The peculiar morphology of the irregular galaxy NGC 1427A

Multicolor surface photometry and fragmentary low-resolution spectroscopy of the irregular galaxy NGC 1427A are presented. This galaxy, a member of the Fornax Cluster, has not been studied in detail previously. It shows a very distinctive morphology: a low surface brightness stellar background with several bright knots forming a distorted ring-like structure. A faint plume and several diffused filaments connect the northern part of the main body of the galaxy with an object having elliptical isophotes. The overall aspect of NGC 1427A, then, resembles that of known interacting galaxies. The very blue colors of the bright knots show that they are composed by young stars, and several of them also show emission lines. The northern object, which has itself a couple of these blue knots, is bluer than the background of the main body of the galaxy. This fact indicates that the star formation histories in both objects have been different. Morphologically, the northern object is similar to the numerous dwarf elliptical or irregular galaxies that populate the Fornax Cluster. The possibility of an interaction being the cause of the particular structure of this galaxy is discussed. (C) 1997 American Astronomical Society.