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Session 4 - Low Luminosity AGN and Starburst Galaxies.
Display session, Monday, June 10
Tripp Commons,
Collisionally produced 'ring-galaxies' usually display vigorous star formation in an expanding ring or arc of high density gas. This star formation dominates the appearance of these galaxies in the optical, the nucleus often being faint and sometimes not observed at these wavelengths. Near-infrared images show that the older stellar disk population has also been swept into an outwardly expanding density/material wave which can be slightly displaced from the gas ring. A dominant feature of the optical appearance of many of these ring-galaxies is the clumpy nature of the star forming regions along the arc or around the ring of gas. We have gathered data from the literature (H \alpha and K-band images, as well as CO luminosities and line widths) on several of these galaxies and compare it with our detailed numerical three-dimensional models. The latter are obtained from simulations of collisions of varying impact parameter between a rotating disk galaxy, containing both stars and gas, and a gas-free elliptical of varying mass. These simulations were computed using a combined n-body/SPH (Smoothed Particle Hydrodynamics) code including full self-gravity of all components of the system. The comparison of models with real systems gives valuable information on timescales and the global dynamics of the collision. Further, we compare observations of the star forming regions and the nuclei with the corresponding physical characteristics of the stars and gas in the models and, in this way, further our undertanding of the parameters that determine the characteristics of global star formation in these and other density wave driven star forming regions.
