The HI gas and star formation in star-forming galaxies selected from ALFALFA

Abstract This paper presents the results of H α imaging of 169 galaxies randomly selected from the α.40 - SDSS catalog. The sample has excluded all low surface brightness galaxies (LSBGs) whose central surface brightness in B band (μ 0 ( B )) fainter than 22.5 mag arcsec −2 . It can be used as the counterparts sample to LSBGs. We observed their H α and R band images by using the 2.16 m telescope at the Xinglong Observatory of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC). The main goal of this work is to present the properties of those galaxies, together with H α flux and star formation-, gas-, stellar mass- surface density. In addition, we confirm the correlations among HI content, stellar mass and star formation in ALFALFA galaxies. The HI mass increases with stellar mass, and the slope slows down at the higher stellar mass. The overall trend was that the specific star formation rate (sSFR) decreases with stellar mass, and the sSFR dropped sharply when the stellar mass is close to 10 10.3 ∼ 10 10.5 M ⊙ . The weak correlation between SFR/M HI and M HI implies the HI contribute little to star formation. Our sample, which are mostly star-forming galaxies, follows the revisited Kennicutt-Schmidt law as well as the Kennicutt-Schmidt law.