The Relation between H I Gas and Star Formation Properties in Nearby Galaxies

Abstract

In this paper, we present some correlations of neutral hydrogen (H i) gas and physical properties of galaxies to investigate the role of atomic gas in governing galaxy evolution. We build a H i-detected sample including 70 galaxies that are detected by ALFALFA in a 15 deg2 region, and derive their star formation distribution based on the images of Hα narrowband observed here. In general, H i-detected galaxies have low surface density of stellar mass and active star formation. Additionally, most of the galaxies are in good agreement with the star-forming main sequence, consistent with the previous findings. We confirm the dependence of star formation (SF) in galaxies on H i gas at least on global scale, i.e., star formation rate (SFR) generally increases with H i mass, specific star formation rate (SSFR ≡ SFR/M*) increases with H i fraction (fH i) even for a given stellar mass, and H i-based star formation efficiency (SFE) mildly increases with the stellar mass and SFR surface density. Based on the distribution of stellar mass and star formation, we calculate the morphology indices of the sample, and analyze the dependence of fH i and SFE on them. The weak correlations between SFE and morphological indexes imply a weak physical link between H i and star formation in small scale. We find that fH i mildly increases with the asymmetry and decreases with the concentration of galaxies, suggesting that the H i gas supply and its effect are likely correlated with external processes in the extended disks of galaxies.