Title:

Dark Matter Density Distributions in Dwarf Galaxies


Leo Blitz
University of California - Berkeley



Abstract:

       Simulations of galaxy evolution in CDM cosmologies make a robust
prediction that galaxy halos have a universal density distribution
inversely proportional to distance from the nucleus within about 1 kpc
from the center.  This prediction is best probed experimentally in dwarf
and low surface brightness galaxies because they tend to have the largest
ratio of dark/luminous matter.  We present the results of measurements
of two-dimensional velocity fields in a number of dwarfs constraining
the systematic uncertainties to a level that makes it possible to test
the computational simulations.  We show that there is no universal inner
density distribution and suggest that the problem lies not with CDM,
but with the simulations themselves.  As part of our program we have
serendipitously found an object that appears to be a starless galaxy:
a rotating distribution of hydrogen gas, held together by dark matter and
containing no stars.  Other anomalies include galaxies in the local group
in which v/sigma = 1, but show no evidence for rotational flattening.