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G. G. Byrd (Univ. of Alabama, Tuscaloosa), T. Freeman (Bevill State Brewer Campus, Fayette, AL), R. Buta (Univ. of Alabama, Tuscaloosa)
We have used our HST observations of the inner and outer resonance rings of the galaxy NGC3081 (Buta, Byrd, & Freeman 2003) and self-gravitating n-body simulations to confirm a new analytical formulation of inner and outer rings near co-rotation (Byrd, Freeman & Buta 2006). We showed how inner ring shape gives the strength of the bar perturbation and the surface mass density variation around the ring for NGC3081 or other similar galaxies. Here we calculate the bar strengths of a sample of disk galaxies with inner rings. This bar strength calculation depends only on the straightforward dynamics of the inner ring with no assumption about M/L of the disk material. We find a correlation between the bar strength and the outer spiral pattern. We carry out a grid of bar strength versus time simulations to ascertain if this is a function of time as well as bar strength. If two-fold and circularly symmetric intensities are available, one can also calculate an unperturbed disk surface mass density near the inner and outer rings as we did for NGC3081. We found that the disk M/L of NGC3081 varies with radius. We compare our sample’s bar strengths to those assuming constant M/L over the disk. Where possible, we calculate the unperturbed disk surface mass density for our sample galaxies.
Grant support: NASA/STScI GO 8707 and NSF AST-0206177.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.