Harassment origin for kinematic substructures in dwarf elliptical galaxies?

Instituto de Astrofísica de Canarias, via Láctea s/n, 38200 La Laguna, Spain e-mail: [cglez;jalfonso;balcells]@iac.es

Received: 11 January 2005
Accepted: 25 August 2005

Abstract

We have run high resolution N-body models simulating the encounter of a dwarf galaxy with a bright elliptical galaxy. The dwarf absorbs orbital angular momentum and shows counter-rotating features in the external regions of the galaxy. To explain the core-envelope kinematic decoupling observed in some dwarf galaxies in high-density environments requires nearly head-on collisions and very little dark matter bound to the dwarf. These kinematic structures appear under rather restrictive conditions. As a consequence, in a cluster like Virgo ~1% of dwarf galaxies may present counter-rotation formed by harassment.