Morphological evolution of dwarf galaxies in the Local Group

Department of Astronomy, University of Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: chiosi@pd.astro.it; carraro@pd.astro.it

Corresponding author: S. Pasetto, pasetto@pd.astro.it

Received: 2 April 2002
Accepted: 16 April 2003

Abstract

The dwarf galaxies of the Local Group can be separated in three morphological groups: irregular, elliptical and spheroidal. As in the large galaxy clusters, there seems to be a morphology-position relationship: irregular galaxies are preferentially found in the outskirts (low density regions) of the Local Group, whereas dwarf ellipticals and spheroidals are more frequent in the central, high density regions. To cast light on the nature and origin of dwarf galaxies in the Local Group, Mayer et al. (2001a) have suggested that a dwarf irregular galaxy tidally interacting with a galaxy of much larger mass may be re-shaped into a dwarf spheroidal or elliptical object. In this paper we check by means of N-body Tree-SPH simulations whether this is possible for a selected sample of galaxies of the Local Group. Using the best data available in literature to fix the dynamical and kinematical status of a few dwarf galaxies in the Local Group, we follow the evolution of an ideal satellite, which supposedly started as an irregular object during its orbital motion around the Milky Way. We find that the tidal interactions with the Milky Way remove a large fraction of the mass of the dwarf irregular and gradually reshape it into a spherical object.