Program: GN-2015A-Q-25

Very massive galaxy clusters are extremely rare objects that are disproportionally valuable for cosmological and astrophysical studies. Specifically, they constitute powerful gravitational telescopes whose amplification allows us to probe the Universe to unprecedented depth, as underlined impressively by recent results on the galaxy UV luminosity function at z>7 from the HST Frontier Fields project. Extending MACS to z∼0.9, eMACS uses PanSTARRS 3π color images to optically screen and identify X-ray sources from the ROSAT All-Sky Survey. As demonstrated before, our identification and target selection strategy is highly efficient. As we enter the final phase of the compilation of our sample, we request the equivalent of 1 Gemini/GMOS night for deep four-filter imaging of the most distant eMACS clusters, in preparation for the next generation of in-depth studies of extragalactic structure formation and evolution at ever increasing redshifts.