Herschel-ATLAS: The far-infrared--radio correlation at z<0.5
  We use data from the Herschel-ATLAS to investigate the evolution of the
far-infrared--radio correlation over the redshift range 0<z<0.5. Using the
total far-infrared luminosity of all >5sigma sources in the Herschel-ATLAS
Science Demonstration Field and cross-matching these data with radio data from
the Faint Images of the Radio Sky at Twenty-Centimetres (FIRST) survey and the
NRAO VLA Northern Sky Survey (NVSS), we obtain 104 radio counterparts to the
Herschel sources. With these data we find no evidence for evolution in the
far-infrared--radio correlation over the redshift range 0<z<0.5, where the
median value for the ratio between far-infrared and radio luminosity, $q_{\rm
IR}$, over this range is $q_{\rm IR} = 2.40\pm 0.12$ (and a mean of $q_{\rm
IR}=2.52 \pm 0.03$ accounting for the lower limits), consistent with both the
local value determined from {\em IRAS} and values derived from surveys
targeting the high-redshift Universe. By comparing the radio fluxes of our
sample measured from both FIRST and NVSS we show that previous results
suggesting an increase in the value of $q_{\rm IR}$ from high to low redshift
may be the result of resolving out extended emission of the low-redshift
sources with relatively high-resolution interferometric data, although AGN
contamination could still play a significant role.
  We also find tentative evidence that the longer wavelength, cooler dust is
heated by an evolved stellar population which does not trace the star-formation
rate as closely as the shorter wavelength $\ltsim 250~\mu$m emission or the
radio emission, supporting suggestions based on detailed models of individual
galaxies.
