Neutral Hydrogen in Arp 158

Abstract

We present 21 cm observations of Arp 158. We have performed a study of the neutral hydrogen (HI) to help us understand the overall formation and evolution of this system. This is a disturbed system with distinct optical knots connected by a linear structure embedded in luminous material. There is also a diffuse spray to the southeast. The HI seems to be made up of three distinct, kinematically separate systems. Arp 158 bears a certain optical resemblance to NGC 520 (Arp 157), which has been identified as a mid-stage merger. From our 21 cm observations of Arp 158, we also see a comparable HI content with NGC 520. These similarities suggest that Arp 158 is also an intermediate stage merger.