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 3.5m. 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 (SSC) mechanisms, respectively, with hot-spot magnetic field strengths ~3 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 cut-off in the fitted synchrotron spectra provides strong evidence for electron acceleration in the hot spots.