Structure and evolution of NGC 5128
New photographic and spectroscopic observations have been made of the nearby radio galaxy NGC 5128 with the CTIO 4 m telescope. A deep blue photograph shows some faint streamers in the NW quadrant, several arc minutes from the nucleus. No indication of a concentration of globular clusters associated with the galaxy is seen in this photograph. Velocities are given for the gaseous and stellar components of the galaxy. The main body of NGC 5128 resembles in many respects a normal giant elliptical galaxy. Concentric with it, is an inclined rotating disk which contains both stars and gas. In parts of the galaxy, material in the disk gives rise to prominent sharp interstellar absorption lines. The heliocentric velocity indicated by emission lines originating from gas near the nucleus is 548 +- 5 km s/sup -1/. This is consistent with the mean velocity given by the diffuse absorption lines from unresolved stars in the elliptical component, 536 +- 30 km s/sup -1/. A rotation curve for the disk is derived. If a distance of 5 Mpc is assumed, an approximate value for the mass of the galaxy is 3 x 10/sup 11/ M/sub sun/ to a distance of 11 kpc from the nucleus. No rotation is observed in the elliptical component greater than 30 km s/sup -1/ at a distance of 1.5 kpc in any direction from the nucleus. The origin and evolution of the galaxy are discussed. One possibility is that the optical and radio characteristics of the galaxy have developed from the merger of a gas cloud or small galaxy with a giant elliptical galaxy about 10/sup 9/ years ago. The main radio characteristics and the unusual activity in the nucleus of NGC 5128 appear to be a consequence rather than the cause of the peculiar structural features of the galaxy.
- Research Organization:
- Cerro Tololo Inter-American Observatory, La Serena, Chile
- OSTI ID:
- 5939612
- Journal Information:
- Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 232:1; ISSN ASJOA
- Country of Publication:
- United States
- Language:
- English
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& X-Ray Sources-- (-1987)
640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
EMISSION SPECTRA
ENERGY SPECTRA
GALACTIC EVOLUTION
GALAXIES
H2 REGIONS
MOTION
PHOTOGRAPHY
RADIATIONS
RADIO GALAXIES
RADIOWAVE RADIATION
ROTATION
SPECTRA
SPECTROSCOPY