Deviations from the FIR-radio correlation at large FIR luminosities

We have investigated the radio properties of FIR-luminous galaxies with the VLA (at 1.4, 5, and some at 15.4 GHz), the Cambridge 5-km telescope (at 5 GHz) and the Cambridge Low-Frequency Synthesis Telescope (CLFST at 151 MHz). The existence of a very strong correlation between FIR and radio luminosities has been noted by a large number of authors and is known to extend from dwarf systems to starburst galaxies. However, for some of our sample we find large deviations from the FIR-radio correlation in the sense that these galaxies lie towards the FIR-bright/radio-faint region of the diagram, particularly at 151 MHz. The spectrum of Arp 220 has an unusual low-frequency turnover which we model successfully as a thermally absorbed synchrotron source.