Spitzer Space Telescope - General Observer Proposal #3630


Very Deep IRAC imaging of MS1054-03:  the nature of high redshift,
near IR selected galaxies

Principal Investigator: Marijn Franx
           Institution: Leiden Observatory

Co-Investigators: 
Pieter van Dokkum, Yale University                                    
Natascha Forster Schreiber, MPE- Garching                             
Ivo Labbe, Leiden Observatory                                         
Greg Rudnick, MPA Garching                                            
Hans-Walter Rix, MPIA Heidelberg                                      
Paul van der Werf, Leiden Observatory                                 
Garth Illingworth, UC Santa Cruz                                      
Alan Moorwood, ESO                                                    
Jiasheng Huang, Harvard Smithsonian Center for Astrophysics           
Mariska Kriek, Leiden Observatory                                     
Stijn Wuyts, Leiden Observatory                                       

Science Category: high-z galaxies (z>0.5) 
 Observing Modes: IracMap 
  Hours Approved: 7.2 

Abstract:
We have obtained deep very Js, H, Ks imaging with the VLT on several
fields with excellent optical imaging, in order to study high redshift
galaxies.  Using these Near-IR images, we identified a class of
galaxies with Js - Ks color larger than 2.3.  Photometric redshifts
and spectroscopic follow-up showed that their mean redshift is 2.5 +-
0.7.  These galaxies are complementary to Lyman break selected
galaxies:  the overlap is minimal, and the rest-frame optical colors
of the J-K selected galaxies are much redder.  Their contribution to
the stellar mass density is comparable to that of Lyman breaks in our
fields.  We propose to obtain images of these galaxies with IRAF on
Spitzer from 3.6 to 8 micron, covering our field around the cluster
MS1054--03.  This field is unique as it has the largest number of
spectroscopically confirmed Js - Ks selected objects, and has several
galaxies with rest frame optical spectroscopy.  The Spitzer images
will allow much improved photometric redshifts, SED modeling and mass
estimates of these "red" galaxies, providing unique insight into their
star formation history and evolutionary status.  The deep Spitzer
imaging will be one of the essential pieces to understand the link
between these galaxies and "normal" Lyman break galaxies, and to
obtain a comprehensive view of galaxy formation.