Clumpy ultracompact HII regions -- III. Cometary morphologies around stationary stars

Abstract

Cometary ultracompact HII regions have been modelled as the interaction of the hypersonic wind from a moving star with the molecular cloud which surrounds the star. We here show that a similar morphology can ensue even if the star is stationary with respect to the cloud material. We assume that the HII region is within a stellar wind bubble which is strongly mass loaded: the cometary shape results from a gradient in the distribution of mass loading sources. This model circumvents problems associated with the necessarily high spatial velocities of stars in the moving star models.

6 pages with MN LaTeX macros, includes 5 postscript figures. Also available at http://axp2.ast.man.ac.uk:8000/Preprints.html