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On the overconcentration problem of strong lensing clusters


Sereno, M; Jetzer, P; Lubini, M (2010). On the overconcentration problem of strong lensing clusters. Monthly Notices of the Royal Astronomical Society, 403(4):2077-2087.

Abstract

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.

Abstract

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.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:April 2010
Deposited On:02 Mar 2011 15:32
Last Modified:05 Apr 2016 14:09
Publisher:Wiley-Blackwell
ISSN:0035-8711
Additional Information:The definitive version is available at www.blackwell-synergy.com
Publisher DOI:https://doi.org/10.1111/j.1365-2966.2010.16248.x
Related URLs:http://arxiv.org/abs/1001.1696

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