Photometry and kinematics of two minor merger candidate galaxies

Abstract

We observationally investigate the properties of disk galaxies undergoing minor merger or capture events. In this context, the properties of two double-nucleus candidate galaxies, ESO 381–IG23 andMCG 3-35-14, are analyzed. Both are disk-dominated Sc–Scd galaxies that show a bright knot superposed on their disk body. The size and surface brightness of these knots are in both cases comparable to those of the galaxy nucleus, which has led previous work to classify these galaxies as double-nucleus galaxies. We present results from observations made with the SOAR 4.1 m, CASLEO 2.15 m, and Bosque Alegre 1.54 m telescopes. We determined the values for the apparent and absolute magnitudes of the nuclei and the bright regions and analyzed the surface brightness profiles and colors. We also study the kinematics of the galaxies via their rotation curves. Analytical mass models were fitted under the constraints of both kinematic and photometric observational data. It is found that ESO 381–IG 23 has an absolute magnitude MB = −19:59 and mass M= (3.0±0.2) x 1010 Mʘ, and its nuclear spectrum shows strong emission lines typical of starbursts. MCG −3-35-14 has MB = 19.97 and M=(9.6 ± 0.5) x 1010 Mʘ. Both galaxies are morphologically normal disk galaxies. They have a bulge-to-disk ratio of ~0.1 and show no significant signatures of dynamical perturbation in their rotation curves. The secondary nuclei candidates are found to be giant H ii regions, rather than nuclei of captured companions. They have masses of (2.2±0.2) x 106 Mʘ (ESO 381–IG 23) and (4.1±0.2) x 106 Mʘ (MCG 3-35-14), and ages of 6.6±0.1 and 8.0±1.0 Myr, respectively.