Radio continuum emission from HII regions in the Magellanic Clouds

Abstract

A considerable proportion of the radio emission at high frequencies from the Galaxy is of thermal origin. This thermal radiation appears to originate both in very extended regions and in discrete sources. It has always been difficult to compare the radio and optical data for these HII regions as galactic optical observations are hampered by heavy obscuration. However, the HII regions in the Magellanic Clouds are relatively free from obscuration, and spectrophotometry by Dickel, Aller, and Faulkner (this volume, paper 63) and Henize (1956) have provided very good measurements of Hβ and Hα flux densities and the relative intensities of the OII, OIII lines. Also the distance to the Clouds is fairly well known (about 55 kpc) so that the linear dimensions of the HII regions may be estimated with some degree of accuracy in contrast to the galactic emission nebulae.