HII regions at 76.2MHz synchrotron emissivities

We develop a new method of emissivity calculation by taking advantage of the Haslam et al. (1981A&A...100..209H) map and known spectral indices, which enable us to simultaneously derive the emissivity and the optical depth of HII regions at each frequency.

We show our derived synchrotron emissivities based on 152 absorption features of HII regions using both the method previously adopted in the literature and our improved method. We derive the synchrotron emissivity from HII regions to the Galactic edge along the line of sight and, for the first time, derive the emissivity from HII regions to the Sun. These results provide direct information on the distribution of the Galactic magnetic field and cosmic ray electrons for future modelling.