Optimal PSF modeling for weak lensing: complexity and sparsity

Understand

We investigate the impact of point spread function (PSF) fitting errors on cosmic shear measurements using the concepts of complexity and sparsity.

• Complexity, introduced in a previous paper, characterizes the number of degrees of freedom of the PSF.
• For instance, fitting an underlying PSF with a model with low complexity will lead to small statistical errors on the model parameters, however these parameters could suffer from large biases.
• Alternatively, fitting with a large number of parameters will tend to reduce biases at the expense of statistical errors.