A Fast Bar in the Post-Interaction Galaxy NGC 1023

We measured the bar pattern speed, $\om$, of the SB0 galaxy NGC 1023 using the Tremaine-Weinberg (1984) method with stellar-absorption slit spectroscopy. The morphology and kinematics of the \hi gas outside NGC 1023 suggest it suffered a tidal interaction, sometime in the past, with one of its dwarf companions. At present, however, the optical disc is relaxed. If the disc had been stabilized by a massive dark matter halo and formed its bar in the interaction, then the bar would have to be slow. We found $\om = 5.0 \pm 1.8$ \kmsa, so that the bar ends near its co-rotation radius. It is therefore rotating rapidly and must have a maximum disc.