Chandra detection of the radio and optical double hot spot of 3C 351

In this Letter, we report a Chandra X-ray detection of the double northern hot spot of the radio quasar 3C 351. The hot spot has also been observed in the optical with the Hubble Space Telescope (R band) and with the 3.5 m Telescopio Nazionale Galileo (B band). The radio-to-optical and X-ray spectra are interpreted as the results of the synchrotron and synchrotron self-Compton mechanisms, respectively, with hot spot magnetic field strengths similar to3 times smaller than the equipartition values. In the framework of shock acceleration theory, we show that the requirement for such a relatively small field strength is in agreement with the fitted synchrotron spectral models and with the sizes of the hot spots. Finally, we show that the combination of a lower magnetic field strength with the high frequencies of the synchrotron cutoff in the fitted synchrotron spectra provides strong evidence for electron acceleration in the hot spots.