A Distant Extended Spiral Arm in the Fourth Quadrant of the Milky Way
Published 2004 May 4 •
© 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A.
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Citation N. M. McClure-Griffiths et al 2004 ApJ 607 L127DOI 10.1086/422031
This article is corrected by 2004 ApJ 611 L145
N. M. McClure-Griffiths
AFFILIATIONS
Australia Telescope National Facility, CSIRO, P.O. Box 76, Epping NSW 1710, Australia
John M. Dickey
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Department of Astronomy, University of Minnesota, 116 Church Street Southeast, Minneapolis, MN 55455
B. M. Gaensler
AFFILIATIONS
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-6, Cambridge, MA 02138
A. J. Green
AFFILIATIONS
School of Physics, Sydney University, NSW 2006, Australia
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Dates
- Received 2003 December 8
- Accepted 2004 April 21
- Published 2004 May 4
Abstract
Using data from the Southern Galactic Plane Survey, we present a possible distant spiral arm in the fourth quadrant of the Milky Way. The very distinct and cohesive feature can be traced for over 70° as the most extreme positive velocity feature in the longitude-velocity diagram. The feature is at a Galactic radius between 18 and 24 kpc and appears to be the last major structure before the end of the H I disk. We compare the feature with a Galactic spiral model and show that it is well reproduced by a spiral arm of pitch angle i ~ 9°. The arm is quite well confined to the Galactic plane, dropping at most 1 kpc below the Galactic equator. Over most of its length, the arm is 1-2 kpc thick.