Galaxy Distribution as a Probe of the Ringlike Dark Matter Structure in   the Galaxy Cluster Cl0024+17
  In a galaxy cluster, galaxies are mostly collisionless particles in recent epoches. They resemble collisionless cold dark matter particles in some way. Therefore, the spatial distributions of dark matter and cluster galaxies might be expected to possess similar features in the gravitational potential of a cluster. Here we use the galaxy distribution in cluster Cl0024+17 to probe for the ringlike dark matter structure recently discovered by means of strong and weak lensing observations. The galaxies are taken from the catalog of Czoske et al., which contains 650 objects with measured redshifts, of which ~300 galaxies have redshifts in the range 0.37<z<0.41 (and are therefore probable cluster members). We find that, at about the 3-sigma level, the ringlike structure seen in the dark matter measurement is not observed in the projected two-dimensional galaxy distribution. 
Bo Qin, Huan-Yuan Shan, Andre Tilquin