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Published February 1, 2013 | Published
Journal Article Open

The X-Ray-Optical Relations for Nine Clusters at z = 0.7-1.1 from the ORELSE Survey


We use Chandra observations of nine optically and X-ray-selected clusters in five different structures at z ~ 0.7-1.1 from the Observations of Redshift Evolution in Large-Scale Environments survey to study diffuse X-ray emission from galaxy clusters. X-ray gas temperatures and bolometric rest-frame luminosities are measured for each cluster in the sample. We present new redshift measurements, derived from data obtained using the Deep Imaging Multi-Object Spectrograph on the Keck 10 m telescope, for two clusters in the RX J0910 supercluster at z ~ 1.1, from which velocity dispersions are measured. Dispersions for all clusters are combined with X-ray luminosities and gas temperatures to evaluate how the cluster properties compare to low-redshift scaling relations. We also measure the degree of substructure in each cluster by examining the velocity histograms, performing Dressler-Shectman tests, and computing the offsets between the X-ray emission center and optically derived centroids. We find that only two clusters show clear indications of being unrelaxed, based on their scaling relations and other dynamical state diagnostics. Using our sample, we evaluate the redshift evolution of the Lx -T relation and investigate the implications of our results for precision cosmology surveys.

Additional Information

© 2013 American Astronomical Society. Received 2012 June 30; accepted 2012 December 12; published 2013 January 16. This work is supported by the Chandra General Observing Program under award numbers GO6-7114X, GO7-8126X, GO8-9123A, and GO9-0139A. In addition, we acknowledge support by the National Science Foundation under grant AST- 0907858. Spectrographic data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. As always, we thank the indigenous Hawaiian community for allowing us to be guests on their sacred mountain. We are most fortunate to be able to conduct observations from this site.

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