The peculiar galaxy HRG 705: A possible on-going merging?

Abstract

ABSTRACT We report the results of the first spectroscopic study of the galaxy HRG 705, which belongs to the Solitaire class of peculiar (collisional) Ring Galaxies, which, in turn, are little studied. The nuclear emission-line spectrum resembles that of a star-forming galaxy (H ii galaxy), with $\boldsymbol z = 0.0305$ and heliocentric velocity of $v = 9\, 144\, \pm \, 36~ {\rm km\, s}^{-1}$. The nuclear region is dominated by intermediate and old stellar populations, in addition to a contribution of 8 per cent of young stars. Based on the complex velocity profile along the slit position angle of 59°, we suggest that the nuclear region is composed by two bodies in gravitational interaction (a possible on-going merging). Analysis of the surface brightness distribution confirmed the existence of the second body, a probable intruder, which lies inside a central pseudo-bulge/disc. HRG 705 does not appear to be oxygen-rich, but it is slightly more (O/H)-enriched than the galaxies of our nearby Universe.