arXiv subjects

Weibin Sun

Publications and source records attributed to Weibin Sun.

12 recordsLinked to original sources

arXiv2026

A Strong Stellar Age-Metallicity Gradient Relation in Nearby Dwarf Galaxies Driven by Stellar Migration and Environmental Quenching

Stellar metallicity gradients ($\nabla[Z/H]$) provide a fossil record of the assembly history of galaxies. We present an analysis of $\nabla[Z/H]$ for 90 nearby low-mass galaxies using VLT/MUSE IFU spectroscopy, spanning stellar masses from $10^{6.5}$ to $10^{10} M_\odot$ (median $\sim 10^{8.5} M_\odot$) and significantly extending the mass coverage of existing IFU surveys into the classical dwarf regime. Our primary finding is a robust negative correlation between $\nabla[Z/H]$ and light-weighted stellar age ($|r|\gtrsim 0.7$) measured out to $\sim$ 2$\times$ effective radius: older dwarf galaxies have steeper (more negative) gradients. This holds regardless of stellar mass, structural compactness, or large-scale environment (group/field), and is strongest in the intermediate-mass regime ($8.2\lesssim\log M_\star/M_\odot\lesssim9.0$). The slope of the age-$\nabla[Z/H]$ relation is close to that in the FIRE-2 simulations, indicating that stellar radial migration driven by feedback-induced potential fluctuations may be fundamental in dwarf evolution. But this apparent consistency is likely coincidental given the simulations' overly efficient feedback and chemical mixing. On the other hand, the H\,\textsc{i} deficiency parameter, an indicator of past environmental stripping, shows a moderate yet highly significant correlation with $\nabla[Z/H]$, second only to stellar age in strength: galaxies with higher H\,\textsc{i} deficiency tend to have more negative gradients, strongly indicating that environment-driven outside-in quenching and the ensuing gradual truncation of metal enrichment re-shape the stellar metallicity distribution. Our analysis suggests that the chemical evolution of dwarf galaxies likely arises from a synergy of feedback-driven dynamical heating and external environmental processing, though only the latter has robust observational support.

astro-ph.GA↗

arXiv2026

Transformer-Based Source Detection and Morphological Classification in LOFAR Deep-Field Continuum Images

Radio source detection and morphological classification are fundamental for exploiting the scientific potential of modern radio continuum surveys. However, the rapidly increasing data volumes and the wide diversity of radio morphologies make traditional visual inspection infeasible and pose significant challenges for automated source finding. We apply a transformer-based set-prediction detector (RF-DETR) to 150\,MHz continuum images from the LOFAR Deep Fields for instance-level source detection and morphological classification. The method is adapted to multi-frequency-synthesis images of interferometric data and trained with a morphology-driven scheme using five mutually exclusive classes. The model is trained on the ELAIS-N1 Deep Field, where it achieves high detection and classification performance ($\mathrm{F1}\simeq 91$ per cent), and is then applied without retraining to the other three LOFAR Deep Fields. Across all four fields, the model yields consistent catalogues with modest field-to-field differences arising from survey depth and calibration. Compared with widely used PyBDSF catalogues, RF-DETR recovers the majority of PyBDSF sources while representing classical multi-component radio galaxies as single source-level detections rather than fragmented Gaussian components. Artefact-affected and spurious detections are identified as explicit classes, allowing these detections to be distinguished from general astrophysical sources in the resulting catalogues. As external validation, RF-DETR recovers the majority of visually identified extended and giant radio galaxies in the LOFAR Deep Fields and assigns them predominantly to extended morphological classes. These results indicate that transformer-based detectors provide a practical, scalable, morphology-aware approach to source finding in deep radio surveys, with clear relevance for forthcoming facilities such as SKA-Low.

astro-ph.IM↗

arXiv2026

AVID: A Near-Major Post-Merger of Late-Type Dwarfs beneath a Regularly Rotating HI Disk (VCC 693)

On the periphery of galaxy clusters, moderately high galaxy densities and velocity dispersions favour interactions and mergers that influence galaxy evolution prior to cluster infall. Observational studies of this phase in dwarfs remain rare. We present a high-resolution study of the merger remnant VCC 693 in the outskirts of Virgo cluster, using observations from the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) project. We explore the origin of VCC 693 and the consequences of the merger on its star formation and structure through a joint analysis of VLA and FAST HI emission line observations, together with complementary optical imaging and spectroscopy. We employ hydrodynamical simulations to help interpret the observations. Our analysis favours a near-major merger between two dwarfs with a stellar mass ratio of 3:1-4:1, with one likely gas-poor progenitor (i.e., a damp merger). The optical appearance of VCC 693 is dominated by complex tidal structures throughout the system, whereas the HI gas has settled to a regular rotating disk. Compared with similar-mass dwarfs, the central star formation and gas-phase metallicity are moderately enhanced. The global star formation rate, HI gas content, and HI-to-optical size ratio of VCC 693 are broadly consistent with those of typical dwarfs of similar mass, albeit somewhat lower. Decomposition of the HI rotation curve into baryonic and dark matter indicates a high halo concentration, suggesting post-merger relaxation into a more centrally peaked configuration. Together with two recent studies of AVID post-merger systems, these results support the view that even major dwarf mergers can produce remnants with overall stellar structures indistinguishable from ordinary dwarfs, and that the environmental effects in cluster outskirts can promote damp or mixed mergers, constituting an integral part of galactic pre-processing.

astro-ph.GA↗

arXiv2025

Unveiling the nature and fate of the almost-dark cloud AGC 226178 through HI mapping

The origin of extragalactic, almost dark HI clouds with extreme gas-to-stellar mass ratios remains poorly understood. We investigate the nature and fate of the "almost dark" cloud AGC 226178, projected within the Virgo cluster, with an HI-to-stellar mass ratio of ~1000. We present deep single-dish HI mapping from the Five-hundred-meter Aperture Spherical Telescope (FAST), complemented by high-resolution interferometric data from the Very Large Array (VLA), as part of the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) project. These observations provide the highest-quality HI analysis to date of such a cloud, combining resolution and sensitivity. FAST data reveal a short, low-velocity tail toward the dwarf galaxy VCC 2034, previously proposed as a possible origin for AGC 226178. However, VCC 2034 shows a line-of-sight asymmetric HI feature and cometary morphology indicating a stripping event unrelated to AGC 226178. VLA data reveal a velocity gradient across AGC 226178 and a clumpy internal structure. The velocity dispersion exceeds the thermal linewidth, implying turbulence or unresolved motions. The cloud cannot be gravitationally bound by atomic gas alone. The resolved HI clumps follow standard HI mass-star formation rate and mass-size relations, with those forming stars reaching surface densities above the threshold for self-shielding. We conclude that AGC 226178 is a free-floating HI cloud of unknown origin. The system appears to be in the process of disintegration. It is likely located well outside the Virgo cluster, as the preservation of its extended HI morphology within the cluster environment would otherwise require a substantial reservoir of unseen molecular gas with a mass exceeding that of the observed HI content. While confinement pressure from the hot intracluster medium may aid its stability, it is unlikely to be the dominant factor preventing its disruption.

astro-ph.GA↗

arXiv2025

AVID: Formation and evolution of a coalesced major merger of late-type dwarf galaxies (VCC 479) on the outskirts of the Virgo cluster

Dwarf-dwarf galaxy mergers are among the least explored aspects of dwarf galaxy pre-processing as they fall into clusters. We present the first case study of a coalesced late-type dwarf major merger (VCC 479; stellar mass $\sim\,8\,\times\,10^7\,\rm M_\odot$) that has undergone significant environmental influence, with the aim of exploring dwarf galaxy evolution under the combined effects of galaxy interactions and environmental processes, and understanding its relevance to the diversity of dwarf galaxies in cluster environments. Our analysis is based on VLA and FAST HI emission line mapping from the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) survey. We also perform idealized hydrodynamical simulations of dwarf-dwarf mergers to help interpret the observations. We identify symmetric stellar shell structures in VCC 479, indicative of a coalesced major merger of dwarf galaxies. The galaxy features a central starburst, initiated $\sim$600 Myr ago, embedded within an exponential disk quenched $\sim$1 Gyr ago. The starburst contributes only 2.9$\pm$0.5\% of the total stellar mass, and VCC 479's global star formation rate is 0.3 dex lower than typical dwarfs of similar mass. The galaxy is highly HI deficient, with most HI gas concentrated within the central 1 kpc and little extended HI envelope. The misalignment of the HI velocity field with the stellar body is best explained by merger-triggered gas inflow, as seen in our simulations. Our analysis is consistent with a scenario that the majority of HI gas of the progenitor galaxies was removed by the cluster environment prior to the final coalescence. The merger concentrates the remaining gas toward the galaxy center, triggering a central starburst. The combined effect of environment stripping and galaxy merger has transformed VCC 479 into a blue-core dwarf undergoing morphological transition from a late-type to an early-type galaxy.

astro-ph.GA↗

arXiv2025

The $M_{\rm BH}-M_\star$ Relation of the hyperluminous Dust-obscured Quasars up to $z \sim 4$

Hot dust-obscured galaxies (Hot DOGs) are a rare population of hyperluminous dust-obscured quasars discovered by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. The heavy circumnuclear dust obscuration allows only a small amount of scattered light from the obscured quasar to escape, enabling the decomposition of the stellar component from the total flux. The presence of scattered light enables the redshift of the source and the properties of the black hole to be obtained from SDSS and SDSS-related literature. From WISE and SDSS data, we select 11 hyperluminous Hot DOGs at $z=1.5-3.7$ with bolometric luminosities $L_{\rm bol} \gtrsim 10^{47}\,\mathrm{erg \ s^{-1}}$. We investigate the $M_{\rm BH}-M_\star$ relation in these sources using Bayesian spectral energy distribution (SED) fitting or with extra constraints from \textit{Hubble Space Telescope} (HST) image decomposition. Stellar masses are successfully derived for eight Hot DOGs. We find high Eddington ratios $\lambda_{\rm Edd}$ in these Hot DOGs, with the median value of 1.05 and the maximum value close to 3. The super-Eddington accretion may be associated with the overdense environments of Hot DOGs. We find no significant differences in the $M_{\rm BH}/M_\star$ of these Hot DOGs compared to the local relation, suggesting that these dust-obscured quasars are the progenitors of massive early-type galaxies. We speculate that the subsequent evolution of Hot DOGs may be significantly influenced by AGN feedback and remain on the local relation.

astro-ph.GA↗

arXiv2024

Multiwavelength Properties of Infrared-Faint Radio Sources Based on Spectral Energy Distribution Analysis

Infrared-faint radio sources (IFRSs) are believed to be a rare class of radio-loud active galactic nuclei (RL AGN) characterized by their high radio-to-infrared flux density ratios of up to several thousands. Previous studies have shown that a fraction of IFRSs are likely to be hosted in dust-obscured galaxies (DOGs). In this paper, our aim was to probe the dust properties, star formation rate (SFR), and AGN activity of IFRSs by modeling the UV-to-infrared spectral energy distribution (SED) of 20 IFRSs with spectroscopic redshifts ranging from 1.2 to 3.7. We compare the Bayesian evidence of a three-component model (stellar, AGN and cold dust) with that of a two-component model (stellar and cold dust) for six IFRSs in our sample with far-infrared (FIR) photometry and find that the three-component model has significantly higher Bayesian evidence, suggesting that IFRSs are most likely to be AGN. The median SED of our IFRS sample shows similarities to AGN-starburst composite in the IR regime. The derived IR luminosities of IFRSs indicate that they are low-luminosity counterparts of high-redshift radio galaxies. We disentangle the contributions of AGN-heated and star-formation-heated dust to the IR luminosity of IFRSs and find that our sample is likely AGN-dominated. However, despite the evidence for significant impact of AGN on the host galaxy, the AGN luminosity of our sample does not show correlation with the SFR of the sources.

astro-ph.GA↗

arXiv2024

A new approach to constraining properties of AGN host galaxies by combining image and SED decomposition: testing upon the MBH-M* relation

The outshining light from active galactic nuclei (AGNs) poses significant challenges in studying the properties of AGN host galaxies. To address this issue, we propose a novel approach which combines image decomposition and spectral energy distribution (SED) decomposition to constrain properties of AGN host galaxies. Image decomposition allows us to disentangle optical flux into AGN and stellar components, thereby providing additional constraints on the SED models to derive more refined stellar mass. To test the viability of this approach, we obtained a sample of 24 X-ray selected type-I AGNs with redshifts ranging from 0.73 to 2.47. We estimated the stellar masses for our sample and found that our results are generally consistent with earlier estimates based on different methods. Through examining the posterior distribution of stellar masses, we find that our method could derive better constrained results compared to previous SED decomposition methods. With the derived stellar masses, we further studied the MBH-M* relation of our sample, finding a higher intrinsic scatter in the correlation for our entire sample compared to the local quiescent correlation, which could be caused by a few black hole monsters in our sample. We propose that based on our method, future works could extend to larger samples of high-redshift AGN host galaxies, thereby enhancing our understanding of their properties.

astro-ph.GA↗

arXiv2024

Physical properties of hyperluminous, dust-obscured quasars at $z \sim 3$: multiwavelength Spectral Energy Distribution analysis and cold gas content revealed by ALMA

We present a UV to millimeter spectral energy distribution (SED) analysis of 16 hyperluminous, dust-obscured quasars at z $\sim$ 3, selected by the \textit{Wide-field Infrared Survey Explorer}. We aim to investigate the physical properties of these quasars, with a focus on their molecular gas content. We decompose the SEDs into three components: stellar, cold dust, and active galactic nucleus (AGN). By doing so, we are able to derive and analyze the relevant properties of each component. We determine the molecular gas mass from CO line emission based on Atacama Large Millimeter/submillimeter Array (ALMA) observations. By including ALMA observations in the multiwavelength SED analysis, we derive the molecular gas fractions, gas depletion timescales, and star formation efficiencies (SFEs). Their sample median and 16th-84th quartile ranges are $f_{\rm gas}\,\sim\,0.33_{-0.17}^{+0.33}$, $t_{\rm depl}\,\sim$ 39$_{-28}^{+85}$ Myr, SFE $\sim\,$ 297$_{-195}^{+659}$ $\rm K\,\rm km\,\rm s^{-1}\,\rm pc^{-2}$. Compared to main-sequence galaxies, they have a lower molecular gas content and higher SFEs, similar to quasars in the literature. This suggests that the gas in these quasars is rapidly depleted, likely as the result of intense starburst activity and AGN feedback. The observed correlations between these properties and the AGN luminosities further support this scenario. Additionally, we infer the black hole to stellar mass ratio and black hole mass growth rate, which indicate a significant central black hole mass assembly over short timescales. Our results are consistent with the scenario that our sample represents a short transition phase toward unobscured quasars.

astro-ph.GA↗

arXiv2020

OralCam: Enabling Self-Examination and Awareness of Oral Health Using a Smartphone Camera

Due to a lack of medical resources or oral health awareness, oral diseases are often left unexamined and untreated, affecting a large population worldwide. With the advent of low-cost, sensor-equipped smartphones, mobile apps offer a promising possibility for promoting oral health. However, to the best of our knowledge, no mobile health (mHealth) solutions can directly support a user to self-examine their oral health condition. This paper presents OralCam, the first interactive app that enables end-users' self-examination of five common oral conditions (diseases or early disease signals) by taking smartphone photos of one's oral cavity. OralCam allows a user to annotate additional information (e.g. living habits, pain, and bleeding) to augment the input image, and presents the output hierarchically, probabilistically and with visual explanations to help a laymen user understand examination results. Developed on our in-house dataset that consists of 3,182 oral photos annotated by dental experts, our deep learning based framework achieved an average detection sensitivity of 0.787 over five conditions with high localization accuracy. In a week-long in-the-wild user study (N=18), most participants had no trouble using OralCam and interpreting the examination results. Two expert interviews further validate the feasibility of OralCam for promoting users' awareness of oral health.

cs.HC↗

arXiv2014

Pruning, Pushdown Exception-Flow Analysis

Statically reasoning in the presence of exceptions and about the effects of exceptions is challenging: exception-flows are mutually determined by traditional control-flow and points-to analyses. We tackle the challenge of analyzing exception-flows from two angles. First, from the angle of pruning control-flows (both normal and exceptional), we derive a pushdown framework for an object-oriented language with full-featured exceptions. Unlike traditional analyses, it allows precise matching of throwers to catchers. Second, from the angle of pruning points-to information, we generalize abstract garbage collection to object-oriented programs and enhance it with liveness analysis. We then seamlessly weave the techniques into enhanced reachability computation, yielding highly precise exception-flow analysis, without becoming intractable, even for large applications. We evaluate our pruned, pushdown exception-flow analysis, comparing it with an established analysis on large scale standard Java benchmarks. The results show that our analysis significantly improves analysis precision over traditional analysis within a reasonable analysis time.

cs.PL↗

arXiv2013

Augmenting Operating Systems With the GPU

The most popular heterogeneous many-core platform, the CPU+GPU combination, has received relatively little attention in operating systems research. This platform is already widely deployed: GPUs can be found, in some form, in most desktop and laptop PCs. Used for more than just graphics processing, modern GPUs have proved themselves versatile enough to be adapted to other applications as well. Though GPUs have strengths that can be exploited in systems software, this remains a largely untapped resource. We argue that augmenting the OS kernel with GPU computing power opens the door to a number of new opportunities. GPUs can be used to speed up some kernel functions, make other scale better, and make it feasible to bring some computation-heavy functionality into the kernel. We present our framework for using the GPU as a co-processor from an OS kernel, and demonstrate a prototype in Linux.

cs.OS↗