The Large Scale Jets of Powerful Quasars: Not as Fast, Not as Powerful, but Efficient Particle Accelerators

Thirteen years ago Chandra discovered that the large scale jets of powerful quasars are copious X-ray emitters. The X-rays could be Inverse Compton scattering off CMB photons, provided that the jets remained highly relativistic (Lorentz factors 10-20) and carrying kinetic power comparable to the Eddington luminosity. Alternatively the X-ray could be synchrotron emission, relaxing the power and Lorentz factor requirements, but requiring leptons to be accelerated up to 100 TeV or more. This issue remains open today. In 2006, Georganopoulos et al. proposed a Gamma-ray diagnostic to distinguish between these two radically different cases. Here, we present the Fermi application of this diagnostic to the archetypical source 3C 273. A fast and powerful jet, and therefore an IC interpretation for the X-rays, is strongly disfavored by the data.