Dark and luminous matter in THINGS dwarf galaxies
  We present mass models for the dark matter component of seven dwarf galaxies
taken from "The HI Nearby Galaxy Survey" (THINGS) and compare these with those
from numerical Lambda Cold Dark Matter (LCDM) simulations. The THINGS
high-resolution data significantly reduce observational uncertainties and thus
allow us to derive accurate dark matter distributions in these systems. We here
use the bulk velocity fields when deriving the rotation curves of the galaxies.
Compared to other types of velocity fields, the bulk velocity field minimizes
the effect of small-scale random motions more effectively and traces the
underlying kinematics of a galaxy more properly. The "Spitzer Infrared Nearby
Galaxies Survey" (SINGS) 3.6 micron and ancillary optical data are used for
separating the baryons from their total matter content in the galaxies. The
sample dwarf galaxies are found to be dark matter dominated over most radii. We
find discrepancies between the derived dark matter distributions of the
galaxies and those of LCDM simulations, even after corrections for non-circular
motions have been applied. The observed solid body-like rotation curves of the
galaxies rise too slowly to reflect the cusp-like dark matter distribution in
CDM halos. Instead, they are better described by core-like models such as
pseudo-isothermal halo models dominated by a central constant-density core. The
mean value of the logarithmic inner slopes of the mass density profiles is
alpha = -0.29 +- 0.07. They are significantly different from the steep slope of
~ -1.0 inferred from previous dark-matter-only simulations, and are more
consistent with shallower slopes found in recent LCDM simulations of dwarf
galaxies in which the effects of baryonic feedback processes are included.
