arXiv subjects

Xinfeng Xu

Publications and source records attributed to Xinfeng Xu.

At least 19 recordsLinked to original sources

arXiv2026

CLASSY. XV. Kinematics and Spatial Distributions of Outflows in Local Highly Star-Forming Galaxies

Star-forming galaxies drive massive outflows that play an important role in galaxy evolution by regulating feedback and influencing the dynamics of surrounding media. Measuring galactic outflow rates is essential for quantifying feedback efficiency and the amount of mass, momentum, and energy deposited into the circumgalactic medium. In this paper, we examine 17 galactic outflows from the CLASSY survey with radiative transfer modeling of UV absorption lines presented in M. Huberty et al. (2024), to study their spatial distributions and kinematic properties. We study the SiII, SiIII, and SiIV ionization states that trace the cool and warm phases of the outflows and find that SiII traced winds generally behave differently than the warmer SiIII and SiIV traced winds. We derive the mass, momentum, and energy loading factors, which we find scale inversely proportional to stellar mass. We find that our measurements of the mass and momentum loading factors are in agreement with the hydrodynamic FIRE-2 simulations. We model the velocity profiles of the winds, with profiles reaching a maximum velocity of 620 km/s on average, in agreement with hydrodynamic simulations from CGOLS. We also investigate the relationship between outflow properties and the age of the stellar population from SED fitting. We find that outflows associated with young star forming regions are more likely to have a column density dominated by cooler gas and have mass outflow rates which decrease with radius.

astro-ph.GA↗

arXiv2026

Discovery of four Narrow-line Type-1 Quasars at z = 2.54 -- 6.06 with Subaru 'Onohi'ula PFS-SSP

We report the discovery of four narrow-line type-1 quasars (NLQ1s) from the Subaru 'Onohi'ula Prime Focus Spectrograph Subaru Strategic Program (PFS-SSP). To extend a comprehensive understanding of this population to the distant universe, we searched for broad-line AGNs (quasars) whose rest-UV spectral shapes resemble those of local NLS1 galaxies, utilizing the Ly$\alpha$ line profile. We identified four NLQ1s, including one candidate, at $z=2.54$ -- $6.06$. The obtained spectra show a prominent Ly$\alpha$ emission line with a very low continuum level. The measured full width at half maximum (FWHM) of Ly$\alpha$ ranges from $1410 \ \mathrm{km\,s^{-1}}$ to $1510 \ \mathrm{km\,s^{-1}}$ with a mean of $\sim 1430 \,\mathrm{km\,s^{-1}}$. Although we used only line width information for the NLQ1 selection, the resulting equivalent widths (EW) of Ly$\alpha$ are higher (the mean $\sim 190$\,\AA \ in the rest frame) than the typical values of quasars. Two quasars have exceptionally large Ly$\alpha$ luminosity, accounting for $\sim 3$ -- $4$\% of the bolometric luminosity. We measured black hole masses and Eddington ratios for three objects whose C\,\textsc{iv} line is available. The resulting black hole masses are $\sim 10^{6.9}$ -- $10^{7.7}\, M_{\odot}$ with high Eddington ratios ($> 0.1$), consistent with those of NLS1 galaxies reported in the low-$z$ universe. N\,\textsc{v} and C\,\textsc{iv} broad absorption lines are detected in one object. This quasar can be classified as a mini-BAL quasar, which further supports the idea that this NLQ1 is indeed a luminous version of an NLS1 galaxy.

astro-ph.GA↗

arXiv2026

Scaling Relations of Galactic Outflows Across Cosmic Time: New Insights from Cosmic Noon

Galactic outflows play a significant role in regulating galaxy evolution. Scaling relations between stellar mass ($M_\ast$), star formation (SFR), and outflow properties have been extensively studied at low redshifts ($z<1$) but less so beyond $z \sim 2$. We construct a joint sample of 387 galaxies from $z \sim$ 0-9, including 98 new Cosmic Noon galaxies from the Keck Baryonic Structure Survey and the Keck Lyman Continuum Spectroscopic Survey. Using high signal-to-noise emission lines (SNR $>$ 50 for H$\alpha$ or [OIII] $\lambda5007$) from Keck/MOSFIRE spectra, we detect warm-ionized outflows by decomposing lines into narrow and broad components. With the joint sample, we explore the redshift evolution of outflow scaling relations. On average, outflows at Cosmic Noon have higher maximum velocities than those at low$-z$ by up to a factor of 3 for a fixed $M_\ast$, SFR, or SFR surface density. They also have higher mass outflow rates for a fixed $M_\ast$. Despite faster and stronger outflows, there is no evolution in the mass loading factor for a fixed $M_\ast$. We find evidence for galactic fountains, as the majority of outflowing gas is recycled at a radius of $\sim$0.03 R$_\textrm{vir}$. We also constrain the overall outflow occurrence rate in our galaxy sample to be at least 30$\%$ when taking galaxy orientation and outflow geometry into account. By analyzing the largest sample of warm-ionized outflows at Cosmic Noon to date and compiling large galaxy samples across all redshifts, we present a comprehensive analysis of galactic outflows throughout cosmic time.

astro-ph.GA↗

arXiv2026

The Importance of Galaxy-Wide Star Formation in Driving Winds at z~1

In this work, we study winds for a representative sample of 86 star-forming galaxies (SFGs) at z~1 with $M_\star = 10^{9.0}-10^{11.5} M_\odot$, by measuring the Mg II line profiles in deep Keck spectra. A total of 50 (58\%) are found to have winds. Unlike local starburst galaxies, the wind detection rate does not exhibit a threshold in star-formation rate (SFR) density $\Sigma_\mathrm{SFR}$ at 0.1 Msun/yr/kpc$^2$, but shows a gradual decline around this value. We find correlations between wind velocity $v_\mathrm{wind}$ and SFR, $\Sigma_\mathrm{SFR}$, and stellar mass, as per previous studies. Intriguingly, the z~1 SFGs appear to follow the same $v_\mathrm{wind}$-SFR relation as local starbursts. A combined fit gives: log $v_\mathrm{wind}$ = 0.16 log SFR + 2.4 (3-sigma significance). This unified relation spans over 4 dex in SFR and agrees with Illustris-TNG. No unified relation is found between $v_\mathrm{wind}$ and stellar mass, sSFR, or $\Sigma_\mathrm{SFR}$. This suggests winds might be most closely associated with SFR. We examine whether winds in z~1 SFGs are driven by their most compact star-forming regions. To do so, we consider whether the relation between $v_\mathrm{wind}$ and the $\Sigma_\mathrm{SFR}$ measured from only these regions is stronger than that for the galaxy-wide $\Sigma_\mathrm{SFR}$. We do not find a stronger correlation, suggesting that winds are most related to $\Sigma_\mathrm{SFR}$ of the entire galaxy. Collectively, these findings suggest a picture in which galaxy-wide star formation plays an important role in driving winds at z~1. Wind bubbles from all star-forming regions could combine momentum and help lift their entrained gas out of the galaxy.

astro-ph.GA↗

arXiv2026

CASISR: Circular Arbitrary-Scale Image Super-Resolution

The generalization performance (GP) of deep learning-based arbitrary-scale image super-resolution (ASISR) methods is subject to limited training datasets and unlimited testing datasets. It is vitally significant to enhance the GP of the pretrained ASISR models by making full use of the testing samples. The ASISR models usually employ an open-loop architecture from low-resolution (LR) images to super-resolution (SR) images. The degradation model from SR samples to LR samples is known bicubic down-sampling for the classical ASISR, is supposed down-sampling with additive random noise for the blind ASISR, and is learnable for the real-world ASISR. Combining the ASISR and degradation models, it is potentially possible to adopt a closed-loop architecture based on the automatic control theory for strengthening the GP of the ASISR methods. Therefore, this paper proposes a closed-loop architecture, circular ASISR (CASISR), to lift the capability of image reconstruction. A mathematical nonlinear loop equation is established to describe the CASISR, the reasonability of the CASISR is proven by conditional probability theory, and the stability of the CASISR is proven by Taylor series approximation. The first-order and second-order absolute difference images are defined to compare the image reconstruction performance of the ASISR and the CASISR methods. Comprehensive simulation experiments show that the proposed CASISR approach outperforms the eight state-of-the-art ASISR approaches in the quality of image reconstruction. Especially, the proposed CASISR is extraordinarily suitable for fractional SR scale factors and is extremely effective for text and stripe images with drastically changed edges.

cs.CV↗

arXiv2026

Resolving the Unresolved Galactic Winds in Multi-phase Models. I. Methodology and Application

Galactic winds shape galaxy evolution; however, the outflowing gas is complex: it consists of multiple ionization phases, and its properties vary spatially. Therefore, methods that combine high-fidelity observations with state-of-the-art galactic-wind models are limited. Here we investigate methods for fitting the column density profiles derived from high-quality outflow observations with the multiphase, multiscale wind model from Fielding & Bryan 2022. We identify three key outflow parameters: the initial hot-phase mass-loading factor ($\eta_\text{ M,hot,0}$), the initial cool-phase mass-loading factor ($\eta_\text{ M,cool,0}$), and the initial cool-cloud mass. We obtain good fits for most galaxies, with tight constraints on $\eta_\text{ M,cool,0}$ and moderate constraints on the other two parameters. We find the inferred $\eta_\text{ M,cool,0}$ and $\eta_\text{ M,hot,0}$ are mostly of order unity, with significant scatter. The constraints on $\eta_\text{ M,hot,0}$ suggest that the interaction between the cool and hot phases allows us to indirectly constrain the properties of the hot wind from cool-outflow observations. The model also predicts various radial trends. First, for all galaxies, the cool-phase outflow velocity increases between $1-2$ times of the half-light radius, then reaches a plateau. Second, most galaxies exhibit increasing $\eta_\text{ M,cool}$ and decreasing $\eta_\text{ M,hot}$ with radius, with a few showing the reverse trends. These results are effective, model-conditional constraints, and are consistent with other recent multiphase simulations and observations. This highlights that the velocity-radius mapping encoded in UV absorption profiles enables recovery of outflow spatial structures from spatially integrated spectra. Our method paves the way for future broad parameter studies and guides updates of outflow simulations in future work.

astro-ph.GA↗

arXiv2026

Galactic Archaeology with the Subaru `\=Onohi`ula Prime Focus Spectrograph Strategic Program

The recently commissioned Subaru `\=Onohi`ula Prime Focus Spectrograph (PFS) will obtain spectra from nearly 2,400 fibers that cover 1.24 square degrees. The 360 night Subaru Strategic Program for PFS is dedicating approximately one-third of its allocation (130 nights) to study the structure and evolution of galaxies in the Local Group. This Galactic Archaeological survey has three pillars. (1) We will determine whether the mass density profiles of dwarf galaxies are consistent with cusps, as expected for cold dark matter, or cores, as expected from alternative dark matter theories or baryonic feedback. We will deduce the density profiles as a function of radius from modeling of the full line-of-sight velocity and abundance distributions for six dwarf galaxies. Our total sample will consist of 18,000 member stars to beyond the nominal tidal radius of each system. (2) From measurements of the [alpha/Fe] abundance ratio, we will learn the difference in assembly history of the two most massive galaxies in the Local Group: M31 and the Milky Way. We will observe 30,000 member stars over 45 square degrees of M31's halo and outer disk. (3) We will uncover how the most fragile (outer) part of the Milky Way responded to accretion events both in the distant past (such as Gaia-Sausage Enceladus) and in more recent history (such as the Sagittarius dwarf spheroidal galaxy). To support this study, PFS will provide velocities and metallicities--from which, in combination with photometry, we will deduce ages--for tens of thousands of main-sequence stars out to a Galactocentric distance of ~30 kpc.

astro-ph.GA↗

arXiv2026

Kinematically Coherent Multiphase Galactic Winds in Star-Forming Galaxies Revealed by Unified Radiative Transfer Modeling of UV Emission and Absorption Lines

We present PEACOCK, a three-dimensional Monte Carlo radiative transfer (RT) framework designed to self-consistently model rest-frame ultraviolet emission and absorption lines arising from multiphase, clumpy galactic winds. Applied to deep HST/COS spectra of 50 nearby star-forming galaxies, PEACOCK reproduces 220 observed profiles of Ly-alpha, Si II, C II, Si III, Si IV, and C IV spanning absorption, emission, and P-Cygni-like morphologies within a single CGM model. By combining Monte Carlo RT with deep-learning acceleration and nested sampling, the framework enables fully converged multi-line inference at a small fraction of the cost of traditional RT grids. Systematic experiments show that ion column densities, bulk outflow velocities, and turbulent motions leave distinct imprints on line profiles, allowing the underlying gas properties to be constrained with minimal degeneracy. Purely radial accelerating flows often fail to reproduce the observed absorption morphologies, whereas macroscopic velocity dispersion naturally produces the broad asymmetric troughs seen in the data, indicating that turbulent motions are a key component of outflow kinematics. The inferred kinematics reveal strong coherence among low- and high-ionization metal lines in both bulk and turbulent velocities, consistent with a dynamically coupled multiphase wind. In contrast, neutral hydrogen shows weaker correspondence with metals, suggesting incomplete mixing and a distinct kinematic structure. By unifying emission and absorption diagnostics across multiple ions, PEACOCK provides a physically grounded bridge between UV observations and theoretical models of galactic winds.

astro-ph.GA↗

arXiv2026

The Prevalence of Turbulence-Regulated Multiphase Galactic Winds in Star-Forming Galaxies

We build upon our previously developed multi-ion radiative transfer (RT) framework, PEACOCK, to investigate the kinematic and energetic structure of cool-to-warm galactic winds in a sample of 50 nearby star-forming galaxies. Using self-consistent constraints derived from joint modeling of Ly-alpha and multiple ultraviolet metal lines, we analyze how bulk outflows and turbulent motions contribute to the dynamics and energy budget of galactic winds in the circumgalactic medium (CGM). We find that macroscopic turbulent velocities are often comparable to, and sometimes exceed, the coherent bulk outflow velocity. The associated turbulent pressure frequently dominates over both microscopic pressure and ram pressure, indicating that turbulence is a major contributor to the kinetic energy budget of the CGM wind. Wind kinematics, ionic column densities, and metal mass outflow rates all scale systematically with stellar mass and star formation rate, demonstrating a strong coupling between stellar feedback and CGM structure. Including turbulent motions strengthens these CGM-galaxy scaling relations and favors an energy-driven feedback regime. The total kinetic energy flux of the cool-to-warm CGM correlates tightly with the mechanical energy injection rate from star formation, implying that stellar feedback provides sufficient power to sustain both coherent outflows and turbulence. Comparisons with phenomenological line-profile fitting methods further show that simplified treatments can introduce systematic biases in inferred wind properties. Together these results support a turbulence-regulated picture of galactic winds in which a substantial fraction of feedback energy is stored in turbulent motions within a multiphase CGM.

astro-ph.GA↗

arXiv2025

Spatially Resolved Physical Properties of Young Star Clusters and Star-forming Clumps in the Brightest z>6 Galaxy, the Strongly Lensed Cosmic Spear at z=6.2

We present spatially resolved analysis of stellar populations in the brightest $z>6$ galaxy known to date (AB mag 23), the strongly lensed MACS0308$-$zD1 (dubbed the ``Cosmic Spear'') at $z_{\rm spec}=6.2$. New JWST NIRCam imaging and high-resolution NIRSpec IFU spectroscopy span the rest-frame ultraviolet to optical. The NIRCam imaging reveals bright star-forming clumps and a tail consisting of three distinct, extremely compact star clusters that are multiply-imaged by gravitational lensing. The star clusters have effective radii of $R_{\rm{eff}} \sim 5$ pc, stellar masses of $M_{*} \sim 10^{6}-10^{7}\,M_{\odot}$, and high stellar mass surface densities of $\Sigma_{*} > 10^{4}\,M_{\odot}~\rm{pc}^{-2}$. While their stellar populations are very young ($\sim 5-9$ Myr), their dynamical ages exceed unity, consistent with the clusters being gravitationally bound systems. Placing the star clusters in the size vs.~stellar mass density plane, we find they occupy a region similar to other high-redshift star clusters within galaxies observed recently with JWST, being significantly more massive and denser than local star clusters. Spatially resolved analysis of the brightest clump reveals a compact, intensely star-forming core. The ionizing photon production efficiency ($\xi_{\rm{ion}}$) is slightly suppressed in this central region, potentially indicating a locally elevated Lyman continuum escape fraction facilitated by feedback-driven channels.

astro-ph.GA↗

arXiv2025

CLASSY XIV: The Nitrogen Exception -- Multi-Phase Enrichment and Feedback in High-$z$ Analogs

We present a first-of-its-kind analysis of the metal content across two interstellar medium (ISM) phases in a sample of 31 local star-forming galaxies from the COS Legacy Archive Spectroscopic SurveY (CLASSY), selected as analogues of high-$z$ systems. Using co-spatial UV absorption and optical emission-line spectroscopy, we compare abundances of N, O, S, and Fe in the low-ionization (neutral) and high-ionization (ionized) gas, providing a multi-phase view of enrichment shortly after the current starburst and over longer timescales when ejecta from previous episodes have cooled and mixed. We find that O and S, produced predominantly in short-lived massive stars, are well mixed between the two phases, with scatter reflecting local inhomogeneities. Fe, predominantly produced by Type Ia supernovae on $\sim$1 Gyr timescales, is higher in the neutral gas, reflecting either delayed mixing of older Fe-enriched material or preferential depletion of Fe from the ionized phase through dust formation in core-collapse supernova ejecta. N exhibits the largest phase offset, with N/H$_{ion}$ systematically $\sim$0.7 dex higher than N/H$_{neu}$, and the magnitude of this offset correlates with stellar mass, metallicity, star-formation rate, and most strongly with the ISM outflow velocity. N/O ratios in the ionized phase rise rapidly within 3-6 Myr relative to the neutral gas, consistent with N enrichment dominated by Wolf-Rayet stars rather than intermediate-mass AGB stars on longer timescales. These results demonstrate that localized stellar feedback, outflows, and phase-dependent mixing collectively regulate the chemical evolution of star-forming galaxies, providing key insight into the extreme N/O abundances recently observed in galaxies at cosmic dawn.

astro-ph.GA↗

arXiv2025

A Comprehensive JWST/NIRSpec Census of Broad-Line Active Galactic Nuclei: Faint, Tiny, but Highly Accreting Sources in the Remote Universe

We present a sample of 252 broad-line Active Galactic Nuclei (BLAGNs), incorporating 171 newly identified sources, spanning a redshift interval from $z$ = 0.8 to 7.2. We have analyzed spectroscopic data from the NIRSpec instrument aboard the James Webb Space Telescope, using the G140H, G140M, G235H, G235M, G395H, and G395M gratings to survey N $\sim$ 80,000 galaxies for BLAGNs. Through emission-line fitting, using a sum of Gaussian models for {H$\alpha$}, {H$\beta$}, [N II] $\lambda\lambda6548, 6584$, and [O III] $ \lambda\lambda4959, 5007$, we separate AGN broad-line components from narrow-line emission. We find the detection rate of BLAGNs to be relatively consistent across our redshift range. Compared to typical low-$z$ AGNs ($z$ $\lesssim$ 1), the high-$z$ BLAGNs are systematically fainter and less massive, yet they accrete more efficiently, with most showing Eddington ratios between 0.1 and 1.0. This confirms the rapid black hole growth during the early cosmic epochs. The detection of faint, low-mass BLAGNs at high redshift also helps bridge the observational gap between local supermassive black holes and remote luminous quasars, providing a more complete view of black hole-galaxy coevolution across cosmic time.

astro-ph.GA↗

arXiv2025

CLASSY XIII. Cutting through the Clouds - Comparing Indirect Tracers of Ionizing Photon Escape

The Epoch of Reionization (EoR) provides critical insights into the role of early galaxies in shaping the ionization state of the universe. However, because of the opacity of the intergalactic medium, it is often not possible to make direct measurements of the ionizing photon escape fraction ($f_{\mathrm{esc}}^{\: \mathrm{LyC}}$) of high-redshift ($z \gtrsim 4$) galaxies. To explore the agreement and systematics of common indirect approaches, we applied six empirically calibrated diagnostics to predict $f_{\mathrm{esc}}^{\: \mathrm{LyC}}$ for the 45 nearby star-forming galaxies from the COS Legacy Spectroscopic SurveY (CLASSY). These methods- based on ultraviolet (UV) absorption lines, the UV continuum slope, Ly$\alpha$ kinematics, a multivariate model, radiation-hydrodynamic simulations, and nebular emission line ratios- enable us to explore systematic differences between predictions and assess how galactic properties influence inferred LyC escape. Despite significant variations in method predictions, there is broad consistency in the resulting weak and strong LyC leaker classifications, with approximately half exhibiting predicted escape fractions $>$1%. We find evidence for two different pathways of LyC escape in nearby star-forming galaxies: (1) an early escape model driven by very young stellar populations, and (2) a delayed escape model that is consistent with supernova-driven outflows and time-dependent ISM clearing. The early escape model is favored among galaxies with a single, intense burst of recent star formation. In contrast, the delayed escape model is common among galaxies with more extended starburst histories. To interpret ionizing photon escape during the EoR, it will be necessary to recognize and understand this diversity in LyC escape mechanisms.

astro-ph.GA↗

arXiv2025

Supernovae Driven Winds Impede Lyman Continuum Escape from Dwarf Galaxies in First 10 Myr

Observations suggest that UV-bright, compact star-forming galaxies produce enough ionizing (Lyman continuum; LyC) photons to reionize the Universe. Yet, the efficiency of LyC escape and the roles of radiation, stellar winds, and supernovae remain uncertain. Using medium-resolution spectra of six nearly identical local star-forming galaxies, we directly trace, for the first time, the evolution of a multiphase wind through individual spectral lines alongside measurements of the LyC escape fraction. We find that LyC escape peaks early, during a period dominated by intense radiation and stellar winds but lacking a fast galactic wind. As the starbursts age, supernovae drive and accelerate the wind, progressively suppressing LyC escape. These results highlight the need for cosmological simulations to incorporate early feedback as a key driver of reionization.

astro-ph.GA↗

arXiv2025

JWST/MIRI-MRS view of the metal-poor galaxy CGCG 007-025: the spatial location of PAHs and very highly ionized gas

Polycyclic Aromatic Hydrocarbons (PAHs) are key diagnostics of the physical conditions in the interstellar medium and are widely used to trace star formation in the mid-infrared (mid-IR). The relative strengths of mid-IR PAH emission features (e.g., 6.2, 7.7, 11.3 um) are sensitive to both the size and ionization state of the molecules and can be strongly influenced by the local radiation field. However, at low metallicities ( Z < 0.2 Zsun), detecting PAHs remains notoriously difficult, likely reflecting a combination of suppressed formation and enhanced destruction mechanisms. We present new JWST/MIRI MRS observations of the metal-poor (Z = 0.1 Zsun) dwarf galaxy CGCG 007-025. We confirm the tentative PAH detection previously reported from Spitzer data and, for the first time, identify a compact (approx. 50 pc) PAH-emitting region nearly co-spatial with the newly detected [NeV](I.P. = 97 eV) emission and the galaxy's most metal-poor, strongly star-forming region. The 11.3 and 12.7 um PAH features are detected, while no emission is found from the other typically brighter features, suggesting a PAH population dominated by large, neutral molecules resilient to hard ionizing fields. When compared with models, mid-IR line ratios involving [NeIII], [OIV], and [NeV] can only be reproduced by a combination of star formation and AGN ionization, with the latter contributing 4--8%. The [OIV] and [NeV] luminosities exceed what massive stars or shocks can produce, highlighting a puzzling scenario in line with recent JWST observations of similar galaxies. This work provides a crucial reference for studying the physical conditions of the dust and star formation in low-metallicity starburst regions, environments typical of the early universe.

astro-ph.GA↗

arXiv2025

The Ly$\alpha$ and Continuum Origins Survey. III. Investigating the Link between Galaxy Morphology, Merger Properties and LyC Escape

Characterizing the mechanisms and galaxy properties conducive to the emission and escape of ionizing (LyC) emission is necessary to accurately model the Epoch of Reionization, and identify the sources that powered it. The Ly$\alpha$ and Continuum Origins Survey (LaCOS) is the first program to obtain uniform, multi-wavelength subkiloparsec imaging for a large sample (42) of galaxies observed in LyC and enable statistically robust studies between LyC and resolved galaxy properties. Here, we characterize the morphology and galaxy merger properties of LaCOS galaxies and investigate their connection with the escape fraction of LyC emission $f_{esc}^{LyC}$. We find strong anticorrelations between $f_{esc}^{LyC}$ and size ($r_{20}$, $r_{50}$, and $r_{80}$) measured in filters containing emission from star-forming regions, and with the asymmetry and clumpiness in F150LP, the bluest filter in our dataset, tracing UV continuum and Ly$\alpha$. We find that $\geq48\%$ of LaCOS galaxies, and $\geq41\%$ of LaCOS LyC-emitters are visually classified as galaxy mergers. Galaxies robustly identified as mergers in LaCOS are at advanced stages of interaction, close to coalescence. The $f_{esc}^{LyC}$ properties of robust mergers and low-probability mergers cannot be differentiated statistically, and we only find significant difference between the two populations in terms of their of their sizes and LyC luminosity: robust mergers having larger values. We conclude that (i) $f_{esc}^{LyC}$ tends to be larger in galaxies with a small number of compact, centrally-located, UV-emitting star-forming regions, (ii) at advanced stages of interaction represent a sizable fraction of LyC-emitting samples at $z\sim0.3$, $z\sim0$, and (iii) mergers can facilitate the escape of LyC photons from galaxies.

astro-ph.GA↗

arXiv2025

CECGSR: Circular ECG Super-Resolution

Background and Objective: The electrocardiogram (ECG) plays a crucial role in the diagnosis and treatment of various cardiac diseases. ECG signals suffer from low-resolution (LR) due to the use of convenient acquisition devices, as well as internal and external noises and artifacts. Classical ECG super-resolution (ECGSR) methods adopt an open-loop architecture that converts LR ECG signals to super-resolution (SR) ones. According to the theory of automatic control, a closed-loop framework exhibits superior dynamic and static performance compared with its open-loop counterpart. Methods: This paper proposes a closed-loop approach, termed circular ECGSR (CECGSR), which models the degradation process from SR ECG signals to LR ones. The negative feedback mechanism of the closed-loop system is based on the differences between the LR ECG signals. A mathematical loop equation is constructed to characterize the closed-loop infrastructure. The Taylor series expansion is employed to demonstrate the near-zero steady-state error of the proposed method. A Plug-and-Play strategy is considered to establish the SR unit of the proposed architecture, leveraging any existing advanced open-loop ECGSR methods. This paper also presents Transformer model based open-loop ECGSR and closed-loop CECGSR algorithms. Results: Simulation experiments on both noiseless and noisy subsets of the Physikalisch-Technische Bundesanstalt-Extra Large (PTB-XL) datasets demonstrate that the proposed CECGSR outperforms state-of-the-art open-loop ECGSR algorithms in the reconstruction performance of ECG signals. Conclusions: The proposed method will efficiently enrich ECG signal details and remove ECG signal artifacts in clinical applications.

eess.SP↗

arXiv2025

CLASSY XII: Nitrogen Enrichment Shaped by Gas Density and Feedback

We investigate the chemical evolution of N/O using a sample of 45 local star-forming galaxies (SFGs) from the CLASSY survey. This sample spans a wide range of galaxy properties, with robust determinations of nitrogen and oxygen abundances via the direct-$T_{\rm e}$ method. We explore how N/O relates to density structure, stellar mass, star formation rate (SFR), stellar age, compactness, and gas kinematics. In addition, we compare our results with those of galaxies at $z =2-10$ where N/O ratios were derived from optical or UV nitrogen lines, aiming to identify chemical enrichment pathways across cosmic time. Our analysis shows that the N/O-O/H relation in CLASSY galaxies aligns with the trends seen in local galaxies and extragalactic HII regions, and that galaxies at $z = 2-6$ exhibit similar N/O values, indicating no significant redshift evolution in N/O for a fixed metallicity. We identify a significant correlation between electron density $n_{\rm e}$([S II]) and N/O, suggesting that density structure contributes to the scatter in the N/O-O/H relation. The CLASSY galaxies with high SFRs or compact star formation show elevated N/O, though no strong correlation with stellar mass is found. We also find that high-velocity outflows (v$_{out}$ > 350 km/s) and low mass-loading factors are linked to elevated N/O, indicating that feedback plays a significant role. These results highlight the importance of density, star formation, and feedback from young stellar populations in shaping N/O enrichment and provide key insights for interpreting high-$z$ galaxies observed with JWST.

astro-ph.GA↗