An optical/NIR survey of globular clusters in early-type galaxies. I. Introduction and data reduction procedures
Larsen, S. S.; Kuntschner, H.; Chies-Santos, A. L.; Strader, J.; Brodie, J. P.; Wehner, E. M.
Netherlands, Canada, Germany, United States
Abstract
Context. The combination of optical and near-infrared (NIR) colours has the potential to break the age/metallicity degeneracy and offers a better metallicity sensitivity than optical colours alone. Previous tudies of extragalactic globular clusters (GCs) with this colour combination, however, have suffered from small samples or have been restricted to a few galaxies.
Aims: We compile a homogeneous and representative sample of GC systems with multi-band photometry to be used in subsequent papers where ages and metallicity distributions will be studied.
Methods: We acquired deep K-band images of 14 bright nearby early-type galaxies. The images were obtained with the LIRIS near-infrared spectrograph and imager at the William Herschel Telescope (WHT) and combined with optical ACS g and z images from the Hubble Space Telescope public archive.
Results: For the first time we present homogeneous GC photometry in this wavelength regime for a large sample of galaxies, 14. We achieved a limiting magnitude of K ~ 20-21. For the majority of the galaxies we detect about 70 GCs each. NGC 4486 and NGC 4649, the cluster-richest galaxies in the sample contain 301 and 167 GCs, respectively. We present tables containing coordinates, photometry and sizes of the GCs.