Thermo-dynamic and chemical properties of the intra-cluster medium

¹ Università degli Studi di Milano, Dip. di Fisica, via Celoria 16, 20133 Milano, Italy e-mail: silvano@iasf-milano.inaf.it
² INAF-IASF Milano, via Bassini 15, 20133 Milano, Italy

Received: 8 August 2009
Accepted: 22 October 2009

Abstract

Aims. We aim to provide constraints on evolutionary scenarios in clusters. One of our main goals is to understand whether, as claimed by some, the cool core/non-cool core division is established once and for all during the early history of a cluster.

Methods. We employ a sample of 60 objects to classify clusters according to different properties. We characterize cluster cores in terms of their thermo-dynamic and chemical properties and clusters as a whole in terms of their dynamical properties.

Results. We find that I) the vast majority of merging systems feature high-entropy cores (HEC) and II) objects with lower entropy cores feature more pronounced metallicity peaks than objects with higher entropy cores. We identify a small number of medium (MEC) and high (HEC) entropy core systems that, unlike most other such objects, feature a high central metallicity. The majority of these outliers are mergers, i.e. systems far from their equilibrium configuration.

Conclusions. We surmise that medium (MEC) and high (HEC) entropy core systems with a high central metallicity have recently evolved from low-entropy core (LEC) clusters that have experienced a heating event associated to AGN or merger activity.