Spitzer Space Telescope - General Observer Proposal #20427


Accurate Far-Infrared Spectral Energy Distributions of
60-Micron-Selected Ultraluminous Infrared Galaxies at Redshifts from
0.2 to 1

Principal Investigator: Charles Dowell
           Institution: Jet Propulsion Laboratory

Co-Investigators: 
Colin Borys, California Institute of Technology                       
Thomas Greve, California Institute of Technology                      
Min Yang, California Institute of Technology                          

Science Category: ULIRGS/LIRGS/HLIRGS 
 Observing Modes: MipsPhot 
  Hours Approved: 5.1 

Abstract:
We propose MIPS 160  micron observations of Ultraluminous Infrared
Galaxies (ULIRGs) at redshifts z = 0.2 to 1 selected from the Stanford
et al.  IRAS FSC/FIRST sample.  The upper end of the galaxy luminosity
function during the period z = 1 to the present day has been studied
little, yet this is the redshift interval during which the number of
ULIRGs changed by the greatest amount.  Our approach is to compile and
characterize the complete mid- and far-infrared spectral energy
distributions of 21 ULIRGs from which we can derive luminosities and
mean dust temperatures to 10% uncertainty and examine dust temperature
distributions.  The key new information regarding these sources will
be MIPS 160  micron photometry (under this GO proposal) accurately
defining the spectral peak and IRS spectra (under an independent GTO
program) characterizing the warm dust and gas;  these data will be
combined with existing IRAS 60  and 100  micron photometry and a
ground-based 350  micron survey which has already detected half of the
sources.  We will be able to separate the emission from AGN,
starburst, and cirrus components and to study evolutionary trends and
correlations between the mid-IR and far-IR spectra.