A Radio Study of the Seyfert Galaxy IC 5063: Evidence for Fast Gas Outflow

New radio continuum (8 GHz and 1.4 GHz) and HI 21 cm line observations of theSeyfert 2 galaxy IC 5063 (PKS 2048-572) were obtained with the AustraliaTelescope Compact Array (ATCA). The 8 GHz image reveals a linear triplestructure (~4'', 1.5 kpc) oriented perpendicular to the optical polarizationposition angle. It is aligned with the inner dust lane and shows strongmorphological association with the narrow emission line region (NLR). At 21 cm,very broad (~700 km/s) HI absorption is observed against the strong continuumsource. This absorption is almost entirely blueshifted, indicating a fast netoutflow, but a faint and narrow redshifted component is also present. In IC5063 we see clear evidence for strong shocks resulting from the radioplasma-ISM interaction in the central few kpc. However, the energy flux in theradio plasma is an order of magnitude smaller than the energy emitted inemission lines. Thus, shocks are unlikely to account solely for the globalionization of the emission line region, particularly at large distances. The HI emission outlines a warped disk associated with the system of dustlanes some ~2' (~38 kpc) in radius. The lack of kinematically disturbed gasoutside the central few kpc, coupled with the disk warp and close morphologicalconnection of the inner dust lanes and the large-scale ionized gas, support theidea that the gas at large radii is photoionized by the central region, whileshadowing effects are important in defining its X-shaped morphology. Thekinematics of the ionized and of the neutral gas suggests the existence of adark halo.