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Thin discs, thick dwarfs and the effects of stellar feedback

Rubén Sánchez-Janssen (ESO)

I will present an investigation on the role of stellar mass in shaping the
intrinsic thickness of galaxy discs by determining the probability
distribution of apparent axis ratios (b/a) for two different samples that
probe the faint end of the galaxy luminosity function. We find that the
b/a distribution has a characteristic ’U-shape’ and identify a limiting
mass M ≈ 2×109 Msun below which low-mass galaxies start to be
systematically thicker. This tendency holds for very faint (MB ≈ -8)
dwarfs in the Local Volume, which are essentially spheroidal systems. We
argue that galaxy shape is the result of the complex interplay between
mass, specific angular momentum and stellar feedback effects. Thus, the
increasing importance of turbulent motions in lower mass galaxies leads to
the formation of thicker systems, a result supported by the latest
hydrodynamical simulations of dwarf galaxy formation and other theoretical
expectations. I will discuss several implications of this finding,
including the formation of bars in faint galaxies, the deprojection of HI
line profiles and simulations of environmental effects on the dwarf galaxy