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A Neutral Hydrogen Self-absorption Cloud in the Southern Galactic Plane Survey


Kavars, DW and Dickey, JM and McClure-Griffiths, NM and Gaensler, BM and Green, AJ, A Neutral Hydrogen Self-absorption Cloud in the Southern Galactic Plane Survey, The Astrophysical Journal, 598, (2) pp. 1048-1060. ISSN 0004-637X (2003) [Refereed Article]

DOI: doi:10.1086/379114


Using data from the Southern Galactic Plane Survey (SGPS) we analyze an H I self-absorption cloud centered on l = 318.°0, b = -0.°5 with velocity v = -1.1 km s-1. The cloud was observed with the Australia Telescope Compact Array (ATCA) and the Parkes Radio Telescope and is at a near-kinematic distance of ≲ 400 pc, with derived dimensions of ≲ 5 × 11 pc. We apply two different methods to find the optical depth and spin temperature. In both methods we find upper limit spin temperatures ranging from 20 to 25 K and lower limit optical depths of ∼1. We look into the nature of the H I emission and find that 60%-70% originates behind the cloud. We analyze a second cloud at the same velocity, centered on l = 319°, b = 0.°4, with an upper limit spin temperature of 20 K and a lower limit optical depth of 1.6. The similarities in spin temperature, optical depth, velocity, and spatial location are evidence that the clouds are associated, possibly as one large cloud consisting of smaller clumps of gas. We compare H I emission data with 12CO emission and find a physical association of the H I self-absorption cloud with molecular gas.

Item Details

Item Type:Refereed Article
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Dickey, JM (Professor John Dickey)
ID Code:46589
Year Published:2003
Web of Science® Times Cited:25
Deposited By:Physics
Deposited On:2007-08-28
Last Modified:2011-11-29

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