Fermi Gamma-ray Space Telescope

Fermi gamma-ray detection of the radiogalaxy 3C120 and its connection with the VLBI jet

Carolina Casadio

Abstract:

The radiogalaxy 3C120, as other misaligned AGN in the Fermi catalog, is characterized by a low gamma-ray flux, but two clear detection have been registered from Fermi LAT at the end of 2008 and 2012. In order to study the behavior of the source during these two high states of gamma-ray flux we collected VLBA 15 GHz data from the MOJAVE program from June 2008 to August 2013, and VLBA 43 GHz data from the VLBA-BU-BLAZAR program covering the period of the second gamma-ray detection, from January 2012 to February 2014. No clear correlation between the first gamma-ray detection and the VLBI core at 15 GHz has been found, but one of the jet components is observed to progressively increase its flux density until it outshines the core flux by a factor of more than two in mid 2009. The second gamma-ray detection instead is associated with an increase in the flux density of the radio core at 43 and 15 GHz, accompanied by the ejection of a new component in the 43 GHz VLBA images. This would correspond to the first association of gamma-ray emission and the ejection of a new radio component from the core in a low power misaligned AGN, resembling the case of the FRII radiogalaxy 3C111.