arXiv subjects

Bingqiu Chen

Publications and source records attributed to Bingqiu Chen.

At least 19 recordsLinked to original sources

arXiv2026

An All-Sky Catalog of 6.5 Million Primary Red Clump Stars from Gaia DR3 XP Spectra

Red clump (RC) stars are excellent standard candles for mapping the three-dimensional structure of the Milky Way. We construct an all-sky catalog of 6.5 million primary RC stars using spectroscopic estimates of asteroseismic parameters inferred from Gaia DR3 low-resolution XP spectra. We train a mixture density network (MDN) on a cross-matched sample. The network maps each 343-dimensional corrected XP spectrum to estimates of $\Delta\Pi_{1}$, the asymptotic period spacing of dipole gravity modes, and $\Delta\nu$, the large frequency separation. We select primary RC stars using these two estimates. We release two complementary catalogs defined by different parameter-space cuts and thresholds: a high-purity Tier 1 sample of 532,189 stars with 97% purity and a high-completeness Tier 2 sample of 6,534,931 stars with 86% completeness. Both catalogs cover the full celestial sphere. We provide distances and extinction values for all stars. We obtain a median photometric distance precision of 6% for Tier 1 RC stars. Using the resultant distances, we independently calibrate the Gaia DR3 parallax zero-point offset. The three-dimensional density distribution traced by the Tier 2 sample extends continuously to $R\approx25$ kpc. Both catalogs are publicly available. These catalogs provide a valuable resource for Galactic archaeology, delivering a homogeneous dataset to trace the chemo-dynamical evolution of the Milky Way and to calibrate models of stellar populations.

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arXiv2026

A Face-on View of Interstellar Dust in the Galactic Plane

Interstellar dust is a fundamental component of the Milky Way, influencing star formation, galactic evolution, and observations across the electromagnetic spectrum. Using red clump stars selected from near- and mid-infrared photometry, together with stellar catalogs from previous studies, we construct dust density maps of the Galactic plane ({$|Z|<25$}\,pc) covering the full $360^\circ$ in longitude and reaching distances up to $7$\,kpc. By applying a U-Net convolutional neural network to invert the line-of-sight extinction distribution, we obtain dust density maps at resolutions of $10$, $50$, and $100$\,pc, which reveal detailed structures including spiral arms, inter-arm spurs, and giant cavities. The dust distribution in the Galactic plane exhibits a morphology closely resembling that of the so-called Phantom galaxy M74. The derived exponential scale length of the Galactic dust disk is $2.90$\,kpc, slightly larger than that of the stellar thin disk. Our publicly available dust maps provide a new benchmark for extinction correction, studies of Galactic structure, and the investigation of the interplay between star formation and the interstellar medium.

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arXiv2026

GSED: The Galactic Stellar Extinction Database

Reliable extinction correction is essential for nearly all astrophysical studies within the Galaxy. We present the Galactic Stellar Extinction Database (GSED, https://nadc.china-vo.org/data/gsed/), a homogenised database that unifies six representative 3D extinction datasets under a common $E(B-V)$ and parallax-distance baseline. A six-layer multilayer perceptron is designed to correct the systematic differences in both extinction and distance across the heterogeneous input catalogues. Applying the trained models yields a catalogue of over 1.9 billion homogenised entries, which is built into a publicly accessible, real-time query service: a user supplies a coordinate and a search radius, the system retrieves the data, fits the distance--extinction relation, returns $E(B-V)$ together with $E(G_{\rm BP}-G_{\rm RP})$ and $A_V$, and allows the raw catalogue and the fitted curve to be downloaded. By delivering extinction as raw stellar measurements rather than voxelised map products and retaining the capacity to incorporate future datasets, GSED provides a flexible, traceable, and extensible new tool for Galactic extinction correction and dust-structure studies.

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arXiv2026

A Planetary Nebula from a 5.7 $M_{\odot}$ Progenitor in a 90 Myr M31 Star Cluster

Planetary nebulae (PNe) trace the late evolution of low-to-intermediate-mass stars, yet the masses of their progenitors are rarely measured directly. Here we present a PN physically associated with a young star cluster in M31, providing an unprecedented extragalactic empirical anchor in the poorly constrained high-mass regime of PN progenitors. High-resolution Hubble Space Telescope imaging shows that the nebula lies near the cluster center, and spectral decomposition of the blended cluster-plus-nebula spectrum yields consistent stellar and nebular radial velocities, strongly supporting a physical association. Isochrone fitting to the color-magnitude diagram indicates a cluster age of ~90 Myr and a near-solar metallicity, implying a progenitor initial mass of $5.66^{+0.42}_{-0.37}\,M_{\odot}$. This value is among the highest empirical progenitor-mass constraints yet reported for any PN and approaches the lower boundary of the super-asymptotic giant branch (super-AGB) regime. We further find that the nebula is strongly nitrogen-enhanced, with an N/O ratio ~7 times the solar value, broadly consistent with hot bottom burning in a relatively massive AGB progenitor. This system therefore provides a rare opportunity to test PN formation and nucleosynthesis at the high-mass end of the PN progenitor distribution.

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arXiv2026

Evidence of triggered star formation in the Pillars of Creation from JWST observations

Stars form in molecular clouds under the influence of their local environments, yet the role of massive stellar feedback in either triggering or suppressing star formation remains a fundamental question in astrophysics. The Pillars of Creation in the Eagle Nebula, sculpted by ionizing radiation and stellar winds from massive stars in NGC 6611, offer a natural laboratory for investigating this question. Here we present high-resolution observations of the Pillars of Creation using the JWST Near Infrared Camera and Mid-Infrared Instrument, revealing 253 young stellar object (YSO) candidates. These YSO candidates show spatial correlations with the edges of feedback-driven structures, with overdensities along the boundaries. A weak trend of decreasing stellar age with increasing distance from the ionizing source was tentatively observed. There also appears to be an enhancement in the star formation rate within the past 1 Myr in this region. Such age and spatial associations suggest that while the bulk of the YSOs may have formed contemporaneously with the central cluster, a subset could be associated with triggered star formation. The JWST image of intricate structures, including a spiral-like disk and bi-reflection nebulae at the tips of Pillar I and Pillar II, further highlights the complexity of star formation processes.

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arXiv2026

Extinction Distributions in Nearby Star-resolved Galaxies. II. M33

Extinction maps are essential for tracing interstellar dust and enabling accurate stellar population studies in galaxies. Here, a high-resolution extinction distribution of nearby galaxy M33 is constructed by fitting multiband color indexes of the individually resolved red giant branch (RGB) stars from the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER) survey. Achieving an angular resolution of approximately 6$^{\prime\prime}$ ($\sim$ 24.4 pc), the extinction map reveals the intricate and heterogeneous distribution of dust throughout the entire disk of M33, with distinct delineation of spiral arms, inter-arm regions, and compact dust clouds. In addition, it exhibits strong spatial correspondence with the distributions of total hydrogen, H I, and CO, underscoring the reliability of the extinction map for tracing both diffuse and dense components of the interstellar medium. The derived $V$-band extinction reaches up to 2.5 mag per pixel, with a mean value of about 1.05 mag. Beyond providing new insights into the dust structure of M33, the extinction map offers a robust foundation for accurate extinction corrections and will support future studies, including upcoming observations with the Chinese Space Station Telescope.

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arXiv2026

SGR 1935+2154's Quiet Local Environment: Clues for Its Progenitor

Magnetars are highly magnetized neutron stars (NSs) whose evolution and radiation are governed by the decay and/or reconfiguration of their magnetic fields. The origin of magnetars remains an open question, with proposed progenitor scenarios including core-collapse (CC) of very massive stars ($\ge 25~M_\odot$) or non-very massive stars ($8<M_*<25~M_\odot$), mergers of stellar systems, and accretion-induced collapse (AIC) of white dwarfs (WDs). Investigating the environments of magnetars can offer valuable clues to this issue. In this work, we study the local (a radius of $0.87^\circ$, $\sim 100$ pc at 6.6 kpc) stellar environment of SGR 1935+2154, which is spatially associated with the supernova remnant (SNR) G57.2+0.8, based on astrometry from Gaia DR3 and multi-band photometry from optical to infrared (IR). We discover that the upper limit of the surface density of massive stars around SGR 1935+2154 is only a quarter of that of the solar neighborhood, where the star formation rate is modest in the Galaxy. This quiet environment implies that the magnetar was likely formed by the CC of either a non-very massive star or a binary merger product rather than the CC of a very massive star. Although alternative channels cannot be excluded, their probabilities may be substantially lower. The studies of magnetars associated with SNRs consistently favor non-very massive progenitors, implying that such progenitors may produce a considerable fraction of magnetars. We also backtrack the trajectories of SGR 1935+2154 and its surrounding stars to search for its potential massive companions, yet no such companions are found.

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arXiv2026

Radiative Compression of Dense Cores in the Pillars of Creation as Revealed by JWST Extinction Mapping

The Pillars of Creation in M16 represent an iconic star-forming region where stellar feedback shapes molecular cloud evolution. We present a detailed investigation of dust extinction and density structure in the Pillars of Creation using multiband photometric observations from \emph{JWST} NIRCam. A high-resolution (2\arcsec) extinction map reaching depths of $A_V\sim 100$ mag has been constructed using NIRCam filters F090W, F200W, F335M, and F444W. This map clearly reveals the intricate structure of dense gas within the molecular cloud in the Pillars of Creation region. Analysis of the column density probability distribution function (N-PDF) exhibits a characteristic lognormal distribution at intermediate extinctions ($A_V\approx10-30$\,mag), which transitions to a power-law tail at high extinctions ($A_V\gtrsim$ 30\,mag) where star-forming cores reside. The power-law slope $\alpha$ displays significant spatial variation, steepening from $\alpha\approx 2.0$ at the pillar tips facing the NGC 6611 cluster to $\alpha\approx$4.0 in regions distant from the cluster. This systematic gradient demonstrates that stellar feedback not only disperses molecular clouds but can also locally enhance the formation of dense, self-gravitating structures through radiative compression.

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arXiv2026

The Spectroscopic and Photometric Study of a Star Cluster Sample in Andromeda Halo

Halo star clusters serve as vital tracers for the formation and evolution of the Andromeda galaxy. In this work, we present physical parameters for 29 M31 halo star clusters, derived from a combination of spectroscopic and photometric data. Low-resolution spectra were acquired using the BFOSC spectrograph on the NAOC Xinglong 2.16-m telescope. For the photometric analysis, we utilized uSC and vSAGE bands from the SAGE survey, complemented by archival data from GALEX(NUV, FUV), PAN-STARRS(grizy) and the 2MASS(JHK). Ages and metallicities were determined via ULySS (Vazdekis et al. and pegase-hr) SSP model and the Bruzual & Charlot (2003) (BC03) stellar population synthesis models. The derived parameters show good agreement with literature values. Notably, for three of these clusters, this study represents the first combined photometric and spectroscopic analysis.

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arXiv2026

A Tale of Two Dust Disks in Our Milky Way

Cosmic dust plays a vital role in stellar and galactic formation and evolution, but its three-dimensional structure in the Milky Way has remained unclear due to insufficient precise reddening and distance measurements. Although early studies typically adopted a single-disk model, we detect two distinct components at Galactocentric distances of 5-14 kpc, enabled by photometric, spectroscopic, and astrometric measurements of over 5 million stars. The thin dust disk's scale height increases radially from 60 to 200 pc, while the thick disk grows from 300 to 800 pc. For the first time, we find the thin and thick dust disk correlates spatially with molecular and atomic hydrogen disk, respectively. The thin, thick, and combined disks have scale lengths of 9.6+1.2-1.1 kpc, 4.2+0.4-0.3 kpc, and 6.6+0.3-0.3 kpc, respectively. The gas-to-dust ratio shows an exponential radial gradient, increasing from around 60 at 5 kpc to around 470 at 14 kpc. These findings provide new insights into dust morphology in the Galaxy and raise fundamental questions that require further investigation.

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arXiv2026

Discovery of an Extremely Luminous Type II Cepheid in the Andromeda Giant Stellar Stream: Evidence for a Hierarchical Triple with an Inner Binary Merger

We report the discovery of LAMOST J0041+3948, the most luminous post-AGB Type II Cepheid (TIIC) known, located in the Andromeda Giant Stellar Stream. Its spectral energy distribution (SED) exhibits a strong near-infrared excess, indicating the presence of a circumbinary dusty disk and hence binarity. SED fitting yields an effective temperature of $T_{\rm eff}=6738_{-262}^{+234}\,$K and a post-AGB luminosity of $\log(L/L_{\odot})=4.32_{-0.08}^{+0.07}$. Comparison with theoretical evolutionary tracks suggests a ~$2.0$-$4.0\,M_{\odot}$ progenitor when accounting for a possible scattered-light contribution. ZTF Light curves reveal a pulsation period of 89d that lies close to the period-luminosity relation for long-period RV Tauri stars. Follow-up spectroscopy reveals clear $s$-process enrichment and signatures consistent with an accretion disk around the companion. The inferred progenitor is significantly younger and more massive than a typical stream member, suggesting that an additional mechanism such as a stellar merger is required. We propose a formation channel in which the present post-AGB binary descends from a hierarchical triple system. In this scenario, the inner binary merged after the system was displaced to its current location by the galaxy merger event, and the resulting massive merger remnant subsequently evolved into the extremely luminous post-AGB star observed today.

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arXiv2025

Variation of the 2175 {\AA} extinction feature in Andromeda galaxy

Extinction curves contain key information on interstellar dust composition and size distribution, with the 2175 {\AA} bump being the most prominent feature. We analyze 20 sightlines toward M31 using HST/STIS UV spectroscopy combined with multi-band photometry to characterize this feature. The extinction curves show substantial diversity, from MW-like shapes to flatter profiles with $R_V$ reaching up to $\sim5.8$. The strength of the 2175 {\AA} feature varies widely, including two sightlines where the bump is essentially absent. The bump central wavelength spans a broader range than previously reported, while its width remains consistent with earlier studies. A moderate positive correlation is found between bump strength ($c_3$) and width ($\gamma$). We derive an average UV extinction curve toward M31 with $R_V \approx 3.53$. These results provide new constraints on dust properties and their spatial variations in this galaxy.

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arXiv2025

A large, long-lived, slowly-expanding superbubble across the Perseus Arm

Stellar feedback is a crucial mechanism in galactic evolution, as demonstrated by the widespread bubbles observed with JWST. In this study, we combine data from Gaia and LAMOST to obtain a sample of young O-B2 stars with full three-dimensional velocity information. Focusing on the largest known superbubble in the Milky Way, we identify groups of O-B2 stars at its periphery, exhibiting a transverse velocity of 25.8 km/s and an expansion velocity of 6.2 km/s. Using these velocities, we calculate a crossing time t_cross ~ 20 Myr and an expansion timescale t_expansion ~ 80 Myr. We estimate a survival timescale t_survival ~ 250 Myr and a supernova interval t_SN ~ 0.1 Myr. Together with the Galactic shear timescale t_shear ~ 30 Myr, these values satisfy t_SN < t_shear < t_survival. The energy and momentum from supernovae are sufficient to sustain the bubble's growth against ambient pressure. This indicates that repeated supernovae replenish energy faster than shear and turbulent distort the cavity. Our analysis classifies the Giant Oval Cavity as a large, quasi-stationary superbubble, similar to the Phantom Bubble observed by JWST, stabilised by the interplay between stellar feedback and Galactic disk dynamics.

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arXiv2025

Observational Evidence of Dust Evolution in Supernova Remnants: Size Redistribution Toward Larger Grains in Early Sedov Phase

Recent observations have revealed that dust is widespread and abundant in galaxies up to $z\,{\backsimeq}\,8$, significantly influencing their appearance and spectral properties. In the early Universe, dust is thought to form primarily in supernova (SN) ejecta, but also undergoes destruction by the reverse shock. Studying dust in local supernova remnants (SNRs) of different sizes and ages thus provides key constraints on dust formation and evolution during cosmic dawn. Using the newly released 3D $R_{\rm V}$ map, we derived local $R_{\rm V} \equiv A_{\rm V}/E(B-V)$ values for dust in 14 Galactic SNRs in the early Sedov phase and their surrounding interstellar medium (ISM). For the first time, we detect a moderately strong positive correlation between the difference in SNR and ISM $R_{\rm V}$ ($\Delta R_{\rm V}$) and SNR radius ($R_{\rm SNR}$), with a Spearman coefficient of $r_{\rm s}\,{=}\,0.62\,{\pm}\,0.14$. This trend offers direct observational evidence for a redistribution of dust grain sizes toward larger grains during SN shock processing, consistent with theoretical models. Our findings provide essential observational constraints on dust size evolution in SNRs and important implications for understanding the rapid enrichment and survival of dust in the early Universe.

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arXiv2025

An all-sky 3D dust map Based on Gaia and LAMOST

We present a comprehensive 3D dust reddening map covering the entire Milky Way, constructed by combining reddening estimates based on LAMOST low-resolution spectra (E(B$-$V)$_{\rm LAMOST}$) with those derived from $Gaia$ XP spectra (E(B$-$V)$_{\rm XP}$), along with revised $Gaia$ distances. E(B$-$V)$_{\rm LAMOST}$ values of $\sim$ 4.6 million unique sources were obtained with the standard-pair analysis using LAMOST DR11 stellar parameters and synthesized $B/V$-band photometry from $Gaia$ XP spectra, showing a typical precision of $\sim$ 0.01 mag. The E(B$-$V)$_{\rm XP}$ from the catalog of \citet{zhang2023}, which was derived using forward modeling of $Gaia$ XP spectra, were cross-validated with E(B$-$V)$_{\rm LAMOST}$, leading to the selection of $\sim$ 150 million high-reliability measurements. The combined dataset achieves a median precision of $\sim$ 0.03 mag for E(B$-$V). To model the reddening -- distance relationship along various lines-of-sight, we implemented a parametric approach that accounts for contributions from the local bubble, diffuse interstellar-medium, and multiple potential molecular clouds. The sky was adaptively partitioned based on stellar density, resulting in angular resolutions ranging from 3.4$^{\prime}$ to 58$^{\prime}$, with about half of the sky having a resolution better than 6.9$^{\prime}$. The reddening precision of our 3D map for individual stars reaches $\sim$ 0.01 mag in most regions at $|b| > 20^\circ$, but degrades to 0.01-0.05 mag at $|b| < 20^\circ$. The map reaches a maximum distance of 3-5 kpc in high-extinction regions with $|b| < 5^\circ$, and extends to 10-15 kpc elsewhere. An interactive platform and Python package have been developed for utilization of the 3D dust map. Available online: https://nadc.china-vo.org/data/dustmaps/.

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arXiv2025

A Comprehensive All-Sky Catalog of 3345 Molecular Clouds from Three-dimensional Dust Extinction

Understanding the distribution and properties of molecular clouds is crucial for tracing the structure and evolution of the interstellar medium and the large-scale morphology of the Milky Way. Here we present an all-sky catalog of 3,345 molecular clouds identified from our previous three-dimensional dust reddening map using a dendrogram-based clustering method with distance-adaptive parameters. The catalog spans heliocentric distances from 90 pc to 4.3 kpc and includes key physical properties for each cloud, including position, size, mass, surface density, and dust density. Approximately 650 clouds in our catalog are associated with the boundary of the Local Bubble, while around 740 clouds (excluding those associated with the Local Bubble) are located at high Galactic latitudes ($|b| > 20^\circ$). The spatial distribution of the cataloged clouds reveals prominent large-scale features in the Galactic disk, including coherent spur-like structures, large-scale cavities, and a more detailed view of the Local Bubble shell. These findings refine our understanding of how molecular clouds trace the Galactic spiral arm network and provide new insight into the spatial structure of the Local Bubble. The catalog serves as a valuable resource for future studies of star formation, Galactic structure, and the interaction between molecular clouds and large-scale ISM features.

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arXiv2025

A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for In Situ Massive Star Formation Beyond the Optical Radius

While massive stars are known to shape galactic ecosystems, their formation has long been assumed to require the high-density environments of inner galactic disks. This paradigm is challenged by mounting evidence of young massive stars in extended galaxy outskirts, yet direct confirmation of in situ massive star formation in such extreme low-density environments remains scarce. Here, we present the discovery of LAMOST J0048+4154, a massive yellow supergiant situated at a deprojected galactocentric distance of ~34 kpc in M31, making it the most distant massive star confirmed in this galaxy. Through spectroscopic and photometric analyses, we classify J0048+4154 as an F5-F8I supergiant with an effective temperature of $6357^{+121}_{-118}$ K and a luminosity of $\log L/L_{\odot} = 5.00^{+0.06}_{-0.06}$, corresponding to an ~18 $M_{\odot}$ progenitor and an age of ~10 Myr. FAST H I observations reveal close spatial and kinematic alignment between the star and a faint H I external arm, suggesting in situ formation in a region of low gas density. The presence of other UV-bright, early-type stars in the vicinity further supports low-level recent star formation in M31's very outer disk. These findings challenge the prevailing assumption that massive star formation is confined to inner disks or classical star-forming regions and underscore the need to re-examine the role of spiral galaxy outskirts in fueling and sustaining star formation. J0048+4154 thereby expands our understanding of the extent of M31's young stellar component and exemplifies how outer disks may harbor conditions conducive to forming massive stars, despite low-density environments.

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arXiv2025

Unveiling a young thick disk in the Milky Way

The thickness of a galaxy's disk provides a valuable probe of its formation and evolution history. Observations of the Milky Way and local galaxies have revealed an ubiquitous disk structure with two distinctive components: an old thick disk and a relatively young thin disk. The formation of this dual-disk structure and the mechanisms that develop the thickness of the disk are still unclear. Whether the disk thickness inherit from the birth environment or is established through secular dynamical heating after formation is under debate. In this work we identify a relatively young ($\sim$6.6 billion years old) geometric thick disk in the Milky Way, with a scale height of $0.64$ kpc at the Solar Circle. This young thick component exhibits comparable thickness and flaring strength to the canonical old thick disk but is more radially extended and systematically younger. We also identify thin disk components that formed before and after this young thick disk. Detailed analysis of the solar vicinity structure suggests that the young thick disk marks the onset of a new phase of upside-down disk formation. These findings strongly discount the role of secular dynamical heating and support a turbulent, bursty birth environment as the primary mechanism behind thick disk formation. The existence of two thick disk components suggests that the Milky Way has undergone at least two episodes of turbulent and bursty star formation, likely triggered by galaxy mergers.

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