X-Ray Synchrotron Spectral Hardenings from Compton and Synchrotron Losses in Extended [ITAL]Chandra[/ITAL] 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 γ ≈ 2 × 10 8 /[Γ(1 + z )] owing to Klein-Nishina energy losses on the cosmic microwave background radiation. Here Γ is the bulk Lorentz factor of the outflow and z is the source redshift. This produces a flattening in the spectrum at frequencies of ≳8 × 10 16 δ B μG /[Γ 2 (1 + z ) 3 ] Hz, where B μG is the magnetic field in the comoving plasma frame in units of microgauss and δ 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.