Centaurus A: multiple outbursts or bursting bubble?

We present new radio observations of the brighter region of the northern lo be (the northern middle lobe, NML) of Centaurus A obtained at 20 cm with th e Australia Telescope Compact Array. The angular resolutions are similar to 50 and similar to 130 arcsec, therefore much higher than for the previousl y available radio images of this region. The most interesting feature detec ted in our images is a large-scale jet that connects the inner radio lobe a nd the NML, and which is imaged for the first time. The NML itself appears as diffuse emission with a relatively bright ridge on the eastern side. The radio morphology of Centaurus A and, in particular, its NML could be th e result of a precessing jet that has undergone a strong interaction with t he environment at least on the northern side. The very big drop in intensit y between the inner jet and the large-scale jet can be explained with a seq uence of bursts of activity at different epochs in the life of the source. Alternatively (or additionally) a 'bursting bubble' model is proposed to ex plain this big drop in intensity, which could also explain the good collima tion of the large-scale jet. In this model, the plasma accumulated in the i nner lobe would be able to 'burst' out only through one nozzle, which would be the region where the large-scale jet forms. The location of the nozzle would represent a region where the pressure gradient is more favourable. From the comparison between the radio emission and the regions of Ionized g as discovered by Graham & Price (the so-called optical filaments) we find t hat the inner optical filament (similar to 8 kpc from the centre) falls abo ut 2 arcmin (similar to 2 kpc) away from the large-scale radio jet. Thus, t he inner filament does not seem to have experienced a direct interaction wi th the radio plasma. The complex velocity field observed in this filament c ould therefore be the result of strong instabilities produced by the 'burst ing bubble'. The outer filaments appear to be, in projection, closer to and aligned with the radio emission in the transition region between the jet a nd the lobe, suggesting a direct interaction with the radio jet, However, a lso in this case a more complicated interaction than assumed so far has to be occurring because of the relative position of the ionized and neutral ga s regions compared with the radio jet as well as the kinematics of the ioni zed gas.