ABSTRACT

We have made new N-body simulations of ringed, barred spiral galaxies that extend and improve upon the previous work of M. P. Schwarz. Using a comprehensive database of multicolor images of a large sample of ringed galaxies, we are able to morphologically “match” galaxies to simulation frames that differ in bar pattern speed and time step. From these matches, we can reliably identify both low and high pattern speed galaxies.

INTRODUCTION

It is now well-established that the rings commonly observed in disk galaxies are probably caused by orbital resonances with a bar or bar-like potential in the disk (see Buta and Crocker 1991, A. J., 102, 1715, hereafter BC; 1993, A. J., 105, 1344, for recent discussions). In a pioneering N-body investigation, Schwarz (1981, Ap. J., 247, 77) simulated the behavior of gas clouds in two dimensional rotating bar potentials, and identified the outer Lindblad resonance (OLR), the inner 4:1 resonance (UHR), and the inner Lindblad resonance (ILR) as the resonances responsible for the features known as outer, inner, and nuclear rings, respectively. To better understand ring formation and evolution, we have carried out new simulations at many more bar pattern speeds (Ωp) than Schwarz with more particles and an improved treatment of cloud collisions. We also take advantage of a recently acquired database of BVI CCD images of 150 ringed galaxies for comparison.