People involved at OAB: Cappi.
A. Cappi is involved in a project (MUSIC, MUltiwavelength Sample of
Interacting Clusters) with researchers at the Observatoire de la
Côte d'Azur (S. Maurogordato, C. Benoist, A. Bijaoui, E. Slezak),
the CEA/CEN in Saclay (M. Arnaud, J-L. Sauvageot), and Innsbruck
University (C. Ferrari) aiming at a multiwavelength
study of galaxy and gas dynamics in a selected sample of galaxy clusters.
The final aim of the project is the realization of a homogeneous database of
clusters in different evolutionary phases, suited for a systematic
statistical study and a quantitative comparison with theoretical predictions.
This project is based on
optical observations (mainly at the ESO 3.6m and CFHT telescopes,
but presently also at the VLT) and on X-ray
observations with XMM-Newton and Chandra, while
complementary radio observations are now carried out in collaboration with
Luigina Feretti (IRA-CNR). The first object studied in this survey is
A521, a complex, relatively
rich cluster at 
, in the middle of two filamentary
structures, with on-going merging (Maurogordato et al. 2000; Ferrari, ... Cappi et al. 2003).
New spectroscopic observations have increased the number of known redshifts,
giving a detailed map of the substructure and dynamics of this complex
system, which appears to be at least qualitatively consistent with the
expectations of hierarchical models of structure formation.
Another cluster we have studied in detail is A3921, which appears to be
characterized by a bimodal structure, and
for which we have obtained deep photometric catalogues and measured more than
230 new redshifts, while XMM-Newton/EPIC observations have been obtained by
our CEA/CEN collaborators (see Ferrari, ... Cappi et al. 2004).
One important aspect of the merging process is the way it may affect
star-formation in galaxies, and we have planned
more imaging and spectroscopic observations to map the distribution
and properties of star-forming galaxies in interacting clusters.
In particular, we are at present carrying out
observations with VIMOS at the VLT, in order to obtain a large number
of high resolution spectra for A2163, a cluster at 
. Moreover, a
dynamical study is currently carried out also on another, regular
cluster, A1413, for which the Sunyaev-Zeldovich effect has also been
detected, and A1750. Other clusters will also be observed in the optical,
X-ray and radio passbands, to cover the main phases of cluster evolution.