NGC 4027: an Interacting One-armed Spiral Galaxy with a Warped Ring
Abstract
We present high-resolution (VLA C-array) H I observations of the pair of galaxies NGC 4027-4027A. The companion galaxy NGC 4027A appears to be undergoing severe tidal stripping, as evidenced by a stream of gas being torn out of it. NGC 4027 itself appears to be surrounded by a ring of H I consisting of gas torn out from NGC 4027A in previous orbital passages. The ring is warped and inclined to the plane of NGC 4027. Assuming that the H I stream traces the path of the interaction, we use it and the ring to obtain the approximate elements of the orbit of the companion. From arguments of dynamical friction we deduce that there is a dark-matter halo around NGC 4027 extending to at least 1.5 times its present separation from NGC 4027A. From a 2.1 micron image of the galaxy we determine that in addition to the m = 1 mode there is a significant m = 2 mode. We argue that disk-to-halo mass ratio and disk velocity dispersion allowed both modes to grow through swing amplification, and that the extraordinary prominence of the m = 1 mode is due to the strong stimulus provided by the close interaction.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1992
- DOI:
- 10.1086/172014
- Bibcode:
- 1992ApJ...400..516P
- Keywords:
-
- H I Regions;
- Interacting Galaxies;
- Radio Spectra;
- Spiral Galaxies;
- Atomic Spectra;
- Ring Structures;
- Astrophysics;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 4027;
- GALAXIES: INTERACTIONS;
- GALAXIES: SPIRAL;
- RADIO LINES: ATOMIC