VLA observations of the radio galaxy Hydra A (3C 218)

An extensive series of observations of the radio galaxy Hydra A using the VLA is reported. The radio emission consists of two components: (1) a pair of well-collimated, curved jets with S-symmetry, each of which makes a turn through about 40 deg between the core and the lobe, and (2) diffuse radio lobes, also rotation-symmetric, although straighter, which extend north out to 5 arcmin (420 kpc) and south out to 3 arcmin (250 kpc). Rotation measures (RMs) ranging from -1000 to +3300 rad/sq m are found in the northern lobe with gradients in the RM of up to 1000 rad/sq m/arcsec. In the southern lobe the RM gradients are probably in excess of + or - 3750 rad/sq m, the maximum value that can be unambiguously determined here. 48 refs.