The Dependence of Gas Richness and Disk Building on Galaxy Mass

Sheila Kannappan

U North Carolina

Galaxies are known to transition from largely blue and disk-dominated to largely red and spheroid-dominated as they increase in mass across the "bimodality" scale at a stellar mass of M_* ~ 3x10^10 Msun. I will present converging lines of evidence suggesting that the beginning of this transition occurs at another mass scale of interest: a "threshold" mass at M_* ~ 5x10^9 Msun, where shifts in both gas richness and galaxy structure mark the dwarf/giant galaxy divide. Combining different lines of evidence, I will examine the phenomena and physical processes underlying this transition.