Extending the infrared radio correlation

Abstract

Co-addition of deep (rms ∼ 30 μJy) 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-μm sources in stacked images with rms < 1 μJy. We confirm that the infrared–radio correlation extends to f_(24 μm) = 100 μJy but with a significantly lower coefficient, f_(20 cm) = 0.039f_(24 μm) [q_(24) = log (f_(24 μm)/f20 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 μm) < 1 mJy.