Thursday

Insight into the Far-infrared Radio Correlation with LOFAR

The FIRC is a tight empirical relation between radio and far-infrared luminosities for star-forming galaxies. This linear relation appears to be consistent, with little scatter, over a large range of infrared colours, radio luminosities, redshifts, and galaxy types. Though we understand the existence of a star-forming FIRC arises from the influence of massive stars upon dust heating and cosmic ray acceleration, we do not expect such tight linearity. Indeed, from simulations (e.g. Lacki et al. 2010) we know that a conspiracy of many finely-tuned physical processes are required to maintain a flat ratio between the radio and far-infrared luminosities across a wide dynamical range of environments.
The FIRC is frequently used as a means of calibrating radio star-formation rate, based on the assumption of linearly. Given that the SKA and its pathfinders will routinely probe populations without infrared or optical detections, we need a more trustworthy star-formation rate indicator based in the radio.
Using the new 150MHz LOFAR/H-ATLAS catalogue, we probe the FIRC over WISE mid-infrared colours and find that the FIRC varies smoothly over normal star-forming galaxies at low frequency. In addition, we find evidence for evolution of the FIRC over low redshifts at low frequency while finding no such evidence for the FIRC at high frequency.
With this additional evidence for a variable FIRC, we set the stage for work on new calibrations for star-formation rates in the radio.