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arXiv · 2607.14584

A Catalog of Compact High-Velocity Clouds from the FAST All-Sky HI Survey (FASHI) DR2

Jin-Long Xu·Chuan-Peng Zhang·Xiao-Lan Liu·Nai-Ping Yu·Mei Ai·Ming Zhu
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Abstract

High-velocity clouds (HVCs) -- especially compact HVCs (CHVCs) -- are thought to serve as gaseous tracers of dark-matter-dominated subhalos, providing a crucial empirical link between the predicted dark matter substructure and observed satellite galaxies. In this paper, we present a new catalog of 192 CHVCs identified from the FAST All-Sky HI Survey (FASHI) Data Release 2 (DR2). Among these, 108 are ultra-compact HVCs (UCHVCs), the majority of which are new discoveries. We find that 185 of the 192 CHVCs are spatially and kinematically concentrated around the Andromeda galaxy (M31), with a median LSR velocity of -296.1 km/s, suggesting physical association with M31. Adopting an M31 distance of 0.8 Mpc, we derive HI masses in the range 1.9*10^{5} to 4.0*10^{6} Msun and dynamical masses from 1.0*10^{7} to 6.3*10^{8} Msun. Approximately half of the CHVCs follow the baryonic Tully--Fisher relation. No optical counterparts are detected in Pan-STARRS1 imaging down to a limiting magnitude of m_g = 22.8. We conclude that these CHVCs likely represent a population of gas-rich, starless minihalos and provide an excellent sample for the search for dark galaxies.

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Jin-Long Xu, Chuan-Peng Zhang, Xiao-Lan Liu, Nai-Ping Yu, Mei Ai, Ming Zhu. 2026-07-16. A Catalog of Compact High-Velocity Clouds from the FAST All-Sky HI Survey (FASHI) DR2. https://arxiv.org/abs/2607.14584

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