http://arxiv.org/abs/1604.06256
We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their rotation is correlated to dynamical youth but only when limiting our analysis to within a 1.5h^{-1}_{70} Mpc radius. The lack of significant such correlations when we increase the radius of analysis to 2.5h^{-1}_{70} Mpc points towards a different mechanism being responsible for the rotation of the inner and outer cluster region. The outer cluster rotation could possibly be related to coherent motions of infalling substructures. Finally, finding rotational modes in galaxy clusters could lead to the necessity of correcting the dynamical cluster mass calculations.
M. Manolopoulou and M. Plionis
Fri, 22 Apr 16
31/54
Comments: 18 pages, 5 tables, 16 figures
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