Sazuna/UAT_keywords huggingface dataset:
The Evolution of Molecular Clouds: Turbulence-regulated Global Radial Collapse. The star formation efficiency (SFE) measures the proportion of molecular gas converted into stars, while the star formation rate (SFR) indicates the rate at which gas is transformed into stars. Here we propose such a model in the framework of a turbulence-regulated global radial collapse in molecular clouds being in quasi-virial equilibrium, where the collapse velocity depends on the density profile and the initial mass-to-radius ratio of molecular clouds, with the collapse velocity accelerating during the collapse process. This simplified analytical model allows us to estimate a lifetime of giant molecular clouds of approximately 0.44‑7.36 × 107 yr, and a star formation timescale of approximately 0.5–5.88 × 106 yr. Additionally, we can predict an SFE of approximately 1.59%, and an SFR of roughly 1.85 M⊙ yr‑1 for the Milky Way in agreement with observations.

Keywords: Star formation, Molecular clouds, Interstellar medium
Ab Initio Quantum Dynamics as a Scalable Solution to the Exoplanet Opacity Challenge: A Case Study of CO<SUB>2</SUB> in a Hydrogen Atmosphere. Light–matter interactions lie at the heart of our exploration of exoplanetary atmospheres. Interpreting data obtained by remote sensing is enabled by meticulous, time- and resource-consuming work aiming at deepening our understanding of such interactions (i.e., opacity models). Recently, P. Niraula et al. pointed out that due primarily to limitations on our modeling of broadening and far-wing behaviors, opacity models needed a timely update for exoplanet exploration in the JWST era, and thus argued for a scalable approach. In this proof-of-concept study, we introduce an end-to-end solution from ab initio calculations to pressure broadening, and use a perturbation framework to address the need for precision to a level of ∼10%. We focus on the CO2–H2 system as CO2 is a key absorption feature for exoplanet research (primarily in many gas giants) at ∼4.3 μm as pressure-broadening parameters required for interpreting such observations remain sparse. We compute elastic and inelastic cross sections for the collisions of ortho-H2 with CO2, in the ground vibrational state, and at the coupled-channel fully converged level. For scattering energies above ∼20 cm‑1, moderate precision intermolecular potentials are indistinguishable from high-precision ones in cross sections. Our calculations agree with the currently available measurements within 7%, i.e., well beyond the precision requirements.

Keywords: Spectral line lists, Infrared spectroscopy, Astronomy databases, Laboratory astrophysics, Astronomy data analysis, Transmission spectroscopy, James Webb Space Telescope
You Shall Not Pass! The Propagation of Low-/Moderate-powered Jets Through a Turbulent Interstellar Medium. Feedback from black-hole-powered jets has been invoked in many cosmological simulations to regulate star formation and quench galaxies. Despite this, observational evidence of how jets might be able to affect their hosts remains scarce, especially for low-power jets in halos smaller than clusters. Recent observations of outflows around FR0 galaxies, which host compact radio-loud sources, imply that lower-power jetted active galactic nuclei (AGN) may have a significant impact on their hosts through jet interactions with the interstellar medium (ISM). Using the Arepo code, we launch jets of low and intermediate power (1038–1043 erg s‑1) within a ∼kiloparsec-scale periodic box with driven turbulence, to study how the jets propagate through a turbulent ISM. Our simulation results broadly fit into three different scenarios—jets penetrating easily through the ISM, becoming completely stalled, or, an interesting intermediate stage, jets being highly disturbed and redirected. We suggest that intermediate-power jets do not have enough ram pressure to affect the turbulent structure of the ISM and so only fill preexisting cavities. Low-power jets are able to drive outflows in a hot phase (&gt;104.4 K). However, warm (∼104 K) ionized gas outflows appear under certain conditions. This work is part of the "Learning the Universe" collaboration, aiming to build next-generation cosmological simulations that incorporate a new prescription for AGN feedback.

Keywords: Hydrodynamical simulations, Low-luminosity active galactic nuclei, Active galactic nuclei, Galaxy jets
Observing Rayleigh–Taylor Stable and Unstable Accretion Through a Kalman Filter Analysis of X-Ray Pulsars in the Small Magellanic Cloud. Global, three-dimensional magnetohydrodynamic simulations of Rayleigh–Taylor instabilities at the disk–magnetosphere boundary of rotating, magnetized compact stellar objects reveal that accretion occurs in three regimes: the stable regime, the chaotic unstable regime, and the ordered unstable regime. Here we track stochastic fluctuations in the pulse period P(t) and aperiodic X-ray luminosity L(t) time series of 24 accretion-powered pulsars in the Small Magellanic Cloud using an unscented Kalman filter to analyze Rossi X-ray Timing Explorer data. We measure time-resolved histories of the magnetocentrifugal fastness parameter ω(t) and we connect ω(t) with the three Rayleigh–Taylor accretion regimes. The 24 objects separate into two distinct groups, with 10 accreting in the stable regime and 14 accreting in the ordered unstable regime. None of the 24 objects except SXP 293 visit the chaotic unstable regime for sustained intervals, although several objects visit it sporadically. The Kalman filter output also reveals a positive temporal cross-correlation between ω(t) and the independently measured pulse amplitude A(t), which agrees with simulation predictions regarding the pulse-forming behavior of magnetospheric funnel flows in the three accretion regimes.

Keywords: Small Magellanic Cloud, High mass x-ray binary stars, Binary pulsars, High energy astrophysics
A Study of Emission Lines in Carbon Stars. Carbon stars are chemically peculiar stars with high carbon abundance, showing strong carbon molecule bands and rare emission lines in their spectra. This paper explores the stellar activity of carbon stars by identifying emission line features in their spectra. An outlier detection method based on morphological feature extraction and interval representation is used to identify 88 targets presenting emission lines from 3546 carbon star spectra. Of these, 55 targets present Balmer series emissions, 35 show forbidden lines ([O I]λ6301 Å, [O III], [N II], [S II], with only 2 of the 35 spectra that present forbidden lines not showing [O I]) and only 2 objects presenting two types of emission lines, and 51 spectra showing Balmer series emissions are C-N stars. This indicates the existence of a continuous stellar wind forming shock waves around the star, suggesting the presence of mass loss or tidal effects and exchange of materials from the companion star. In addition, 23 spectra presenting [O I] emissions are from C-H carbon stars. These are mainly concentrated in a high-Galactic-latitude region with  , where the influence of halo clusters could lead to relatively strong magnetic activity. Other objects in the Galactic disk may also show stronger magnetic activity due to the influence of a dense medium or magnetic field, rotation, and convection within stars. In addition, one spectrum shows both [O I] and Balmer series emissions, probably caused by magnetic activity and wave shock. Another spectrum shows both Balmer series and [O III] emissions, presumably contaminated by an unknown nebula.

Keywords: Stellar winds, Carbon stars, Astronomical methods, Stellar activity
Introducing the Condor Array Telescope. VI. Discovery of Extensive Ionized Gaseous Filaments of the Cosmic Web in the Direction of the M81 Group. We used the Condor Array Telescope to obtain deep imaging observations through luminance broadband and He II, [O III], He I, Hα, [N II], and [S II] narrowband filters of an extended region of the M81 Group spanning ≈8 × 8 deg2 on the sky centered near M81 and M82. Here, we report aspects of these observations that are specifically related to (1) a remarkable filament known as the "Ursa Major Arc" that stretches ≈30° across the sky roughly in the direction of Ursa Major, (2) a "giant shell of ionized gas" that stretches ≈0.8 deg across the sky located ≈0.6 deg northwest of M82, and (3) a remarkable network of ionized gaseous filaments revealed by the new Condor observations that appear to connect the arc, the shell, and various galaxies of the M81 Group and, by extension, the group itself. We measure flux ratios between the various ions to help to distinguish photoionized from shock-ionized gas, and we find that the flux ratios of the arc and shell are not indicative of shock ionization. This provides strong evidence against a previous interpretation of the arc as an interstellar shock produced by an unrecognized supernova. We suggest that all of these objects, including the arc, are associated with the M81 Group and are located at roughly the distance (≈3.6 Mpc) of M81, that the arc is an intergalactic filament, and that the objects are associated with the low-redshift cosmic web.

Keywords: Galaxy interactions, Galaxy tails, Galaxy photometry, Galaxy mergers, Galaxy groups, Interacting galaxies, Galaxies, Low surface brightness galaxies
The JWST Resolved Stellar Populations Early Release Science Program. VIII. The Spatially Resolved Star Formation History of WLM. Radial stellar population gradients within dwarf galaxies provide a promising avenue for disentangling the drivers of galaxy evolution, including environment. Within the Local Volume, radial stellar age gradient slopes correlate with interaction history, contrary to model predictions, so dwarfs that are isolated provide a critical control sample. We measure radial stellar age gradients in the relatively isolated gas-rich dwarf irregular Wolf–Lundmark–Melotte Galaxy (WLM), combining JWST NIRCam and NIRISS imaging with six archival Hubble Space Telescope fields over semimajor axis equivalent distances of 0 ≲ RSMA ≲ 4 kpc (≲3 Rhl). Fitting lifetime star formation histories to resolved color–magnitude diagrams, radial age gradients are quantified using τ90 and τ50, the lookback times to form 90% and 50% of the cumulative stellar mass. We find that globally, the outskirts of WLM are older on average, with (δτ90, δτ50)/δRSMA = (0.82 , 1.60 ) Gyr kpc‑1 (stat.), in good agreement with simulations. However, we also detect an azimuthal dependence of radial stellar age gradients, finding that stars on the leading edge of WLM (relative to its proper motion) are both younger and have a flatter age gradient compared to the trailing edge. This difference persists over 0.6 ≲ RSMA ≲ 3.2 kpc (∼0.5–2.5 Rhl) and lookback times up to ∼8 Gyr, and is robust to the assumed stellar evolutionary model. Our results are consistent with star formation triggered by ram pressure stripping from a circumgalactic and/or intergalactic medium, suggested by recent H I observations. If confirmed, processes typifying dense environments, such as ram pressure stripping, may be more relevant to the evolution of isolated galaxies than previously thought.

Keywords: Local Group, Dwarf irregular galaxies, Galaxy environments, Dwarf galaxies, Galaxy stellar content, Star formation
The Starburst Acceleration of High-velocity Clouds in the Galactic Center. High-velocity clouds (HVCs) in the Galactic center have garnered significant attention due to their mysterious formation, potentially linked to starburst events or supermassive black hole activity in the region. However, it remains challenging to explain the observed column density and velocity distribution of HVCs. The discovery of high-velocity molecular clouds, which are denser and more massive, adds to this complexity. To address this, we conduct three-dimensional numerical simulations to explore the origin and magnetohydrodynamic evolution of HVCs in the context of a starburst in the Galactic center. By incorporating magnetic fields and an initial tangential velocity for the clouds, our simulation results align with the observed properties of HVCs, supporting the notion that these clouds can originate from a starburst process. In addition, ∼5% of the total mass of initial clouds can survive after 3.5 Myr; as a result, the following star formation will be more efficient than a feedback process that destroys all cool clouds.

Keywords: Milky Way Galaxy fountains, Hydrodynamical simulations, High-velocity clouds, Starburst galaxies
A Study of Abundance Patterns in the Sextans and Sculptor Dwarf Spheroidal Galaxies. In this work, we employ a multicomponent decomposition model to study the Sextans and Sculptor dwarf spheroidal galaxies, which have distinct evolutionary histories. Sextans exhibits massive stars dominating in the early stages of its evolution and a lower contribution from type Ia supernovae (SNe Ia). With increasing metallicity, the evolution of massive stars in Sextans shows two turning points, at [Fe/H] ∼ ‑2.8 and [Fe/H] ∼ ‑2.0, indicating episodes of accretion events and galactic winds during its evolution. In the late stages, influenced by galactic winds, the contribution from massive stars ceases, and SNe Ia become the dominant evolutionary process. Sculptor exhibits contributions from the main r-process, early very massive stars, massive stars, SNe Ia, and asymptotic giant branch (AGB) stars. In its early stages, the contributions from early very massive stars and massive stars are dominant, while the contribution from SNe Ia is low. Around [Fe/H] ∼ ‑2, the contribution from early very massive stars starts to decline, while the contributions from SNe Ia and massive stars continue to increase. At [Fe/H] ∼ ‑1.7, the contribution from massive stars gradually decreases and approaches the level of the solar neighborhood, while the contribution from AGB stars continues to rise with increasing metallicity. Both dwarf galaxies exhibit characteristic features of similar initial mass functions, but the Sextans dwarf galaxy exhibits a high-mass cutoff, while the Sculptor dwarf galaxy does not. Additionally, through decomposition, we can analyze the contributions of different astrophysical processes to [α/Fe] versus [Fe/H], [iron-group/Fe] versus [Fe/H], and [neutron-capture/Fe] versus [Fe/H].

Keywords: Astrophysical processes, Dwarf spheroidal galaxies
Galactic Structure Dependence of Cloud─Cloud-collision-driven Star Formation in the Barred Galaxy NGC 3627. While cloud─cloud collisions (CCCs) have been proposed as a mechanism for triggering massive star formation, it is suggested that higher collision velocities (vcol) and lower giant molecular cloud (GMC) mass (MGMC) and/or density (ΣGMC) tend to suppress star formation. In this study, we choose the nearby barred galaxy NGC 3627 to examine the star formation rate and star formation efficiency (SFE) of a colliding GMC (  and ϵCCC) and explore the connections between   and ϵCCC, MGMC(ΣGMC) and vcol, and galactic structures (disk, bar, and bar end). Using Atacama Large Millimeter/submillimeter Array CO (2─1) data (60 pc resolution), we estimated vcol within 500 pc apertures, based on line-of-sight GMC velocities, assuming random motion in a two-dimensional plane. We extracted apertures where at least 0.1 collisions occur per 1 Myr, identifying them as regions dominated by CCC-driven star formation, and then calculated   and ϵCCC using attenuation-corrected Hα data from MUSE on the Very Large Telescope. We found that both   and ϵCCC are lower in the bar (median values: 103.84 M⊙ and 0.18%) and higher in the bar end (104.89 M⊙ and 1.10%) compared to the disk (104.28 M⊙ and 0.75%). Furthermore, we found that structural differences within the parameter space of vcol and MGMC(ΣGMC), with higher MGMC(ΣGMC) in the bar end and higher vcol in the bar compared to the disk, lead to higher star formation activity in the bar end and lower activity in the bar. Our results support the scenario in which variations in CCC properties across different galactic structures can explain the observed differences in SFE on a kiloparsec scale within a disk galaxy.

Keywords: Molecular gas, Giant molecular clouds, Star formation, Interstellar medium, Barred spiral galaxies
Deep Learning for Active Region Classification: A Systematic Study from Convolutional Neural Networks to Vision Transformers. Solar active regions can significantly disrupt the Sun–Earth space environment, leading to severe space weather events such as solar flares or coronal mass ejections. Consequently, the automatic classification of active region groups is a crucial starting point for accurately and promptly predicting solar activity. This study presents our application of deep learning techniques to classify active region cutouts based on the Mount Wilson classification scheme. We explore the latest advantages in image classification architectures, ranging from convolutional neural networks to vision transformers, alongside modern training procedures, including on-the-fly data augmentations and transfer learning. We aim at evaluating the respective strengths and limitations of different neural network architectures in classifying solar active region cutouts. We observed that combining magnetogram and continuum image types enhances model performance by leveraging complementary features from diverse inputs. When considering only magnetograms, data-efficient image transformers achieve the best performance, suggesting that these models can better capture the spatial complexity of magnetograms. Models trained exclusively on continuum images exhibit overall lower performance, suggesting that continuum images, due to their more homogeneous nature, offer less spatial variability.

Keywords: Space weather, Solar active regions, Convolutional neural networks
Velocity Structure and Molecular Formation in the Polaris Molecular Cloud. We present a wide-field   study of a dense region within the Polaris Flare using 12CO, 13CO, and C18O (J = 1–0) observations at 15″ resolution, obtained with the Nobeyama 45 m Radio Telescope. The analysis reveals molecular gas formation occurring at column densities up to ∼1021 cm‑2, evidenced by an anticorrelation between H I and CO distributions, indicating active atomic-to-molecular gas conversion. We found a threshold column density for molecular formation at ∼5 × 1020 cm‑2, which is common among more evolved molecular clouds. The CO-to-H2 conversion factor, XCO, was found to be 0.7 × 1020 H2 cm‑2 (K km s‑1)‑1, lower than the solar neighborhood average. Our chemical models estimate the cloud's age to be ∼105–106 yr, suggesting an early stage of molecular cloud evolution. This interpretation is consistent with the observed low XCO factor. While virial analysis suggests that the entire cloud is gravitationally unbound, we identified several filamentary structures extending from the main cloud body. These filaments show systematic velocity gradients of 0.5–1.5 km s‑1 pc‑1, and analysis of the velocities shows that the molecular gas within them is falling toward the main cloud body, following a freefall model. This suggests ongoing mass accumulation processes through the filaments, demonstrating that gravitational processes can be important even at column densities of ∼1021 cm‑2.

Keywords: Molecular clouds, Interstellar medium
Search for Neutrino Doublets and Triplets Using 11.4 yr of IceCube Data. We report a search for high-energy astrophysical neutrino multiplets, detections of multiple neutrino clusters in the same direction within 30 days, based on an analysis of 11.4 yr of IceCube data. A new search method optimized for transient neutrino emission with a monthly timescale is employed, providing a higher sensitivity to neutrino fluxes. This result is sensitive to neutrino transient emission, reaching per-flavor flux of approximately   from the Northern Sky in the energy range E ≳ 50 TeV. The number of doublets and triplets identified in this search is compatible with the atmospheric background hypothesis, which leads us to set limits on the nature of neutrino transient sources with emission timescales of one month.

Keywords: Neutrino astronomy
Probing Conditions for Strong Clumping by the Streaming Instability: Small Dust Grains and Low Dust-to-gas Density Ratio. The streaming instability (SI) is a leading mechanism for concentrating solid particles into regions dense enough to form planetesimals. Its efficiency in clumping particles depends primarily on the dimensionless stopping time (τs, a proxy for particle size) and dust-to-gas surface density ratio (Z). Previous simulations identified a critical Z (Zcrit) above which strong clumping occurs, where particle densities exceed the Hill density (thus satisfying a condition for gravitational collapse), over a wide range of τs. These works found that, for τs ≤ 0.01, Zcrit was above the interstellar medium value (∼0.01). In this work, we reexamine the clumping threshold using 2D axisymmetric, stratified simulations at high resolution and with relatively large (compared to many previous simulations) domain sizes. Our main results are as follows: First, when τs = 0.01, strong clumping occurs even at Z ≲ 0.01, lower than Zcrit found in all previous studies. Consequently, we revise a previously published fit to the Zcrit curve to account for this updated Zcrit. Second, higher resolution results in a thicker dust layer, which may result from other instabilities manifesting, such as the vertically shearing SI. Third, despite this thicker layer, higher resolution can lead to strong clumping even with a lower midplane dust-to-gas density ratios (which results from the thicker particle layer) so long as Z ≳ Zcrit. Our results demonstrate the efficiency of the SI in clumping small particles at Z ∼ 0.01, which is a significant refinement of the conditions for planetesimal formation by the SI.

Keywords: Gas-to-dust ratio, Hydrodynamics, Protoplanetary disks, Planetesimals, Planet formation
The Emergence of the Star Formation Main Sequence with Redshift Unfolded by JWST. We investigate the correlation between stellar mass (M⋆) and star formation rate (SFR) across the stellar mass range  . We consider almost 50,000 star-forming galaxies at z ≈ 3–7, leveraging data from COSMOS/SMUVS, JADES/GOODS-S, and MIDIS/XDF. This is the first study spanning such a wide M⋆ range without relying on gravitational lensing effects. We locate our galaxies on the SFR–M⋆ plane to assess how the location of galaxies in the star formation main sequence (MS) and starburst (SB) region evolves with M⋆ and redshift. We find that the two star-forming modes tend to converge at  , with all galaxies found in the SB mode. However, deeper observations will be instrumental for reaching lower SFRs and M⋆ to further validate this scenario. By dissecting our galaxy sample in M⋆ and redshift, we show that the emergence of the star formation MS is M⋆ dependent: while in galaxies with   the MS is already well in place at z = 5–7, for galaxies with   it only becomes significant at z &lt; 4. Overall, our results are in line with previous findings that the SB mode dominates among low stellar-mass galaxies. The earlier emergence of the MS for massive galaxies is consistent with galaxy downsizing.

Keywords: Starburst galaxies, Galaxy formation, James Webb Space Telescope, Galaxy evolution, Reionization