CHANDRA OBSERVATIONS OF THE RADIO GALAXY 3C 445 AND THE HOT SPOT X-RAY EMISSION MECHANISM

We present new Chandra observations of the radio galaxy 3C 445, centered on its southern radio hot spot. Our observations detect X-ray emission displaced upstream and to the west of the radio-optical hot spot. Attempting to reproduce both the observed spectral energy distribution and the displacement excludes all one-zone models. Modeling of the radio-optical hot spot spectrum suggests that the electron distribution has a low-energy cutoff or break approximately at the proton rest mass energy. The X-rays could be due to external Compton scattering of the cosmic microwave background coming from the fast (Lorentz factor Γ ∼ 4) part of a decelerating flow, but this requires a small angle between the jet velocity and the observer's line of sight (θ ∼ 140). Alternatively, the X-ray emission can be synchrotron from a separate population of electrons. This last interpretation does not require the X-ray emission to be beamed.