Observational constraints on the central mass distribution of galaxy clusters provide a key test of the nature of dark matter and contain invaluable information on the formation and evolution of the clusters and their brightest cluster galaxies. Scientists at the MPA have used an advanced lens modelling technique to map the mass distribution of the galaxy cluster MACS J1149.5+2223 over a wide range of distances. They found that this cluster has a large core and its mass profile therefore has to be shallower than what is expected from cold dark matter N-body numerical simulations.

Top.Contours of the cluster mass distribution including scaled cluster galaxies for two different models (blue: position based modelling; red: hybrid modelling). The grey background shows the same observation as in figure 1, but in just one colour filter (F555W).

For a little more insight into the project see this：http://www.mpa-garching.mpg.de/mpa/research/current_research/hl2014-9/hl2014-9-en.html