MULTIWAVELENGTH OBSERVATIONS OF COLLISIONAL RING GALAXIES .1. BROAD-BAND IMAGES, GLOBAL PROPERTIES, AND RADIAL COLORS OF THE SAMPLE GALAXIES

This is one of a series of papers discussing the optical, infrared and radio continuum properties of a sample of collisional ring galaxies. The present paper concentrates on the global broad-band optical (B, V and R) and near-IR (J, H and K) images of the galaxies and describe th eir global properties. An analysis of the colors of the galaxies over a variety of wavelength baselines is described. In the B and V bands, the bluest colors are found in the outer bright ring. The B - V colors of the sample of galaxies are blue, the mean value for the sample is B - V = 0.60, and V - K = 2.37 mag. The IR morphology of the galaxies is, in most cases, very similar to that of the B-band data, suggesting that the clumpy appearance of the star formation in the outer rings i s real, and not a result of patchy dust obscuration. Only in one ring (WN1, a Seyfert ring galaxy) was the IR morphology different from the optical, suggesting the presence of significant dust in the disk. In I I Hz 4, faint spiral arms are seen within the ring. There is a suggest ion that the larger rings have redder V-K colors, which may be due to an increased incidence of nuclear bulges in larger ring galaxies. Radi al profiles of surface brightness and color are presented for four gal axies. In all cases, the colors becomes bluer as one proceeds radially outwards, but in two galaxies, the rings redden again outside the mai n ring, suggesting the existence of a red stellar population that may have pre-dated the collisions. (C) 1997 American Astronomical Society.