Cosmic shear cosmology beyond two-point statistics: a combined peak count and correlation function analysis of DES-Y1

We constrain cosmological parameters from a joint cosmic shear analysis of peak-counts and the two-point shear correlation functions, as measured from the Dark Energy Survey (DES-Y1). We find the structure growth parameter S-8 equivalent to root Omega(m)/0.3 = 0.766(-0.038)(+0.033) which, at 4.8 percent precision, provides one of the tightest constraints on S-8 from the DES-Y1 weak lensing data. In our simulation-based method we determine the expected DES-Y1 peak-count signal for a range of cosmologies sampled in four w cold dark matter parameters (Omega(m), sigma(8), h, w(0)). We also determine the joint covariance matrix with over 1000 realizations at our fiducial cosmology. With mock DES-Y1 data we calibrate the impact of photometric redshift and shear calibration uncertainty on the peak-count, marginalizing over these uncertainties in our cosmological analysis. Using dedicated training samples we show that our measurements are unaffected by mass resolution limits in the simulation, and that our constraints are robust against uncertainty in the effect of baryon feedback. Accurate modelling for the impact of intrinsic alignments on the tomographic peak-count remains a challenge, currently limiting our exploitation of cross-correlated peak counts between high and low redshift bins. We demonstrate that once calibrated, a fully tomographic joint peak-count and correlation functions analysis has the potential to reach a 3 percent precision on S-8 for DES-Y1. Our methodology can be adopted to model any statistic that is sensitive to the non-Gaussian information encoded in the shear field. In order to accelerate the development of these beyond-two-point cosmic shear studies, our simulations are made available to the community upon request.

Automated summary

In this study, cosmological parameters are constrained through a joint analysis of peak counts and two-point shear correlation functions from the Dark Energy Survey (DES-Y1). The structure growth parameter S-8 is determined to be 0.766(-0.038)(+0.033), providing one of the tightest constraints on S-8 from DES-Y1 weak lensing data with 4.8 percent precision. Through simulations, the expected DES-Y1 peak-count signal for various cosmologies is determined, and the impact of photometric redshift and shear calibration uncertainty is calibrated in the cosmological analysis.