Globular Clusters in NGC 5128: The IMACS survey

To extend our recent study of structural parameters of Globular Clusters (GCs) in the giant elliptical NGC 5128 (Gómez et al. 2006), we have obtained new high resolution images with the Magellan 6.5m telescope at Las Campanas Observatory and the IMACS camera. Our images cover an area of ∼1.2x1.2 square degrees and have a seeing between 0.4" and 0.7", thus making it possible to resolve a significant fraction of the GC population, which is now virtually entirely observed given the large spatial and magnitude range. Convolution techniques allow us to find and to study the cluster candidates using the stellar PSF and analytical profiles for their light distribution. We therefore are able to derive structural parameters like size (effective and core radii), ellipticity, position angle and concentration. This is combined with the extensive database in the Washington photometric system by Harris et al. (2004) to select clusters according to shape, extendedness and Washington magnitudes and colours, which has proven very useful in discriminating GCs from foreground stars and background galaxies and for deriving metallicities. This is a progress report and we present here a brief summary of the observations and techniques. First results are compared with our previous study and other cluster systems.