CLUSTERS OF GALAXIES IN X-RAYS FABIO GASTALDELLO INAF IASF-MILANO Silvano Molendi INAF IASF-Milano Silvano Molendi INAF IASF-Milano Pasquale Mazzotta Univ Roma Tor Vergata Pasquale Mazzotta Univ Roma Tor Vergata Paolo Tozzi INAF OA Trieste Paolo Tozzi INAF OA Trieste Stefano Ettori INAF OA Bologna Stefano Ettori INAF OA Bologna RESEARCH UNITS INAF IASF-MILANO: 6 members, 862 ks (XMM+Chandra) + 1 Ms (Integral) INAF OA BOLOGNA + UNIVERSITA BOLOGNA: 14 members, 1 Ms (XMM+Chandra) UNIVERSITA ROMA TOR VERGATA + IASF-ROMA: 8 members, 1.5 Ms (XMM+Chandra) INAF OA TRIESTE + UNIVERSITA TRIESTE: 5 members, 489 ks (XMM+Chandra) THE LARGEST VIRIALIZED STRUCTURES TODAY AND FAIR ARCHIVES OF THE UNIVERSE Coma cluster in the optical Coma cluster in X-rays CLUSTERS IN A NUTSHELL Coma cluster in the opticalComa cluster in X-rays Galaxies (5%) Intra-cluster medium (ICM) Thermal plasma X-rays (10-30%) Dark Matter Gravitational potential 1E THE BULLET CLUSTER Relativistic particles Radio CLUSTERS IN A NUTSHELL RELAXED or COOL CORE Peaked SB and spherical symmetry T drop at the center Low central cooling time (t cool