Sazuna/UAT_keywords huggingface dataset:
Little Red Dots at an Inflection Point: Ubiquitous V-shaped Turnover Consistently Occurs at the Balmer Limit. Among the most puzzling early discoveries of JWST are "little red dots" (LRDs), compact red sources that host broad Balmer emission lines, and in many cases exhibit a "V-shaped" change in slope in the rest-optical. The physical properties of LRDs currently have order-of-magnitude uncertainties, because models to explain the continuum of these sources differ immensely. Here, we leverage the complete selection of red sources in the RUBIES program, supplemented with public PRISM spectra, to study the origin of this V shape. By fitting a broken power law with a flexible inflection point, we find that a large fraction of red Hα emitters at 2 &lt; z &lt; 6 exhibit a strong change in slope, and that all strong inflections appear associated with the Balmer limit (0.3645 μm). Using a simple model of a reddened active galactic nucleus (AGN) with an unobscured scattered-light component, we demonstrate that the observed V shape in LRDs is unlikely to occur at any specific wavelength if the entire continuum is dominated by light from a power-law AGN continuum. In contrast, models with an intrinsic feature at the Balmer limit, such as those that are dominated by an evolved stellar population, can produce the observed spectral shapes, provided that a reddened component picks up sufficiently redward of the break. While no model can comfortably explain the full LRD spectral energy distribution, the common inflection location suggests that a single component consistently dominates the rest-frame UV optical in LRDs, and that this component is associated with T ∼ 104 K hydrogen.

Keywords: Galaxy evolution, Active galactic nuclei, High-redshift galaxies, Near infrared astronomy
Mass Transport, Turbulent Mixing, and Inflow in Black Hole Accretion. We investigate mass transport, mixing, and disk evolution in nonradiative black hole accretion flows using Lagrangian tracer particles embedded in general-relativistic magnetohydrodynamics simulations. Our simulation suite spans magnetically arrested disk (MAD) and standard and normal evolution (SANE) states across a range of black hole spins. By tracking tracer trajectories, we directly measure both advective inflow and stochastic spreading of fluid elements. The tracer distributions are well described by a combination of coherent inward drift and Gaussian-like broadening, consistent with an advection-diffusion picture. MADs exhibit systematically faster inflow than SANEs, with retrograde flows showing the most rapid infall; the innermost stable circular orbit leaves little imprint in MADs but remains more visible in SANEs. Turbulent fluctuations drive strong radial dispersion in all cases, with a superdiffusive scaling of σ ∝ t 0.95 in MADs and σ ∝ t 0.75 in SANEs for high-spin prograde disks. Mixing times decrease toward the event horizon and are consistently shorter in MADs and retrograde configurations. Tracers also reveal how accretion sources shift over time: Turbulence draws inflow from a broad range of initial radii, with rapid torus depletion in MADs driving the mean source radius outward as rcyl ∝ t 2/3, while SANEs evolve more gradually with rcyl ∝ t 1/2. We show that the finite mass of the initial torus has a strong influence on late-time behavior, especially in MADs, where imprints of differently sized initial conditions may be accessible as early as t ≍ 104 GM/c3.

Keywords: Accretion, Magnetohydrodynamics, Astrophysical black holes, Magnetohydrodynamical simulations
Long-term Monitoring of Scintillation in the Pulsar J0332+5434. Changes in a pulsar's scintillation characteristics over time can be a useful way to probe the properties of the interstellar medium. Monitoring the scintillation bandwidth can be useful for correcting for scattering delay in pulse arrival time, which could be a significant source of error for precision pulsar timing projects. To better understand the magnitude and trend of scintillation bandwidth changes over long timescales (months─years), we performed long-term monitoring of PSR J0332+5434 with the Allen Telescope Array at radio frequencies ranging from 900 to 1956 MHz. In total, we collected more than 300 observations of PSR J0332+5434 over the course of 10 months, with observations taken daily to weekly. We find a mean scintillation bandwidth of 2.6 MHz (scattering delay of 0.06 μs) with a standard deviation of 1.3 MHz (0.03 μs) at 1140 MHz and a mean of 14.7 MHz (0.011 μs) with a standard deviation of 9.1 MHz (0.006 μs) at 1668 MHz. We see significant change over time on a timescale of ∼200 days, suggesting that, for pulsars that are timed with submicrosecond precision, correcting for similar changes over time will be vital. We find no evidence for periodicity in the scattering delays. We describe a novel method for measuring the scaling index and compare it to established methods. We find the mean scintillation bandwidth frequency scaling goes as ν3.1 ± 1.0.

Keywords: Observational astronomy, Pulsars, Radio telescopes, Interstellar medium, Interstellar scintillation, Interstellar scattering, Radio astronomy, Radio pulsars
Hyperaccretion-driven Relativistic Jets from Massive Collapsars in Active Galactic Nucleus Disks. The observable characteristics of gamma-ray bursts embedded in the accretion disk of active galactic nuclei (AGNs) are mainly determined by the jet propagation within the disk. In the massive collapsar scenario, we consider that the mass and metallicity of progenitor stars can significantly affect the jet durations and luminosities, which in turn influence whether the jet can break out from AGN disks. For the cases with low metallicity, massive stars tend to keep their massive envelopes. Thus the hyperaccretion of these envelopes onto the newborn black holes (BHs) can prolong the activity duration of the central engine, thereby allowing the jets to potentially break out from the disks. For successful jets, we further study their prompt emission and afterglows for different supermassive BHs and locations and discuss the detectability of these signals by instruments such as Swift and Einstein Probe. Future related observations will help constrain the structure, components, and evolutionary history of AGN disks and the massive stars embedded within them.

Keywords: Gamma-ray bursts, Black holes, Massive stars, Relativistic jets, Active galactic nuclei
Bridging Scales in Black Hole Accretion and Feedback: Relativistic Jet Linking the Horizon to the Host Galaxy. Simulating black hole (BH) accretion and feedback from the BH horizon to galactic scales is extremely challenging, as it involves a vast range of scales. Recently, our multizone method has successfully achieved global dynamical steady states of hot accretion flows in 3D general relativistic magnetohydrodynamic simulations by tracking the bidirectional interaction between a nonspinning BH and its host galaxy. In this paper, we present technical improvements to the method and apply it to spin a* = 0.9 BHs, which power relativistic jets. We first test the new multizone setup with a smaller Bondi radius, RB ≍ 400 rg, where rg is the gravitational radius. The strongly magnetized accretion launches a relativistic jet with an intermediate feedback efficiency η ∼ 30%, in between that of a prograde (η ∼ 100%) and retrograde (η ∼ 10%) torus. Interestingly, both prograde and retrograde simulations also eventually converge to the same intermediate efficiency when evolved long enough, as accumulated magnetic fields remove gas rotation. We then extend strongly magnetized simulations to larger Bondi radii, RB ≍ 2 × 103, 2 × 104, 2 × 105 rg. We find that the BH accretion rate  Ṁ  is suppressed with respect to the Bondi rate  ṀB  as  Ṁ/ṀB∝RB−1/2 . However, despite some variability, the time-averaged feedback efficiency remains at η ∼ 30%, independent of RB. This suggests that BH feedback efficiency in hot accretion flows is mainly governed by the BH spin (a*) rather than by the galactic properties (RB). From these first-principles simulations, we provide a feedback subgrid prescription for cosmological simulations:  Ėfb=2×10−3[RB/(2×105rg)]−1/2ṀBc2  for BH spin a* = 0.9.

Keywords: Accretion, Supermassive black holes, Hydrodynamical simulations, Kerr black holes, Bondi accretion, Relativistic jets, Active galactic nuclei
Can Big Black Holes Merge with the Smallest Black Holes?. Gravitational-wave measurements of the binary black hole (BBH) population provide insights into the evolution of merging binaries. We explore potential correlation between mass and mass ratio with phenomenological population models where the minimum mass of the smaller (secondary) black hole can change with the mass of the bigger (primary) black hole. We use BBH signals from the third Gravitational-Wave Transient Catalog with and without the relatively extreme mass-ratio GW190814. When excluding GW190814, models with a variable minimum mass are disfavored compared to one with a constant minimum mass, with log Bayes factors of −2.49 to −0.98, indicating that the biggest black holes can merge with the smallest. When including GW190814, a parabola model that allows the minimum mass to decrease with increasing primary mass is favored over a constant minimum-mass model with a log Bayes factor of 4.44. When allowing the minimum mass to decrease, the overall population distributions remain similar whether or not GW190814 is included. This shows that with added model flexibility, we can reconcile potential outlier observations within our population. These investigations motivate further explorations of correlations between mass ratio and component masses in order to understand how evolutionary processes may leave an imprint on these distributions.

Keywords: Bayesian statistics, Multiple star evolution, Stellar mass black holes, Gravitational wave sources, Gravitational wave astronomy
Possible Coronal Geometry in the Hard and Soft States of Black Hole X-Ray Binaries from MONK Simulations. Understanding the coronal geometry in different states of black hole X-ray binaries is important for more accurate modeling of the system. However, it is difficult to distinguish different geometries by fitting the observed Comptonization spectra. In this work, we use the Monte Carlo ray-tracing code MONK to simulate the spectra for three simple corona toy models widely proposed in observational studies: sandwich, spherical, and lamppost, varying their optical depth and size (height). By fitting the simulated NuSTAR observations with the simplcut*kerrbb model, we infer the possible parameter space for the hard state and soft state of different coronal geometries. The influence of the disk inclination angle, black hole spin, and coronal temperature is discussed. We find that in the lamppost model, if we exclude the case of a very extended corona, the disk emission is always dominant, making lamppost geometry incompatible with the hard state. While the sandwich and spherical models can produce similar spectra in both the hard and soft states, the simulated IXPE polarimetric spectra show the potential to break this degeneracy. Geometrical effects arising from the limited size of the corona become evident in lower-spin black holes and affect the spectral fitting, where the larger ISCO reduces the corona coverage of the inner disk.

Keywords: Accretion, Stellar mass black holes, X-ray astronomy, Astrophysical black holes
Identification of Large-scale (&gt;100 kpc) Radio Jets in Narrow-line Seyfert 1 Galaxies. Powerful, large-scale relativistic jets are usually associated with massive, old elliptical galaxies. This paradigm has recently been challenged by the identification of narrow-line Seyfert 1 (NLSy1) galaxies, thought to be young active galactic nuclei with low-mass black holes, harboring relativistic jets. Among them, sources hosting &gt;100 kpc radio jets are extremely rare. Here, we report the discovery of large-scale, double-lobed radio structures in 33 NLSy1s with the projected linear size of at least 100 kpc from a recently published catalog of 22,656 NLSy1 galaxies. These 33 include 29 confirmed double-lobed sources and 4 candidates whose radio structure require further study. We suggest that their low black hole masses are unlikely to be due to their small angles of inclination to the line of sight. These enigmatic sources were identified by examining the radio observations taken with the Faint Images of the Radio Sky at Twenty Centimeters, Very Large Array Sky Survey, Low Frequency Array, and Rapid ASKAP Continuum Survey. Among them, the NLSy1 source J1318+2626 (z = 0.62) is found to host a radio jet with the projected linear size of 4.3 Mpc, making it the only NLSy1 galaxy hosting a Mpc-scale radio jet known as of today. We conclude that future observations of NLSy1 sources with the next generation of sensitive telescopes may reveal a much larger population harboring large-scale jets, thus providing crucial clues on their origin, propagation, and interaction with the ambient environment.

Keywords: Seyfert galaxies, Active galactic nuclei, Fanaroff-Riley radio galaxies, Radio jets
ODIN: Probing the LAE Lyα Luminosity Function across Cosmic Time and Different Environments. The ubiquity and relative ease of discovery make 2 ≲ z ≲ 5 Lyα emitting galaxies (LAEs) ideal tracers for large-scale structure of the distant Universe. In addition, because Lyα is a resonance line, but frequently observed at large equivalent width, it is potentially a probe of galaxy evolution. The LAE Lyα luminosity function (LF) is an essential measurement for making progress on both of these topics. Although several studies have computed the LAE LF, very few have delved into how the function varies with environment. The large area and depth of the One-hundred-deg2 DECam Imaging in Narrowbands (ODIN) survey makes such measurements possible at the cosmic noon redshifts of z ∼ 2.4, 3.1, and 4.5. In this initial work, we present algorithms needed to rigorously compute the LAE LF, and test them on the ∼16,000 ODIN LAEs found in the extended COSMOS field. Using these limited samples, we find weak evidence that protocluster environments suppress the numbers of faint LAEs compared to the field. We also find that the LF decreases in number density and evolves towards a steeper faint-end slope over cosmic time from z ∼ 4.5 to z ∼ 2.4.

Keywords: Luminosity function, Lyman-alpha galaxies, Galaxy environments
How the External Medium Outside Prestellar Cores Affects Protostellar Growth: Variations in Accretion Rate and Evolution of Disks and Outflows. We investigate how the external medium surrounding prestellar cores affects the star formation process by conducting three-dimensional resistive magnetohydrodynamic simulations. The initial cores follow critical Bonnor─Ebert profiles and are embedded in environments with different ambient densities. The simulations follow the evolution at least until the envelope mass within a radius equal to twice the critical Bonnor─Ebert radius drops to 35% of the initial cloud mass. We reveal that in environments with higher external density, enhanced mass inflow from the envelope leads to Bondi-like accretion as the protostellar mass increases. The continued inflow substantially increases the final stellar mass, resulting in star formation efficiencies that appear to exceed unity in dense environments. The external medium also influences the evolution of circumstellar disks and protostellar outflows: with the high-density external medium, disks grow rapidly, but their mass becomes smaller relative to the protostellar mass, and the outflow is sustained over a long duration. However, the ratio of angular momentum removed by outflows and magnetic braking to that introduced by inflowing gas decreases with increasing external density. These results suggest that the density of the external medium regulates not only protostellar mass growth but also the inflow─outflow balance and angular momentum transport in magnetized, rotating star-forming cores.

Keywords: Stellar jets, Stellar dynamics, Circumstellar disks, Protostars, Magnetohydrodynamical simulations
Discovery of 79 δ Scuti Stars in NGC 3532 Suggests a Decrease of Pulsator Occurrence with Age. Many A─F type stars do not display δ Scuti pulsations, despite being located within the instability strip. Open clusters provide a unique opportunity to study δ Scuti pulsations among coeval populations with uniform chemical composition. Here we use data from the Transiting Exoplanet Survey Satellite Mission to discover 79 δ Scuti pulsators in the 300 Myr old open cluster NGC 3532, the largest number found within a single open cluster to date. We report a 50% ± 5% pulsator fraction in NGC 3532, considerably lower than in younger stellar populations, such the Pleiades (110 Myr), NGC 2516 (100 Myr), and the Cep-Her Complex (≤80 Myr), and similar to the pulsator fraction found among field star samples. We introduce the concept of pulsator occurrence, which corrects for incompleteness, and find it to be 63% ± 6%. For the stars that do pulsate, we find that the hotter stars occupy a distinct branch in the color─magnitude diagram due to faster rotation (&gt;150 km s−1) than their nonpulsating counterparts. These results suggest that pulsator occurrence decreases with age and that rapid rotation is important in maintaining δ Scuti pulsations over time. We also investigate the period─luminosity (P─L) relation and the  νmax ─Teff relation of δ Scuti stars in NGC 3532. We find much scatter in the P─L relation of the dominant mode and two distinct branches in the  νmax ─Teff relation, similar to the Cep-Her Complex.

Keywords: Open star clusters, Delta Scuti variable stars, Variable stars, Stellar pulsations
Morphological and Kinematic Diagnostic of FU Orionis-type Outburst Mechanisms. We investigated the possibility of determining the mechanism of FU Orionis-type outbursts based on molecular line observations of protoplanetary disks with synthetic observations of distinct numerical burst models. The morphology of the synthetic C18O emission is sensitive to gas temperature and does not coincide with the actual gas disk structures, particularly in the magnetorotational instability (MRI) and clump-infall models, which exhibit peculiar temperature distributions. This highlights the need for careful interpretation of morphologies of line emission from disks under accretion outbursts. The synthetic C18O emission of each model exhibits distinct kinematic features that can be used to distinguish outburst scenarios. In the MRI model, kinematic features of the gravitational instability, which fuels MRI-driven accretion bursts, are small in both amplitude and spatial extent, resulting in no prominent local features in the residual velocity map at a typical distance for FU Orionis-type objects. In contrast, the clump-infall model shows a clear sign of gas expansion along a spiral, which is caused by exchange of angular momentum between an infalling clump and surrounding gas. The intruder model exhibits a highly asymmetric velocity structure with respect to the systemic velocity of the primary protostar in velocity channel maps. These distinct kinematic features may serve as promising diagnostics for distinguishing the physical mechanisms responsible for FU Orionis-type outbursts.

Keywords: FU Orionis stars, Young stellar objects, Star formation, Protoplanetary disks, Circumstellar disks, Stellar accretion disks, Protostars
Coronal Mass Ejections Deflected by Newly Emerging Flux: A Combined Analytic and Numerical Study. Newly emerging flux (NEF) has been widely studied as a trigger of solar filament eruptions, but its influence on the subsequent dynamics remains poorly explored. Because NEF typically emerges adjacent to filaments, it imposes magnetic asymmetry that can drive nonradial eruptions and complicate space-weather forecasting. We bridge analytic catastrophe theory with 2D resistive MHD simulations: analytic solutions provide magnetic configurations containing a flux rope at the loss-of-equilibrium point, which are then used as initial conditions for simulations to examine the following dynamics. We find that NEF governs the kinematics of filament eruptions in two ways. First, by reshaping coronal stability, NEF can create or eliminate a higher equilibrium in the corona, thereby producing failed eruptions or coronal mass ejections (CMEs). In the transitional situation where a metastable equilibrium appears, the rising filament decelerates and stalls before reaccelerating into a CME, consistent with observed two-step eruptions. Second, by breaking symmetry, NEF deflects eruptions away from the radial direction: depending on its polarity, it acts as a repulsor or an attractor on eruptive filaments, and the deflection magnitude increases with the degree of asymmetry. Our theory yields two characteristic angles that predict the deflection directions of CMEs and failed eruptions, and simulations closely align with these predictors. These results highlight the NEF not only as a trigger but also as a key factor that governs both the acceleration and deflection of eruptions during their propagation in the low corona.

Keywords: Solar magnetic flux emergence, Solar coronal mass ejections, Solar filament eruptions
Measuring Star Formation Histories from Asymptotic Giant Branch Stars. I. A Demonstration in M31. We demonstrate how near-infrared (NIR) imaging of resolved luminous asymptotic giant branch (AGB) stars can be used to measure well-constrained star formation histories (SFHs) across cosmic time. Using UKIRT J and K-band imaging of M31, we first show excellent agreement over the past ∼8 Gyr between the Panchromatic Hubble Andromeda Treasury SFH of M31's outer disk derived from a deep optical color─magnitude diagram (CMD; ∼3.3 × 107 stars with MF814W ≲ +2), and our spatially matched SFH based only on modeling AGB stars on an NIR CMD (∼7.7 × 103 stars with MJ ≲ −6). We find that only ∼1000 AGB stars are needed for reliable SFH recovery, owing to their excellent age sensitivity in the NIR. We then measure the spatially resolved SFH of M31's inner stellar halo (DM31,projected ∼ 20─30 kpc) using ∼104 AGB stars. We find: (i) a dominant burst of star formation across M31's stellar halo 3─5 Gyr ago and lower level, spatially distributed star formation ∼1─3 Gyr ago; (ii)  M⋆≍3−1+5×109M⊙  formed over the past ∼8 Gyr. We discuss some caveats and the enormous potential of resolved AGB stars in the NIR for measuring SFHs back to ancient epochs (∼14 Gyr ago) in galaxies to large distances (D ≳ 20 Mpc) with JWST, Roman, and Euclid.

Keywords: Asymptotic giant branch, Stellar populations, Galaxy stellar halos, Asymptotic giant branch stars, Andromeda Galaxy, Near infrared astronomy