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R. Mushotzky (NASA/GSFC), A. Hicks (University of Colorado)
An enduring enigma in X-ray astronomy is the "missing mass" in cooling flow clusters of galaxies. Though the X-ray temperature often drops by a factor of three within the central 100 kpc, there is seldom an indication of enough mass at temperatures cooler than ~2 keV to uphold mass deposition rates predicted by the cooling flow model. One possible depository for recently cooled gas is in recent star formation.
Here we present recent results from an investigation of star formation rates in cooling flow clusters of galaxies utilizeing archival XMM-Newton Optical Monitor UV data and J band IR flux information from the 2MASS survey. To establish what constitutes excess star formation, we first calibrate the relationship between these two wavebands in passively evolving cluster galaxies. We then apply the technique to cD galaxies in the cores of clusters, focusing primarily on cooling flow clusters. A high UV/IR ratio is a strong indication of the existence of hot young stars and thus a direct indication of copious recent star formation. Our initial results demonstrate a clear UV excess in many, but not all, cooling flow cDs. This finding is largely consistent with the outcome of earlier studies. An expansion of the study toward higher redshift is also discussed, including preliminary results at moderate redshifts (z~0.25).
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.