The Minimum Amount of Stars a Galaxy Will Form

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 H I mass-to-light ratios (M HI /L B), stellar luminosities, and surface brightnesses. Combining the results with those of four other well-studied dwarf galaxies known for their unusually large H I contents, we 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. We also find that the star density systematically decreases with increasing M HI /L B, making the galaxies optically more elusive. 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 produce 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 the minimum quantity of stars necessary to maintain a stable gas disk. Show more