Bar-driven evolution of SOs: the edge-on galaxy NGC 4570

We present circumstantial evidence that the central region of the edge-on SO galaxy NGC 4570, which harbours a 150-pc scale nuclear disc in addition to its main outer disc, has been shaped under the influence of a small (similar to 500 pc) bar. This is based on the discovery of two edge-on rings, the locations of which are consistent with the inner Lindblad and ultraharmonic resonances of a rapidly tumbling triaxial potential. Observed features in the photometry and rotation curve correspond nicely with the positions of the main resonances, strengthening the case for a tumbling bar potential. The relative blue colour of the ILR ring, and the complete absence of any detected ISM, indicates that the nuclear ring is made of relatively young (less than or similar to 2 Gyr) stars. We discuss a possible secular evolution scenario for this complex multicomponent galaxy, which may also apply to many other SO galaxies with observed rings and/or multiple disc components.