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Session 77 - Structures of Galaxies.
Display session, Friday, January 09
Exhibit Hall,

[77.08] Resonance Ring Galaxies II: Analytically Calculating DiskSurface Densities, M/L's and Disk/Halo Masses

C. Dalla Piazza (Lycoming College), G. Byrd, D. Domingue, D. Ousley (U. Alabama, Tuscaloosa)

Most SB galaxies show rings outside and/or interior to the bar which are made of gas clouds plus recently formed stars. These rings apparently result from resonances of the gravitational field of the turning bar with the disk objects' circular orbital motion and oscillation. In paper I, we described and used an analytical formulation of resonance ring orbits along with the ring morphology, and rotation curve to obtain bar pattern speed and strength as a function of radius. In this paper, II, we use the analytical formulation of resonance ring orbits and with the pattern speed and bar strength to obtain additional disk parameters. The analytic formulation permits the disk inclination and line of nodes to be determined. Additional data needed as a function of radius is long wavelength disk surface brightness plus either disk ellipticity or Fourier components. The disk surface mass density, mass/luminosity and halo/disk ratios can then be obtained as a function of radius. We calculate these values for NGC 30

Dalla Piazza was supported by NSF REU grant AST-9424226, Ousley by a McWane Undergraduate Research Fellowship. We thank R. Buta and G. Purcell for allowing us to use figures and data from their paper on NGC 3081.

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