AAS 203rd Meeting, January 2004
Session 111 Interstellar Medium II
Poster, Thursday, January 8, 2004, 9:20am-4:00pm, Grand Hall

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[111.06] Chlorine in the Galactic Interstellar Medium with FUSE

P. Sonnentrucker (JHU), D. G. York, D. E. Welty (Chicago Univ.), S. D. Friedman (STScI)

Due to its unique chemistry, chlorine plays an important role in characterizing the neutral gas components in the interstellar medium (ISM). Cl II is the dominant form of chlorine when hydrogen is mostly in the form of H I. Cl I, on the other hand, is the dominant form of chlorine in cold neutral components once H2 is optically thick. The detection of both species therefore allows us to disentangle the molecular gas components from the cold neutral atomic gas along often complicated sight lines. This ability to identify molecular clumps in complex sight lines bears tremendous importance in searching for translucent clumps where H is expected to be nearly all molecular. Accurate determination of the Cl II and Cl I column densities are, however, required to identify those translucent clumps. While Cl II is only detectable in the FUSE bandpass, Cl I can be observed by FUSE and HST/STIS. Since only 4 out 53 FUV Cl I lines have experimentally determined f-values, we obtained FUSE Cycle 4 time to empirically determine the f-values of, at least, 4 additional Cl I lines occurring in the FUSE range. We present our preliminary estimates of the f-values for these four Cl I lines and discuss the impact of our measurements on the search for translucent clouds and the structure of the Galactic ISM. P.S. acknowledges support from NASA contract NAS5-32985 to JHU.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.