High Resolution CO and HI Observations of an Interacting Galaxy NGC 3627.

Summary

ABSTRACT

A nearby interacting galaxy NGC 3627 was observed in the CO (1–0) transition and in H I using aperture synthesis technique. The combined CO and H I data indicated that, the gravitational torque experienced by NGC 3627 during its close encounter with NGC 3628 triggered a sequence of dynamical processes, including the formation of prominent spiral structures, the central concentration of both the stellar and gaseous mass, the formation of two widely separated and outwardly located Inner Lindblad Resonances, and the formation of a gaseous bar inside the inner resonance. These processes in coordination allow the continuous and efficient radial mass accretion across the entire galactic disk. The observational result in the current work provides a detailed picture of a nearby interacting galaxy which is very likely in the process of evolving into a nuclear active galaxy. It also suggests one of the possible mechanisms for the formation of successive instabilities in the post-interacting galaxies, which facilitates the central channeling of interstellar medium to fuel nuclear activities.

INTRODUCTION

In the recent years, it has become increasingly apparent that the interaction among galaxies plays an important role in the evolution of a disk galaxy (Barnes and Hernquist 1992 and the references therein). It is well known that the gravitational tide excited during the galaxy interaction could induce significant inflow of gas to fuel nuclear activities. But since very few interacting galaxies have so far been mapped with high resolution, a detailed picture of the type of instabilities that occur after galaxy interaction, and of the mass accretion process in the inner kiloparsec region of the galaxy is still lacking.