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Multiwavelength Studies of Dust Associated With Galactic HII Regions

Charles Robert Kerton

Doctor of Philosophy 1999
Graduate Department of Astronomy, University of Toronto

The first part of this thesis describes the construction of a high resolution (~1 arcminute) atlas of mid-infrared emission along part of the Galactic plane using Infrared Astronomical Satellite (IRAS) data processed using the HIRES algorithm. This emission generally arises from the smallest dust components in the interstellar medium (ISM) and is bright near HII regions due to the enhanced radiation field. The atlas (MIGA: Mid-Infrared Galaxy Atlas) has been combined with radio and far-infrared data as part of the Canadian Galactic Plane Survey.

The remainder of the thesis presents the results of multiwavelength studies using MIGA. An accurate study of dust associated with HII regions requires a careful study of all of the components of an HII region and the surrounding ISM. A comparative study of the mid-infrared and radio continuum morphology of HII regions is presented. Understanding of this morphology is critical for the calculation of infrared fluxes and for the accurate association of infrared emission with a given HII region.

Infrared ratio maps are a useful tool to study the properties of interstellar dust, but the construction of these maps is a non-trivial task with HIRES data. A new technique to construct these maps has been developed and is evaluated.

For many HII regions of small angular extent the only available measurements are the global infrared luminosity and radio flux. An investigation was made of how much information about the structure of the HII region can be obtained from an analysis of these quantities. Accurate knowledge of the stellar content of an HII region is vital for the quantitative study of dust around HII regions. A new O-star spectral classification line ratio for heavily reddened OB stars has been developed.

The HII region KR 140 is the subject of a multiwavelength study. KR 140 appears to be a region of spontaneous massive star formation. Submillimetre observations reveal complementary information about the dust, molecular cores, and possible protostars.

Finally, infrared colour variations within molecular material surrounding the W5 HII region are investigated and ideas for further projects are presented.

Reproduced with permission by Marlene Cummins
November 29 1999