XMM-Newton Detection of X-Ray Emission from the Compact Steep-Spectrum Radio Galaxy 3C 303.1

Using XMM-Newton we detect faint unresolved X-ray emission from the compact steep-spectrum radio galaxy 3C 303.1. We detect a thermal component at kT ≃ 0.8 keV, which seems likely to be produced in the interstellar medium (ISM) of the host galaxy. There is evidence for a second component in the spectrum whose nature is currently ambiguous. Plausible hypotheses for the second component include (1) hot gas shocked by the expansion of the radio source, and (2) synchrotron self-Compton emission from the southern radio lobe if the magnetic field is below the equipartition value by a factor of ~3.5.