Spitzer Space Telescope - Legacy General Observer Proposal #30323


A Spitzer Spectroscopic Survey of a Complete Sample of Luminous
Infrared Galaxies in the Local Universe

Principal Investigator: Lee Armus
           Institution: IPAC

Co-Investigators: 
Phil Appleton, SSC                                                    
Ben Chan, IPAC                                                        
Vassilis Charmandaris, University of Crete                            
Aaron Evans, Stony Broook                                             
David Frayer, SSC                                                     
Justin Howell, IPAC                                                   
Lisa Kewley, University of Hawaii                                     
Steve Lord, IPAC                                                      
Jason Marshall, Cornell University                                    
Joseph Mazzarella, IPAC                                               
David Sanders, University of Hawaii                                   
Shobita Satyapal, George Mason University                             
Henrik Spoon, Cornell University                                      
Eckhard Sturm, MPE                                                    
Jason Surace, SSC                                                     
Sylvain Veilleux, University of Maryland                              

Science Category: ULIRGS/LIRGS/HLIRGS 
 Observing Modes: IrsStare 
  Hours Approved: 160.0 

Abstract:
The IRAS Revised Bright Galaxy Sample (RBGS) is a complete sample of
extragalactic objects with IRAS 60-micron flux densities above 5.24
Jy, covering the full sky above abs(b) > 5 degrees.  The RBGS objects
are the brightest 60-micron sources in the extragalactic sky.  The 21
ULIRGs and 182 LIRGs in the RBGS form a complete sample of 203
infrared luminous, local galaxies which are excellent analogs for
comparisons with infrared and sub-mm selected galaxies at high
redshift.  We propose to obtain IRS low and high-resolution spectra of
158 LIRGs in the RBGS which, when taken to gether with the existing or
planned GO and GTO observations of the remaining LIRGs and ULIRGs in
the RBGS, will provide an unprecedented spectroscopic database of a
complete sample of luminous infrared galaxies in the local Universe.
The total requested time for this program, including all overheads, is
160  hrs.  The primary goals of this proposal are to use the low and
high-resolution IRS spectra to (1) search for buried AGN and determine
their contribution to the bolometric luminosity, (2) determine the
star-formation rates and ages, (3) characterize the state of the
ionized and molecular gas, and (4) study the properties of the small
and large dust grains and determine if all of these properties are a
function of luminosity and/or merger stage.  By observing a large
sample of LIRGs with the IRS, we can build a unique spectral library
that will be invaluable long after the helium on Spitzer runs out.
This library will be an essential tool for understanding the galactic
merger process, and the genesis of the bulk of the infrared activity
at all epochs.  The IRS spectra will stand on their own merits,
however, when coupled with the IRAC and MIPS images, the ground-based
near-infrared data, and the HST ACS and GALEX images, the spectra we
request here will form a critical component of a comprehensive,
multi-wavelength dataset that will serve as a lasting resource in the
true spirit of the Spitzer Legacy program.