Comparison of Cluster Lensing Profiles with Lambda CDM Predictions

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Abstract
We derive lens distortion and magnification profiles of four well known clusters observed with Subaru. Each cluster is very well fitted by the general form predicted for Cold Dark Matter (CDM) dominated halos, with good consistency found between the independent distortion and magnification measurements. The inferred level of mass concentration is surprisingly high, 8 < c_{vir} < 15 ( = 10.39 \pm 0.91), compared to the relatively shallow profiles predicted by the LCDM model, c_{vir} = 5.06 \pm 1.10 (for =1.25\times 10^{15} M_{\odot}/h). This represents a 4\sigma discrepancy, and includes the relatively modest effects of projection bias and profile evolution derived from N-body simulations, which oppose each other with little residual effect. In the context of CDM based cosmologies, this discrepancy implies some modification of the widely assumed spectrum of initial density perturbations, so clusters collapse earlier (z > 1) than predicted (z<0.5) when the Universe was correspondingly denser.

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