Star formation rates in cooling flow clusters:: A UV pilot study with archival XMM-Newton optical monitor data

We have analyzed XMM-Newton Optical Monitor UV (180 - 400 nm) data for a sample of 33 galaxies. Thirty are cluster member galaxies, and nine are central cluster galaxies (CCGs) in cooling flow clusters having mass deposition rates between 8 and 525 M-circle dot yr(-1). By comparing the ratio of UV to 2MASS J-band fluxes, we find a significant UV excess in many, but not all, cooling flow CCGs, consistent with several previous studies based on optical imaging data (McNamara & O'Connell; Cardiel et al.; Crawford et al.). This UV excess is a direct indication of the presence of young massive stars and, therefore, recent star formation. Using the Starburst99 model of continuous star formation over a 900 Myr period, we derive star formation rates of 0.2-219 M-circle dot yr(-1) for the cooling flow sample. For two-thirds of this sample, it is possible to equate Chandra/XMM cooling flow mass deposition rates with UV-inferred star formation rates, for a combination of starburst lifetime and IMF slope. This is a pilot study of the well-populated XMM UV cluster archive, and a more extensive follow-up study is currently underway.