your ID: 0069 
First Name: Loretta 
Last Name: Gregorini 
Affiliation: Dept. of Physics - University of Bologna 
Title: Radio and optical properties of the faint radio population 
Authors: Gregorini L., Prandoni I. et al. 
Topic: 1 
Session: oral 
Abstract: A sub-region previously covered by the sub-mJy ATESP 1.4 GHz (Prandoni et al. 2000a, b) 
was observed with the ATCA at 5 GHz. In the same region deep optical imaging in 
UBVRI (I(AB)~ 26) was available. 
The data may help to constrain the origin of the radio emission in such faint radio sources 
and may be fundamental in understanding eventual links to the optical light. 
Preliminary results of the analysis of these data are: 
a) The 5 GHz counts do not show evidence of flattening down to the survey limit. 
b) A flattening of the spectral index with decreasing flux densities was found. 
At mJy level we have mostly steep-spectrum synchrotron radio sources, while 
at sub-mJy flux densities we have a composite population, with ~ 60% of the 
5 GHz sources showing flat spectra and a significant fraction (~ 30% at 5 GHz) 
of inverted-spectrum sources. 
c) Optical properties of the identified radio sources (i.e.photometric redshifts, galaxy classification etc.) 
were obtained.