Extending the infrared radio correlation

Co-addition of deep (rms similar to 30 mu Jy) 20-cm data obtained with the Australia Telescope Compact Array at the location of Spitzer Wide Field Survey (SWIRE) sources has yielded statistics of radio source counterparts to faint 24-mu m sources in stacked images with rms < 1 mu Jy. We confirm that the infrared-radio correlation extends to f(24 mu m) = 100 mu Jy but with a significantly lower coefficient, f(20 cm) = 0.039f(24 mu m) [q(24) = log (f(24 mu m)/f(20 cm)) = 1.39 +/- 0.02] than hitherto reported. We postulate that this may be due to a change in the mean q(24) value ratio for objects with f(24 mu m) < 1 mJy.