Gappy Weak Lensing: KL Interpolation of Shear Fields

Jake VanderPlas
(University of Washington)


Surveys of gravitational shear due to large-scale structure are becoming an important tool for precise measurements of cosmological parameters, including the possible evolution of dark energy. Many of the new statistical tools being developed in this field rely on obtaining unbiased lensing mass maps over large fields: fields which will, in general, have complicated geometries and masking due to inhomogeneous sky coverage, foreground sources, etc. We have developed an interpolation procedure for gappy shear fields based on Karhunen-Loeve (KL) decomposition. Along with interpolation, the KL analysis results in a suppression of noise on scales relevant to cosmological studies using shear peaks. In this talk, I will review recent studies of the cosmological information encoded in high-convergence regions of shear fields, and show how our new KL framework addresses some potential problems with this approach..