Title:
The Mass and Structure of X-ray Luminous Galaxy Clusters at z=0.2 -- The
View from Hubble and Chandra.


Graham Smith
Caltech



Abstract:

We present Hubble Space Telescope observations of ten X-ray luminous
galaxy clusters at z=0.2.  These data reveal numerous previously
undetected gravitationally-lensed galaxies.  We use this lensing
signal to constrain a detailed model of the gravitational potential of
each cluster core, and thus to measure the mass and structure of the
clusters on projected scales of r<=500kpc.  Our models provide an
unprecedented view of cluster morphology, revealing that 60% of the
sample contain significant substructure.  Chandra X ray observations
confirm that this is a signature of dynamical immaturity.  The mean
temperature of the intra cluster medium of the morphologically complex
clusters is 30% hotter than than the regular clusters.  This offset
results in a critical and previously unexplored 20% systematic
uncertainty in the use of clusters to normalize the matter power
spectrum.  Our results demonstrate the power of detailed gravitational
lensing studies of objectively selected samples of massive clusters.
This work lays the foundation for our detailed wide-field weak lensing
(CFH12k) and X-ray (XMM-Newton) study of this unique sample and will
be a benchmark for comparison with similar samples at higher redshift,
for example drawn from the MACS survey.