The ring galaxy HRG 54 103: a first study

摘要

Aims. We report the first study of the peculiar ring galaxy HRG54103 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 characteristicsof this almost isolated galaxy. The colour distribution of HRG54103 was examined through direct CCD BVRI Kron-Cousinssystem imagery. Color–color diagrams of the bulge and ring are displayed and further compared with the star-forming ring galaxyHRG 2302.Results. The results of image enhancement of the morphological structure of this galaxy are discussed. The nuclear emission-linespectrum resembles that of a Seyfert2/LINER object, with z = 0.022 and heliocentric V = 6483 ± 18 km s-1, in agreement with theliterature. The nuclear, bulge and ring section radial velocities along the ring major axis show a peculiar distribution, which togetherwith the Nii/Hα and S ii/Hα ratios and image enhancement suggest an offset nucleus and an internal tilted ring or shell.Conclusions. HRG54103 is a peculiar galaxy with an intermediate activity region, probably due to a residual excitation effect throughthe central AGN phenomenon. The individual sections of the color–color map are redder than a typical star-forming ring galaxy, inagreement 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 itsformation.