Picture processing analysis of the optical structure of NGC 5128 (Centarurus A)
The spatial luminosity and color structure of the peculiar elliptical radio galaxy NGC 5128 are studied using photoelectrically calibrated photometry from plates taken with the CTIO 4-m telescope under conditions of excellent seeing (approx.1 arcsec). Using picture processing systems at KPNO and at the NASA Johnson Space Center, 10/sup 6/-pixel maps were constructed of the UBV surface brightness and of the color indices: U-B, B-V, and Q= (U-B)-0.72(B-V) over a 15.5 x 15.5-arcmin region centered on the nucleus of NGC 5128. The color maps reveal the existence of a young stellar population situated in a disk within the elliptical component of NGC 5128 that was previously masked by the absorption ''lane'' across the galaxy. The projection of the disk in the plane of the sky, as defined by OB stars and HII regions, is an ellipse with the major axis in PA=122/sup 0/ +- 4/sup 0/. If circular, the inclination of the plane of the disk in the sky is i=72/sup 0/ +- 3/sup 0/. At an assumed distance of 6 Mpc for NGC 5128, the diameter of the disk is approx.13 kpc. Vigorous star formation is occurring, mostly in elongated structures throughout the disk, with the greatest activity along most of its outer perimeter, where apparently the largest amounts of dust are present. The ages of blue associations in the disk vary from approx.2 x 10/sup 6/ to approx.4 x 10/sup 7/ yr, with most in the range (1--3) x 10/sup 7/ yr. The luminosity distribution of the elliptical component of NGC 5128 follows de Vaucouleurs's law over the range 20< or approx. =sigma/sub B/< or approx. =25 mag arcsec/sup -2/ in a manner that is similar to normal E2 galaxies. Optical emission above that expected from the elliptical population was marginally detected in the inner northeast and southwest radio lobes. The maximim B surface brightness of this emission was sigma/sub B/=25.1 mag arcsec/sup -2/ in the strongest regions of the northeast radio lobe. This emission may be an optical counterpart of synchrotron emission in the radio lobes.
- Research Organization:
- Rice University, Houston, Texas 77001
- OSTI ID:
- 6470255
- Journal Information:
- Astron. J.; (United States), Journal Name: Astron. J.; (United States) Vol. 84:3; ISSN ANJOA
- Country of Publication:
- United States
- Language:
- English
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Radio
& X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
BREMSSTRAHLUNG
COSMIC RADIO SOURCES
DATA FORMS
ELECTROMAGNETIC RADIATION
GALAXIES
GRAPHS
H2 REGIONS
LUMINOSITY
MAPS
OPTICAL PROPERTIES
PHOTOMETRY
PHYSICAL PROPERTIES
RADIATIONS
RADIO GALAXIES
STAR CLUSTERS
STAR EVOLUTION
SYNCHROTRON RADIATION