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arXiv · 2509.11891

The impact of external gas accretion on the distribution of HI gas in galaxies

Qianhan Zhang·Min Bao·Yanmei Chen·Niankun Yu·Yong Shi·Luis C. Ho
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Abstract

Using the data from Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) and HI-MaNGA surveys, we build a sample of 37 gas-star misaligned galaxies with robust HI detections, which are believed to have undergone external gas accretion processes. Both star-forming (SF) and quiescent (QS) misaligned galaxies exhibit narrower HI linewidths compared to their gas-star aligned controls. The HI profiles of SF misaligned galaxies tend to be single-peaked, displaying a slightly higher fraction of single-peaked shape compared to their aligned controls. The QS misaligned galaxies exhibit prominently single-peaked HI profiles, while their aligned controls show distinct double-horned profiles. The shape of HI profiles is expected to change with the HI surface density radial gradients through external gas accretion -- the interaction between the accreted gas and the pre-existing gas leads to the re-distribution of angular momentum and induces gas inflow. It suggests that the progenitors of SF misaligned galaxies are central HI-enriched, in this case, the shape of HI profiles is insensitive to the further increase of central HI surface density. The progenitors of QS misaligned galaxies are central HI-deficient, hence the transition from central HI-deficient to HI-enriched surface density leads to significantly more single-peaked HI profiles.

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Qianhan Zhang, Min Bao, Yanmei Chen, Niankun Yu, Yong Shi, Luis C. Ho. 2025-09-15. The impact of external gas accretion on the distribution of HI gas in galaxies. https://arxiv.org/abs/2509.11891

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