An evolution of the infrared-radio correlation at very low flux densities?

Abstract

In this paper, we investigate the radio-mid-infrared (MIR) correlation at very low flux densities using extremely deep 1.4-GHz subarcsec angular resolution Multi-Element Radio-Linked Interferometer + Very Large Array observations of a field centred upon the Hubble Deep Field-North, in conjunction with Spitzer 24-μm data. From these results, the MIR-radio correlation is extended to the very faint (∼μJy) radio source population. Tentatively, we detect a small deviation from the correlation at the faintest infrared flux densities. We suggest that this small observed change in the gradient of the correlation is the result of a suppression of the MIR emission in faint star-forming galaxies. This deviation potentially has significant implications for using either the MIR or non-thermal radio emission as a star formation tracer of very low luminosity galaxies. © 2008 RAS.