http://arxiv.org/abs/1612.00852
Accurate forward modeling of weak lensing (WL) observables from cosmological parameters is necessary for upcoming galaxy surveys. Because WL probes structures in the non–linear regime, analytical forward modeling is very challenging, if not impossible. Numerical simulations of WL features rely on ray–tracing through the outputs of $N$–body simulations, which requires knowledge of the gravitational potential and accurate solvers for light ray trajectories. A less accurate procedure, based on the Born approximation, only requires knowledge of the density field, and can be implemented more efficiently and at a lower computational cost. In this work, we use simulations to show that deviations of the Born–approximated convergence power spectrum, skewness and kurtosis from their fully ray–traced counterparts are consistent with the smallest non–trivial post–Born corrections (so-called geodesic and lens-lens terms). We find, however, that the perturbative approach for the geodesic correction breaks down at higher orders. We also find that cosmological parameter biases induced by the Born approximation are negligible even for an LSST–like survey, once galaxy shape noise is considered, and we conclude that the Born approximation is sufficient for future galaxy WL analyses. Using the \ttt{LensTools} software suite, we show that the Born approximation saves a factor of 4 in computing time with respect to the full ray–tracing in reconstructing the convergence.
A. Petri, Z. Haiman and M. May
Tue, 6 Dec 16
57/71
Comments: 10 pages, 6 figures, submitted to PRD