The intrinsic shapes of dwarf irregular galaxies
  We use the measured B band axial ratios of galaxies from an updated catalog
of Local Volume galaxies to determine the intrinsic shape of dwarf irregular
galaxies (de Vacouleurs' morphological types 8, 9 and 10). We find that the
shapes change systematically with luminosity, with fainter galaxies being
thicker. In particular, we divide our sample into sub-samples and find that the
most luminous dwarfs (-19.6 < M_B < -14.8) have thin discs (thickness ~ 0.2),
with the disc being slightly elliptical (axial ratio ~ 0.8). At intermediate
luminosity, viz. -14.8 < M_B < -12.6, the galaxies are still characterized by
elliptical discs (axial ratio ~ 0.7), but the discs are somewhat thicker
(thickness ~ 0.4). The faintest dwarfs, viz. those with -12.6 < M_B < -6.7 are
well described as being oblate spheroids with an axial ratio ~ 0.5. The
increasing thickness of the stellar discs of dwarf irregulars with decreasing
luminosity is compatible with the increasing ratio of velocity dispersion to
rotational velocity with decreasing galaxy size.
