A fast bar in the post-interaction galaxy NGC 1023

We measured the bar pattern speed, Omega(p), of the SB0 galaxy NGC 1023 using the Tremaine-Weinberg method with stellar-absorption slit spectroscopy. The morphology and kinematics of the H I 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 Omega(p) = 5.0 +/- 1.8 km s(-1) arcsec(-1), so that the bar ends near its corotation radius. It is therefore rotating rapidly and must have a maximum disc.