We present mass models for the dark matter component of 7 dwarf galaxies taken from “ The H i Nearby Galaxy Survey ” ( THINGS ) and compare these with those from numerical \Lambda Cold Dark Matter ( \Lambda CDM ) 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 \mu m 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 .
The relation between total baryonic ( stars + gas ) mass and maximum rotation velocity of the galaxies is roughly consistent with the Baryonic Tully \ - - Fisher relation calibrated from a larger sample of gas dominated low mass galaxies .
We find discrepancies between the derived dark matter distributions of the galaxies and those of \Lambda CDM 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 \pm 0.07 .
They are significantly different from the steep slope of \sim -1.0 inferred from previous dark-matter-only simulations , and are more consistent with shallower slopes found in recent \Lambda CDM simulations of dwarf galaxies in which the effects of baryonic feedback processes are included .