Journal Article

On the overconcentration problem of strong lensing clusters

M. Sereno, Ph. Jetzer and M. Lubini

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 403, issue 4, pages 2077-2087
Published in print April 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16248.x
On the overconcentration problem of strong lensing clusters

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Λ cold dark matter paradigm predicts that galaxy clusters follow a universal mass density profile and fit a well-defined mass–concentration relation, with lensing clusters being preferentially triaxial haloes elongated along the line of sight. Oddly, recent strong and weak lensing analyses of clusters with a large Einstein radius suggested those haloes to be highly overconcentrated. Here, we investigate what intrinsic shape and orientation a halo should have to account for both theoretical predictions and observations. We considered a sample of 10 strong lensing clusters. We first measured their elongation assuming a given mass–concentration relation. Then, for each cluster, we found the intrinsic shape and orientation which are compatible with the inferred elongation and the measured projected ellipticity. We distinguished two groups. The first one (nearly one-half) seems to be composed of outliers of the mass–concentration relation, which they would fit only if they were characterized by a filamentary structure extremely elongated along the line of sight, that is not plausible considering standard scenarios of structure formations. The second sample supports expectations of N-body simulations which prefer mildly triaxial lensing clusters with a strong orientation bias.

Keywords: gravitational lensing; methods: statistical; galaxies: clusters: general; cosmology: observations

Journal Article.  7867 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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