Kavli Affiliate: Masahiro Takada
| First 5 Authors: Tianqing Zhang, Xiangchong Li, Roohi Dalal, Rachel Mandelbaum, Michael A. Strauss
| Summary:
Cosmological weak lensing measurements rely on a precise measurement of the
shear two-point correlation function (2PCF) along with a deep understanding of
systematics that affect it. In this work, we demonstrate a general framework
for detecting and modeling the impact of PSF systematics on the cosmic shear
2PCF, and mitigating its impact on cosmological analysis. Our framework can
describe leakage and modeling error from all spin-2 quantities contributed by
the PSF second and higher moments, rather than just the second moments, using
the cross-correlations between galaxy shapes and PSF moments. We interpret null
tests using the HSC Year 3 (Y3) catalogs with this formalism, and find that
leakage from the spin-2 combination of PSF fourth moments is the leading
contributor to additive shear systematics, with total contamination that is an
order of magnitude higher than that contributed by PSF second moments alone. We
conducted a mock cosmic shear analysis for HSC Y3, and find that, if
uncorrected, PSF systematics can bias the cosmological parameters $Omega_m$
and $S_8$ by $sim$0.3$sigma$. The traditional second moment-based model can
only correct for a 0.1$sigma$ bias, leaving the contamination largely
uncorrected. We conclude it is necessary to model both PSF second and fourth
moment contamination for HSC Y3 cosmic shear analysis. We also reanalyze the
HSC Y1 cosmic shear analysis with our updated systematics model, and identify a
0.07$sigma$ bias on $Omega_m$ when using the more restricted second moment
model from the original analysis. We demonstrate how to self-consistently use
the method in both real space and Fourier space, assess shear systematics in
tomographic bins, and test for PSF model overfitting.
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