RUI: Resonance Rings and Bars: Keys to Galaxy Properties

Bevill State Community College, Jasper AL

Investigators

Abstract

AST 0206177 Freeman Resonance rings are important in most SB type galaxies. In a simple analytic formulation or in simulation models, the rings result from a disk's turning bar perturbation. If the perturbation is not too strong, the disk gas clouds' motions are reduced to a damped harmonic oscillation about the circular orbit. Rings of luminous young stars occur via gentle cloud collisions which occur near oscillation resonances with the turning bar. The projected ring morphology of a galaxy plus radial velocity data can give the galaxy's three dimensional orientation, bar strength and pattern speed. Formation of stellar associations is promoted in rings where gas clouds are crowded near the end of the bar. As these associations orbit, they age as they move along the periodic orbits making up the rings. Age determinations are important for checking star formation models in other galaxies. In this project, Drs. Tarsh Freeman and Gene Byrd will carefully model Hubble Space Telescope observations of the galaxy NGC3081's inner and also outer rings, and they will theoretically investigate NGC 4736 and NGC 1291, the two nearest resonance ring galaxies. Byrd and Freeman have successfully simulated the self-gravitational aggregation of ring gas clouds into "associations" near the ends of the inner ring of NGC3081. Larger clumps can be made to form by increasing the contribution of the gas cloud disk to the total centripetal acceleration (i.e. increasing disk gas surface mass density). Freeman and Byrd will extend these studies of the outer ring of NGC3081 and the rings of NGC 4736 and NGC 1291 to simulate formation of smaller associations, aging, and the importance of disk self-gravity relative to high velocity dispersion halo or disk components. ***