A slow bar in a dark matter dominated galaxy

We report on an estimate of the bar pattern speed Omega_p for the low surface brightness spiral galaxy UGC 628. We applied the Tremaine-Weinberg method to high resolution Halpha velocity and integrated emission maps of this dark matter dominated galaxy. Observations were made at the CFHT using the optical Fabry-Perot interferometer, FaNTOmM. The Tremaine-Weinberg method estimates a bar pattern speed of (11.3 +/- 2.0) km/s/kpc for UGC 628, which is among the lowest values found for a spiral galaxy. The corotation radius Rc of the bar and the gaseous disc is Rc = 9.8 (+2.9/-2.0) kpc, implying a ratio R = Rc/Ab of 2.0 (+0.5/-0.3), where Ab is the bar radius. The ratio is well beyond the usual range of values, 1.0< R
5 pages, 6 figures, accepted for publication in A&A