Collisionless evaporation from cluster elliptical galaxies

A contributor to the intracluster stellar population

¹ Observatoire de Genève, chemin des Maillettes 51, 1290 Sauverny, Suisse
² Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: luca.ciotti@unibo.it

Corresponding author: V. Muccione, veruska.muccione@obs.unige.ch

Received: 22 December 2003
Accepted: 3 April 2004

Abstract

By means of simple numerical models we discuss whether collisionless stellar evaporation from cluster elliptical galaxies could be an effective mechanism for the production of intracluster stellar populations. The effectiveness of this mechanism is due to the fact that, for realistic galaxy and cluster models, the galaxy oscillation periods near equilibrium configurations in the cluster tidal field are of the same order of stellar orbital times in the external parts of the galaxies themselves. With the aid of Monte-Carlo simulations we explore the evolution of stellar orbits in oscillating galaxies placed near different equilibrium positions. We found that, over an Hubble time, the main effect is a substantial expansion of the galactic outskirts, particularly affecting the galaxy at the cluster center and those orbiting near the cluster core radius: overall, approximately the 10% of the galaxy mass is affected. Thus, the proposed mechanism could be of some importance in the shaping of the halo of cD galaxies and in making easier “galaxy harassment” in the formation of the intracluster stellar population.