Journal Article

LoCuSS: first results from strong-lensing analysis of 20 massive galaxy clusters at <i>z</i>= 0.2

Johan Richard, Graham P. Smith, Jean-Paul Kneib, Richard S. Ellis, A. J. R. Sanderson, L. Pei, T. A. Targett, D. J. Sand, A. M. Swinbank, H. Dannerbauer, P. Mazzotta, M. Limousin, E. Egami, E. Jullo, V. Hamilton-Morris and S. M. Moran

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 404, issue 1, pages 325-349
Published in print May 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.16274.x
LoCuSS: first results from strong-lensing analysis of 20 massive galaxy clusters at z= 0.2

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We present a statistical analysis of a sample of 20 strong lensing clusters drawn from the Local Cluster Substructure Survey, based on high-resolution Hubble Space Telescope imaging of the cluster cores and follow-up spectroscopic observations using the Keck-I telescope. We use detailed parametrized models of the mass distribution in the cluster cores, to measure the total cluster mass and fraction of that mass associated with substructures within R≤ 250 kpc. These measurements are compared with the distribution of baryons in the cores, as traced by the old stellar populations and the X-ray emitting intracluster medium. Our main results include: (i) the distribution of Einstein radii is lognormal, with a peak and 1σ width of 〈log10θE(z= 2)〉= 1.16 ± 0.28; (ii) we detect an X-ray/lensing mass discrepancy of 〈MSL/MX〉= 1.3 at 3σ significance – clusters with larger substructure fractions displaying greater mass discrepancies, and thus greater departures from hydrostatic equilibrium and (iii) cluster substructure fraction is also correlated with the slope of the gas density profile on small scales, implying a connection between cluster–cluster mergers and gas cooling. Overall our results are consistent with the view that cluster–cluster mergers play a prominent role in shaping the properties of cluster cores, in particular causing departures from hydrostatic equilibrium, and possibly disturbing cool cores. Our results do not support recent claims that large Einstein radius clusters present a challenge to the cold dark matter paradigm.

Keywords: gravitational lensing; galaxies: clusters: general

Journal Article.  13705 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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