|   | 
				
					
	
		  | 
	 
	
		| Paper: | 
		Radio and Optical Properties of the Faint Radio Population | 
	 
	
		| Volume: | 
		373, The Central Engine of Active Galactic Nuclei | 
	 
	
		| Page: | 
		738 | 
	 
	
		| Authors: | 
		Gregorini, L.; Prandoni, I.; Mignano, A.; Parma, P.; de Ruiter, H.R.; Wieringa, M.H.; Vettolani, G.; Ekers, R.D. | 
	 
	
	
		| Abstract: | 
		We 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. | 
	 
	
		| 
			
			
		 | 
	 
	
		  | 
	 
 
					 
				 | 
				  |