Letter to the Editor

The early evolution of tidal dwarf galaxies

¹ Institute of Astronomy, Vienna University, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: [recchi;theis;hensler]@astro.univie.ac.at
² INAF - Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy e-mail: recchi@oats.inaf.it
³ Argelander Institute for Astronomy, Bonn University, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: pavel@astro.uni-bonn.de

Received: 9 February 2007
Accepted: 29 May 2007

Abstract

Context.Dwarf galaxies can arise from self-gravitating structures emerging from tidal tails. What fraction of the known dwarf galaxies in the Local Universe can have this origin is still a matter of debate.

Aims.In our effort to understand the origin and evolution of tidal dwarf galaxies and their correspondence with local objects, the first step is to understand how these galaxies (which are supposed to have a limited amount of dark matter) react to the feedback of the ongoing star formation.

Methods.We make use of 2-D chemodynamical calculations in order to study the early evolution of isolated, dark matter-free dwarf galaxies. We present models in which feedback parameters are varied. We also compare the results with dark matter-dominated dwarf galaxy models.

Results.All the considered models show that the star formation proceeds for more than 300 Myr, therefore dwarf galaxies without large dark matter halos are not necessarily quickly destroyed. The chemical evolution of these objects is consistent with the main chemical properties of the dSphs of the Local Group. Models with large dark matter halos show results consistent with models free of dark matter, indicating that the distribution of gas is more important than the depth of the potential well in determining the global behaviour of dSph-sized dwarf galaxies.