Systematic vs. Statistical Uncertainties in Masses and Magnifications of
  the Hubble Frontier Fields
  The Hubble Frontier Fields data, along with multiple data sets obtained by
other telescopes, have provided some of the most extensive constraints on
cluster lenses to date. Multiple lens modeling teams analyzed the fields and
made public a number of deliverables. By comparing these results, we can then
undertake a unique and vital test of the state of cluster lens modeling.
Specifically, we see how well the different teams can reproduce similar
magnifications and mass profiles. We find that the circularly averaged mass
profiles of the fields are remarkably constrained (scatter <5%) at distances of
1 arcmin from the cluster core, yet magnifications can vary significantly.
Averaged across the six fields, we find a bias of -6% (-17%) and a scatter of
~40% (~65%) at a modest magnification of 3 (10). Statistical errors reported by
individual teams are often significantly smaller than the differences among all
the teams, indicating the importance of continued systematics studies in
cluster lensing.
