An Interpretation of the Galactic Continuum Radiation using a New Model of Galactic Spiral Structure

Abstract

A new composite map of galactic spiral structure has been obtained by combining the model of Georgelin, based on observations of H II regions, with the map of neutral hydrogen outside the solar circle of Verschuur. Using models which relate the galactic magnetic field and relativistic electron distribution to this structure, profiles of the synchrotron radio emission along the galactic plane are predicted for $${30}^{\circ}\lt{l}^{11}\lt{330}^{\circ}$$. These are compared with the observed profiles at 150 MHz and 408 MHz corrected for thermal emission, local sources and extragalactic background. There is good agreement with regard to the general features. Detailed comparison gives some preference for a uniform distribution of electrons in the parts of the galaxy contributing to the profile. There is evidence that the observed magnitude of the galactic magnetic field in the neighbourhood of the Sun is more typical of an interarm than an arm region. A field which, in the Galaxy as a whole, can be decomposed into random and regular components of approximately equal magnitude, is indicated.