Journal Article

Spatial distribution of Galactic H<span class="smallCaps">ii</span> regions

R. Paladini, R. D. Davies and G. DeZotti

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 347, issue 1, pages 237-245
Published in print January 2004 | ISSN: 0035-8711
Published online January 2004 | e-ISSN: 1365-2966 | DOI:
Spatial distribution of Galactic Hii regions

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We present a new, detailed, analysis of the spatial distribution of Galactic H ii regions, exploiting a far richer data base than used in previous analyses. Galactocentric distances have been derived for 550 objects. Distances from the Sun could be unambiguously derived from velocity data for 117 of them, lying either outside the solar circle (84) or on a line of sight tangential to their orbit (33). For 177 further sources, distance estimates are made possible by the use of auxiliary data. A highly significant correlation between luminosity and linear diameter was found and the corresponding least-squares linear relationship in the log–log plane was used to resolve the distance ambiguity for an additional 256 sources. Within the solar circle the thickness of the distribution of H ii regions around the Galactic plane was found to be comparable to that of OB stars. At larger galactocentric radii the shape of the distribution reflects that of the warp, and its thickness along the z axis increases with increasing distance from the Galactic centre. We also confirm, for a much larger sample, the previously reported positive gradient of electron temperature with galactocentric distance.

Keywords: Hii regions; Galaxy: structure; radio continuum: ISM

Journal Article.  4665 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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