High-resolution mass models of dwarf galaxies from LITTLE THINGS
  We present high-resolution rotation curves and mass models of 26 dwarf
galaxies from LITTLE THINGS. LITTLE THINGS is a high-resolution Very Large
Array HI survey for nearby dwarf galaxies in the local volume within 11 Mpc.
The rotation curves of the sample galaxies derived in a homogeneous and
consistent manner are combined with Spitzer archival 3.6 micron and ancillary
optical U, B, and V images to construct mass models of the galaxies. We
decompose the rotation curves in terms of the dynamical contributions by
baryons and dark matter halos, and compare the latter with those of dwarf
galaxies from THINGS as well as Lambda CDM SPH simulations in which the effect
of baryonic feedback processes is included. Being generally consistent with
THINGS and simulated dwarf galaxies, most of the LITTLE THINGS sample galaxies
show a linear increase of the rotation curve in their inner regions, which
gives shallower logarithmic inner slopes alpha of their dark matter density
profiles. The mean value of the slopes of the 26 LITTLE THINGS dwarf galaxies
is alpha =-0.32 +/- 0.24 which is in accordance with the previous results found
for low surface brightness galaxies (alpha = -0.2 +/- 0.2) as well as the seven
THINGS dwarf galaxies (alpha =-0.29 +/- 0.07). However, this significantly
deviates from the cusp-like dark matter distribution predicted by
dark-matter-only Lambda CDM simulations. Instead our results are more in line
with the shallower slopes found in the Lambda CDM SPH simulations of dwarf
galaxies in which the effect of baryonic feedback processes is included. In
addition, we discuss the central dark matter distribution of DDO 210 whose
stellar mass is relatively low in our sample to examine the scenario of
inefficient supernova feedback in low mass dwarf galaxies predicted from recent
Lambda SPH simulations of dwarf galaxies where central cusps still remain.
