9534(  1) - 12/06/01 12:43  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9534
                                                       Version: 1
                                                       Check-in Date: 06-Dec-2001
                                                                      11:47:14

1.Proposal Title:
Interstellar Thermal Pressures from C I Fine-structure Excitation
------------------------------------------------------------------------------------
2. Proposal For  3. Cycle
AR               11
------------------------------------------------------------------------------------
4. Investigators
                                                                                     Contact?
    PI: Edward Jenkins                    Princeton University Observatory
   CoI: Dr. Todd Tripp                    Princeton University Observatory              N

------------------------------------------------------------------------------------
5. Abstract

We propose to analyze absorption features of interstellar C I in the STIS E140H
spectra of about 60 early-type stars in the disk of the Galaxy, using chiefly the
archival data produced by the Cycle 8 SNAP program of Lauroesch (to study ISM
abundances). Our objective will be to expand on what we have recently learned about
the distribution of interstellar thermal pressures from a survey of the relative
populations of C I in excited fine-structure states toward 21 stars (Jenkins & Tripp
2001). We plan to invoke a very efficient, special analysis technique developed in
the earlier study to unravel the blended features in different multiplets, a method
that allows us to bypass time-consuming, iterative profile fitting procedures. Most
of the earlier targets were confined to the CVZ, which limited the coverage of
Galactic longitudes. The new archival survey will give more even coverage of the sky
(and quadruple the number of sight lines), and it will allow us to investigate a
broader range of circumstances for interesting phenomena we uncovered earlier, such
as the link of pressure enhancements to the gas kinematics and the discovery of
ubiquitous, small fractions of gas at extreme pressures (our interpretation is that
they are probably produced by collisions of turbulent flows).
------------------------------------------------------------------------------------
                                                9534(  1) - 12/06/01 12:43  - [  2]

            Summary Form for Proposal  9534

  Item                         Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
  Proposal Category            AR
------------------------------------------------------------------------------------------------------------------------------------