A dust scattered halo in starburst galaxy M82?
The source of the halo about M82 has been under discussion for several years. One explanation for it is the dust model of Solinger, Morrison and Markert in which they propose a diffuse cloud of dust through the M81 group, with M82 traveling through the group holding a denser cloud of dust around it. The feasibility of the dust theory is examined in the X-ray range, using the halo in the X-ray image of M82 taken by the Einstein Observatory. To this end the X-ray cross section for dust is presented, along with the single scattered image of an X-ray source surrounded by a dust cloud; multiply scattered images were simulated with a Monte Carlo program; profiles of the halo along the major and minor axes of M82 are presented. Also presented is an accounting for line spectrographs of M82 that show unusual splitting, using the dust model. The final model proposed for the X-ray image requires dust of radius 50 to 300 A, with density on the order of 10 to the -7th power cu cm, out to a distance of about 9 kpc for some regions.