Spitzer Space Telescope - General Observer Proposal #60034


The IRAC Lensing Survey: Achieving JWST depth with Spitzer

Principal Investigator: Eiichi Egami
           Institution: University of Arizona

     Technical Contact: Eiichi Egami, University of Arizona

Co-Investigators: 
Richard Ellis, Caltech                                                
Giovanni Fazio, CfA                                                   
Jiasheng Huang, CfA                                                   
Linghua Jiang, University of Arizona                                  
Jean-Paul Kneib, Laboratoire d'Astrophysique de Marseille             
Roser Pello, Observatoire Midi-Pyrenees                               
Johan Richard, University of Durham                                   
George Rieke, University of Arizona                                   
Daniel Schaerer, Observatoire de Geneve                               
Graham Smith, University of Birmingham                                
Daniel Stark, University of Cambridge                                 
Mike Werner, JPL                                                      

Science Category: high-z galaxies (z>0.5) 
 Observing Modes: IracPostCryoMap 
  Hours Approved: 526.4 

Abstract:
Massive clusters of galaxies are now recognized as very effective "cosmic
telescopes". Because of the gravitational lensing effect, they can amplify
significantly the background sources - by factors of a few tens - thereby
bringing into view faint sources that would otherwise be unobservable. Note that
in the background-limited case, which is applicable to IRAC observations, a
factor of 20-30 gravitational amplification translates into increasing the
integration time by a factor of 400-900. Because of this tremendous gain in
sensitivity, IRAC imaging of lensing clusters will allow us to achieve JWST
depth (~10 nJy) with Spitzer. Despite this great possibility, however, the full
potential of the lensing cluster technique has not yet been realized due to the
small number of clusters that have well-constrained accurate mass models. Here,
we propose to conduct an IRAC imaging survey of 47 massive lensing clusters (5
hours/band, 2 bands) for which we have constructed accurate mass models through
many years of intensive imaging/spectroscopic campaigns with HST, Keck, and VLT
telescopes. This is the first time when such a large, statistical sample of
clusters will be systematically employed to probe high-redshift Universe, and
this proposed IRAC survey is a key component of our comprehensive program, which
includes HST/WFC3 and Herschel observations starting next year. Scientifically,
we will use the obtained IRAC data to (1) characterize z>6 galaxies (expecting
~50 z~7-8 galaxy detections), (2) support future Herschel and ALMA surveys, and
(3) search for z>6 supernovae. The resultant data set will be a great legacy of
Spitzer, allowing us to start tackling JWST sciences well before its launch.