The Minimum Amount of Stars a Galaxy Will Form

TL;DR

This study investigates the relationship between hydrogen content, stellar properties, and environment in late-type galaxies, revealing an empirical limit on star formation related to baryonic mass and environmental factors.

Contribution

It identifies an upper envelope for the HI-to-light ratio as a function of galaxy luminosity and links galaxy environment to gas retention and star formation efficiency.

Findings

High M_HI/L_B galaxies are more common in low-density environments.

Dwarf irregulars follow the same M_HI/L_B trend as larger galaxies but are underluminous for their rotation velocity.

Isolated galaxies with shallow dark matter potentials retain more baryonic gas and form fewer stars.

Abstract

We present an analysis of the atomic hydrogen and stellar properties of 38 late-type galaxies in the local Universe covering a wide range of HI mass-to-light ratios (M_HI/L_B), stellar luminosities, and surface brightnesses. From these data we have identified an upper envelope for the M_HI/L_B as a function of galaxy luminosity. This implies an empirical relation between the minimum amount of stars a galaxy will form and its initial baryonic mass. While the stellar mass of a galaxy seems to be only loosely connected to its baryonic mass, the latter quantity is strongly linked to the galaxy's dynamical mass as it is observed in the baryonic Tully-Fisher relation. We find that dwarf irregular galaxies with generally high M_HI/L_B-ratios follow the same trend as defined by lower M_HI/L_B giant galaxies, but are underluminous for their rotation velocity to follow the trend in a stellar mass Tully-Fisher relation, suggesting that the baryonic mass of the dwarf galaxies is normal but they have failed to produced a sufficient amount of stars. Finally, we present a three dimensional equivalent to the morphology-density relation which shows that high M_HI/L_B galaxies preferentially evolve and/or survive in low-density environments. We conclude that an isolated galaxy with a shallow dark matter potential can retain a large portion of its baryonic matter in the form of gas, only producing a minimum quantity of stars necessary to maintain a stable gas disk.