Vera A. F. Martin

The ring galaxy HRG 54103: a first study

Aims. We report the first study of the peculiar ring galaxy HRG 54103 which was previously classified as a Saturn-like type galaxy. Methods. The study is based on low resolution spectroscopy and photometric observations in the optical band to highlight the characteristics of this almost isolated galaxy. The colour distribution of HRG 54103 was examined through direct CCD BVRI Kron-Cousins system imagery. Color–color diagrams of the bulge and ring are displayed and further compared with the star-forming ring galaxy HRG 2302. Results. The results of image enhancement of the morphological structure of this galaxy are discussed. The nuclear emission-line spectrum resembles that of a Seyfert2/LINER object, with z = 0.022 and heliocentric V = 6483 ± 18 km s −1 , in agreement with the literature. The nuclear, bulge and ring section radial velocities along the ring major axis show a peculiar distribution, which together with the [N ii]/Hα and [S ii]/Hα ratios and image enhancement suggest an offset nucleus and an internal tilted ring or shell. Conclusions. HRG 54103 is a peculiar galaxy with an intermediate activity region, probably due to a residual excitation effect through the central AGN phenomenon. The individual sections of the color–color map are redder than a typical star-forming ring galaxy, in agreement with the behavior of the [S ii]/Hα versus [N ii]/Hα diagnostic diagram. The two bulge satellites, the plume-like appendix, and the disk-ring asymmetry suggest a possible merger event in the recent past of this object, which could also have caused its formation.