By measuring the coherent distortion induced on faint background galaxies (`weak shear') we use gravitational lensing techniques to reconstruct the 2D projected surface mass density of the Abell 901/902 supercluster, composed of three rich clusters at z~0.17. The clusters themselves exhibit a range of mass-to-light (M/L) ratios,  X-ray properties, and galaxy populations.  We find that, on average, the light from the early-type galaxies traces the dark matter fairly well, although one cluster is a notable exception to this rule.  A straightforward cross-correlation of the light from the colour-selected early-type supercluster galaxies and the lensing mass map reveals that a single M/L ratio is not adequate to fully describe the mass-light relation in the supercluster.   Finally, there is evidence of inter-cluster filamentary structure, seen in both the galaxy and dark matter distributions, and we discuss the effects of cluster-cluster and cluster-filament interactions as a means to reconcile the disparate descriptions of the supercluster.

Initial results from the deep R-band image and supplemental B-band image were presented in Probing the distribution of dark matter in the Abell 901/902 supercluster with weak lensing (ApJ 2002, vol 568, pp 141-162).  The project will be further extended to explore mass-light correlations throughout the entire COMBO-17 dataset.
 

Contact person:  Meghan Gray, ROE

More information available at the Edinburgh lensing homepage and the Bonn lensing homepage.

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