Spitzer Space Telescope - General Observer Proposal #3605


Molecular Gas in IR-Bright Galaxies:  Masses and Physical Conditions

Principal Investigator: Charles Bradford
           Institution: Jet Propulsion Laboratory, California Institute of

Co-Investigators: 
Colin Borys, California Institute of Technology                       
John-David Smith, Steward Observatory, University of Arizona          
Thomas Phillips, California Institute of Technology                   

Science Category: nearby galaxies (z<0.05, v_sys<15,000 km/s) 
 Observing Modes: IrsStare 
  Hours Approved: 15.7 

Abstract:
We propose a program of mid-infrared and submillimeter spectroscopy of
molecular gas probes in a sample of 24 IR-bright galaxies.  We will
combine Spitzer observations of the pure rotational transitions of
molecular hydrogen with observations of optically-thin CO isotopes
only possible with sensitive receivers at the Caltech Submillimeter
Observatory (CSO).  The two measurements are complementary, and the
combination with existing datasets will allow estimates of total
molecular gas mass and the run of temperature with mass in its warm
components.  The results will test theories of gas heating and cooling
and star formation in massive dusty galaxies, and guide extrapolations
to the more distant ULIGs and the high-redshift submillimeter galaxy
popluation.  Our sample is carefully selected from the much larger
Submillimeter Local Galaxy Sample (SLUGS), and benefits from ongoing
spectral and continuum observations which will benefit our analysis.