The Effect of Structure and Star Formation on the Gas Content of Nearby Galaxies

TL;DR

This study investigates how galaxy structure and star formation influence gas content, revealing that gas fraction relations are driven by galaxy bimodality and star formation laws, with depletion timescales varying by mass and structure.

Contribution

It demonstrates, for the first time, that gas fraction scaling relations are mainly governed by galaxy bimodality and star formation laws, and suggests depletion timescales depend on galaxy properties.

Findings

Gas fraction relations are driven by galaxy bimodality and star formation laws.

Scaling relations of gas fraction depend on specific star formation rate.

Depletion timescales vary with galaxy mass and structure.

Abstract

We revisit the main HI-to-stellar mass ratio (gas fraction) scaling relations, taking advantage of the HI spectral stacking technique to understand the dependence of gas content on the structural and star formation properties of nearby galaxies. This work uses a volume-limited, multi-wavelength sample of ~25,000 galaxies, selected according to stellar mass (10^9 M_sol < M_* < 10^11.5 M_sol) and redshift (0.02 < z < 0.05) from the Sloan Digital Sky Survey, and with HI data from the Arecibo Legacy Fast ALFA survey. We bin according to multiple parameters of galaxies spanning the full gas-poor to -rich regime in order to disentangle the dominance of different components and processes in influencing gas content. For the first time, we show that the scaling relations of gas fraction with stellar mass and stellar surface density are primarily driven by a combination of the underlying galaxy bimodality in specific star formation rate and the integrated Kennicutt-Schmidt law. Finally, we produce tentative evidence that the timescales of HI depletion are dependent upon galaxy mass and structure, at fixed specific star formation rate.