Optical and X-Ray Observations of the Merging Cluster AS1063

Creators: Gómez, P. L.; Valkonen, L. E.; Romer, A. K.; Lloyd-Davies, E.; Verdugo, T.; Cantalupo, C. M.; Daub, M. D.; Goldstein, J. H.; Kuo, C. L.; Lange, A. E.; Lueker, M.; Holzapfel, W. L.; Peterson, J. B.; Ruhl, J.; Runyan, M. C.; Reichardt, C. L.; Sabirli, K.

Abstract

We present the first in-depth analysis of the massive cluster AS1063. This is one of the hottest X-ray clusters discovered to date and is undergoing a major merging event. The average temperature of the hot intracluster medium has been measured, using Chandra/ACIS-I, and found to be >11.5 keV. Optical spectroscopy, from GMOS-S, has provided a mean redshift of 0.3461 and a large velocity dispersion of 1840^(+230)_(–150) km s^(–1). Both the large velocity dispersion and high X-ray temperature suggest a very massive cluster (M_(200) > 2.5 × 10^(15) M_☉) and/or a merger system. The merger model is supported by a small offset between the galaxy density and the peak of the X-ray emission, the presence of offset and twisted X-ray isophotes, and a non-Gaussian galaxy velocity distribution. We also report that the velocity distribution is better represented by the velocity dispersion produced during a merger than by the velocity distribution of a relaxed cluster. Moreover, we find that two non-concentric beta models are a better description for the distribution of the cluster gas than a single beta model. Therefore, we propose that a recent merger event close to the plane of the sky is responsible for the observed properties of the cluster. In addition, optical imaging, from SuSI2 on the New Technology Telescope and GMOS-S at Gemini, has also uncovered the presence of several gravitational arcs that have been used to further constrain the mass and dynamics of the cluster.

Additional Information

© 2012 American Astronomical Society. Received 2012 April 12; accepted 2012 June 28; published 2012 August 9. This research was possible with financial support from: (1) NASA (via the XMM and Chandra Guest Observer programs and the Long Term Space Astrophysics program, grant Nos. NAG5-7926, NAG5-12999, NAG5-20453, GO4-5141X); (2) the European Commission (via a Marie Curie Reintegration Grant, grant number EIF-OIF-IIF-IRG-ERG; Project 513676); (3) AAS (via international travel grants for 2003 and 2004 and a small research grant); (4) STFC (the UK Science and Technology Facilities Council) (K.R., P.G.); (5) the Osk. Huttunen Foundation for a PhD studentship (L.V.); (6) the Magnus Ehrnrooth Foundation for a travel grant (L.V.); and (7) the University of Sussex Physics and Astronomy Department for a Graduate Teaching Assistantship (L.V.). In addition P.L.G. thanks the kindness of the Sussex Astronomy Centre during month long visits in 2006 and 2007. P.L.G. also thanks the European Southern Observatory (ESO) for two short stays at their Headquarters in Santiago where a large fraction of the final version of this paper was written. Finally, we thank the referees for helping us write a more concise, accurate, and hopefully interesting paper. This work is based on observations obtained from (1) the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministrio da Cincia e Tecnologia (Brazil), and SECYT (Argentina); (2) the Chandra X-Ray Observatory (Chandra) is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060; and (3) the ESO telescopes at La Silla under program 70.A-0074.

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