Abstract
We constrain cosmological parameters from a joint cosmic shear analysis of
peak-counts and the two-point shear correlation function, as measured from the
Dark Energy Survey (DES-Y1). We find the structure growth parameter $S_8\equiv
\sigma_8Ømega_m/0.3 = 0.766^+0.033_-0.038$, which at 4.8%
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 $w$CDM
parameters ($Ømega_m$, $\sigma_8$, $h$, $w_0$). We also determine the
joint peak-correlation function covariance matrix with over 1000 realisations
at our fiducial cosmology. With mock DES-Y1 data we calibrate the impact of
photometric redshift and shear calibration uncertainty on the peak-count,
marginalising 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 function analysis has the
potential to reach a 3% 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, on request.
Description
Cosmic Shear Cosmology Beyond 2-Point Statistics: A Combined Peak Count and Correlation Function Analysis of DES-Y1
Links and resources
Tags