A comprehensive survey of X-ray luminous clusters of galaxies at z=0.2, 
and a new method for extracting galaxy shapes from images

Sarah Bridle
Observatoire Midi-Pyrénées, Toulouse, France
Oliver Czoske
Observatoire Midi-Pyrénées, Toulouse, France & IfA


In a bottom-up hierarchical scenario of the evolution of large-scale
structure in the Universe, the population of massive clusters of
galaxies marks the boundary between linear and nonlinear
evolution. The mass function of clusters follows from linear theory in
a robust and straightforward manner and depends strongly on the 
cosmological parameters Omega_M and sigma_8. However, the relations
between cluster mass and astronomical observables, such as galaxy
velocity dispersions, X-ray temperature and luminosity and background
galaxy shear, is nontrivial and both the shapes of these relations and the
scatter around them must be calibrated observationally. 

We are conducting a combined HST/CFHT/XMM survey of a homogeneously
selected sample of 12 X-ray luminous clusters of galaxies at z=0.2
with the principal aim of calibrating the relations between cluster
masses, as derived from strong and weak lensing, and X-ray temperature
and luminosity. Oliver will review the current status of the project and
present preliminary results from the HST/WFPC2 and CFHT/CFH12k
observations.  

For the weak lensing analysis of the CFH12k data we will use a new
method for extracting galaxy shapes from images, which is currently
being developed by Sarah. She will introduce this new method and
summarise the maximum entropy lens reconstruction method of Bridle et
al. (1998, MNRAS, 299, 895; 2001 MNRAS submitted,
astro-ph/0010387). She will also show results from Keck and HST data
on MS1054, and on a low X-ray luminosity sample observed with
HST.