"Panchromatic Studies of Distant Clusters of Galaxies"

I will present results from an unprecedented multi-wavelength study we are carrying out on two of the most distant massive clusters of galaxies known to date in the southern sky, at z=0.84 and z=1.24, selected from the ROSAT Deep Cluster Survey. The dataset in hand includes very deep wide-area near-IR imaging with VLT and NTT, X-ray data from Chandra and XMM and optical high angular resolution imaging with HST/ACS. An extensive spectroscopic survey carried out with VLT/FORS on both clusters has yielded so far 78 secure cluster members for the z=0.84 system and 36 secure members for the z=1.24 cluster. Results on the internal structure of these clusters derived from the X-ray and spectroscopic data will be shown as well as some results on their galaxy populations. The color-magnitude diagram at redshift z=1.24 from optical ACS data and near-IR VLT imaging will be also presented together with its implications for early type galaxy evolution.