2000ApJ...544L..23T

We propose that the X-ray emission detected by Chandra from the 100 kpc-scale jet of PKS 0637-752 is produced through inverse Compton scattering of the cosmic microwave background (CMB). We analyze the physical state of the jet and show that inverse Compton scattering from the CMB is consistent with the equipartition for a moderate beaming of the emission, with a Doppler factor δ∼10. The power transported by the jet is then similar to that of other powerful blazars, L_j∼10⁴⁸ ergs.s^–1, and the jet has low radiative efficiency. The radiative cooling times of the electrons are a few thousand years, compatible with the size of the knot. The low-energy cutoff of the electron distribution is constrained to be γ_min∼10, the first such constraint from spectral considerations. A parallel analysis for the synchrotron self-Compton model yields far less reasonable physical conditions.