ABSTRACT Ring galaxies are commonly known as objects where a burst of star formation was triggered by a close encounter with an intruder. Here we present a self-consistent approach to reproduce the observed morphological and photometric behaviour of a sample of ring galaxies using updated N-body simulations and evolutionary synthesis model from UV to far-IR wavelengths.

INTRODUCTION

Galaxies were selected from the list of Appleton and Struck-Marcell (1987). BVRI CCD observations of seven ring galaxies were carried out at Padova-Asiago Observatory using a GEC CCD with a pixel size of 22 μm, corresponding to 0.28 arcsec. Fluxes have been translated to the standard BVRI Johnson's system. In the following we briefly outline fundamentals of our models and summarize our results in section 2. Far-IR (FIR) data come from IRAS catalogue (Version 2).

N-Body Simulations

We performed numerical simulations of collisions between stellar disks (embedded in static massive halos) and suitable intruders. The code used is the Hernquist's (1987) TREECODE. The companions used as intruders are massive points or small King spheres, having different masses and different radii. A series of collisions have been performed varying the direction of the companion's velocity. These numerical experiments represent something new with respect to the previous work on the formation of ring structures (Appleton and James 1990) because of the careful and realistic production of the disk target (for details see Curir et al., these proceedings). The passage of the intruder through the disk generates a transient ring-shaped mass distribution. The ring is produced by a single density wave propagating through the disk.