A RADIO STUDY OF THE SEYFERT-GALAXY IC-5063 - EVIDENCE FOR FAST GAS OUTFLOW

We present new radio continuum (8 and 1.4 GHz) and H I 21 cm line obse rvations of the Seyfert 2 galaxy IC 5063 (PKS 2048-572), obtained with the Australia Telescope Compact Array. The high-resolution 8 GHz imag e reveals a linear triple structure similar to 4'' (1.3 kpc) in size. This small-scale radio emission shows a strong morphological associati on with the narrow-line region (NLR), the inner part of the optical em ission-line region. It is aligned with the inner dust lane and is orie nted perpendicularly to the position angle of the optical polarization . We identify the radio nucleus as the central blob of the radio emiss ion. At 21 cm, very broad (similar to 700 km s(-1)) H I absorption is observed against the strong continuum source. This absorption is almos t entirely blueshifted, indicating a fast net outflow, but a faint and narrow redshifted component is also present. In IC 5063 we see clear evidence, both morphological and kinematic, of strong shocks resulting from the interaction between the radio plasma and the interstellar me dium (ISM) in the central few kiloparsecs. However, we estimate the en ergy flux in the radio plasma to be an order of magnitude smaller than the energy flux emitted in emission lines. Thus, although strong shoc ks associated with the jet/ISM interaction occur, and could contribute locally to the ionization of the NLR, they are unlikely to account so lely for the global ionization of the emission-line region, particular ly at large distances. The main structure of the H I emission is a war ped disk associated with the system of dust lanes of R similar to 2' ( similar to 38 kpc, corresponding to similar to 5 effective radii). The lack of kinematically disturbed gas (both neutral and ionized) outsid e the central few kiloparsecs, the warped structure of the large-scale disk, and the close morphological connection between the inner dust l anes and the large-scale ionized gas all support the idea that the gas at large radii is photoionized by the central region, while shadowing effects are important in defining its X-shaped morphology. From the k inematics of the ionized and neutral gas, we find evidence for a dark halo in IC 5063, with properties very similar to those observed in som e other early-type galaxies.