We present strong-lensing analyses of three galaxy clusters, RXJ2129.4+0009 (z=0.235), MS0451.6-0305 (z=0.55), and MACSJ2129.4-0741 (z=0.589), using the powerful combination of Hubble Space Telescope (HST) multi-band observations, and Multi-Unit Spec
troscopic Explorer (MUSE) spectroscopy. In RXJ2129, we newly spectroscopically confirm 15 cluster members. Our resulting mass model uses 8 multiple image systems as we include a galaxy-galaxy lensing system North-East of the cluster, and is composed of 71 halos including one dark matter cluster-scale halo and 2 galaxy-scale halos optimized individually. For MS0451, we report the spectroscopic identification of 2 new systems of multiple images in the Northern region, and 112 cluster members. Our mass model uses 16 multiple image systems, and 146 halos, including 2 large-scale halos, and 7 galaxy-scale halos independently optimized. For MACSJ2129, we report the spectroscopic identification of one new multiple image system at z=4.41, and newly measure spectroscopic redshifts for 4 cluster members. Our mass model uses 14 multiple image systems, and is composed of 151 halos, including 2 large-scale halos and 4 galaxy-scale halos independently optimized. Our best models have rms of 0.29, 0.6, 0.74 in the image plane for RXJ2129, MS0451, and MACSJ2129 respectively. This analysis presents a detailed comparison with the existing literature showing excellent agreements, and discuss specific studies of lensed galaxies, e.g. a group of submilimeter galaxies at z=2.9 in MS0451, and a bright z=2.1472 red singly imaged galaxy in MACSJ2129.
We present a multi-wavelength analysis of the core of the massive galaxy cluster MACS,J0417.5-1154 ($z = 0.441$; MACS;J0417). Our analysis takes advantage of VLT/MUSE observations which allow the spectroscopic confirmation of three strongly-lensed sy
stems. One of these, nick-named emph{The Doughnut}, consists of three complete images of a complex ring galaxy at $z = 0.8718$ and a fourth, partial and radial image close to the Brightest Cluster Galaxy (BCG) only discernible thanks to its strong [OII] line emission. The best-fit mass model (rms of 0.38arcsec) yields a two-dimensional enclosed mass of $M({rm R < 200,kpc}) = (1.77pm0.03)times10^{14},msun$ and almost perfect alignment between the peaks of the BCG light and the dark matter of ($0.5pm0.5$)arcsec . Our finding that a significant misalignment results when the radial image of emph{The Doughnut} is omitted serves as an important caveat for studies of BCG-dark matter offsets in galaxy clusters. Using emph{Chandra} data to map the intra-cluster gas, we observe an offset between the gas and dark-matter peaks of ($1.7pm0.5$)arcsec, and excellent alignment of the X-ray peak with the location of optical emission line associated with the BCG. We interpret all observational evidence in the framework of on-going merger activity, noting specifically that the coincidence between the gas peak and the peak of blue light from the BCG may be evidence of dense, cold gas leading to direct star formation. We use the surface area $sigma_{mu}$ above a given magnification factor $mu$ as a metric to estimate the lensing power of MACS,J0417. We obtain $sigma(mu > 3) = 0.22$,arcmin$^2$ confirming MACS,J0417 as an efficient gravitational lens. Finally, we discuss the differences between our mass model and Mahler et al. (2018).
We present a high-precision mass model of galaxy cluster Abell 2744, based on a strong-gravitational-lensing analysis of the emph{Hubble Space Telescope Frontier Fields} (HFF) imaging data, which now include both emph{Advanced Camera for Surveys} and
emph{Wide-Field Camera 3} observations to the final depth. Taking advantage of the unprecedented depth of the visible and near-infrared data, we identify 34 new multiply imaged galaxies, bringing the total to 61, comprising 181 individual lensed images. In the process, we correct previous erroneous identifications and positions of multiple systems in the northern part of the cluster core. With the textsc{Lenstool} software and the new sets of multiple images, we model the cluster using two cluster-scale dark matter halos plus galaxy-scale halos for the cluster members. Our best-fit model predicts image positions with an emph{RMS} error of 0.69$arcsec$, which constitutes an improvement by almost a factor of two over previous parametric models of this cluster. We measure the total projected mass inside a 200~kpc aperture as ($2.162pm 0.005$)$times 10^{14}M_{odot}$, thus reaching 1% level precision for the second time, following the recent HFF measurement of MACSJ0416.1-2403. Importantly, the higher quality of the mass model translates into an overall improvement by a factor of 4 of the derived magnification factor. % for the high-redshift lensed background galaxies. Together with our previous HFF gravitational lensing analysis, this work demonstrates that the HFF data enables high-precision mass measurements for massive galaxy clusters and the derivation of robust magnification maps to probe the early Universe.
We use a joint optical/X-ray analysis to constrain the geometry and history of the ongoing merging event in the massive galaxy cluster MACSJ0416.1-2403 (z=0.397). Our investigation of cluster substructure rests primarily on a combined strong- and wea
k-lensing mass reconstruction based on the deep, high-resolution images obtained for the Hubble Frontier Fields initiative. To reveal the systems dynamics, we complement this lensing analysis with a study of the intra-cluster gas using shallow Chandra data, and a three-dimensional model of the distribution and motions of cluster galaxies derived from over 100 spectroscopic redshifts. The multi-scale grid model obtained from our combined lensing analysis extends the high-precision strong-lensing mass reconstruction recently performed to cluster-centric distances of almost 1 Mpc. Our analysis detects the two well known mass concentrations in the cluster core. A pronounced offset between collisional and collisionless matter is only observed for the SW cluster component, while excellent alignment is found for the NE cluster. Both the lensing analysis and the distribution of cluster light strongly suggest the presence of a third massive structure, almost 2 arcmin SW of the cluster centre. Since no X-ray emission is detected in this region, we conclude that this structure is non-virialised and speculate that it might be part of a large-scale filament almost aligned with our line of sight. Combining all evidence from the distribution of dark and luminous matter, we propose two alternative scenarios for the trajectories of the components of MACSJ0416.1-2403. Upcoming deep X-ray observations that allow the detection of shock fronts, cold cores, and sloshing gas (all key diagnostics for studies of cluster collisions) will allow us to test, and distinguish between these two scenarios.
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 $(1.60pm0.01)times 10^{14} M_odot$, 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 $sim$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.
