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Published Online June 1, 2006
Science DOI: 10.1126/science.1128455

Reports

Submitted on April 7, 2006
Accepted on May 22, 2006

The Spiral Structure of the Outer Milky Way in Hydrogen

E. S. Levine 1*, Leo Blitz 1, Carl Heiles 1

1 Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720, USA.

* To whom correspondence should be addressed.
E. S. Levine , E-mail: elevine{at}astron.berkeley.edu.

We produce a detailed map of the perturbed surface density of neutral hydrogen in the outer Milky Way disk demonstrating that the Galaxy is a non-axisymmetric multi-armed spiral. Spiral structure in the southern half of the Galaxy can be traced out to at least 25 kpc, implying a minimum radius for the gas disk. Overdensities in the surface density are coincident with regions of reduced gas thickness. The ratio of the surface density to the local median surface density is relatively constant along an arm. Logarithmic spirals can be fit to the arms with pitch angles of 20° to 25°.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Galactic spiral structure.
C. Francis and E. Anderson (2009)
Proc R Soc A 465, 3425-3446
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Science. ISSN 0036-8075 (print), 1095-9203 (online)