The Density Profiles of Massive, Relaxed Galaxy Clusters: II. Separating Luminous and Dark Matter in Cluster Cores. (arXiv:1209.1392v1 [astro-ph.CO])

The Density Profiles of Massive, Relaxed Galaxy Clusters: II. Separating Luminous and Dark Matter in Cluster Cores. (arXiv:1209.1392v1 [astro-ph.CO]):
We present stellar and dark matter (DM) density profiles for a sample of 7
massive, relaxed galaxy clusters derived from strong and weak gravitational
lensing and resolved stellar kinematic observations within the
centrally-located brightest cluster galaxies (BCGs). In Paper I of the series,
we demonstrated that the total density profile derived from these data, which
span 3 decades in radius, is consistent with numerical DM-only simulations at
radii \gtrsim 5-10 kpc, despite the significant contribution of stellar
material in the core. Here we decompose the inner mass profiles of these
clusters into stellar and dark components. Parametrizing the DM density profile
as a power law rho_DM \sim r^{-\beta} on small scales, we find a mean slope
<\beta> = 0.50 +- 0.10 (random) +0.14-0.13 (systematic). Alternatively, cored
Navarro-Frenk-White (NFW) profiles with <log rcore/kpc> = 1.14 +- 0.13 (rand.)
+0.14-0.22 (sys.) provide an equally good description. These density profiles
are significantly shallower than canonical NFW models at radii \gtrsim 30 kpc,
comparable to the effective radii of the BCGs. The inner DM profile is
correlated with the distribution of stars in the BCG, demonstrating a close
connection between the inner halo and the assembly of stars in the central
galaxy. The stellar mass-to-light ratio inferred from lensing and stellar
dynamics is consistent with that inferred using stellar population synthesis
models if a Salpeter initial mass function is adopted. We compare these results
to theories describing the interaction between baryons and DM in cluster cores,
including prescriptions for adiabatic contraction, and discuss possible
signatures of alternative DM candidates.