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Session 48 - Spiral & Field Galaxies.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center

[48.04] The Response of Disks to Oscillatory Modes in Galaxies

R. A. Gerber, B. F. Smith, T. Y. Steiman-Cameron (NASA/Ames)

Recent studies suggest that spherical galactic halos can oscillate in normal modes with essentially no damping over a Hubble time. These modes may play an important role in the structure and evolution of disk/halo systems. We assume that most of the mass in a galaxy is in a dark halo. The halo oscillates and the luminous disk material responds to these oscillations.

We are investigating the response of galactic disks to halo oscillations using numerical experiments which include the effects of the disk's self-gravity. We report preliminary results for disks embedded in a radially oscillating gravitational potential. The equilibrium initial disk is represented by an exponential density profile. Considerable care was taken to build an initial disk model that was ``stable'' over long time scales. A control experiment was run with the disk in a static halo potential.

The disk responds to the time-varying potential by developing a ring structure, which forms and disappears during each halo oscillation cycle. This pattern of response persists over time periods approaching a Hubble time. In the oscillating potential, a weak bar develops in the inner disk. This bar is absent when the halo remains static. Specific targets of this study include the implications for large-scale disk structure and the inflow of material into the central regions of the galaxy.

Program listing for Tuesday