From Weak Lensing to non-Gaussianity via Minkowski Functionals
  We present a new harmonic-domain approach for extracting morphological
information, in the form of Minkowski Functionals (MFs), from weak lensing (WL)
convergence maps. Using a perturbative expansion of the MFs, which is expected
to be valid for the range of angular scales probed by most current weak-lensing
surveys, we show that the study of three generalized skewness parameters is
equivalent to the study of the three MFs defined in two dimensions. We then
extend these skewness parameters to three associated skew-spectra which carry
more information about the convergence bispectrum than their one-point
counterparts. We discuss various issues such as noise and incomplete sky
coverage in the context of estimation of these skew-spectra from realistic
data. Our technique provides an alternative to the pixel-space approaches
typically used in the estimation of MFs, and it can be particularly useful in
the presence of masks with non-trivial topology. Analytical modeling of weak
lensing statistics relies on an accurate modeling of the statistics of
underlying density distribution. We apply three different formalisms to model
the underlying dark-matter bispectrum: the hierarchical ansatz, halo model and
a fitting function based on numerical simulations; MFs resulting from each of
these formalisms are computed and compared. We investigate the extent to witch
late-time gravity-induced non-Gaussianity (to which weak lensing is primarily
sensitive) can be separated from primordial non-Gaussianity and how this
separation depends on source redshift and angular scale.
