Marsfield Lecture Theatre

Marcello Giroletti

Marcello Giroletti colloquium: The radio/gamma-ray connection in Active Galactic Nuclei in the Fermi era

The Fermi Large Area Telescope has revolutionized our knowledge of the gamma-ray sky. I present a detailed statistical analysis of the correlation between radio and gamma-ray emission of the active galactic nuclei (AGNs) detected by Fermi during its first year of operation, with the largest data sets ever used for this purpose. We use both archival interferometric 8.4 GHz data (from the Very Large Array and ATCA, for the full sample of 599 sources) and concurrent single-dish 15 GHz measurements from the Owens Valley Radio Observatory (OVRO, for a sub sample of 199 objects). These unprecedentedly large samples provide a highly significant statistical analysis of the correlation, using a surrogate data method. The large sample size allows us also to study the dependence of correlation strength and significance on specific source types and gamma-ray energy band. Finally, I will present some future prospects based on the use of more high energy data and of new radio surveys, also with the aim of reducing the fraction of unassociated gamma-ray sources.