CosmoSClub: 09-10-2018

Date: October 9th 2018

Speaker: Chieh-An Lin (IfA, University of Edinburgh)

Title: Predicting weak-lensing covariance with a fast simulator

Weak lensing has been shown as an outstanding tool to constrain cosmology. The state-of-the-art studies have used the power spectrum and peak counts as estimators, and the combination of the two can break down parameter degeneracies and maximize the information extraction.

To constrain cosmology with both estimators, understanding the joint covariance is crucial. However, calculating it analytically seems to be intractable for peaks, and the empirical approach with N-body simulations will be expensive as the size of lensing surveys increase.

I will present a fast solution to solve this problem. The proposed approach simulates lognormal fields and halo models to predict lensing signals. We compared the resulting joint covariance with the one from a large number of N-body simulations and found an excellent agreement. In addition, our approach is orders of magnitude faster than N-body runs.