Stellar clusters in dwarf galaxies

¹ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile e-mail: lvanzi@eso.org
² CEA/DSM/DAPNIA/Service d'Astrophysique – UMR AIM, CE Saclay, 91191 Gif-sur-Yvette Cedex, France e-mail: msauvage@cea.fr

Received: 28 February 2005
Accepted: 13 October 2005

Abstract

We present new observations in the K_s (2.2 μm) and L' (3.7 μm) infrared bands of a sample of blue dwarf galaxies with the larger aim of studying the population of massive stellar clusters, the occurrence of dust-embedded stellar clusters, and their properties. All K_s images show a rich population of clusters, but only a small fraction of them is bright in L'. Most L' sources have radio counterparts. We derived the luminosity function in K_s for the galaxies IC 4661 and NGC 5408, finding both to be consistent with those of similar galaxies. We also compared the number of clusters and their luminosities with the star-formation rate of the host galaxies and found no compelling evidence of correlation. We conclude that young clusters and embedded clusters are a common feature of blue dwarf galaxies and possibly of galaxies in general, we suggest that their occurrence is due to purely statistical effects rather than a phenomenon related to specific physical conditions. In this sense we expect these objects to be abundant at high red-shift.