9921(  1) - 04/04/03 10:18  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9921
                                                       Version: 1
                                                       Check-in Date: 04-Apr-2003
                                                                      10:17:48

1.Proposal Title:
Surveying Interstellar Carbon Monoxide Via Ultraviolet Absorption
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2. Proposal For  3. Cycle
AR               11
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4. Investigators
                                                                                     Contact?
    PI: Steven Federman                   University of Toledo
   CoI: Dr. David Lambert                 University of Texas at Austin                 N
   CoI: Dr. Yaron Sheffer                 University of Toledo                          N

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5. Abstract

We propose a comprehensive survey of CO column densities in diffuse molecular clouds
extracted from archival spectra. The primary dataset involves STIS high resolution
spectra, supplemented by high quality data obtained with GHRS. We will examine the
12C16O/13C16O ratio in 15 to 20 directions and the CO/H2 ratio in over 30 sight
lines, thereby more than doubling the number of clouds with precisely determined
column densities. The survey will provide the basis for the most thorough comparison
between observations and theoretical models of CO photochemistry. Since CO is used
as a diagnostic of the physical conditions in many astronomical environments,
accurate models are essential. The comparison made with our survey will lead to more
accurate models than those available today. Particular attention will be given to
discerning the CO column where self shielding significantly reduces
photodissociation. The trends in the CO/H2 ratio, especially for CO column densities
much greater than those obtained from observations with the Copernicus satellite,
will provide the means for more precise estimates of molecular cloud masses from CO
emission at radio wavelengths in our Galaxy and others. Better cloud masses are
needed in studies describing how star formation has changed over time.
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                                                9921(  1) - 04/04/03 10:18  - [  2]

            Summary Form for Proposal  9921

  Item                         Used in this proposal
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  Proposal Category            AR
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