The Southern Cluster Survey is an ongoing project to obtain grizH band imaging of all XMM archival pointings that lie within the SPT survey region (roughly south of -30 degrees DEC and between 21hrs and 7hrs RA). There are approximately 200 suitable archival pointings available in this region as of 2007.
The SCS is a collaboration led by Joe Mohr and is related to an effort led by MPE scientist Hans Boehringer and his team to use XMM pointings over the entire sky to select a sample of galaxy clusters at z>1. That project, called the XMM Distant Cluster Project, involves the X-ray analysis of the XMM archival pointings to select targets for optical imaging and spectroscopic followup. The X-ray analysis has been led by Rene Fassbender of MPE.
In the process of selecting high z cluster candidates, Rene naturally finds clusters over the full range of redshift. While not interesting for the XDCP project, these clusters are all important for study in combination with the SPT mm-wave survey and in their own right. Therefore, the SCS collaboration began the systematic imaging of all XMM fields using the MOSAIC camera on the Blanco 4m for griz band imaging and the ISPI NIR camera for H band imaging of selected high z candidates.
We spent 12 nights at the telescope in Fall 2006, but the scheduling was very early in the season, and we were only able to complete 25 fields. We have another 12 nights in Fall 2007, and if the weather is good we should be able to complete coverage of an additional 50 to 80 fields. This Blanco 4m times comes from direct competition on the NOAO TAC and from guaranteed U Illinois time that continues through Fall 2008.
An analysis of the 25 fields from Fall 2006 allows us to probe for optical counterparts in about 100 X-ray selected clusters. We find that approximately 90% of these X-ray selected systems have clear optical counterparts and a larger fraction have either optical or optical+H band counterparts. This is a direct indication that the Fassbender X-ray selection technique is working well.
As the project progresses we will provide updates here as well as submitting publications that describe our comparisons of cluster selection in the X-ray and optical.
