An H$\alpha$ Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40$\%$ ALFALFA \ion{H}{1} Survey

TL;DR

This study measures Hα flux and star formation rates in low-surface-brightness galaxies from the ALFALFA survey, revealing their low star formation efficiency and deviation from the Kennicutt-Schmidt law, suggesting they are stable, slowly evolving systems.

Contribution

First comprehensive Hα imaging survey of LSBGs from the ALFALFA survey, providing new insights into their star formation properties and efficiency.

Findings

LSBGs have low SFRs (<1 M_sun/yr) despite being H I-rich.

LSBGs deviate from the Kennicutt-Schmidt law, indicating low star formation efficiency.

LSBGs are stable systems with infrequent major interactions or mergers.

Abstract

We present the observed H$\alpha$ flux and derived star formation rates (SFRs) for a fall sample of low$-$surface$-$brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40$\%$ ALFALFA {\ion{H}{1}} survey $-$ SDSS DR7 photometric data, and all the $H\alpha$ images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and $H\alpha$ flux was measured in 92 of them. Though almost all the LSBGs in our sample are {\ion{H}{1}}$-$rich, their SFRs derived from the extinction and filter$-$transmission$-$corrected $H\alpha$ flux, are less than 1$M_{\sun}$$yr^{-1}$. LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities, but LSBGs have much lower SFRs and SFR surface densities than star$-$forming galaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt law significantly, which indicate that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support the previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers during their star formation histories.