Hubble Frontier Fields: a high-precision strong-lensing analysis of galaxy cluster MACSJ0416.1-2403 using ∼200 multiple images

We present a high-precision mass model of the galaxy cluster MACSJ0416. 1-2403, based on a strong-gravitational-lensing analysis of the recently acquired Hubble Space Telescope Frontier Fields (HFF) imaging data. Taking advantage of the unprecedented depth provided by HST/ACS observations in three passbands, we identify 51 new multiply imaged galaxies, quadrupling the previous census and bringing the grand total to 68, comprising 194 individual lensed images. Having selected a subset of the 57 most securely identified multiply imaged galaxies, we use the Lenstool software package to constrain a lens model comprised of two cluster-scale dark-matter halos and 98 galaxy-scale halos. Our best-fit model predicts image positions with an RMS error of 0. 68'', which constitutes an improvement of almost a factor of two over previous, pre-HFF models of this cluster. We find the total projected mass inside a 200~kpc aperture to be (1. 600. 01) 10^14\ M_, a measurement that offers a three-fold improvement in precision, reaching the percent level for the first time in any cluster. Finally, we quantify the increase in precision of the derived gravitational magnification of high-redshift galaxies and find an improvement by a factor of 2. 5 in the statistical uncertainty. Our findings impressively confirm that HFF imaging has indeed opened the domain of high-precision mass measurements for massive clusters of galaxies.