Sazuna/UAT_keywords huggingface dataset:
Properties of H<SUB>2</SUB>O Masers and Their Associated Sources in Sagittarius B2. We present high-resolution Karl G. Jansky Very Large Array observations of the 22 GHz H2O maser line in the extended Sagittarius B2 cloud. We detect 499 H2O masers across the observed velocities between −39 and 172 km s−1. To investigate the nature of the masers, we analyze their spatial distribution and crossmatch with catalogs of H II regions and protostellar cores. 62% of masers are associated with protostellar cores and 32% with H II regions. The nature of the remaining 6% of sources was not established but is likely associated with protostellar cores. Based on the spatial extent of the groups of masers, we classify them as either outflow-associated or young stellar object (YSO)─associated. We identify 144 unique sites of maser emission: 23 are associated with H II regions and 94 with protostellar cores, of which 33 are associated with protostellar outflows and 18 with YSOs. The outflow-associated H2O maser emission is confined to within &lt;2000 au of the central continuum source, despite shocked SiO emission extending over tens of thousands of astronomical units. The YSO-associated masers show a lack of detections at 5 &lt; Vrel &lt; 30 km s−1, which we suggest may be due to maser self-absorption. We show how H2O masers trace the large-scale material flow in Sgr B2 North, also seen in SiO and millimeter continuum emission. Finally, we find that protostellar cores with associated H2O masers tend to have brighter 3 mm continuum emission on average, although there is no strong correlation between maser brightness and continuum flux.

Keywords: Star forming regions, Stellar jets, Young stellar objects, Water masers, Star formation, H II regions
Infant Core-collapse Supernovae with Circumstellar Interactions from KMTNet. I. Luminous Transitional Case of KSP-SN-2022c. We present BVi multiband high-cadence observations of a Type II supernova (SN) KSP-SN-2022c from a star-forming galaxy at z ≃ 0.041 from its infant to nebular phase. Early light-curve fitting with a single power law is consistent with the first detection roughly 15 minutes after shock breakout (SBO). The SN light curves feature a rapid rise and decline across its luminous (V ≃ ─18.41 mag) peak together with a short plateau. The presence of the short plateau and rapid postpeak decline place the SN within a small group of transitional type between Type II-P and II-L subtypes. Its broad and asymmetric H profiles with large emission-to-absorption ratios and its near-peak luminosity in excess of predictions from models of SN shock cooling both point to circumstellar interactions in this SN. Early colour evolution exhibits a short-lived blueward motion in B − V within the first few days and continuous reddening in V − i, inconsistent with simple blackbody heating. Our simulations of SN light curves estimate 13 M⊙ and 680 R⊙ for the mass and radius of the progenitor, respectively, together with circumstellar material (CSM) of 0.73 M⊙ to account for the excess luminosity and rapid postpeak declines. We discuss the origin of its short plateau and early colour evolution in the context of partial envelope stripping of the progenitor star and a delayed SN SBO near the edge of the CSM, respectively, as indicated by our simulations. We establish a correlation between postpeak decline rates and CSM mass in Type II SNe, highlighting that CSM interactions play a major role in shaping the postpeak evolution of transitional types.

Keywords: Core-collapse supernovae
A Luminous Red Optical Flare and Hard X-Ray Emission in the Tidal Disruption Event AT 2024kmq. We present the optical discovery and multiwavelength follow-up observations of AT 2024kmq, a likely tidal disruption event (TDE) associated with a supermassive (MBH ∼ 108 M⊙) black hole in a massive galaxy at z = 0.192. The optical light curve of AT 2024kmq exhibits two distinct peaks: an early fast (timescale 1 day) and luminous (M ≍ −20 mag) red peak, then a slower (timescale 1 month) blue peak with a higher optical luminosity (M ≍ −22 mag) and featureless optical spectra. The second component is similar to the spectroscopic class of "featureless TDEs" in the literature, and during this second component we detect highly variable, luminous (LX ≍ 1044 erg s−1), and hard (fν ∝ ν−1.5) X-ray emission. Luminous (1029 erg s−1 Hz−1 at 10 GHz) but unchanging radio emission likely arises from an underlying active galactic nucleus. The luminosity, timescale, and color of the early red optical peak can be explained by synchrotron emission, or alternatively by thermal emission from material at a large radius (R ≍ a few × 1015 cm). Possible physical origins for this early red component include an off-axis relativistic jet, and shocks from self-intersecting debris leading to the formation of the accretion disk. Late-time radio observations will help distinguish between the two possibilities.

Keywords: Surveys, Transient sources, Time domain astronomy
Search for Slow Bars in Two Barred Galaxies with Nuclear Structures: NGC 6951 and NGC 7716. We investigate two barred galaxies with nuclear structures, NGC 6951 and NGC 7716, to examine whether they host slow bars. Using Gemini/GMOS long-slit spectroscopy, we calculate the bar pattern speed with the Tremaine─Weinberg method and detect kinematically decoupled nuclear disks in both galaxies. We also measure the bar length and strength using Pan-STARRs images and identify a nuclear ring in NGC 6951 and a nuclear bar in NGC 7716 from Hubble Space Telescope/Planetary Camera images. Our results indicate that NGC 6951 hosts a slow, long, and strong bar, which likely evolved through interactions with the dark matter halo and contributed to the formation of both the nuclear disk and ring. We also find hints of a rapidly rotating oval structure within the primary bar, although it is not clearly seen in the imaging data. In contrast, the primary bar in NGC 7716 is too weak to be classified as a barred galaxy, while its nuclear disk and nuclear bar are unusually large, possibly due to tidal interactions or the weakness of the primary bar. These findings suggest that slow bars may be more observed in galaxies with nuclear structures and highlight the often underappreciated role of galaxy interactions in bar evolution.

Keywords: Galaxy spectroscopy, Galaxy structure, Galaxy dynamics, Galaxy photometry, Galaxy evolution, Barred spiral galaxies
ALMASOP. A Rotating Feature Rich in Complex Organic Molecules in a Protostellar Core. Interstellar complex organic molecules (COMs) in solar-like young stellar objects (YSOs), particularly within protostellar disks, are of significant interest owing to their potential connection to prebiotic chemistry in emerging planetary systems. We report the discovery of a rotating feature enriched in COMs, including CH3OH, CH3CHO, and NH2CHO, in the protostellar core G192.12-11.10. By constructing a YSO model, we find that the COM-rich feature is likely located within or near the boundary of the Keplerian disk. The image synthesis results suggest that additional heating mechanisms leading to a warm ring or a warm inner disk are required to reproduce the observed emission. We discuss possible origins of the COM-rich feature, particularly accretion shocks as a plausible cause for a warm ring. Additionally, molecules such as C18O, H2CO, DCS, H2S, and OCS exhibit distinct behavior compared to CH3OH, indicating a range of physical and chemical conditions within the region. The observed kinematics of H2S and OCS suggest that OCS resides in regions closer to the central protostar than H2S, consistent with previous experimental studies.

Keywords: Astrochemistry, Pre-biotic astrochemistry, Star formation, Interstellar medium, Circumstellar disks, Protostars, Complex organic molecules
Limits on the 21 cm Power Spectrum at z = 6.5–7.0 from Murchison Widefield Array Observations. This paper presents the spherically averaged 21 cm power spectrum derived from Epoch of Reionization (EoR) observations conducted with the Murchison Widefield Array (MWA). The analysis uses EoR0-field data, centered at (R.A. = 0h, decl. = ‑27∘), collected between 2013 and 2023. Building on the improved methodology described in C. M. Trott et al. (2024), we incorporate additional data quality control techniques introduced in C. D. Nunhokee (2020). We report the lowest-power-level limits on the EoR power spectrum at redshifts z = 6.5, z = 6.8, and z = 7.0. These power levels, measured in the east–west polarization, are (30.2)2 mK2 at k = 0.18 h Mpc‑1, (31.2)2 mK2 at k = 0.18 h Mpc‑1, and (39.1)2 mK2 at k = 0.21 h Mpc‑1, respectively. The total integration time amounts to 268 hr. These results represent the deepest upper limits achieved by the MWA to date and provide the first evidence of the heated intergalactic medium at redshifts z = 6.5 to 7.0.

Keywords: Reionization, H I line emission
Identifying Dwarfs of MC Analog GalaxiEs (ID-MAGE): The Search for Satellites around Low-mass Hosts. We present results from Identifying Dwarfs of MC Analog GalaxiEs (ID-MAGE), a survey aimed at identifying and characterizing unresolved satellite galaxies around 35 nearby LMC- and SMC-mass hosts (D = 4−10 Mpc). We use archival DESI Legacy Survey imaging data and perform an extensive search for dwarf satellites, extending out to a radius of 150 kpc (∼Rvir). We identify 355 candidate satellite galaxies, including 264 new discoveries. Extensive tests with injected galaxies demonstrate that the survey is complete down to MV ∼ −9.0 (assuming the distance of the host) and μ0,V ∼ 26 mag arcsec−2 (assuming an n = 1 Sérsic profile). We perform consistent photometry, via Sérsic profile fitting, on all candidates and have initiated a comprehensive follow-up campaign to confirm and characterize candidates. Through a systematic visual inspection campaign, we classify the top candidates as high-likelihood satellites. On average, we find 4.0 ± 1.4 high-likelihood candidate satellites per LMC-mass host and 2.1 ± 0.6 per SMC-mass host, which is within the range predicted by cosmological models. We use this sample to establish upper and lower estimates on the satellite luminosity function of LMC-/SMC-mass galaxies. ID-MAGE nearly triples the number of low-mass galaxies surveyed for satellites with well-characterized completeness limits, providing a unique data set to explore small-scale structure and dwarf galaxy evolution around low-mass hosts in diverse environments.

Keywords: Dwarf galaxies, Galaxy evolution, Low surface brightness galaxies
First Evidence for a Quasiperiodic Oscillation Triplet and Its Relativistic Precession Origin in RE J1034+396. Quasiperiodic oscillations (QPOs) in active galactic nuclei (AGNs) provide a powerful tool for probing the structure of the innermost accretion flow and corona around supermassive black holes. RE J1034+396, the most prominent AGN known to host an X-ray QPO, exhibits both short-term and long-term QPO evolution, offering a unique opportunity to investigate accretion disk and corona physics through its temporal behavior. We report a possible long-term (∼92.2 days) cyclic evolution of the QPO in RE J1034+396, joining the detected QPO (∼3730 s) and its short-term (∼17 ks) modulation to form a possible QPO triplet, which is potentially the first such structure identified in an AGN. By applying the relativistic precession model to the QPO triplet, we constrain the black hole mass to  1.7‑0.8+0.9×106M⊙ , consistent with independent estimates, and find a low dimensionless black hole spin of  0.017‑0.012+0.028 . We propose an exploratory model that involves a quasiperiodic ultrafast outflow (UFO) within the framework of the relativistic precession model, explaining the QPO lag reversal, the modulation of hard-band QPO amplitude by soft-band flux, and the long-term evolution of timing properties. Supporting evidence includes blueshifted emission and absorption lines indicating a strong UFO at ∼0.3c. This work provides new insights into the inner regions of AGN accretion disks and motivates further efforts in both numerical modeling and high-cadence timing observations.

Keywords: X-ray active galactic nuclei, Active galactic nuclei, Galaxy accretion disks
Investigating the Dainotti Relation in Gamma-Ray Bursts through Multipolar Electromagnetic Radiation. The Dainotti relation empirically connects the isotropic plateau luminosity (LX) in gamma-ray bursts (GRBs) and X-ray afterglows to the rest-frame time at which the plateau ends ( Ta* ), enabling both the standardization of GRBs and their use as cosmological probes. However, the precise physical mechanisms underlying this correlation remain an active area of research. Although magnetars, highly magnetized neutron stars, have been proposed as central engines powering GRB afterglows, traditional dipole spin-down radiation models fail to account for the full diversity of observed behaviors. This limitation necessitates a more comprehensive framework. We propose that multipolar magnetic field emissions from magnetars offer a plausible explanation for the Dainotti relation. Unlike simple dipole fields, higher-order multipolar configurations enable more complex energy dissipation processes. The coexistence of multiple components can plausibly explain the range of afterglow decay indices found from a sample of 238 GRBs with plateau features from the Swift-X-Ray Telescope database up to the end of 2024 December, the majority of which deviate from the dipolar prediction of α = ‑2, and more crucially, the spin-down physics yields a link between LX and  Ta* in a way that preserves the Dainotti correlation with a slope of b = ‑1, independent of the specific multipole order. Moreover, we find that the inclusion of higher-order multipoles can explain the range of plateau energies found in the Dainotti relations. Thus, a unified picture emerges in which multipolar fields are able to reproduce both the slope and the normalization of the correlation.

Keywords: Gamma-ray bursts
Nature or Nurture: LMC-like Dust in the Solar Metallicity Galaxy M31. Using the Hubble Space Telescope/Space Telescope Imaging Spectrograph, ultraviolet (UV) extinction curves have been measured in M31 along 13 new sight lines, increasing the M31 sample to 17. This sample covers a wide area of M31, having galactocentric distances of 5–16 kpc, enabling the analysis of UV extinction curve variations over a large region of an external galaxy similar to the Milky Way with global galactic characteristics such as metallicity for the first time. No correlation is found between the extinction parameters and galactocentric distance, which might be expected if there is a radial metallicity gradient in M31. Most of the new UV extinction curves presented here are significantly different from the average extinction curves of the Milky Way, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC), but the average M31 extinction curve is similar to the average extinction curve in the 30 Dor region of the LMC. The wide range of extinction curves seen in each individual Local Group galaxy suggests that global galactic properties such as metallicity may be less important than the local environmental conditions, such as density, UV radiation field, and shocks along each sight line. The combined behavior of the Milky Way, LMC, SMC, and now M31 UV extinction curves supports the idea that there is a family of curves in the Local Group with overlapping dust grain properties between different galaxies.

Keywords: Local Group, Andromeda Galaxy, Interstellar dust extinction
Influence of Solar Cycle on Magnetohydrodynamic Turbulent Modes at 1 au. We study the effect of the solar cycle on various magnetohydrodynamic (MHD) fluctuation modes using the linear mode decomposition technique developed by G. P. Zank et al. We decompose various MHD modes, including propagating modes: Alfvén (forward and backward), fast (forward and backward), and slow (forward and backward) modes, as well as nonpropagating structures: entropy and magnetic island modes, from solar wind intervals during both the minimum and maximum phases of solar cycle 23. We find that the amplitudes of different modes corresponding to fluctuations in density, magnetic field, and velocity vary over the solar cycle, with larger amplitudes observed during the solar maximum compared to the solar minimum. The fluctuating energy of these modes is ∼1.5–4.5 times larger during the solar maximum. The frequency spectrum shows that the entropy mode exhibits the largest fluctuating power among density fluctuations, surpassing the contributions of fast and slow magnetosonic modes during both solar maximum and minimum intervals. For magnetic field fluctuations, the dominant contributors are the magnetic island mode, followed by the Alfvén modes. The Alfvén modes dominate the overall velocity fluctuations. This study provides observational evidence for the influence of the solar cycle on linear MHD modes.

Keywords: Interplanetary turbulence, Solar cycle
Rapid Spectral Evolution of SGR 1935+2154 during Its 2022 Outburst. During the 2022 outburst of SGR 1935+2154, a fast radio burst (FRB)-like event (FRB 20221014A) and X-ray activities occurred between two spin-up glitches, suggesting these glitches may connect to multiwavelength phenomenology. However, the mechanisms altering the magnetar's magnetosphere to enable radio emission remain unclear. This study presents high-cadence Neutron Star Interior Composition Explorer and Nuclear Spectroscopic Telescope Array observations revealing spectral changes in burst and persistent emission. Hardness ratio and spectral analysis reveal significant changes during an "intermediate flare" 2.5 hr before FRB 20221014A. This 40 s flare, releasing &gt;(6.3 ± 0.2) × 1040 erg, coincides with a rapid spectral softening in both burst and persistent emission, and a notable decrease in the burst occurrence rate. The intermediate flare is bright enough to be detected if placed at a few megaparsecs, and would appear as a fast X-ray transient. This implies that the connection between magnetar X-ray activity and FRBs can be observed in the local Universe. Postflare burst spectra peak near 5 keV, resembling the characteristics of the FRB-associated X-ray burst of 2020. Such change persisted for a few hours, implying magnetospheric evolution on similar timescales. However, no radio emission was detected from postflare bursts, suggesting that FRB emission requires conditions beyond peculiar short bursts. The burst waiting times exhibit a broken power-law distribution, likely resulting from contamination by enhanced persistent emission. Although the bursts appear randomly distributed in the spin phase, the hardness ratio profile as a function of spin phase follows that of the persistent emission, indicating that X-ray bursts originate at low altitudes.

Keywords: Neutron stars, High energy astrophysics, Compact objects, Magnetars, Radio transient sources
The Unreasonable Effectiveness of the nΣv Approximation. In kinetic theory, the classic nΣv approach calculates the rate of particle interactions from local quantities: the number density of particles n, the cross section Σ, and the average relative speed v. In stellar dynamics, this formula is often applied to problems in collisional (i.e., dense) environments such as globular and nuclear star clusters, where blue stragglers, tidal capture binaries, binary ionizations, and microtidal disruptions arise from rare close encounters. The local nΣv approach implicitly assumes the ergodic hypothesis, which is not well motivated for the densest star systems in the Universe. In the centers of globular and nuclear star clusters, orbits close into 1D ellipses because of the degeneracy of the potential (either Keplerian or harmonic). We find that the interaction rate in perfectly Keplerian or harmonic potentials is determined by a global quantity—the number of orbital intersections—and that this rate can be far lower or higher than the ergodic nΣv estimate. However, we find that, in most astrophysical systems, deviations from a perfectly Keplerian or harmonic potential (due to, e.g., granularity or extended mass) trigger sufficient orbital precession to recover the nΣv interaction rate. Astrophysically relevant failures of the nΣv approach only seem to occur for tightly bound stars orbiting intermediate-mass black holes, or for the high-mass end of collisional cascades in certain debris disks.

Keywords: Stellar kinematics, Celestial mechanics
Leveraging Machine Learning for Accurate and Fast Stellar Mass Estimation of Galaxies. Unveiling the evolutionary history of galaxies necessitates a precise understanding of their physical properties. Traditionally, astronomers achieve this through spectral energy distribution (SED) fitting. However, this approach can be computationally intensive and time-consuming, particularly for large data sets. This study investigates the viability of machine learning (ML) algorithms as an alternative to traditional SED fitting for estimating stellar masses in galaxies. We compare a diverse range of unsupervised and supervised learning approaches, including prominent algorithms such as K-means, HDBSCAN, Parametric t-Distributed Stochastic Neighbor Embedding (Pt-SNE), principal component analysis, Random Forest, and self-organizing maps (SOM) against the well-established LePhare code, which performs SED fitting as a benchmark. We train various ML algorithms using simple model SEDs in photometric space, generated with the BC03 code. These trained algorithms are then employed to estimate the stellar masses of galaxies within a subset of the COSMOS survey data set. The performance of these ML methods is subsequently evaluated and compared with the results obtained from LePhare, focusing on both accuracy and execution time. Our evaluation reveals that ML algorithms can achieve comparable accuracy to LePhare while offering significant speed advantages (1000–100,000 times faster). K-means and HDBSCAN emerge as top performers among our selected ML algorithms. Supervised learning algorithms like Random Forest and manifold learning techniques such as Pt-SNE and SOM also show promising results. These findings suggest that ML algorithms hold significant promise as a viable alternative to traditional SED-fitting methods for estimating the stellar masses of galaxies.

Keywords: Galaxy formation, High-redshift galaxies, Spectral energy distribution, Stellar masses