On the globular cluster formation history of NGC 5128

¹ Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK e-mail: skaviraj@astro.ox.ac.uk
² Department of Physics, Institute of Astronomy, ETH Hoenggerberg HPF D8, 8093 Zurich, Switzerland
³ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK

Received: 20 May 2004
Accepted: 13 January 2005

Abstract

We deduce the globular cluster formation history of the nearby elliptical galaxy, NGC 5128, by using a chemical enrichment model to accurately reproduce its observed metallicity distribution function (MDF). We derive the observed MDF using recently obtained U and B photometry of the NGC 5128 GC system, with used as the metallicity indicator. Our results indicate that the GC system in this galaxy could be the product of two major GC formation episodes. The initial formation episode occured 11–12 Gyr ago creating 65–75 percent of the mass in the GC system. This was followed by a second late formation episode which peaked 2–4 Gyr ago and produced the remaining 25–35 percent of GC mass.