X-ray synchrotron spectral hardenings from Compton and synchrotron losses in extended Chandra jets

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 of gamma approximate to 2 x 10(8)/[Gamma(1 + z)] owing to Klein-Nishina 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 of greater than or similar to8 x 10(16)deltaB(mu)G/[Gamma(2)(1 + z)(3)] where B-muG is the magnetic field in the comoving plasma frame in units of microgauss 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.