Electron temperatures in the galactic HII regions Orion A and Orion B from radio continuum observations at 0.33 and 10.7 GHz

Abstract

We have made arcminute resolution maps of Orion A and Orion B at 0.33 GHz where the central parts of both nebulae are highly opaque and at 10.7 GHz where they are fully transparent. The 0.33 GHz maps yield direct estimates of electron temperature towards the peaks of these nebulae, whereas the 10.7 GHz maps are used to estimate ‘best-fit isothermal temperatures’ using an improved version of the approach followed in the past. Based on radio continuum data alone, these two types of estimates provide evidence for a decrease in the electron temperature away from the core region, at least for Orion A.