Pattern Corotation Radii from Potential-Density Phase-Shifts for 153
  OSUBGS Sample Galaxies
  We apply the potential-density phase-shift method to 153 galaxies in the Ohio
State University Bright Galaxy Survey (OSUBGS) to study the general
relationship between pattern corotation radii and the morphology of spiral
galaxies. The analysis is based on deprojected near-infrared H-band images. We
find that multiple pattern speeds are common in disk galaxies. By selecting
those corotation radii close to or slightly larger than the bar radius as being
the bar corotation (CR) radius, we find that the average and standard deviation
of the ratio R = r(CR)/r(bar), is 1.20+/-0.52 for 101 galaxies having
well-defined bars. There is an indication that this ratio depends weakly on
galaxy type in the sense that the average ranges from 1.03+/-0.37 for 65
galaxies of type Sbc and earlier, to 1.50+/-0.63 for 36 galaxies of type Sc and
later. Our bar corotation radii are on average smaller than those estimated
from single-pattern-speed numerical simulations, most likely because these
simulations tend to find the pattern speed which generates a density response
in the gas that best matches the morphology of the outer spiral structure.
Although we find CR radii in most of the sample galaxies that satisfy
conventional ideas about the extent of bars, we also consider the alternative
interpretation that in many cases the bar CR is actually inside the bar and
that the bar ends close to its outer Lindblad resonance instead of its CR. We
see evidence in the phase-shift distributions for ongoing decoupling of
patterns. We also examine how uncertainties in the orientation parameters of
galaxies and in the shapes of bulges affect our results.
