Program: GS-2009B-Q-34

We propose to obtain GMOS spectroscopy of MIPS 24 um sources located in the field of XMMXCS J2215.9-1738 at z=1.46, the most distant X-ray selected galaxy cluster currently known. The observations will be used to measure redshifts for the sources to confirm cluster membership, and search for signs of AGN activity. With secure redshifts in hand, we will estimate the integrated star formation rate within the cluster from the dusty, star forming members. This will extend previous studies of dusty star formation in clusters significantly in terms of lookback time. In addition, the new observations will improve the reliability of SED based stellar mass estimates for these galaxies from our existing ACS, MOIRCS, and IRAC photometry, by reducing the number of free parameters in the fitting, and therefore allow us to perform the first study of downsizing of star formation within a cluster environment at z~1.5.