  We present a quantitative analysis of the largest contiguous maps of
projected mass density obtained from gravitational lensing shear. We use data
from the 154 deg2 covered by the Canada-France-Hawaii Telescope Lensing Survey.
Our study is the first attempt to quantitatively characterize the scientific
value of lensing maps, which could serve in the future as a complementary
approach to the study of the dark universe with gravitational lensing. We show
that mass maps contain unique cosmological information beyond that of
traditional two-points statistical analysis techniques. Using a series of
numerical simulations, we first show how, reproducing the CFHTLenS observing
conditions, gravitational lensing inversion provides a reliable estimate of the
projected matter distribution of large scale structure. We validate our
analysis by quantifying the robustness of the maps with various statistical
estimators. We then apply the same process to the CFHTLenS data. We find that
the 2-points correlation function of the projected mass is consistent with the
cosmological analysis performed on the shear correlation function discussed in
the CFHTLenS companion papers. The maps also lead to a significant measurement
of the third order moment of the projected mass, which is in agreement with
analytic predictions, and to a marginal detection of the fourth order moment.
Tests for residual systematics are found to be consistent with zero for the
statistical estimators we used. A new approach for the comparison of the
reconstructed mass map to that predicted from the galaxy distribution reveals
the existence of giant voids in the dark matter maps as large as 3 degrees on
the sky. Our analysis shows that lensing mass maps can be used for new
techniques such as peak statistics and the morphological analysis of the
projected dark matter distribution.
