Size magnification as a complement to Cosmic Shear

TL;DR

This paper explores how cosmic size magnification can complement cosmic shear in weak lensing surveys, showing it can provide high-precision cosmological estimates with different systematic challenges.

Contribution

It demonstrates that size magnification can be an effective and complementary method for estimating the convergence field in weak lensing, especially with space-based data.

Findings

Size estimation is effective for galaxies larger than the PSF with high SNR.

Size magnification offers similar statistical power to cosmic shear.

Space-based observations enable accurate size magnification measurements.

Abstract

We investigate the extent to which cosmic size magnification may be used to com- plement cosmic shear in weak gravitational lensing surveys, with a view to obtaining high-precision estimates of cosmological parameters. Using simulated galaxy images, we find that size estimation can be an excellent complement, finding that unbiased estimation of the convergence field is possible with galaxies with angular sizes larger than the point-spread function (PSF) and signal-to-noise ratio in excess of 10. The statistical power is similar to, but not quite as good as, cosmic shear, and it is subject to different systematic effects. Application to ground-based data will be challeng- ing, with relatively large empirical corrections required to account for with biases for galaxies which are smaller than the PSF, but for space-based data with 0.1 arcsecond resolution, the size distribution of galaxies brighter than i=24 is ideal for accurate estimation of cosmic size magnification.