Sazuna/UAT_keywords huggingface dataset:
Characterizing the Star Cluster Populations in Stephan's Quintet Using HST and JWST Observations. Stephan's Quintet (SQ) is a local compact galaxy group system that exhibits significant star formation activity. A history of tidal interactions between its four member galaxies and a recent collision between an intruder galaxy and the original group are associated with active star formation, particularly in many shocked regions in the intragroup medium. Using an existing star cluster candidate (SCC) catalog constructed from Hubble Space Telescope (HST) UV/optical images, we integrate flux measurements from five near-infrared filters (F090W, F150W, F200W, F277W, and F356W) obtained from JWST NIRCam observations in 2022. Leveraging the extended photometric baseline from HST and JWST, spanning ∼300 to ∼3500 nm, we perform spectral energy distribution (SED) fitting using the CIGALE code to derive reliable estimates of age, mass, and extinction for the 1588 high-confidence SCCs. We confirm earlier results that very young SCCs (∼a few Myr) are predominantly located along previously identified shock regions near the merging galaxies, while older (&gt;100 Myr) and globular clusters are more widely distributed. Our analysis shows that near-IR photometry helps break the age─extinction degeneracy, reclassifying many SCCs from older to younger, moderately dust-extincted clusters when added to HST-based SED fits. We also observe a strong spatial correlation between young clusters and CO-traced molecular gas, although active star formation is present in several regions with no detectable CO. We find that the two prominent epochs of star formation, around 5 and 200 Myr, correspond to the two major interaction events in SQ that gave rise to the observed extended tidal features.

Keywords: Hickson compact group, Star clusters
Constraint on the Physical Origin of Gamma-Ray Burst Prompt Emission via Its Nondetected Diffuse Neutrino Emission. The physical origin of prompt emission in gamma-ray bursts (GRBs) remains an open question since it has been studied for more than half a century. Three alternative models (i.e., dissipative photosphere, internal shock, and Internal-Collision-induced MAgnetic Reconnection and Turbulence, ICMART) have been proposed to interpret the observations of GRB prompt emission, but none of them can fully interpret all of the observational data collected so far. The question is what is the fraction of these three theoretical models in the prompt emission of GRBs. In this paper, we propose to utilize an innovative method and constrain the fraction of GRB prompt emission models via its nondetected diffuse neutrinos. By adopting two methods (e.g., summing up the individual GRB contributions and assumed luminosity functions of GRB) to calculate diffuse neutrino flux of GRBs for given the benchmark parameters of Γ = 300 and ∊p/∊e = 10, both approaches indicate that most GRBs should be originated from the ICMART model. Moreover, we find that the fractions of the dissipative photosphere model, the internal shock model, and the ICMART model are constrained to be [0, 0.5%], [0, 1.1%], and [98.9%, 1], respectively, for the method of summing up the individual GRB contributions. For the method of luminosity functions, the fractions of above three models are constrained to be [0, 6.1%], [0, 8.2%], and [91.8%, 1], respectively. However, such fractions of different models are also dependent on the parameters of Γ and ∊p/∊e.

Keywords: Neutrino astronomy, Gamma-ray bursts
Evidence for In-Situ Acceleration of Relativistic Particles in the Wings of X-shaped Radio Galaxies. We report evidence for in-situ acceleration/reacceleration of relativistic particles in 11 radio wings out of a total of 68 wings sufficiently well-resolved for spectral mapping, which belong to our sample of 40 X-shaped radio galaxies (XRGs). This representative XRG sample includes 15 XRGs newly reported here, which we selected from the LOTSS-DR2 survey, following well-defined criteria. The evidence for in-situ particle acceleration comes from the observed cessation of steepening, or even flattening (i.e., gradient reversal) of the spectral index profile along the lobe into the associated wing, as determined here by combining the LoTSS-DR2 (144 MHz) and FIRST (1.4 GHz) maps. Interestingly, the aforementioned trends in spectral gradient, indicative of in-situ particle acceleration, are mostly found to set in near the region where the lobe plasma stream bends to connect to the wing. Such a spatial coincidence with the bending of the radio lobe/tail has been noticed in recent years for just a couple of radio galaxies. The large increase in such examples, as reported here, is expected to give a fillip to observational, theoretical, and numerical simulation follow-up investigations of this important clue about the occurrence of in-situ particle acceleration in lobes of radio galaxies.

Keywords: AGN host galaxies, Radio galaxies, Radio jets
The Photospheric Emission of a Short-duration Gamma-Ray Burst Emerging from a Realistic Binary Neutron Star Merger. The almost simultaneous detection of GRB 170817A and GW170817 ushered in nearly a decade of interest in binary neutron star (BNS) mergers and their multimessenger signals, resulting in a greater understanding of the processes that produce short-duration gamma-ray bursts and gravitational waves. However, open questions remain regarding the emission mechanism of these bursts. In this work, we present results from the first study of an electromagnetic signal produced from a realistic treatment of a BNS merger for both on-axis and off-axis observations. We accomplish this by using the PLUTO hydrodynamical code to inject a relativistic jet into the ejecta of a realistic BNS merger, which was itself obtained from the simulation of a 3D BNS merger. Then, we model the prompt photospheric emission that would emerge from this jet using the Monte Carlo Radiation Transfer radiative transfer code. We find that the resulting photon spectra can peak around ∼1 MeV for on-axis emission and fall off noticeably for off-axis observations. We also find distinctly nonthermal low- and high-energy tails in multiple observations, ranging from shallow to slightly off-axis observations. Our on-axis results are consistent with the Amati correlation for short bursts, with some strain evident at higher observing angles. Finally, we find that the radiative efficiency is much lower than seen in previous studies of the photospheric emission of long-duration gamma-ray bursts.

Keywords: Neutron stars, Radiative transfer simulations, Gamma-ray bursts
Resolved Mass Assembly and Star Formation in Milky Way Progenitors since z = 5 from JWST/CANUCS: From Clumps and Mergers to Well-ordered Disks. We present a resolved study of 877 progenitors of Milky Way Analogs (MWAs) at 0.3 &lt; z &lt; 5, selected with abundance matching in the 10 fields of the Canadian NIRISS Unbiased Cluster Survey. Utilizing 18─21 bands of deep NIRCam, NIRISS, and Hubble Space Telescope photometry, we create resolved stellar mass maps and star formation rate (SFR) maps via spectral energy distribution fitting with Dense Basis. We examine their resolved stellar mass and specific SFR (sSFR) profiles as a function of galactocentric radius and find clear evidence for inside-out mass assembly. The total M⋆ of the inner 2 kpc regions of the progenitors remains roughly constant (109.3−9.4M⊙) at 2 &lt; z &lt; 5, while the total M⋆ of the regions beyond 2 kpc increases by 0.8 dex, from 107.5M⊙to 108.3M⊙. Additionally, the sSFRs of the outer regions increase with decreasing redshift, until z ∼ 2. The median Sérsic index of the MWA progenitors stays nearly constant at n ∼ 1 at 2 &lt; z &lt; 5, while the half-mass radii of their stellar mass profiles double. We perform additional morphological measurements on the stellar mass maps via the Gini-M20 plane and asymmetry parameters. They show that the rate of double-peak mergers and disturbances to galaxy structure also increases with redshift, with ∼50% of galaxies at 4 &lt; z &lt; 5 classified as disturbed and ∼20% classified as ongoing mergers. Overall, the early evolution of MWAs is revealed as chaotic, with significant mergers and high SFRs. Mass growth is primarily inside-out and galaxies become more disklike after z = 3.

Keywords: Milky Way evolution, Galaxy evolution
Automated Modeling with AAP-Imfit: Astrometry and Photometry via CASA. Very long baseline interferometry (VLBI) provides the highest-resolution radio intensity maps, crucial for detailed studies of compact sources like active galactic nuclei (AGNs) and their relativistic jets. Analyzing jet components in these maps traditionally involves manual Gaussian fitting, a time-consuming bottleneck for large data sets. To address this, we present an automated batch-processing tool, based on the Gaussian fitting capabilities of the Common Astronomy Software Applications package, designed to streamline VLBI jet component characterization (AAP-Imfit); the algorithm is available as a GitHub repository: https://github.com/Alfred97AstroAGN/AAP-Imfit-aCASA-tool.git). Our algorithm sets a detection limit, performs automatic 2D Gaussian fitting, and removes model artifacts, efficiently extracting component flux densities and positions. This method enables systematic and reproducible analysis, significantly reducing the time required for fitting extensive VLBI datasets. We validated AAP-Imfit by using VLBI observations of the blazars 3C 279 and 3C 454.3, comparing our results with published fits. The close agreement in residual rms values and model/residual-to-map rms ratios confirms the accuracy of our automated approach in reproducing original flux distributions. While visual inspection remains important for complex or faint features, this routine significantly accelerates VLBI component fitting, paving the way for large-scale statistical studies of jet dynamics.

Keywords: Blazars, Very long baseline interferometry, Galaxy jets, Astronomy data analysis, Active galactic nuclei
Mass Stratification in the Globular Cluster System Revealing the Assembly History of the Nearest S0 Galaxy NGC 3115. Galaxy formation and evolution are hierarchical. The most massive galaxies are thought to form their central regions early through violent dissipational processes, then grow inside-out by accreting smaller satellites. While widely supported, direct observational confirmation of this process in individual galaxies remains lacking, except for the Milky Way. We present a detailed analysis of globular cluster (GC) candidates within a  70' (∼190 kpc) radius around the nearest S0 galaxy, NGC 3115, using images in g, r, z bands from the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys and data from Gaia. We report the discovery of mass stratification in the GC system (GCS), evident in two ways: first, the effective radius of the GCS increases monotonically from the bright to faint end, up to the detection limit near the turnover magnitude of the GC luminosity function (GCLF); second, the GCLF shows fainter turnover magnitudes and smaller standard deviations at larger galactocentric radii. This stratification cannot be readily explained by radial migration or tidal dissolution, but most likely reflects the hierarchical assembly of NGC 3115's stellar halo, with later-accreted satellites deposited across broader galactocentric distances. This interpretation is supported by cosmological simulations of subhalos with comparable mass and bulge-to-total mass ratios and is consistent with the negative color gradients observed in the GCS. Additionally, we identify several substructures within the GCS, indicating ongoing assembly of NGC 3115. This work highlights the power of GCS as tracers of galaxy assembly and sets the stage for upcoming space-based wide-field imaging surveys to constrain the assembly of massive galaxies.

Keywords: Globular star clusters, Lenticular galaxies, Galaxies, Gaia, Early-type galaxies
An Excess of Luminous White Dwarfs in the Peculiar Galactic Globular Cluster NGC 2808. We study the white dwarf (WD) cooling sequence of the Galactic Globular Cluster (GGC) NGC 2808 by using deep near-UV data from the Hubble Space Telescope and theoretical models, to investigate if this cluster hosts an excess of WDs. Excess in WDs is a rare phenomenon that has been found to exist only in a few GGCs. We compared star counts from different evolutionary phases on the near-UV color─magnitude diagram to evolutionary times predicted by BaSTI models. The investigation was carried out over a region within a radius of  1.'5  of the cluster center and a region of similar dimension located 5 ' away. We find a WD excess of ≍60%─70% when comparing star counts and evolutionary models of the WD cooling sequence to the main-sequence turn-off, and by using different values and fractions of He enhancement. This excess decreases to ≍30%─40% when the WD cooling sequence is compared to the horizontal branch (HB). The WD excess is slightly larger in the internal field that covers the cluster center; however, the difference with the external field is compatible within the uncertainties. We argue that this excess is possibly related to the existence of SCWDs and He-core WDs in NGC 2808, and might be directly associated with the extended blue HB of this GGC.

Keywords: Globular star clusters, Hertzsprung Russell diagram, White dwarf stars
Measuring the Two-dimensional Thermal Structures of Protoplanetary Disks. We present a flexible, annulus-by-annulus method to constrain the 2D thermal structure of a protoplanetary disk from optically thick spectral line emission. Using synthetic disk models with a known temperature and density structure, we extracted the vertical emission surfaces and brightness temperatures in radial annuli for multiple CO isotopologue transitions and used them to infer the vertical temperature profiles. This approach reliably recovers the injected temperature structure despite noise and finite resolution. We demonstrated that even a modest set of emission lines can constrain the temperature across a wide range of radii and elevations. Nevertheless, biases in the extracted emission surfaces constitute a major source of systematic error. Finally, we applied this method to archival Atacama Large Millimeter/submillimeter Array observations of the HD 163296 disk, revealing that simple parametric radial temperature models may obscure the complexity of real disks and that additional observations are necessary to distinguish between different models of the vertical structure. This flexible framework can be readily applied to other systems, helping to characterize the thermal environments that shape planet formation.

Keywords: Protoplanetary disks
Multiband Optical Photometric and Spectroscopic Monitoring of the 2024 Flare Event in Transition Blazar OP313. Blazars are active galactic nuclei known for their extreme variability, offering unique opportunities to study jet physics and high-energy emission mechanisms. In 2024, the Flat Spectrum Radio Quasar (FSRQ) OP313 underwent a remarkable flare event, during which the gamma-ray flux observed by the Fermi Large Area Telescope increased by a factor of 60 over its average value. The flare peak lasted less than two days. Using optical telescopes, we conducted 100 day timescale observations. Multiwavelength data revealed that OP313 entered an active state 50 days prior to the flare and remained active for at least 50 days afterward. We propose that this prolonged activity resulted from variations in electron density within the shock front due to changes in the accretion rate. Concurrently, OP313's spectrum transitioned from an FSRQ-like state to a BL Lac-like state, characterized by a significant increase in the synchrotron peak frequency and the disappearance of broad-line region emission lines. In the post-flare phase, we observed a decoupling between synchrotron radiation and inverse Compton scattering, along with a possible decrease in the magnetic field strength within the shock front.

Keywords: Blazars, Flat-spectrum radio quasars, BL Lacertae objects
Mechanical Properties of Dust, Pebbles, and Planetesimals Based on Johnson─Kendall─Roberts, Griffith, and Weibull Theories. Mechanical properties of small bodies such as dust, pebbles, and planetesimals are key to better understanding the formation of planetary systems against their collisional destruction. We present a simple mathematical formulation to determine the static tensile strength, elastic modulus, fracture energy, fracture toughness, and sound velocity for solid particles of any composition, size, structure, and porosity. This formulation is based on the Johnson─Kendall─Roberts theory of contact mechanics, the Griffith theory of fracture mechanics, and the Weibull theory of flaw statistics, in which both aggregate particles and monolithic particles are treated as agglomerates of small constituent grains and molecules, respectively. We show that our formulae are consistent with the results of laboratory experiments and molecular dynamics simulations for porous and nonporous particles of silica or ice, irrespective of the sintering process and the internal heterogeneity. This provides us with a great opportunity to infer the internal structure of asteroids and comets from observational data on their tensile strengths.

Keywords: Dust physics, Dust destruction, Solid matter physics, Astrophysical dust processes, Planet formation
Betelgeuse, Betelgeuse, Betelgeuse, Betel-buddy? Constraints on the Dynamical Companion to α Orionis from HST. Recently, two independent analyses have asserted that the cause of the long secondary period (LSP) observed in the variability spectrum of our nearest red supergiant, Betelgeuse (α Ori), is the as yet undetected, low-mass binary companion dubbed α Ori B. In this paper, we present the results of a far-UV (FUV) observational campaign using the Space Telescope Imaging Spectrograph echelle spectrograph on the Hubble Space Telescope aimed at detecting spectral signatures of the companion. The four-quadrant tiling pattern and timing of the observations were optimized to isolate the companion, with observations taking place during a period of maximum angular and velocity separation between Betelgeuse and the putative companion. Spectral differencing between quadrants recovers no spectral features at the companion's velocity in excess of the background or Betelgeuse's chromosphere, i.e., a nondetection. Having determined that α Ori B is most likely a young stellar object (YSO) thanks to constraints from a complementary X-ray campaign with the Chandra X-ray Observatory in a companion paper, comparison of our data against canonical spectra from YSOs in the ULLYSES database allows us to confidently exclude masses ≳ 1.5 M⊙ and companion continuum or line emission in excess of ≍10−14 erg s−1 cm−2 Å−1 in the FUV (≍1200─1700 Å). Future observational campaigns aware of the LSP phase are needed to place deeper constraints on the spectroscopic nature of α Ori B.

Keywords: Binary stars, Red supergiant stars, Close binary stars, Hubble Space Telescope, Massive stars, Ultraviolet astronomy, Young stellar objects, Pre-main sequence stars, Long period variable stars, Spectroscopy, Variable stars
High-velocity Outflows in [O III] Emitters at 2.5 &lt; z &lt; 9 from JWST NIRSpec Medium-resolution Spectroscopy. We identify galaxies hosting ionised-gas high-velocity outflows from the complete sample of medium-resolution (R1000) JWST/NIRSpec MSA spectroscopy taken as part of the JWST Advanced Deep Extragalactic Survey. From a total sample of 1087 [O III]5007 emitters we identify 40 galaxies with a blue-side broadened [O III]5007 line at 2.5 &lt; z &lt; 9. Of these, 34 are strong outflow candidates while 6 sources exhibit broadening potentially driven by rotating clumps. Our outflow candidate sample is mainly composed of star-forming galaxies, including ∼65% starbursts, which span the stellar mass range 7.5 &lt; log10(M*/M⊙) &lt; 11.0. It also includes two candidate type-2 active galactic nuclei and a "little red dot." We report a median outflow velocity of 531 −159+146  km s−1 and an overall incidence rate of 3.4%. These values are significantly higher and lower, respectively, than recent similar works, which we accredit to the limiting resolution of the R1000 spectroscopy and a stricter outflow selection criterion. We find no correlation between the outflow velocity and the galaxy stellar mass or star formation rate. The median ratio between outflow velocity and escape velocity is 0.77 −0.32+0.36 , indicating that most outflows cannot escape the galaxy gravitational potentials. We do find an anti-correlation between mass loading factor and stellar mass up to M* ≍ 1010 M⊙, with most lowest-stellar-mass (M* &lt; 109 M⊙) galaxies reaching values well above unity, as is the case for local starburst galaxies.

Keywords: Galaxy evolution, High-redshift galaxies, Galaxy winds, Infrared astronomy
Signatures of Confined and Eruptive Solar Flares in Microwave Spectra. We describe how microwave spectra of confined flares differ from those of eruptive flares. All 29 confined ≥M1.4 soft X-ray flares from NOAA Active Region 12192 in 2014 October that were observed by the Radio Solar Telescope Network in the &gt;300 MHz microwave range (encompassing RSTN frequencies from 410 to 15,400 MHz) had low-frequency (≥410 MHz) cutoffs in their peak-flux-density spectra, with peak emission &lt;10 solar flux units (sfu) at 410 MHz. Wind/Waves observations at 1 MHz for 20 of these cutoff microwave bursts suggest that few, if any, of the 29 flares were accompanied by escaping electrons. We find a marked difference between microwave spectra for samples of intense (≥M5) confined and eruptive flares from 2011 to 2016: 20 of 21 confined ≥M5 flares had cutoff spectra, while 27 of 30 ≥M5 eruptive flares had peak 410 MHz emission &gt;10 sfu (with a median value of 431 sfu). For the subsets of these events with Wind/Waves observations, only one of 20 confined events was unambiguously accompanied by 1 MHz emission, while 25 of the 29 eruptive flares had peak 1 MHz fluxes &gt;103 sfu (above a background of ∼200─400 sfu), with an overall median peak value of ∼105 sfu. These results indicate that strong confined flares characteristically do not involve or affect open field lines, ruling out interchange reconnection as a confined-flare generation mechanism, leaving reconnection between closed loops as the likely alternative. The microwave spectral signatures of confined and eruptive flares have potential application for the determination of confinement/eruption for flares on solar-type stars.

Keywords: Solar radio flares, Solar coronal mass ejections
The He I D3 Line as a Proxy for Magnetic Activity Using EXPRES Solar Observations. Stellar activity remains one of the primary challenges in the detection and characterization of low-mass exoplanets, as it can induce radial velocity (RV) variations that mask or mimic planetary signals. Identifying reliable activity proxies is essential in order to distinguish stellar variability from genuine planetary signatures. In this study, we examine the variability of the chromospheric He I D3 line in high-resolution solar spectra and assess its potential as an activity indicator. We find a strong correlation between the He I D3 line intensity variation and the Sun's unsigned magnetic flux derived from Solar Dynamics Observatory/Helioseismic and Magnetic Imager data as well as with the solar RVs. Our results suggest that the He I D3 line offers a promising and straightforward proxy for magnetic activity, which may complement existing stellar activity indicators. Its inclusion could help disentangle stellar signals in RV measurements and ultimately improve the detection of Earth-like exoplanets.

Keywords: The Sun, Stellar activity, Solar magnetic fields, Solar activity, Radial velocity