Stellar populations in NGC 5128 with the VLT: Evidence for recent star formation^*

¹ European Southern Observatory, Karl-Schwartzschild-Strasse 2, 85748 Garching, Germany e-mail: dsilva@eso.org
² Department of Astronomy, P. Universidad Católica, Casilla 306, Santiago 22, Chile e-mail: dante@astro.puc.cl
³ School of Physics, University of Sydney 2006, Australia e-mail: bedding@physics.usyd.edu.au

Corresponding author: M. Rejkuba, mrejkuba@eso.org

Received: 31 May 2001
Accepted: 13 September 2001

Abstract

We resolve stars of the nearest giant elliptical galaxy NGC 5128 using VLT with FORS1 and ISAAC. We construct deep U, V and K_s color-magnitude and color-color diagrams in two different halo fields (in the halo and in the north-eastern diffuse shell). In the outer, shell field, at ~14 kpc from the center of the galaxy, there is a significant recent star formation with stars as young as 10 Myr, approximately aligned with the prominent radio and X-ray jet from the nucleus of the host AGN. Ionized gas filaments are evident in ultraviolet images near the area where neutral Hi and CO molecular gas was previously observed. The underlying stellar population of the halo of the giant elliptical is predominantly old with a very broad metallicity distribution. The presence of an extended giant branch reaching mag suggests the existence of a significant intermediate-age AGB population in the halo of this galaxy.