A new sample of faint blazars

The available blazar samples were selected at relatively high limiting flux densities in the radio and X-ray band. Those samples have small sizes (30-50 objects) making it difficult to statistically derive parameters related to beaming effects. Moreover, the estimate of those parameters is based on bright and intrinsically luminous sources. A deeper, larger sample of blazars has been constructed by Perlman et al. (1998) and by Landt et al. (2001): the ``Deep X-ray Radio Blazar Survey". The DXRBS sample is currently the faintest (down to ~ 50 mJy at 5 GHz and power ~ 10^(24) W/Hz and largest blazar sample with nearly complete optical identifications. We have built a complete sample of 103 DXRBS sources selecting those with declination > -20 deg. It is expect that the objects in the DXRBS will be the counterparts of gamma-ray sources detected by the Fermi gamma-ray Observatory.

After 1 year of Fermi observations, nearly 10% of the DXRBS sources in our sample have already been detected. In this presentation we will report on:

• the structure of the sources observed so far with the European VLBI Network at 6cm;
• the results from Effelsberg 100-m telescope simultaneous multi-frequency observations (at 11cm, 6cm, 3.6cm, 2.8cm) to obtain properly measured spectral index, polarisation properties, and check for flux density variability.