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The Halo of Centaurus A



At a distance of about 3.6 Mpc, NGC 5128 (Centaurus A) is the closest high-luminosity AGN, the closest radio galaxy, the closest giant elliptical and one of the closest and best examples of a merger remnant. The galaxy has prominent dust lanes and shells which could be the result of a merger with a small satellite galaxy.

During the first Chilean

run of the Magellan 1 telescope, M. Rejkuba (Pontificia Univ. Católica de Chile and ESO), D. Minniti and F. Courbin (Pontificia Univ. Católica de Chile) observed a field in the north-east part of the halo of the galaxy, approximatelly 8.2 arcmin away from the nucleus. This image is the combination of U, V and I band images taken at Las Campanas Observatory with the 6.5 m Magellan 1 telescope using the Tek#5 direct CCD camera that has 2048x2048 24 micron pixels. The pixel scale is

0.0694 arcsec/pixel. The field of view in the image is 2.2x2.2 arcmin. North is up and east to the left.


The U-band image is a median average of 3 x 1800 sec exposures, the V-band consists of 2 x 900 sec and I-band of 3 x

900 sec + 300sec exposures. The observations were taken on the night of February 22, 2001 under excellent seeing conditions. The mean seeing was 0.38, 0.40 and 0.34 arcsec in the U, V and I-band, respectively.


Most of the brightest objects in the image belong to our Galaxy, but some, like the bright object near the center of the field are globular clusters in NGC 5128. The cluster near the center of our field is the first one discovered in this galaxy by Graham & Phillips in 1980. The high resolution of Magellan and excellent seeing allowed us to resolve the stars in the halo of the elliptical galaxy. The faintest stars resolved in the image have magnitudes of I ~ 26. The underlying population are the old red giant stars. Superposed on it is a bright blue jet of ionized gas. A substantial star formation associated with the ionized gas revealed some young blue supergiants.

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