Journal Article

Cometary and bipolar ultracompact H <span class="smallCaps">ii</span> regions

M. P. Redman, R. J. R. Williams and J. E. Dyson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 298, issue 1, pages 33-41
Published in print July 1998 | ISSN: 0035-8711
Published online July 1998 | e-ISSN: 1365-2966 | DOI:
Cometary and bipolar ultracompact H ii regions

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Mass-loaded models can explain how a cometary morphology, ultracompact HII region can arise around a stationary star. The star is located in a density gradient in the mass-loading sources. Continuous mass-loss from the clumps embedded in the ionized gas allows the region to remain compact. The wind and radiation field from the central star set up a fully supersonic flow that is bounded by a recombination front. We develop the models further by calculating the velocity and density structure in detail for a variety of viewing angles, mass-loading laws and density scaleheights. The results are compared with observational work, and the agreements and differences are highlighted.

We extend this model to show how a massive star located in a dense molecular ridge can give rise to a bipolar or ring morphology, depending on the viewing angle.

Keywords: hydrodynamics; shock waves; stars: mass-loss; Hii regions; ISM: structure.

Journal Article.  0 words. 

Subjects: Astronomy and Astrophysics

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