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

Abstract

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 method is not restricted to the weak regime but applies to the whole area outside the tangential critical curve, where nonlinearity between the surface mass density and the observables extends to a radius of a few arcminutes. 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 Navarro-Frenk-White model, but with a surprisingly large concentration cvir=13.4+5.3-3.3, lying far from the predicted value of cvir~5, corresponding to the measured virial mass, Mvir=(2.1+/-0.2)×1015 Msolar, posing a challenge to the standard assumptions defining the ΛCDM 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 Mvir=(1.5-2.1)×1015 Msolar, and the combined ACS and Subaru 2D mass reconstruction yields a tight constraint on the concentration parameter, cvir=12.7+/-1+/-2.8 (c200~10), improving upon the statistical accuracy of our earlier 1D analysis. Importantly, our best-fitting profile properly reproduces the observed Einstein radius of 45'' (zs=1), in contrast to other weak-lensing work, reporting lower concentration profiles, which underestimate the observed Einstein radius. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan.