The local Tully-Fisher relation for dwarf galaxies
  We study different incarnations of the Tully-Fisher (TF) relation for the
Local Volume (LV) galaxies taken from Updated Nearby Galaxy Catalog. The UNGC
sample contains 656 galaxies with $W_{50}$ HI-line-width estimates, mostly
belonging to low mass dwarfs. Of them, 296 objects have distances measured with
accuracy better than 10%. For the sample of 331 LV galaxies having baryonic
masses $\log M_{bar} > 5.8 \log M_\odot$ we obtain a relation $\log M_{bar}=
2.49 \log W_{50} + 3.97$ with observed scatter of 0.38 dex. The largest factors
affecting the scatter are observational errors in $K$-band magnitudes and
$W_{50}$ line widths for the tiny dwarfs, as well as uncertainty of their
inclinations. We find that accounting for the surface brightness of the LV
galaxies, or their gas fraction, or specific star formation rate, or the
isolation index do not reduce essentially the observed scatter on the baryonic
TF-diagram. We also notice that a sample of 71 dSph satellites of the Milky Way
and M31 with known stellar velocity dispersion $\sigma^*$ tends to follow
nearly the same bTF relation, having slightly lower masses than that of
late-type dwarfs.
