Substructure tests of LCDM from cluster lensing in the HST Frontier Fields.
The HST Frontier Fields data permit exquisite reconstruction of the dark matter substructure distribution in lensing clusters. Comparison of the recovered sub halo mass function with state of the art Illustris simulations reveals concordance with the LCDM model. However, we find that the radial distribution of substructure is not reproduced in the simulations. We discuss implications of these results for the standard cold dark matter paradigm.