Orientation of Galaxies in Clusters |
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Authors: | Fadel A Bukhari Lawrence E Cram |
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Institution: | (1) Faculty of Science, Dept. of Astronomy, King Abdulaziz University, P.O. Box 1540, Jeddah, Saudi Arabia;(2) Faculty of Science, School of Physics A29, Department of Astrophysics, The University of Sydney, Sydney, NSW, 2006, Australia |
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Abstract: | A detailed analysis of the geometry of galaxies in clusters has been undertaken in both two and three dimensional space. The
procedure was applied to the three Abell clusters A1644, A548 E and A548 W. No significant alignment trend of galaxies in
clusters confirmed in three dimensional space was found. This result is consistent with the mixed dark matter model MDM of
galaxy formation. The result is also consistent with Peebles suggestion that protogalaxies acquired angular momentum from
tidal torques exerted by their neighbours in the early universe. The amount of angular momentum predicted by this mechanism
could be described by a single dimensionless papameter λ≈ 0.8. N-body experiments have shown that λ has approximately normal
distribution with mean value about 0.07 and with a standard deviation of about 0.03. From the analyic fit to flat rotation
curves it is found that tidal torque can provide the observed angular momentum if the mean collapse factor is about 20 and
the mean halo-to-disk mass ratio is of order 10. The MDM model does not predict any systematic relation between the tidal
torques among the halos of galaxies and the large scale structures such as the clusters, superclusters of galaxies and giant
voids in between. Further work in this area is still required.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | galaxies: apparent orientation spatial orientation apparentellipticity distribution formation angular momentum- cosmology: formation oflarge scale structures |
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