Continuum Radio Emission and Galactic Structure

Abstract

Recent studies of high latitude brightness have shown that in several regions a significant proportion of it is due to loop features. The largest of these are now thought to be local (within a few hundred parsecs) and perhaps to be due to supernova events.Aperture synthesis maps of 45 external spiral galaxies have shown large-scale continuum nonthermal features in the disks of some and, in general, an absence of spherical halos around the galaxies. This supports the view that the radio emission from our Galaxy can best be described as coming from a thick disk. Any large-scale spherical component could not have a volume emissivity greater than 1.5% of the average volume emissivity of the disk at meter wavelengths.A comparison of the disk radiation with new disk models suggests that the galactic plane radiation has two components: a base disk and a spiral component. Each of these contributes ~50% of the total power output of the disk at 150 MHz.