We report the discovery of two new large H I shells in the direction of the Coalsack Nebula. Both shells were observed with the Parkes Radio Telescope as part of the Southern Galactic Plane Survey. The largest shell, GSH 304-00-12, is at a distance of ̃ 1.2 kpc and has derived physical dimensions of 280 x 200 pc. The second shell, GSH 305+01-24, is at a distance of ̃2.2 kpc and has derived dimensions of 280 x 440 pc. We present a simple numerical model to show that GSH 305+01-24 most likely formed from stellar winds in the Centaurus OBI stellar association. There is associated radio, infrared, and Ha continuum emission. Both shells are situated in the Sagittarius-Carina arm, with GSH 305+01-24 more distant. The far edge of GSH 304-00-12 is at the near side of the arm and opens into the interarm region. We find no evidence of closure at the near side of the shell and therefore describe the geometry as conical. Emission from the near side of the shell may be lost in absorption by the Coalsack Nebula. © 2001. The American Astronomical Society. All rights reserved.

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:	46591
Year Published:	2001
Web of Science® Times Cited:	23
Deposited By:	Physics
Deposited On:	2007-08-28
Last Modified:	2011-08-03
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