| The Great Attractor |
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| © Kraan-Korteweg & Lahav, 1998, Scientific American 279, p.50 |
| The recession velocities of relatively nearby galaxies show systematic deviations from a uniform expansion field. These deviations are believed to be caused by a gravitational perturbation, in the form of a large - hitherto unnoticed - concentration of mass (5 x 1016 Msun) near the southern Milky Way at a redshift-distance of 4350 km/s, named the `Great Attractor' (GA). Attempts to quantify both the nature and extent of the GA have been hampered by the fact that the GA is largely hidden by the disk of the Milky Way. Although there is an excess of optical and IRAS galaxies in this region (Lynden-Bell 1991), no dominant galaxy cluster or other concentration of mass has been identified until recently, when it was found that the Norma cluster (ACO 3627) is a very massive cluster of galaxies located at the heart of the Great Attractor. |
| Studying `the Great Attractor' at UCT |
| Prof. Kraan-Korteweg, Prof. Fairall and Dr. Woudt (all UCT) have been working on a detailed analysis of the Norma cluster at the core of the Great Attractor. The importance of this cluster was realised following a deep optical galaxy search behind the southern Milky Way. Current studies of the Norma cluster include a detailed dynamical analysis of the cluster, deep R-band imaging of the cluster (MSc project of Mr. Karsten Markus) and a redshift-independent distance determination of the Norma cluster using the near-infrared Fundamental Plane analysis, to unambiguously determine the nature of the Great Attractor. |
| Contact persons in the department of Astronomy |
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Prof. R.C. Kraan-Korteweg (kraan@circinus.ast.uct.ac.za) Prof. A.P. Fairall (fairall@science.uct.ac.za) Dr. P.A. Woudt (pwoudt@circinus.ast.uct.ac.za) |
| Links to recent talks and papers on the Great Attractor |
| NASSP Summer school 2005 talk (P. Woudt: Open Office format, 17.8 Mbyte) |
