Spitzer Space Telescope - General Observer Proposal #60095


The IRAC-ORELSE Survey: Galaxy Masses in Large Scale Structures at z=1

Principal Investigator: Roy Gal
           Institution: University of Hawaii 

     Technical Contact: Roy Gal, University of Hawaii 

Co-Investigators: 
Lori Lubin, University of California, Davis                           
Gordon Squires, Spitzer Science Center                                
Dale Kocevski, University of California, Davis                        
Brian Lemaux, University of California, Davis                         
Mark Lacy, Spitzer Science Center                                     
Jason Surace, Spitzer Science Center                                  

Science Category: galaxy clusters and groups(high-z) 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 59.8 

Abstract:
We propose an IRAC mapping campaign of 14 large scale structures at 0.7 < z <
1.3 to obtain stellar mass estimates and photometric redshifts for their
constituent galaxies. As part of the Observations of Redshift Evolution in Large
Scale Environments (ORELSE) Survey, these clusters represent a mix of confirmed
X-ray, optically and radio selected systems. They range from multi-group mergers
to superclusters with multiple clusters and groups, all with existing deep
rizK_s imaging and are the subjects of a Keck-DEIMOS survey that has already
yielded thousands of high-resolution spectra of constituent galaxies. The
wide-area regions around high redshift clusters are are dynamic environments
where galaxies are undergoing many transformative events, including mergers,
tidal encounters, harassment and ram pressure stripping. By targeting known
structures at an active period in their history, we can efficiently examine the
physical processes responsible for the quenching and/or ignition of star
formation and AGN activity, and the transformation of disk (spiral) galaxies to
spheroids (ellipticals) over the last ~9 Gyr as a function of both environment
and galaxy stellar mass. In comparison, field surveys such as COSMOS encounter
only one such structure, while our targeted approach is an efficient means of
generating a statistically significant sample. The IRAC data is essential to
accurately determine photometric redshifts and estimate stellar masses for the
full galaxy population in each structure.