The BeppoSAX High Energy Large Area Survey (HELLAS) -- VI. The radio properties

Abstract

We present results of a complete radio follow-up obtained with the VLA and ATCA radio telescopes down to a 6 cm flux limit of about 0.3 mJy of all the 147 X-ray sources detected in the BeppoSAX HELLAS survey. We found 53 X-ray/radio likely associations, corresponding to about one third of the X-ray sample. Using the two point spectral index alpha_ro=0.35 we divided all the HELLAS X-ray sources in radio quiet and radio loud. We have 26 sources classified as radio-loud objects, corresponding to about 18% of the HELLAS sample. In agreement with previous results, the identified radio-loud sources are associated mainly with Type 1 AGNs with L(5-10 keV) > 10^44 erg/s, while all the identified Type 2 AGNs and Emission Line Galaxies are radio quiet objects with L(5-10 keV) < 10^44 erg/s. The analysis of the radio spectral index suggests that Type 1 AGNs have a mean radio spectral index flatter than Type 2 AGNs and Emission Line Galaxies.