A possible GeV-radio correlation for starburst galaxies

For star-forming regions, there is a correlation of radio and FIR-emission established. The radio emission is caused by synchrotron radiation of electrons, while the FIR emission is attributed to HII regions of OB stars and hot dust powered by those stars. Another possible correlation for star-forming regions might exist between the aforementioned radio emission and the gamma ray emission in the GeV regime. The GeV gamma ray emission of star-forming regions is dominated by the decay of neutral pions formed in collisions of cosmic ray (CR) protons accelerated at supernova remnants (SNRs) with ambient hydrogen, while the electrons generating the synchrotron emission are assumed to be accelerated at the same SNRs. Assuming the same spectral shape for the CR proton and electron distribution and a fixed ratio of CR protons to electrons, the proton- and electron-calorimetry of the star-forming regions can be tested. Furthermore, this provides a method to derive the magnetic field strength in the star-forming region complementary to the existing methods.