Central Mass Profiles of the Nearby Cool-core Galaxy Clusters Hydra A
  and A478
  We perform a weak-lensing study of the nearby cool-core galaxy clusters,
Hydra A ($z=0.0538$) and A478 ($z=0.0881$), of which brightest cluster galaxies
(BCGs) host powerful activities of active galactic nuclei (AGNs). For each
cluster, the observed tangential shear profile is well described either by a
single Navarro--Frenk--White model or a two-component model including the BCG
as an unresolved point mass. For A478, we determine the BCG and its host-halo
masses from a joint fit to weak-lensing and stellar photometry measurements. We
find that the choice of initial mass functions (IMFs) can introduce a factor of
two uncertainty in the BCG mass, whereas the BCG host halo mass is well
constrained by data. We perform a joint analysis of weak-lensing and stellar
kinematics data available for the Hydra A cluster, which allows us to constrain
the central mass profile without assuming specific IMFs. We find that the
central mass profile ($r<300$kpc) determined from the joint analysis is in
excellent agreement with those from independent measurements, including
dynamical masses estimated from the cold gas disk component, X-ray hydrostatic
total mass estimates, and the central stellar mass estimated based on the
Salpeter IMF. The observed dark-matter fraction around the BCG for Hydra A is
found to be smaller than those predicted by adiabatic contraction models,
suggesting the importance of other physical processes, such as the the AGN
feedback and/or dissipationless mergers.
