mass, redshift, inclination, offset in SFR from the main sequence, and active galactic nuclei activity. None of the physically motivated subsamples shows any outflow signature. We report a tentative detection in a subset statistically designed to maximize outflow signatures. We derive upper limits on molecular gas outflow rate and mass loading factors η based on our results and find η ≤ 2.2─35.4, depending on the subsample. Much deeper CO data and observations of alternative tracers are needed to decisively constrain the importance of the cold molecular gas component of outflows relative to other gas phases.

Keywords: Interstellar medium, High-redshift galaxies, Galaxies
Formation and Early Evolution of Protoplanetary Disks under Nonuniform Cosmic-Ray Ionization. Angular momentum transport by magnetic fields is important for formation and evolution of protoplanetary disks. The effects of magnetic fields are suppressed due to nonideal magnetohydrodynamic (MHD) effects such as ambipolar diffusion and Ohmic dissipation, which depend on the degree of ionization. Cosmic rays (CRs) are the primary source of ionization in star-forming clouds, and their distribution is nonuniform as it is affected by gas density and magnetic fields. Therefore, CRs, magnetic fields, and gas interact with each other. In this work, we develop a new fully implicit CR transport module in Athena++ and perform 3D simulations of disk formation from collapse of molecular cloud cores. Since CRs are strongly attenuated in the dense gas at the disk scale, distribution of magnetic fields is considerably altered compared to conventional models assuming a uniform ionization rate. While the total magnetic fluxes accreted onto the disks remain similar as the gas outside the disks remains sufficiently ionized and well coupled, the magnetic fields in the disks are less twisted due to the stronger nonideal MHD effects. As a consequence, magnetic angular momentum transport is strongly suppressed at the disk scale, resulting in more gravitationally unstable disks with more prominent spiral arms. Our simulations demonstrate the influence of nonuniform ionization resulting from CR transport and attenuation on the disk formation and evolution.

Keywords: Computational astronomy, Galactic cosmic rays, Star formation, Protoplanetary disks, Magnetic fields