Radio and gamma-ray emission in faint BL lacs.

Abstract

The advent of Fermi is changing our understanding on the radio and γ-ray emission in Active Galactic Nuclei. In fact, contrary to previous campaigns, Fermi mission reveals that BL Lac objects are the most abundant emitters in γ-ray band. However, since they are relatively weak sources, most of their parsec scale structure as their multifrequency properties are poorly understood and/or not systematically investigated. Our main goal is to analyse, using a multiwavelength approch, the nuclear properties of an homogeneous sample of 42 faint BL Lacs, selected, for the first time in literature, with no contraint on their radio and γ-ray flux densities/emission. We began asking and obtaining new VLBA observations at 8 and 15 GHz for the whole sample. We derived fundamental parameters as radio flux densities, spectral index information, and parsec scale structure. Moreover, we investigated their γ-ray emission properties using the 2LAT Fermi results. Here, we report our preliminary results on the radio and gamma-ray properties of this sample of faint BL Lacs. In the next future, we will complete the multiwavelength analysis.