Radio continuum observations of starburst galaxies

We present radio continuum observations with the VLA at 3.6 and 6 cm and with MERLIN at 18 cm of a sample of mildly active galaxies, including the archetypal starburst galaxies NGC 1808 and 253, both of which have a large number of compact radio components. These observations were made to estimate the spectral indices and brightness temperatures of these features, which could help to clarify the nature of the radio emission. The spectral indices of all the prominent compact components in NGC 1808, and of the five outside the central plateau of emission in NGC 253, are consistent with them being supernova remnants. We discuss some of the properties of these compact radio components and the possible supernova rate in their parent galaxies. We also report the results of our search for compact radio components in the remaining sources of our sample.