Further evidence for large central mass-to-light ratios in massive
  early-type galaxies
  We studied the stellar populations, distribution of dark matter, and
dynamical structure of a sample of 25 early-type galaxies in the Coma and Abell
262 clusters. We derived dynamical mass-to-light ratios and dark matter
densities from orbit-based dynamical models, complemented by the ages,
metallicities, and \alpha-elements abundances of the galaxies from single
stellar population models. Most of the galaxies have a significant detection of
dark matter and their halos are about 10 times denser than in spirals of the
same stellar mass. Calibrating dark matter densities to cosmological
simulations we find assembly redshifts z_{DM} \approx 1-3. The dynamical mass
that follows the light is larger than expected for a Kroupa stellar initial
mass function, especially in galaxies with high velocity dispersion
\sigma_{eff} inside the effective radius r_{eff}. We now have 5 of 25 galaxies
where mass follows light to 1-3 r_{eff}, the dynamical mass-to-light ratio of
all the mass that follows the light is large (\approx 8-10 in the Kron-Cousins
R band), the dark matter fraction is negligible to 1-3 r_{eff}. This could
indicate a "massive" initial mass function in massive early-type galaxies.
Alternatively, some of the dark matter in massive galaxies could follow the
light very closely suggesting a significant degeneracy between luminous and
dark matter.
