'Missing Link' Clouds in the Southern Galactic Plane Survey
journal contribution
posted on 2023-05-16, 17:00 authored by Kavars, DW, John DickeyJohn Dickey, McClure-Griffiths, NM, Gaensler, BM, Green, AJWe present an automated routine to search for H I self-absorption features within the Southern Galactic Plane Survey (SGPS). The data were taken with the Australia Telescope Compact Array (ATCA) and the Parkes Radio Telescope and encompass 3°×105° of sky in the Galactic plane. We apply our routine to this entire region and derive spin temperatures and column densities for 70 of the larger HISA complexes, finding spin temperatures ranging from 6 to 41 K with H I number densities of a few cm -3. These "missing link" clouds fill in the spin temperature and density gaps between dense molecular clouds and diffuse atomic clouds. We compare the H I emission with 12CO emission and find that ∼60% of detected H I self-absorption is correlated in space and in velocity with a molecular counterpart. This is potentially due to a molecular/atomic gas transition. We also compare H I self-absorption with Galactic spiral arms and discuss the possibility of using it as a spiral arm tracer. © 2005. The American Astronomical Society. All rights reserved.
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Publication title
The Astrophysical JournalVolume
626Pagination
887-899ISSN
0004-637XDepartment/School
School of Natural SciencesPublisher
University of Chicago PressPlace of publication
Chicago, USARepository Status
- Restricted
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