paper

H-Alpha Velocity Fields of H II Regions in Nearby Dwarf Irregular Galaxies

arXiv:astro-ph/9712326 · doi:10.1086/300412

Abstract

We present H-alpha velocity fields of thirteen giant H II regions in four nearby dwarf irregular galaxies, NGC 2366, Holmberg II, IC 2574, and WLM. We classify the velocity features as well as the morphologies of the H II regions. The H-alpha velocity features are divided into three categories; three H II regions show chaotic feature with a typical scale of variation of a few 100 pc in size and a few 10 km s^{-1} in velocity, one shows expanding-bubble feature, and the remaining nine have calm velocity fields. There is a correlation between the H-alpha velocity feature and the morphology of H II regions. We measured bulk motion of the H II regions relative to the ambient H I velocity for the H II regions with calm velocity fields and found a typical velocity difference of about 5 km s^{-1}. We discuss a model for origin of star-forming regions based on the presence of the velocity difference between H-alpha and H I gas as well as the H I characteristics.

arXiv commentLaTeX manuscript (use aasms4.sty) + 7 tables (use aj_pt4.sty) + a compilation of PS figures, and two style files (aasms4, aj_pt4). To be appeared in The Astronomical Journal, 1998 July issue. Accepted version of former submission

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