Sazuna/UAT_keywords huggingface dataset:
A Closer Look at an Unusual Ultradiffuse Galaxy. We present a spectroscopic study of the "Disco Ball" (SMDG0038365-064207), a rotationally supported, green-valley, ultradiffuse galaxy (UDG) with a nuclear star cluster, multiple stellar clusters, and active star-forming regions using data obtained with the Keck Cosmic Web Imager on the Keck II Telescope. We calculate that the galaxy hosts 31 ± 11 "globular" clusters (GCs). Kinematic measurements confirm rotation with a peak rotational velocity of at least 39 ± 9 km s‑1 and a dynamical mass within the effective radius of at least 109.1 ± 0.2 M⊙. Our dynamical estimates of the halo mass are consistent with that obtained using the number of GCs and together suggest Mh = 1010.9 ± 0.2 M⊙. Our findings challenge two common assumptions: (1) clusters in some UDGs may be younger than generally assumed, and thus more luminous than standard GCs, affecting GC counts and the derived GC luminosity function in these UDGs, and (2) quiescent UDGs can be rotationally supported, making kinematic measurements viewing angle dependent in such cases. The Disco Ball, while unremarkable in mass, size, projected structural properties, or color, reveals surprising complexity, highlighting the need for detailed studies of more UDGs. *The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: Low surface brightness galaxies, Nucleated dwarf galaxies, Galaxy properties, Galaxy structure, Galaxy nuclei, Star clusters
High-energy Neutrino Emission from a Radiatively Inefficient Accretion Flow with a Three-dimensional General Relativistic Magnetohydrodynamic Simulation. The high-energy particle production in the accretion flow onto black holes can be key physics to explain the high-energy neutrino background. While the single-zone approximation has been commonly adopted in studies of the high-energy neutrino emission around black holes, the effects of the global plasma structure may be nonnegligible. We carry out the first computations of cosmic-ray acceleration and high-energy neutrino emission via the hadronuclear (pp) interaction in global radiatively inefficient accretion flows and outflows around a supermassive black hole, using three-dimensional general relativistic magnetohydrodynamic simulation data. The Fokker–Planck equation for cosmic-ray protons is solved with a phenomenological model for the energy diffusion coefficient to express the turbulent acceleration in the subgrid scale. The inhomogeneous and time variable structure of the accretion flow leads to a variety of particle energy distributions. The spectral energy distributions (SEDs) of neutrinos emitted from the entire region are flatter than those calculated under the single-zone approximation. In our model, the neutrino emission originating from cosmic rays advected with the outflow rather than the inflow predominates the SEDs. Such galactic nuclei can be significant sources of cosmic rays in those galaxies.

Keywords: Accretion, Magnetohydrodynamics, Neutrino astronomy, Active galactic nuclei, General relativity, Particle astrophysics
Cold Gas and Star Formation in the Phoenix Cluster with JWST. We present integral field unit observations of the Phoenix Cluster with the JWST Mid-infrared Instrument's Medium Resolution Spectrometer. We focus this study on the molecular gas, dust, and star formation in the brightest cluster galaxy (BCG). We use precise spectral modeling to produce maps of the silicate dust, molecular gas, and polycyclic aromatic hydrocarbons (PAHs) in the inner ∼50 kpc of the cluster. We measure the optical depth from silicates by comparing the observed H2 line ratios to those predicted by excitation models. We provide updated measurements of the total molecular gas mass of  1.9‑0.4+0.5×1010  M⊙, which agrees with CO-based estimates, providing an estimate of the CO-to-H2 conversion factor of  αCO=0.8±0.2M⊙pc‑2(Kkms‑1)‑1 ; an updated stellar mass of M* = 2.6 ± 0.5 × 1010 M⊙ ; and star formation rates (SFRs) averaged over 10 and 100 Myr of &lt;SFR&gt;10 = 1340 ± 100 M⊙ yr‑1 and &lt;SFR&gt;100 = 740 ± 80 M⊙ yr‑1, respectively. The H2 emission seems to be powered predominantly by shocks and star formation within the central ∼20 kpc, induced by stellar feedback and radio jets from the active galactic nucleus. Additionally, we find nearly an order-of-magnitude drop in the SFRs estimated by PAH fluxes in cool core BCGs compared to field galaxies, suggesting that hot particles from the intracluster medium are destroying PAH grains even in the central-most tens of kiloparsecs.

Keywords: Galaxy clusters, Starburst galaxies, Cooling flows, Active galaxies, Interstellar dust extinction, Infrared astronomy, Intracluster medium, Elliptical galaxies
Anisotropy of Nanohertz Gravitational-wave Background and Source Clustering from Supermassive Binary Black Holes Based on Cosmological Simulation. Several pulsar timing array (PTA) groups have recently claimed the detection of nanohertz gravitational-wave background (GWB), but the origin of this gravitational-wave (GW) signal remains unclear. Nanohertz GWs generated by supermassive binary black holes (SMBBHs) are one of the most important GW sources in the PTA band. Utilizing data from cosmological simulation, we generate multiple realizations of a mock observable universe that self-consistently incorporates the cosmic large-scale structure, enabling a robust statistical analysis of SMBBH populations and their GW signatures. We systematically investigate the merger event distributions and both the isotropic and anisotropic properties of the resulting GWB signals under different hardening timescales. Specifically, we calculate the characteristic amplitude of the GWB signal, and the angular power spectrum for both the total energy density and the energy density in different frequency bins accounting for cosmic variance through different realizations. We also study the clustering pattern of the positional distribution of SMBBHs to examine whether they can reproduce the large-scale structure of galaxies. Furthermore, for the upcoming Chinese Pulsar Timing Array and Square Kilometre Array PTA, we predict the numbers and signal-to-noise ratio (SNR) distributions of resolvable individual GW sources that may be detected with SNR &gt; 8. We finally investigate the impact of weak-lensing effects and find that their influence on the basic characteristics of the GWB signal and individual sources is rather limited.

Keywords: Gravitational wave astronomy, Supermassive black holes, Galaxy mergers
Linearity of Structure Kernels in Main-sequence and Subgiant Solar-like Oscillators. Seismic structure inversions have been used to study the solar interior for decades. With the high-precision frequencies obtained using data from the Kepler mission, it has now become possible to study other solar-like oscillators using structure inversions, including both main-sequence and subgiant stars. Subgiant stars are particularly interesting because they exhibit modes of mixed acoustic-buoyancy nature, which provide the opportunity to probe the deeper region of stellar cores. This work examines whether the structure inversion techniques developed for the pure acoustic modes of the Sun and other main-sequence stars are still valid for mixed modes observed in subgiant stars. We construct two grids of models: one of main-sequence stars and one of early subgiant stars. Using these grids, we examine two different parts of the inversion procedure. First, we examine what we call the "kernel errors," which measure how well the mode sensitivity functions can recover known frequency differences between two models. Second, we test how these kernel errors affect the ability of an inversion to infer known structure differences. On the main sequence, we find that reliable structure inversion results can be obtained across the entire range of masses and large frequency separations we consider. On the subgiant branch, however, the rapid evolution of mixed modes leads to large kernel errors and hence difficulty recovering known structure differences. Our tests show that using mixed modes to infer the structure of subgiant stars reliably will require improvements to current fitting approaches and modifications to the structure inversion techniques.

Keywords: Subgiant stars, Asteroseismology, Low mass stars, Stellar structures
Decoding AGN Feedback with X-arithmetic: From Morphology to Physical Mechanisms. Feedback from active galactic nuclei is a key process in the evolution of massive halos in the Universe. New observational information on feedback is crucial for improving the implementation of the physics in numerical models. In this work, we apply a novel image-manipulation technique, termed "X-arithmetic," to a sample of 15 galaxy clusters and groups deeply observed with Chandra. This technique decomposes perturbations in feedback-dominated regions into images excluding either (1) weak shocks and sound waves, (2) bubbles inflated by jets, or (3) cooling and slow gas motions (isobaric perturbations), enabling efficient spatial identification of these features without involving spectroscopic analysis. We confirm the nature of previously (spectroscopically) identified features and newly establish the origin of other structures. We find that feedback produces multiple shocks in groups and massive galaxies, but only one to two shocks in clusters. Prominent isobaric structures are abundant around inner cavities in clusters, compared to almost no such structures in groups. These differences suggest that feedback effects are stronger in smaller-mass systems, possibly due to the shallower gravitational potential of groups or more violent feedback. Follow-up spectroscopy, guided by the X-arithmetic results, suggests that earlier-identified "isothermal shocks" could be a mix of isobaric and adiabatic structures. We applied X-arithmetic to galaxy cluster simulations, demonstrating its straightforward application and future potential for testing the feedback physics details in simulations. Our feasibility study shows that imaging data from future X-ray observatories like AXIS will be ideal for expanding X-arithmetic application to a larger sample of objects.

Keywords: Galaxy clusters, X-ray astronomy, Cool cores, Intracluster medium, Astronomy image processing
MIDIS: MIRI Uncovers Virgil, the First Little Red Dot with Clear Detection of Its Host Galaxy at z ≃ 6.6. We present Virgil, a Mid-Infrared Instrument (MIRI) extremely red object detected with the F1000W filter as part of the MIRI Deep Imaging Survey observations of the Hubble Ultra Deep Field. Virgil is an Lyα emitter (LAE) at zspec = 6.6312 ± 0.0019 (from the Very Large Telescope/MUSE) with a rest-frame UV-to-optical spectral energy distribution (SED) typical of LAEs at similar redshifts. However, MIRI observations reveal an unexpected extremely red color at rest-frame near-infrared (NIR) wavelengths, F444W − F1000W = 2.33 ± 0.06. Such a steep rise in the NIR, completely missed without MIRI imaging, is poorly reproduced by models including only stellar populations and hints toward the presence of an active galactic nucleus, although alternative explanations such as extreme dust obscuration and strong nebular continuum and emission lines contribution due to young stellar ages cannot be completely ruled out. According to the shape of its overall SED, Virgil belongs to the recently discovered population of little red dots but displays an extended rest-frame UV-optical wavelength morphology following a 2D-Sérsic profile with an average index of  n=0.93−0.31+0.85  and  re=0.49−0.11+0.05  pkpc. Only at MIRI wavelengths, Virgil is unresolved due to the coarser point-spread function. This discovery demonstrates the crucial importance of deep MIRI surveys to reveal the true nature and properties of high-z galaxies that otherwise would be misinterpreted and raises the question of how common Virgil-like objects could be in the early Universe.

Keywords: Galaxy formation, Stellar populations, Galaxy ages, James Webb Space Telescope, Active galactic nuclei, Galaxy evolution, High-redshift galaxies
The 157 Month Swift/BAT All-sky Hard X-Ray Survey. The Burst Alert Telescope (BAT) on board the Neil Gehrels Swift Observatory has been serving as a survey instrument for the hard X-ray sky, and has detected thousands of X-ray sources (e.g., active galactic nuclei, X-ray binaries, etc). BAT monitors these X-ray sources and follows their light curves on timescales from minutes to years. In addition, BAT has discovered hundreds of new X-ray sources in survey images stacked throughout the mission lifetime. We present an updated BAT survey catalog since the last published BAT 105 month survey catalog with additional 4.5 yr of data until 2017 December. Data since 2007 are reprocessed to include updated instrumental calibrations. Analysis in this study shows that additional systematic noise can be seen in the 157 month mosaic images, resulting in decreases in the expected improvement in sensitivity and the number of new detections. The BAT 157 month survey reaches a sensitivity of 8.83 × 10‑12 erg s‑1 cm‑2 for 90% of the sky and 6.44 × 10‑12 erg s‑1 cm‑2 for 10% of the sky. This catalog includes spectra, and monthly and snapshot light curves in eight energy bands (14–20, 20–24, 24–35, 35–50, 50–75, 75–100, 100–150, and 150–195 keV) for 1888 sources, including 256 new detections above a detection threshold of 4.8σ. The light curves, spectra, and tables that summarize the information of the detected-sources are available in the online journal and on the catalog web page: https://swift.gsfc.nasa.gov/results/bs157mon/.

Keywords: X-ray astronomy, Gamma-ray astronomy, Gamma-ray transient sources, X-ray surveys
Where Do Solar Storms Prefer to Originate From: Hemispheric and Longitudinal Patterns in Solar Cycles 23 and 24. Using synoptic maps, we analyzed the relationship between active longitudes, the most populated longitudes of energetic flares, the distribution of magnetically complex active regions, and the preferred locations of those that produced the largest flares. We found that solar activity was stronger in the northern hemisphere during the rising phases of both cycles, shifting to the southern hemisphere around solar maximum. In solar cycle 24, stronger activity returned to the northern hemisphere during the declining phase—a pattern not seen in cycle 23. Strong magnetic elements and large flares showed significant clustering along persistent active longitudes, particularly from the solar maximum through the declining phase. These active longitudes remained stable for four to nine Carrington rotations before shifting by approximately 160°–180°, and their evolution displayed clear periodic behavior with cycles ranging from 0.6 to 2.02 yr, consistently seen both in the magnetic and flare data. During the solar minimum between cycles 23 and 24, active longitudes clustered near 200° longitude for about 3 yr, with cycle 24 beginning with a dominant activity at this location. Furthermore, 71% of β–γ–δ-type active regions that produced X-class flares emerged along these active longitudes. This highlights their significance for the strongest solar eruptions and offers valuable potential information for midterm flare prediction in both hemispheric and longitudinal domains, even at the onset of new cycles.

Keywords: Solar active regions, Active sun
Discoveries of Fine Structures and Secondary Pulses in Coherent Radio Emission from a Magnetic Massive Star. In this paper, we report auroral radio emission from a magnetic B star HD 142990 using the MeerKAT radio telescope at 900–1670 MHz. This star is known to produce such emission (observed as periodic radio pulses) via electron cyclotron maser emission (ECME). However, past studies on ECME from this star were confined to observations at specific rotational phase ranges where one expects to see such pulses. We, for the first time, observed the star for its one complete rotation cycle and discovered that the star also produces "off-pulse" emission, which we term as secondary enhancements. Two such enhancements were observed, one of which is left circularly polarized (LCP) and the other is right circularly polarized, the latter is confirmed to be persistent. Using simulation, we infer that such pulses are likely related to the large misalignment between the stellar rotation and magnetic dipole axes (&gt;80°), leading to the formation of highly complex magnetospheric plasma distribution. In addition, by extracting dynamic spectra for the primary pulses, we discovered prominent fine structures in one of the LCP pulses, with timescales as small as the instrumental time resolution (8 s). This is the first time that such structures are seen from a magnetic hot star, and has the potential to reveal detailed information about how the emission is driven, and the nature of the elementary sources of radiation. To pinpoint the origin of these fine structures and their significance, higher time and spectral resolution observations should be conducted in the future.

Keywords: Early-type stars, Magnetic stars, B stars, Magnetospheric radio emissions, Non-thermal radiation sources, Radio transient sources
Generation of Sunward Ion Cyclotron Waves and the Nature of Right-handed Polarized Ion-scale Waves in the Near-Sun Solar Wind. Observations from the Parker Solar Probe have revealed the ubiquitous presence of right-handed polarized waves in the near-Sun solar wind. While antisunward fast-magnetosonic whistler waves have been commonly considered as their source, sunward ion cyclotron waves (ICWs) are another plausible candidate. Sunward ICWs can directly interact with antisunward ions via cyclotron resonant interactions, suggesting they may play an important role in particle energization processes in the solar wind. However, the generation of sunward ICWs remains poorly understood. In this study, we perform a theoretical instability survey over a broad parameter space to investigate the conditions that favor the generation of sunward ICWs, focusing on two key plasma properties: the temperature anisotropy and the relative streaming speed of the proton beam component. Our results show that sunward ICWs can be excited by proton beams with slow streaming speeds but significant temperature anisotropy. Additionally, the analysis reveals that the growth of this instability is strongly suppressed in environments with high alpha particle concentrations, indicating that sunward ICWs preferentially arise in plasmas with low alpha particle abundance. These findings offer new insights into the generation and nature of ion-scale waves in the near-Sun solar wind.

Keywords: Space plasmas, Solar wind, Plasma physics
Detection of X-Ray Polarization in the Hard State of IGR J17091-3624: Spectropolarimetric Study with IXPE and NuSTAR Data. The class-transition Galactic X-ray binary IGR J17091–3624 was simultaneously monitored by the Imaging X-ray Polarimetry Explorer (IXPE) and NuSTAR satellites. We present a detailed spectropolarimetric study of the source using data from both satellites covering the period from 2025 March 7 to 10. A polarimetric analysis in the 2–8 keV band using a model-independent method reveals a significant detection of polarization degree (PD) of (11.3 ± 2.35)% at a polarization angle (PA) of  82.°7±5.°96  (significant at &gt;4σ). The model-dependent polarization analysis using the polconst and polpow models yields consistent values of PD and PA. In both methods, an energy-dependent increasing trend of PD is observed. In the 6–8 keV band, a maximum PD of (29.9 ± 8.46)% (significant at &gt;3σ) is detected at a PA of 88 .° 0 ± 8 .° 15 (&gt;3σ). The joint spectral analysis using IXPE and NuSTAR data in the 2–70 keV band was performed with four different sets of phenomenological and physical models. Our results indicate a strong dominance of nonthermal photons originating from a "hot" Compton cloud, suggesting that the source was in a hard spectral state. Spectral fitting with the physical kerrbb and TCAF models provides an estimate of the black hole mass  MBH=14.8‑3.4+4.7M⊙  and dimensionless spin parameter a* ∼ 0.54. The requirement of a higher hydrogen column density in the spectral fit of the second NuSTAR observation is attributed to the obscuration of nonthermal photons during the dip phase, likely caused by the presence of wind accreted from the companion star.

Keywords: Accretion, Black hole physics, X-ray binary stars, Black holes, X-ray transient sources, Polarimetry
X-Ray Observations of Nova Sco 2023: Spectroscopic Evidence of Charge Exchange. The supersoft source phase of a nova eruption, observed a few days after the outburst, usually displays an absorbed X-ray thermal continuum with absorption features, emitted by the white dwarf atmosphere. However, the X-ray spectra of many novae in this phase display additional emission lines that likely originate from shocks in the novae ejecta. When the shocked plasma interacts with cold gas, narrow radiative recombination continua (RRCs) and charge exchange (CX) emission are observed. We present the analysis of high-resolution Chandra Low Energy Transmission Grating X-ray grating spectra of Nova Sco 2023, observed 128 and 183 days after the optical peak in 2023 August and October. At both epochs, the absorbed X-ray thermal continuum is well described by a nonlocal thermal equilibrium atmosphere model with a temperature T ≃ 750,000 K (kT ≃ 65 eV). On day 128, the atmosphere is found to be outflowing at v ≃ ‑3500 km s‑1. On day 183, the atmosphere brightened by a factor of ∼2 and slowed down to v ≃ ‑1500 km s‑1. The discrete emission features of the spectrum consist of the C+5, N+5, and N+6 RRCs, indicating a cold electron temperature of kTe ≃ 1 eV on day 128 and kTe ≃ 20 eV on day 183. The observed line series of H-like and He-like C+5, N+5, N+6, and O+6 show enhanced intensities of high-n (principal quantum number) transitions, consistent with a CX model of hot ions at kT ∼ 100 eV. The velocity shift of the CX lines remained at v ∼ ±3000 km s‑1, which can be explained by a bipolar outflow. After Nova Ret 2020 (YZ Ret), Nova Sco 2023 is yet another nova in which we have found exquisite evidence of CX in astrophysical ionized plasma.

Keywords: X-ray astronomy, Spectral line identification, Novae, Spectroscopy, Charge exchange recombination, X-ray novae