2013/07/31 by Eileen T. Meyer, Markos Georganopoulos
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Compton scattering #Electron #Extrapolation #Fermi Gamma-ray Space Telescope #Flux (metallurgy) #Gamma-ray bursts and supernovae #Jet (fluid) #Lorentz factor #Particle acceleration #Photon #Relativity and Gravitational Theory #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1088/2041-8205/780/2/l27
6 pages, 4 figures, 1 table, accepted for publication in ApJ Letters. Revised manuscript essentially unchanged from original submission
arxiv created 2013/11/28 · openalex publication_date 2013/12/17 · arxiv updated 2015/06/16 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The X-ray emission mechanism in large-scale jets of powerful radio quasars has been a source of debate in recent years, with two competing interpretations: either the X-rays are of synchrotron origin, arising from a different electron energy distribution than that producing the radio to optical synchrotron component, or they are due to inverse Compton scattering of cosmic microwave background photons (IC/CMB) by relativistic electrons in a powerful relativistic jet with bulk Lorentz factor Γ ∼ 10–20. These two models imply radically different conditions in the large-scale jet in terms of jet speed, kinetic power, and maximum energy of the particle acceleration mechanism, with important implications for the impact of the jet on the large-scale environment. A large part of the X-ray origin debate has centered on the well-studied source 3C 273. Here we present new observations from Fermi which put an upper limit on the gamma-ray flux from the large-scale jet of 3C 273 that violates at a confidence greater that 99.9% the flux expected from the IC/CMB X-ray model found by extrapolation of the UV to X-ray spectrum of knot A, thus ruling out the IC/CMB interpretation entirely for this source when combined with previous work. Further, this upper limit from Fermi puts a limit on the Doppler beaming factor of at least δ < 9, assuming equipartition fields, and possibly as low as δ < 5, assuming no major deceleration of the jet from knots A through D1.