FEASTS: Radial Distribution of H i Surface Densities Down to 0.01 M⊙ pc−2 of 35 Nearby Galaxies
We present the H i surface density (Σ _H _i ) radial distributions based on total-power H i images obtained by FAST in the FEASTS program, for 35 galaxies with inclinations lower than 72°. We derive the H i radius R _001 , which is the radius for the 0.01 M _⊙ pc ^−2 (~10 ^18.1 cm ^−2 ) isodensity l...
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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/ada95a |
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| Summary: | We present the H i surface density (Σ _H _i ) radial distributions based on total-power H i images obtained by FAST in the FEASTS program, for 35 galaxies with inclinations lower than 72°. We derive the H i radius R _001 , which is the radius for the 0.01 M _⊙ pc ^−2 (~10 ^18.1 cm ^−2 ) isodensity level, 100 times deeper than the 1 M _⊙ pc ^−2 level previously commonly used to measure R _1 . The profile shapes show a large diversity at a given radius in units of kpc, group virial radius, and R _1 , but they align more tightly with the radius normalized by R _001 . The universal H i profile has a scatter of ~0.2 dex and a scale length of ~0.11 R _001 in the outer region. We derive a new R _001 – M _H _i relation, which has a scatter of 0.03 dex and a similar slope of ~0.5 to the previously known R _1 – M _H _i relation. Excluding strongly tidal-interacting galaxies, the ratio R _001 / R _1 (anti)correlates strongly and significantly with the H i -to-stellar mass ratio and specific star formation rate, but not with the stellar mass, M _H _i , dark matter mass, or star formation rate. The strongly tidal-interacting galaxies tend to show deviations from these trends and have the most flattened profiles. These results imply that, in the absence of major tidal interactions, physical processes must cooperate so that Σ _H _i distributes in a self-similar way in the outer region down to the 0.01 M _⊙ pc ^−2 level. Moreover, they may drive gas flows in such a way that H i -richer galaxies have H i disks that not only extend further but also transport H i inward more efficiently from R _001 to R _1 . |
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| ISSN: | 1538-4357 |