Combining Lens Distortion and Depletion to Map the Mass Distribution of A1689

TL;DR

This study presents a detailed 2D mass map of galaxy cluster A1689 using combined lens magnification and distortion data, revealing a high concentration that challenges standard cosmological models.

Contribution

It introduces an entropy-regularized maximum-likelihood method combining magnification and distortion, incorporating strong lensing data, to accurately map cluster mass distribution.

Findings

Mass profile fits NFW model with high concentration c_vir=13.4

Virial mass estimated at (2.1±0.2)×10^15 M_sun

Reproduces observed Einstein radius of 45 arcsec

Abstract

[Abridged] We derive a projected 2D mass map of the well studied galaxy cluster A1689 based on an entropy-regularized maximum-likelihood combination of the lens magnification and distortion of red background galaxies registered in deep Subaru images. The known strong lensing information is also readily incorporated in this approach, represented as a central pixel with a mean surface density close to the critical value. We also utilize the distortion measurements to locally downweight the intrinsic clustering noise, which otherwise perturbs the depletion signal. The projected mass profile continuously steepens with radius and is well fitted by the NFW model, but with a surprising large concentration c_vir=13.4^{+5.3}_{-3.3}, lying far from the predicted value of c_vir ~ 5, corresponding to the measured virial mass, M_vir=(2.1\pm 0.2)\times 10^15M_{\odot}, posing a challenge to the standard assumptions defining the LCDM model. We examine the consistency of our results with estimates derived with the standard weak lensing estimators and by comparison with the inner mass profile obtained from strong lensing. All the reconstructions tested here imply a virial mass in the range, M_vir=(1.5-2.1)\times 10^15M_{\odot}, and the combined ACS and Subaru-2D mass reconstruction yields a tight constraint on the concentration parameter, c_vir=12.7 \pm 1(stat.) \pm 2.8(systematic) (c_200 ~ 10), improving upon the statistical accuracy of our earlier 1D analysis. Importantly, our best fitting profile properly reproduces the observed Einstein radius of 45 arcsec (z_s=1), in contrast to other weak lensing work, reporting lower concentration profiles, which underestimate the observed Einstein radius.