Spitzer Space Telescope - General Observer Proposal #60180


Deep IRAC Imaging of 24-micron Only Sources: Constraining the SEDs

Principal Investigator: Jason Surace
           Institution: Spitzer Science Center

     Technical Contact: Jason Surace, Spitzer Science Center

Co-Investigators: 
David Shupe, Herschel Science Center                                  
Mari Polletta, INAF-IASF                                              
Jessica Krick, Spitzer Science Center                                 

Science Category: high-z galaxies (z>0.5) 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 16.8 

Abstract:
We request 17 hours for deep 3.6 micron IRAC observations of three extraordinary
objects that are very bright at 24 microns, but are undetected at all other
Spitzer, optical, or near-infrared wavelengths. Found in the widest of the
extragalactic areal surveys (SWIRE; 45 square degrees) these are the only such
objects found by Spitzer. Followup infrared spectroscopy centered on the
24-micron band indicates that at least two of the objects are extragalactic in
nature and lie near a redshift of 2.5. However, the photometric non-detections
are not compatible with the spectral energy distribution (SED) of any known
class of objects. The new Spitzer data will lower the detection limits by an
order of magnitude relative to the existing data, providing much stronger limits
on the rest-frame near-IR luminosity.