Sazuna/UAT_keywords huggingface dataset:
SHELLQs. Bridging the Gap: JWST Unveils Obscured Quasars in the Most Luminous Galaxies at z &gt; 6. The unprecedented sensitivity of the James Webb Space Telescope (JWST) has uncovered a surprisingly abundant population of mildly obscured, low-luminosity active galactic nuclei (AGNs) in the epoch of reionization (EoR). However, the link between these objects and classical unobscured quasars remains a mystery. Here we report the discovery of obscured quasars hosted by the most luminous galaxies at z &gt; 6, possibly bridging the gap between the two AGN populations. The 13 objects presented here were originally selected from a rest-frame ultraviolet (UV) imaging survey over &gt;1000 deg2, and were known to have luminous (&gt;1043 erg s−1) Lyα emission. With JWST/NIRSpec follow-up observations, we found that 7 out of 11 objects with narrow Lyα exhibit a broad component in H I Balmer lines and He I lines, but not in [O III] and other forbidden lines. Mild dust obscuration (0 &lt; AV &lt; 3) is inferred from the Balmer decrements. The estimated intrinsic luminosities suggest that our broad-line (BL) objects are the long-sought UV-obscured counterparts of luminous quasars in the EoR. They host supermassive black holes (SMBHs) with masses 107.8−9.1M⊙, undergoing sub-Eddington to Eddington accretion. Most of the BL objects are spatially unresolved and are close to "little red dots" with their blue rest-UV and red rest-optical colors. We estimate the AGN number density among similarly luminous Lyα emitters to be larger than 2 × 10−8 Mpc−3. This density is comparable to that of classical quasars with similar continuum luminosities, suggesting that a substantial fraction of active SMBHs are obscured in the EoR and have been overlooked in past rest-UV surveys.

Keywords: Supermassive black holes, Reionization, High-redshift galaxies, Quasars
Spectroscopic Study of Globular and Fuzzy Clusters in Lenticular Galaxy NGC 1023. We here report the results from spectroscopic observations of a sample of 26 globular cluster (GC) and 21 faint fuzzy (FF) candidates in the lenticular galaxy NGC 1023 using the 10.4 m Gran Telescopio Canarias. Using the recessional velocities and stellar absorption features, we determine that 18 and 9 of the observed candidates are bona fide GCs and FFs, respectively. The majority of the rejected FF candidates are background emission line galaxies for which we determine their redshifts. We used the spectroscopic data to determine velocity, age, metallicity, and extinction of all bona fide clusters. We find that FFs are clearly younger (age = 7─9 Gyr) than GCs (age &gt; 10 Gyr). Both kinds of clusters in this galaxy are metal-rich ([Fe/H] = −0.58 ± 0.33). The ages and metallicities of individual FFs reported here are the first such measurements in any galaxy and agree with the previously reported measurement on stacked spectrum. The kinematical analysis reaffirms that the FFs belong to the disk of the galaxy, suggesting that their progenitors are most likely massive, compact disk clusters that have been able to survive for long timescales. We propose that the fuzzy appearance of FFs as compared to the GCs is a consequence of the dynamical evolution of their progenitor super star clusters in the disks of low-mass galaxies.

Keywords: Lenticular galaxies, Globular star clusters, Spectroscopy, Extragalactic astronomy, Star clusters
Joint Modeling of Quasar Variability and Accretion Disk Reprocessing Using Latent Stochastic Differential Equations. Quasars are bright active galactic nuclei powered by the accretion of matter around supermassive black holes at the center of galaxies. Their stochastic brightness variability depends on the physical properties of the accretion disk and black hole. The upcoming Rubin Observatory Legacy Survey of Space and Time (LSST) is expected to observe tens of millions of quasars, so there is a need for efficient techniques like machine learning that can handle the large volume of data. Quasar variability is believed to be driven by an X-ray corona, which is reprocessed by the accretion disk and emitted as UV/optical variability. We are the first to introduce an auto-differentiable simulation of the accretion disk and reprocessing. We use the simulation as a direct component of our neural network to jointly model the driving variability and reprocessing, trained with supervised learning on simulated LSST-like 10 yr quasar light curves. We encode the light curves using a transformer encoder, and the driving variability is reconstructed using latent stochastic differential equations, a physically motivated generative deep learning method that can model continuous-time stochastic dynamics. By embedding the physical processes of the driving signal and reprocessing into our network, we achieve a model that is more robust and interpretable. We demonstrate that our model outperforms a Gaussian process regression baseline and can infer accretion disk parameters and time delays between wave bands, even for out-of-distribution driving signals. Our approach provides a powerful framework that can be adapted to solve other inverse problems in multivariate time series.

Keywords: Neural networks, Quasars, Irregular cadence, Active galactic nuclei, Time series analysis
The Samples and Binary Fractions of Red Supergiants in M31 and M33 by the HST Observations. The binarity of red supergiants (RSGs) influences their evolution and the fate of supernovae. We investigate the binary fraction of RSGs in the Andromeda galaxy (M31) and Triangulum galaxy (M33) using photometry from the Hubble Space Telescope (HST), which offers high spatial resolution to resolve more RSGs. A preliminary step involves identifying a reliable and complete RSG sample using the F110W − F160W versus F160W diagram, yielding 2612 RSGs from the Panchromatic Hubble Andromeda Treasury (PHAT) survey of M31 and 3294 RSGs from the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region survey of M33. These samples suggest total RSG populations in M31 and M33 of 6563 and 7572, respectively. These estimates significantly exceed previous ones from the ground-based observations, an increase attributed to the superior spatial resolution of the HST. The stellar parameters of these RSGs, including effective temperature (Teff), radius (R), and luminosity (L), are derived by fitting their spectral energy distribution (SED) across optical and near-infrared bands. Binary candidates are identified by detecting ultraviolet excesses in their SEDs compared to the single-star RSG model prediction. The binary fraction is determined to be 33.4% ± 0.9% for M31 and 30.9% ± 0.8% for M33. For more luminous RSGs with log L/L⊙ &gt; 4.0, the binary fraction decreases to 31.6% ± 1.9% in M31 and increases to 34.7% ± 1.8% in M33, respectively. These results are in good agreement with predictions from the Binary Population and Spectral Synthesis binary evolution model.

Keywords: Binary stars, Red supergiant stars, Triangulum Galaxy, Spectral energy distribution, Andromeda Galaxy
SN 2023ixf in the Pinwheel Galaxy M101: From Shock Breakout to the Nebular Phase. We present photometric and spectroscopic observations of supernova SN 2023ixf covering from day 1 to 442 days after explosion. SN 2023ixf reached a peak V-band absolute magnitude of ‑18.2 ± 0.07, and light curves show that it has a relatively short "plateau" phase (∼72 days), and can be classified either as an SN IIL or a transitional event between IIP and IIL. Early-time spectra of SN 2023ixf exhibit strong, very narrow emission lines from ionized circumstellar matter (CSM), possibly indicating a Type IIn classification. But these flash/shock-ionization emission features faded after the first week and the spectrum evolved in a manner similar to that of typical Type II SNe, unlike the case of most genuine SNe IIn in which the ejecta interact with CSM for an extended period of time and develop intermediate-width emission lines. We compare observed spectra of SN 2023ixf with various model spectra to understand the physics behind SN 2023ixf. Our nebular spectra (between 200 and 400 days) match best with the model spectra from a 15 M⊙ progenitor that experienced enhanced mass loss a few years before explosion. A last-stage mass-loss rate of  Ṁ=0.01M⊙yr‑1  from the r1w6 model matches best with the early-time spectra, higher than  Ṁ≈2.4×10‑3M⊙yr‑1  derived from the ionized Hα luminosity at 1.58 days. We also use SN 2023ixf as a distance indicator and fit the light curves to derive the Hubble constant by adding SN 2023ixf to the existing sample; we obtain  H0=73.1‑3.50+3.68  km s‑1 Mpc‑1, consistent with the results from SNe Ia and many other independent methods.

Keywords: Type II supernovae, Supernovae
Hyperactive Repeating Fast Radio Bursts from Rotation-modulated Starquakes on Magnetars. The nondetection of periodicity related to rotation challenges magnetar models for fast radio bursts (FRBs) with FRB emission from close to the magnetar surface. Moreover, a bimodal distribution of the burst waiting times is widely observed in hyperactive FRBs, a significant deviation from the exponential distribution expected from stationary Poisson processes. By combining the epidemic-type aftershock sequence earthquake model and the rotating vector model involving the rotation of the magnetar and orientations of the spin and magnetic axes, we find that starquake events modulated by the rotation of FRB-emitting magnetar can explain the bimodal distribution of FRB waiting times, as well as the nondetection of periodicity in hyperactive repeating FRBs. We analyze data from multiple FRB sources, demonstrating that differences in waiting time distributions, and to some extent, observed energies can be explained by varying parameters related to geometric properties of the magnetar FRB emission and starquake dynamics. Our results show that the assumption that all FRBs are repeaters is compatible with our model. Notably, we find that hyperactive repeaters tend to have small magnetic inclination angles in order to hide their periodicity. We also show that our model can reproduce the waiting time distribution of a pulsar phase of the galactic magnetar SGR J1935+2154 with a larger inclination angle than the hyperactive repeaters, which could explain the detection of spin period and the relatively low observed energy for FRBs from the magnetar. The spin periods of hyperactive repeaters are not well constrained, but most likely fall in the valley region between the two peaks of the waiting time distributions.

Keywords: Neutron stars, Magnetars, Radio transient sources
Streams and Bubbles: Tidal Shaping of Hydrodynamic Planetary Outflows. Planets, especially those close to their host stars, lose mass to atmospheric outflows, a process that is thought to shape the bimodal population of gaseous giant and rocky terrestrial exoplanets in close orbits. We model the hydrodynamic escape of planetary atmospheres in idealized, three-dimensional gas dynamic simulations in order to study their emergent morphology. As we vary the simulated system parameters, model outflows show a range of shapes from fast, isotropic outflows bounded by bow shocks to slower motion confined to thin streams. We show that a crucial factor is the role of the tidal gravity and orbiting reference frame in which planets lose mass. Flows can be characterized by the dimensionless Rossby number evaluated at the scale of the Hill sphere. Flows with a low Rossby number are significantly deviated and shaped by the stellar gravity, while those with a high Rossby number are comparatively unaffected. Rossby number alone is sufficient to predict outflow morphology as well as kinematic gradients across transit. Hydrodynamic outflows from the known exoplanet population should span a range of outflow Rossby numbers and therefore exhibit a range of morphologies. In realistic systems, shaping from gravity and hydrodynamics alone can be supplemented by the effects of stellar-wind collisions and magnetic stresses.

Keywords: Exoplanet atmospheric dynamics, Tidal interaction, Transits
Thermal Radiation Transport with Tensor Trains. We present a novel tensor network algorithm to solve the time-dependent, gray thermal radiation transport equation. The method invokes a tensor train (TT) decomposition for the specific intensity. The efficiency of this approach is dictated by the rank of the decomposition. When the solution is "low rank," the memory footprint of the specific intensity solution vector may be significantly compressed. The algorithm, following a step-then-truncate approach of a traditional discrete ordinates method, operates directly on the compressed state vector, thereby enabling large speedups for low-rank solutions. To achieve these speedups, we rely on a recently developed rounding approach based on the Gram-SVD. We detail how familiar SN algorithms for (gray) thermal transport can be mapped to this TT framework and present several numerical examples testing both the optically thick and thin regimes. The TT framework finds low-rank structure and supplies up to ≃60× speedups and ≃1000× compressions for problems demanding large angle counts, thereby enabling previously intractable SN calculations and supplying a promising avenue to mitigate ray effects.

Keywords: Computational astronomy, Radiative transfer
The Hourglass Simulation: A Catalog for the Roman High-latitude Time-domain Core Community Survey. We present a simulation of the time-domain catalog for the Nancy Grace Roman Space Telescope's High-Latitude Time-Domain Core Community Survey. This simulation, called the Hourglass simulation, uses the most up-to-date spectral energy distribution models and rate measurements for 10 extragalactic time-domain sources. We simulate these models through the design reference Roman Space Telescope survey: four filters per tier, a five-day cadence, over 2 yr, a wide tier of 19 deg2, and a deep tier of 4.2 deg2, with ∼20% of those areas also covered with prism observations. We find that a science-independent Roman time-domain catalog, assuming a signal-to-noise ratio at a max of &gt;5, would have approximately 21,000 Type Ia supernovae, 40,000 core-collapse supernovae, around 70 superluminous supernovae, ∼35 tidal disruption events, three kilonovae, and possibly pair-instability supernovae. In total, Hourglass has over 64,000 transient objects, 11,000,000 photometric observations, and 500,000 spectra. Additionally, Hourglass is a useful data set to train machine learning classification algorithms. We show that SCONE is able to photometrically classify Type Ia supernovae with high precision (∼95%) to a z &gt; 2. Finally, we present the first realistic simulations of non-Type Ia supernovae spectral time series data from Roman's prism.

Keywords: Astronomical simulations, Surveys, Time domain astronomy, Space telescopes, Catalogs
Orbital Decay of the Ultra-hot Jupiter TOI-2109b: Tidal Constraints and Transit-timing Analysis. TOI-2109b is the ultra-hot Jupiter with the shortest orbital period (∼16 hr) yet discovered. At this close distance, strong tidal interactions can produce a significant exchange of angular momentum with the star. Since the orbital period of this planet is shorter than the stellar rotation period, TOI-2109b may be an optimal candidate for studying orbital decay. This process depends on how efficiently the star and the planet dissipate energy, due mainly to interior mechanisms that are poorly constrained in exoplanet systems. In this work, we study for the first time the tidal evolution of TOI-2109b under a formalism of inertial waves (IWs) in convective envelopes and internal gravity waves (IGWs) in stellar radiative regions. We find that uncertainties in the age of TOI-2109 (t⋆,age) significantly affect the rate of orbital evolution, as IWs and IGWs interact differently depending on t⋆,age. For an "old" host star, we find that TOI-2109b would undergo fast orbital decay. Conversely, if TOI-2109b orbits a "young" host star, a rather slow decay rate for  Q⋆'&gt;2.3×107  would suggest a constant-period orbit. Our calculated mid-transit times and transit-timing variations (TTVs) support a "young" host star with  Q⋆'&gt;3.7×107 , suggesting a decay rate  Ṗ∼4msyr‑1  that could lead to mid-transit-time shifts ≲10 s over three years. Orbital decay and other TTV-inducing effects will be confirmed or ruled out with future higher-quality timing data. The results presented here aim at constraining the current modeling of tides and TTVs for TOI-2109b, helping us further understand light-curve changes associated with the long-term evolution of ultra-short-period planets.

Keywords: Tidal friction, Hot Jupiters, Exoplanet astronomy, Transit timing variation method, Tidal interaction
Electron Acceleration at Shock Ripples: Role of Pitch-angle Diffusion. Suprathermal electrons are routinely observed in interplanetary space. At higher energies, there are in-situ evidences that shocks, both interplanetary shocks, often driven by fast coronal mass ejections, and terrestrial bow shocks, can accelerate electrons up to transrelativistic energies (∼MeVs). The acceleration mechanism responsible for these energetic electrons is still under debate. In this work, we study the effects of large-scale shock ripples on electron acceleration at a quasi-perpendicular shock in a 2D system. For tractability of the numerical simulation, we consider the scenario where the magnetic field line contains ripples, and the shock is assumed planar and piecewise. The propagation of gyrophase-averaged electrons is governed by the focused transport equation, where the effect of the turbulent magnetic field is modeled by the pitch-angle diffusion, described by the quasi-linear theory. A Monte Carlo simulation on the equivalent time-forward Itô stochastic differential equation is performed within a periodic box to obtain the phase-space distribution function of the accelerated electrons. Our model predicts power-law energy spectra with a cutoff at high-energy ends, whereas their spectral indices are softer than those predicted by the diffusive shock acceleration theory. We demonstrate that, with a suitable choice of pitch-angle diffusion strength, a small fraction of electrons can experience magnetic traps in multiple ripples along the shock surface, boosting their energies to ∼MeVs. Our results therefore provide a framework for a better understanding of relativistic electron events associated with shocks within the heliosphere.

Keywords: Solar energetic particles, Shocks, Interplanetary particle acceleration
Wind-fed Supermassive Black Hole Accretion by the Nuclear Star Cluster: The Case of M31*. The central supermassive black hole (SMBH) of the Andromeda galaxy, known as M31*, exhibits dim electromagnetic emission and is inferred to have an extremely low accretion rate for its remarkable mass (∼108 M⊙). In this work, we use three-dimensional hydrodynamical simulations to explore a previously untested scenario, in which M31* is fed by the collective stellar mass loss from its surrounding nuclear star cluster, manifested as a famous eccentric disk of predominantly old stellar populations. The stellar mass loss is assumed to be dominated by the slow and cold winds from 100 asymptotic giant-branch stars, which follow well-constrained Keplerian orbits around M31* and together provide a mass injection rate of ∼4 × 10−5 M⊙ yr−1. The simulations achieve a quasi-steady state on a megayear timescale, at which point a quasi-Keplerian, cool (T ∼ 103─104 K) gas disk extending several parsecs is established. This disk is continuously supplied by the stellar winds and itself feeds the central SMBH. At the end of the simulations at 2 Myr, an accretion rate of ∼2 × 10−5 M⊙ yr−1 is found but could vary by a factor of a few depending on whether the subdominant gravity of the NSC or a moderate global inflow is included. The predicted X-ray luminosity of ∼1036 erg s−1, dominated by the hot (T ∼ 107─108 K) plasma within 0.2 pc of the SMBH, is consistent with Chandra observations. We conclude that the feeding mechanism of M31* is successfully identified, which has important implications for the working of dormant SMBHs prevalent in the local Universe.

Keywords: Accretion, Supermassive black holes, Hydrodynamical simulations, Stellar winds, Andromeda Galaxy, Star clusters
Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars. The circumgalactic medium (CGM) is poorly constrained at the subparsec scales relevant to turbulent energy dissipation and regulation of multiphase structure. Fast radio bursts are sensitive to small-scale plasma density fluctuations, which can induce multipath propagation (scattering). The amount of scattering depends on the density fluctuation spectrum, including its amplitude  Cn2 , spectral index β, and dissipation scale li. We use quasar observations of CGM turbulence at ≳pc scales to infer  Cn2 , finding it to be  10‑16≲Cn2≲10‑9  m‑20/3 for hot (T &gt; 106 K) gas and  10‑8≲Cn2≲10‑4  m‑20/3 for cool (104 ≲ T ≲ 105 K) gas, depending on the gas sound speed and density. These values of  Cn2  are much smaller than those inferred in the interstellar medium at similar physical scales. The resulting scattering delays from the hot CGM are negligible (≪1 μs at 1 GHz), but they are more detectable from the cool gas as either radio pulse broadening or scintillation, depending on the observing frequency and sightline geometry. Joint quasar-FRB observations of individual galaxies can yield lower limits on li, even if the CGM is not a significant scattering site. An initial comparison between quasar and FRB observations (albeit for different systems) suggests li ≳ 750 km in ∼104 K gas in order for the quasar and FRB constraints to be consistent. If a foreground CGM is completely ruled out as a source of scattering along an FRB sightline, then li may be comparable to the smallest cloud sizes (≲pc) inferred from photoionization modeling of quasar absorption lines.

Keywords: Quasar absorption line spectroscopy, Quasars, Extragalactic radio sources, Radio bursts, Circumgalactic medium, Radio transient sources
Major Mergers Mean Major Offset: Drivers of Intrinsic Scatter in the M<SUB>GCS</SUB>─M<SUB>h</SUB> Scaling Relation for Massive Elliptical Galaxies. In this work, we determine the total globular cluster (GC) counts and globular cluster system (GCS) total mass estimates for 27 extremely massive elliptical galaxies. The GC 2D spatial distributions of these galaxies were created from photometry of Hubble Space Telescope images using DOLPHOT in the near-IR wavelength range. The projected radial density profiles of these GCSs were determined using a Voronoi-tessellation-based technique introduced in our previous paper. We then plot these galaxies on the GCS─halo mass relation alongside previously studied galaxies in the literature. The relation now extends across seven decades of halo mass. We find that the 1:1 slope of this relation holds out to the highest-mass galaxies, although extremely massive BCG galaxies are shifted to higher GCS masses than their lower-mass galaxy counterparts. We find a negative correlation with massive galaxies' offset from the GCS─halo mass relation and the steepness of their GCS density profiles, and that this is being driven by the red GC populations. We suggest that the biggest influence in intrinsic scatter in the GCS─halo mass relation for massive galaxies is through a few major mergers resulting in accretion of massive satellites with old, red GC populations, rather than many accretions of small satellites with younger, blue GC populations.

Keywords: Globular star clusters, Brightest cluster galaxies, Giant elliptical galaxies, Scaling relations