A GIANT EMISSION-LINE ARC IN THE INTERMEDIATE REDSHIFT RADIO GALAXY PKS 2250-41

We present observations of the southern radio galaxy PKS2250-41 (z=0.3 10) which show an emission line arc circumscribing the western radio l obe, and provide some of the clearest evidence yet for the strong infl uence of radio jets on the distribution and ionization of the warm gas in radio galaxies. The arc, situated some 36kpc from the nucleus of t he host galaxy, has a relatively low ionization state and is associate d with a blue, low polarization continuum source. We interpret these o bservations in terms of an interaction between the radio jet and a den ser than average region of the ISM/IGM - perhaps associated with mergi ng companion galaxies or intergalactic clouds.