ROSAT OBSERVATIONS OF THE RADIO GALAXY B2-1122+39

We report X-ray obervations of the radio galaxy B2 1122+39 (NGC 3665), associated with two radio jets, carried out by the Rosat PSPC and HRI instruments. We have detected extended X-ray emission, with a brightn ess profile consistent with a beta hydrostatic model, that originates from a hot corona (kT approximate to 0.5) that surrounds the galaxy. T hese X-ray data, combined with VLA radio observations, lead to conclud e that the thermal pressure of the hot gas is larger than the jet equi partition pressure of relativistic electrons, implying that the assump tions made in the computation of the internal pressure may not be vali d. The jet structure has been satisfactorily modeled assuming that the jets are confined by the X-ray emitting atmosphere. We also found tha t the amount of dark matter in the galactic corona is negligible.