Radio and optical properties of faint radio population

none8We used the Australia Telescope Compact Array (ATCA) to follow-up at 5 GHz part of the region previously covered by the sub-mJy ATESP 1.4 GHz survey. We imaged a one-square degree area where extensive UBVRIJKs deep imaging is available through the multicolor ESO Deep Public Survey. The 1.4 and 5 GHz information allowed us to study the radio spectral properties of the ATESP radio sources. We found a significant flattening of the 1.4-5 GHz spectral indices going to fainter flux. Such a flattening is consistent with a flattening for the 5 GHz source counts occuring at fluxes ≤ 0.5 mJy. We then used the optical information available to assess the nature of the ATESP sub-mJy sources and the physical processes responsible for such a flattening. Preliminary results indicate that flat/inverted sources are more probably triggered by nuclear activity than by star formation.noneGregorini L.; Prandoni I.; Mignano A.; Parma P.; de Ruiter H.R.; Wieringa M.H.; Vettolani G.; Ekers R.D.Gregorini L.; Prandoni I.; Mignano A.; Parma P.; de Ruiter H.R.; Wieringa M.H.; Vettolani G.; Ekers R.D