X-ray Synchrotron Spectral Hardenings from Compton and Synchrotron Losses in Extended Chandra Jets

Abstract

Chandra observations of knots and hot spots in spatially resolved X-ray jets of radio galaxies show that the X-ray fluxes often lie above an extrapolation from the radio-to-optical continuum fluxes. We show that combined synchrotron and Compton losses on a single power-law electron injection function can produce a hardening in the electron spectrum at electron Lorentz factors \gamma \~ 2e8/[\Gamma(1+z)] due to KN energy losses on the cosmic microwave background radiation. Here \Gamma is the bulk Lorentz factor of the outflow, and z is the source redshift. This produces a flattening in the spectrum at frequencies >~ 8e16 \delta B_{\mu G}/[\Gamma^2(1+z)^3] Hz, where B_{\mu G} is the magnetic field in the comoving plasma frame in units of micro-Gauss and \delta is the Doppler factor. A single population of synchrotron-emitting electrons may therefore produce the radio-to-X-ray continuum in some radio galaxy knots, such as those in 3C 273.