2016MNRAS.457.2029J

We present a high-precision mass model of the galaxy cluster MACS J1149.6+ 2223, based on a strong gravitational lensing analysis of Hubble Space Telescope Frontier Fields (HFF) imaging data and spectroscopic follow-up with Gemini/Gemini Multi-Object Spectrographs (GMOS) and Very Large Telescope (VLT)/Multi Unit Spectroscopic Explorer (MUSE). Our model includes 12 new multiply imaged galaxies, bringing the total to 22, composed of 65 individual lensed images. Unlike the first two HFF clusters, Abell 2744 and MACS J0416.1-2403, MACS J1149 does not reveal as many multiple images in the HFF data. Using the lenstool software package and the new sets of multiple images, we model the cluster with several cluster-scale dark matter haloes and additional galaxy-scale haloes for the cluster members. Consistent with previous analyses, we find the system to be complex, composed of five cluster-scale haloes. Their spatial distribution and lower mass, however, makes MACS J1149 a less powerful lens. Our best-fitting model predicts image positions with an rms of 0.91 arcsec. We measure the total projected mass inside a 200-kpc aperture as (1.840±0.006) x 10¹⁴ M_☉, thus reaching again 1 per cent precision, following our previous HFF analyses of MACS J0416.1-2403 and Abell 2744. In light of the discovery of the first resolved quadruply lensed supernova, SN Refsdal, in one of the multiply imaged galaxies identified in MACS J1149, we use our revised mass model to investigate the time delays and predict the rise of the next image between 2015 November and 2016 January.