Simulating a slow bar in the low surface brightness galaxy UGC 628
  We present a disc-halo N-body model of the low surface brightness galaxy UGC
628, one of the few systems that harbours a "slow" bar with a ratio of
corotation radius to bar length of $\mathcal{R} \equiv R_c/a_b \sim 2$. We
select our initial conditions using SDSS DR10 photometry, a physically
motivated radially variable mass-to-light ratio profile, and rotation curve
data from the literature. A global bar instability grows in our submaximal disc
model, and the disc morphology and dynamics agree broadly with the photometry
and kinematics of UGC 628 at times between peak bar strength and the onset of
buckling. Prior to bar formation, the disc and halo contribute roughly equally
to the potential in the galaxy's inner region, giving the disc enough self
gravity for bar modes to grow. After bar formation there is significant mass
redistribution, creating a baryon dominated inner and dark matter dominated
outer disc. This implies that, unlike most other low surface brightness
galaxies, UGC 628 is not dark matter dominated everywhere. Our model
nonetheless implies that UGC 628 falls on same the relationship between dark
matter fraction and rotation velocity found for high surface brightness
galaxies, and lends credence to the argument that the disc mass fraction
measured at the location where its contribution to the potential peaks is not a
reliable indicator of its dynamical importance at all radii.
