Spitzer Space Telescope - Directors Discretionary Time Proposal #279


IRS Verification of Candidate z>8 Sources

Principal Investigator: Mark Lacy
           Institution: Spitzer Science Center

Co-Investigators: 
Richard Ellis, Caltech                                                
Daniel Stark, Caltech                                                 
Johan Richard, Caltech                                                
Harry Teplitz, SSC                                                    

Science Category: Cosmology 
 Observing Modes: IrsMap 
  Hours Approved: 47.2 

Abstract:
The reionization of neutral hydrogen which rendered the Universe
transparent to UV photons and terminated the `dark ages' was a
landmark event in cosmic history.  Determining the nature and redshift
distribution of the sources responsible represents the current
frontier in studies of the first galactic systems.  We request 47.2
hours with IRS to verify the redshifts of two candidate Ly-alpha
emitters located from a comprehensive survey for lensed sources in the
redshift range 8<z<10.  Spectroscopic confirmation of only 1-2 objects
would suggest that low luminosity star-forming sources provide a
significant contribution to the UV flux necessary for cosmic
reionization.