The Universality Of The Far-infrared Radio Correlation
Shaun Read
Hertfordshire University
Daniel Smith (Herts)
The Universality Of The Far-infrared Radio Correlation

Accurate star formation rates are essential to understanding the evolutionary history of galaxies. Far-infrared measurements allow SFRs to be extracted from the emission from dust heated by the obscured young stars. Radio frequency observations are also used as a highly indirect probe of star formation, relying on poorly-understood cosmic ray physics. Indeed, one of the main motivations for using such an indirect method is the curiously tight correlation with far-infrared luminosities. Previous studies suggest that it holds over at least five orders of magnitude independent of redshift, environment, and galaxy type. In fact, it is thought that rather than IR and radio both tracking SFR well, IR and radio independently fail to probe star formation, with a conspiracy of factors producing the observed linear relation.

Using new 150MHz measurements from LOFAR accompanied by 250um data from Herschel, and spectroscopic information from SDSS, we have found evidence for a statistically significant gradient in the FIRC across the colour magnitude diagram and WISE diagnostic colour spaces. This supports the idea that the FIRC cannot be universal and that much thought is needed to exploit the extreme radio continuum sensitivity of the SKA (and its pathfinders) to probe star formation in galaxies.