People involved at OAB: Bardelli, Cappi, Zucca.
Cappi is involved in a project (MUSIC, MUltiwavelength Sample of
Interacting Clusters) with researchers at the Observatoire
de la Côte d'Azur (Maurogordato, Benoist, Bijaoui, Ferrari, Slezak) and
at the CEA/CEN in Saclay (M. Arnaud, J-L. Sauvageot), aiming at a combined
optical and X-ray study of galaxy and gas dynamics in a selected sample of
galaxy clusters. This project is mainly based on optical observations at the
ESO 3.6m and CFHT telescopes, and on X-ray observations with ASCA and ROSAT,
and with Chandra and XMM-Newton. A number of results have been obtained
for A521, a complex, relatively rich cluster at 
, in the middle
of two filamentary structures, with on-going merging
(Maurogordato et al. 2000, Ferrari et al. 2002, in preparation).
New spectroscopic observations have
increased the number of known redshifts, giving a detailed map of the
substructures and dynamics of this complex system, while more imaging and
spectroscopic observations are scheduled to study the star-forming
galaxies in the cluster and their distribution. A dynamical study is
currently carried out also on another, regular cluster, A1413, for which the
Sunyaev-Zeldovich effect has also been detected. Other clusters have been or
will be observed and will consititute a database suited for a systematic study
of merging clusters.
Bardelli, Cappi and Zucca, in collaboration with a group in Padova (L. Moscardini et al.) and in Milano (S. De Grandi et al.) and with S. Ettori (ESO) have obtained Beppo-SaX observations of two cluster pairs in the Corona Borealis Supercluster; in combination with the available redshifts, it will be possible to analyse the consequences of the merging event on the energetics, internal structure and dynamics of clusters and the interplay between the ambient density, the dark mass, the gas and the galaxy population.