The radio spectral index of sub-mJy sources and physical processes associated

Mignano A., Prandoni I., et al.

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We used the ATCA to follow-up at 5GHz a 1 sq. deg. region previously covered by the sub-mJy ATESP 1.4 GHz survey. In the same area, extensive UBVRIJK deep optical imaging is available. The 1.4 and 5 GHz information allowed us to study the radio spectral properties. We found a significant flattening of the spectral indeces going to fainter fluxes. We used the optical information available to assess the nature of the ATESP sources and the physical processes responsible for such a flattening.