Astronomy and Astrophysics, volume 529A, 16-16 (2011/5-1)
γ-rays in flat-spectrum AGN: revisiting the fast jet hypothesis with the CJF sample.
KAROUZOS M., BRITZEN S., WITZEL A., ZENSUS J.A. and ECKART A.
Abstract (from CDS):
The recent release of the First Fermi-LAT Source Catalog solidified the predominant association of extragalactic γ-ray emitters to active galaxies, in particular blazars. A tight connection between AGN jet kinematics and γ-ray properties has been argued for, attributing the energetic emission from active galaxies to their highly relativistic outflows. We investigate the Caltech-Jodrell Bank flat-spectrum (CJF) sample to study the connection between AGN jet kinematics and their γ-ray properties. The high number of sources included in the sample, in addition to the excellent kinematic data available, allows us to investigate the origin of γ-ray emission in AGN. We identify the CJF sources detected in γ-rays (by Fermi-LAT and EGRET). We use γ-ray luminosities and the available VLBI kinematic data to look for correlations between γ-ray and kinematic properties, as well as for differences between AGN classes (quasars, BL Lacs, radio galaxies). We also check the kinematics of the TeV sources in the CJF. 21.8% of the CJF has been detected in the γ-ray regime. We find the detectability of BL Lacs significantly higher compared to quasars. Sources detected in the γ-rays show a wider apparent jet velocity distribution compared to the non-detected ones, but the maxima of both distributions are at similar values. No strong link between γ-ray detectability and fast apparent jet speeds is found. A tentative correlation is found between γ-ray luminosity and maximum apparent jet speeds, stronger for BL Lac and γ-variable sources. We find non-radial jet motions to be important to γ-ray emission. We suggest two-zone, spine-sheath models as a possible explanation for our results. Two out of four CJF TeV sources show superluminal jet speeds, in contrast to previous studies.