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Thin discs, thick dwarfs, and the importance of feedback effects

We investigate the role of stellar mass in shaping the intrinsic thickness of faint systems by determining the probability distribution of apparent axis ratios for two different samples that probe the faint end of the galaxy luminosity function (M_B < -8). We find that the (b/a) distribution is a strong function of M*, and identify a limiting stellar mass M* ~ 2x10^9 Msun below which galaxies start to be systematically thicker. We argue that this is the result of the complex interplay between galaxy mass, specific angular momentum and stellar feedback effects: the increasing importance of turbulent motions in lower mass galaxies leads to the formation of thicker systems. We find a good agreement between our results and the latest numerical simulations of dwarf galaxy formation, and discuss several further implications of this finding --including the formation of bars and spirals in faint galaxies, the deprojection of HI line profiles and simulations of environmental effects on dwarf galaxies.