THE RELATION BETWEEN AGN GAMMA-RAY EMISSION AND PARSEC-SCALE RADIO JETS

We have compared the radio emission from a sample of parsec-scale active galactic nucleus (AGN) jets as measured by the VLBA at 15 GHz, with their associated. gamma-ray properties that are reported in the Fermi Large Area Telescope (LAT) three month bright source list. We find in our radio-selected sample that the. gamma-ray photon flux correlates well with the quasi-simultaneously measured compact radio flux density. The LAT-detected jets in our radio-selected complete sample generally have higher compact radio flux densities, and their parsec-scale cores are brighter (i.e., have higher brightness temperature) than the jets in the LAT nondetected objects. This suggests that the jets of bright. gamma-ray AGN have preferentially higher Doppler-boosting factors. In addition, AGN jets tend to be found in a more active radio state within several months from LAT-detection of their strong. gamma-ray emission. This result becomes more pronounced for confirmed. gamma-ray flaring sources. We identify the parsec-scale radio core as a likely location for both the. gamma-ray and radio flares, which appear within typical timescales of up to a few months of each other.