Bar driven evolution of S0s: the edge-on galaxy NGC 4570

Abstract

We present circumstantial evidence that the central region of the edge-on S0 galaxy NGC 4570, which harbors a 150 pc scale nuclear disc in addition to its main outer disc, has been shaped under the influence of a small (approx. 500pc) bar. This is based on the finding of two edge-on rings, whose locations are consistent with the Inner Lindblad and Ultra Harmonic Resonances of a rapidly tumbling triaxial potential. Observed features in the photometry and rotation curve nicely correspond 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 (< 2 Gyr) stars. We discuss a possible secular-evolution scenario for this complex multi-component galaxy, which may also apply to many other S0-galaxies with observed rings and/or multiple disc-components.