Spitzer Space Telescope - Guaranteed Time Observer Proposal #50333


The Highest Redshift Galaxy Cluster

Principal Investigator: Giovanni Fazio
           Institution: Harvard-Smithsonian Astrophysical Observatory

     Technical Contact: Peter Eisenhardt, JPL

Co-Investigators: 
Adam Stanford, UC-Davis/LLNL                                          
Daniel Stern, JPL                                                     

Science Category: galaxy clusters and groups(high-z) 
 Observing Modes: IracMap MipsPhot 
  Hours Approved: 1.6 

Abstract:
We propose to obtain IRAC four band and MIPS 24 micron imaging of XCS 2215-1738,
the highest redshift galaxy cluster currently known, with z = 1.46. Optical
spectroscopy at Keck and the VLT has identified 21 galaxies as having concurrent
redshifts at z=1.46 and a velocity dispersion of 680 km/s. The approximate X-ray
temperature, based on XMM archival data, is kT = 6.5 +/- 2.1 keV, also
indicating that 2215-1738 is a massive cluster. The proposed IRAC data will
reach to a depth of 2 magnitudes below L*. The MIPS data will detect starburst
galaxies with IR luminosities above 3E11 Lsun. We will use the new data, in
conjunction with existing optical and near-IR photometry, to estimate the
stellar masses of the cluster galaxies, and to test for the presence of any
dusty, star-forming cluster members.