SKA Weak Lensing II: Simulated Performance and Survey Design Considerations

TL;DR

This paper develops a simulation pipeline for SKA weak lensing surveys, optimizing survey parameters like frequency band and area to enhance dark energy constraints, and forecasts improved performance with SKA2.

Contribution

The paper introduces a comprehensive simulation pipeline for SKA weak lensing surveys and provides optimized survey design recommendations based on signal-to-noise and dark energy metrics.

Findings

Higher frequency Band 2 (950-1760 MHz) is preferred over Band 1.

Optimal survey area is around 5,000 square degrees for SKA1.

SKA2 significantly improves weak lensing survey performance and dark energy constraints.

Abstract

We construct a pipeline for simulating weak lensing cosmology surveys with the Square Kilometre Array (SKA), taking as inputs telescope sensitivity curves; correlated source flux, size and redshift distributions; a simple ionospheric model; source redshift and ellipticity measurement errors. We then use this simulation pipeline to optimise a 2-year weak lensing survey performed with the first deployment of the SKA (SKA1). Our assessments are based on the total signal-to-noise of the recovered shear power spectra, a metric that we find to correlate very well with a standard dark energy figure of merit. We first consider the choice of frequency band, trading off increases in number counts at lower frequencies against poorer resolution; our analysis strongly prefers the higher frequency Band 2 (950-1760 MHz) channel of the SKA-MID telescope to the lower frequency Band 1 (350-1050 MHz). Best results would be obtained by allowing the centre of Band 2 to shift towards lower frequency, around 1.1 GHz. We then move on to consider survey size, finding that an area of 5,000 square degrees is optimal for most SKA1 instrumental configurations. Finally, we forecast the performance of a weak lensing survey with the second deployment of the SKA. The increased survey size (3$\pi$\,steradian) and sensitivity improves both the signal-to-noise and the dark energy metrics by two orders of magnitude.