The structure of the merging RCS 231953+00 supercluster at z ~ 0.9
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Author
Faloon, A. J.
Webb, T. M. A.
Ellingson, E.
Yan, R.
Gilbank, David G.
Geach, J. E.
Noble, A. G.
Barrientos, L. F.
Yee, H. K. C.
Gladders, M.
Richard, J.
Attention
2299/10750
Abstract
The RCS2319+00 supercluster is a massive supercluster at z = 0.9 comprising three optically selected, spectroscopically confirmed clusters separated by <3Mpc on the plane of the sky. This supercluster is one of a few known examples of the progenitors of present-day massive clusters (1015 M ☉ by z ~ 0.5). We present an extensive spectroscopic campaign carried out on the supercluster field resulting, in conjunction with previously published data, in 1961 high-confidence galaxy redshifts. We find 302 structure members spanning three distinct redshift walls separated from one another by ~65Mpc (Δ z = 0.03). The component clusters have spectroscopic redshifts of 0.901, 0.905, and 0.905. The velocity dispersions are consistent with those predicted from X-ray data, giving estimated cluster masses of ~10 14.5-10 14.9 M ☉. The Dressler-Shectman test finds evidence of substructure in the supercluster field and a friends-of-friends analysis identified five groups in the supercluster, including a filamentary structure stretching between two cluster cores previously identified in the infrared by Coppin etal. The galaxy colors further show this filamentary structure to be a unique region of activity within the supercluster, comprised mainly of blue galaxies compared to the ~43%-77% red-sequence galaxies present in the other groups and cluster cores. Richness estimates from stacked luminosity function fits result in average group mass estimates consistent with ~1013 M ☉ halos. Currently, 22% of our confirmed members reside in 1013 M ☉ groups/clusters destined to merge onto the most massive cluster, in agreement with the massive halo galaxy fractions important in cluster galaxy pre-processing in N-body simulation merger tree studies