Synchrotron versus Compton Interpretations for Extended X‐Ray Jets

Abstract

A widely discussed explanation for the origin of the X-ray emission observed from knots in extended quasar jets with the Chandra X-Ray Observatory is Compton-scattered cosmic microwave background radiation by electrons with Lorentz factors γ'~102. This model faces difficulties in terms of total energy requirements and in explaining the spatial profiles of the radio, optical, and X-ray knots in sources such as PKS 0637-752, 3C 273, or PKS 1127-145. These difficulties can be resolved in the framework of one- and two-component synchrotron models. We propose a model in which the broadband radio-to-X-ray synchrotron emission in quasar jets is powered by collimated beams of ultrahigh energy neutrons and γ-rays formed in the subparsec-scale jets. The decay of the neutral beam in the intergalactic medium drives relativistic shocks to accelerate nonthermal electrons of the ambient medium. A second synchrotron component arises from the injection of leptons with Lorentz factors >>107 that appear in the extended jet in the process of decay of ultrahigh energy γ-rays. This approach could account for qualitative differences in the extended X-ray jets of Fanaroff-Riley (FR) 1 and 2 galaxies. Detection of high-energy neutrinos from blazars and core-dominated quasars will provide strong evidence for this model.