Spitzer Space Telescope - General Observer Proposal #50126


IRS spectroscopy of a complete, unbiased sample of submm galaxies

Principal Investigator: Chris Carilli
           Institution: National Radio Astronomy Observatory (NRAO)

     Technical Contact: Chris Carilli, National Radio Astronomy Observatory (NRAO)

Co-Investigators: 
Kartik Sheth, Spitzer Science Center                                  
Frank Bertoldi, Bonn University                                       
Eva Schinnerer, Max-Planck Institute for Astronomy                    
Dave Sanders, University of Hawaii                                    
Nick Scoville, Caltech                                                
Herve Aussel, CNRS, Saclay                                            
Manuel Aravena, Bonn University                                       
James Aguirre, University of Colorado                                 

Science Category: high-z galaxies (z>0.5) 
 Observing Modes: IrsStare 
  Hours Approved: 51.5 

Abstract:
We propose 51.5 hours of IRS spectroscopy of a complete, luminosity limited
sample of 12 submm galaxies detected at high significance at 250 GHz (> 5sigma)
in the Cosmos field. These observations will address two fundamental questions
concerning the submm galaxies: (i) do starbursts dominate the energetics of
these systems, and if so, how do the physical conditions compare to lower z,
lower luminosity starbursts?, and (ii) is there a substantial (up to 30%) high
redshift tail (z > 3.6) of hyper-luminous IR galaxies? Such a high redshift tail
provides key leverage into models of massive galaxy formation in the early
universe. A major legacy of Spitzer has been the demonstration that accurate
redshifts for distant, luminous, dust-obscured star forming galaxies can be
derived from the PAH features, in addition to the important physical diagnostics
on dust heating and composition that come from such spectra. Observing the high
S/N, unbiased Cosmos/MAMBO sample will complete this legacy, and test the theory
that submm galaxies represent the formation of large elliptical galaxies in
massive, dusty starbursts in dense environments at high redshift.