A Unified Catalog-level Reanalysis of Stage-III Cosmic Shear Surveys

Longley, Emily Phillips; Chang, C.; Walter, Christopher W.; Zuntz, Joe; Ishak, Mustapha; Mandelbaum, Rachel; Miyatake, Hironao; Nicola, Andrina; Pedersen, Eske M.; Pereira, M. E. S.; Prat, J.; Sánchez, J.; Tröster, Tilman; Troxel, M. A.; Wright, Angus H.; Collaboration, The LSST Dark Energy Science

doi:10.48550/arxiv.2208.07179

Cited by 1 publication

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“…Carrying out combined analyses that add the statistical power of different experiments [8,10,16,[22][23][24][25] is key to improving their individual cosmological constraints, and to test the robustness of these constraints to instrumental or observational systematics. This is JCAP01(2023)025 often challenging when surveys targeting potentially different source populations share part of the sky, due to the non-trivial survey geometry effects, and the need to characterise the noise properties of the sources common to both datasets.…”

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confidence: 99%

Combining cosmic shear data with correlated photo-z uncertainties: constraints from DESY1 and HSC-DR1

García-García

Alonso

Ferreira

et al. 2023

J. Cosmol. Astropart. Phys.

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An accurate calibration of the source redshift distribution p(z) is a key aspect in the analysis of cosmic shear data. This, one way or another, requires the use of spectroscopic or high-quality photometric samples. However, the difficulty to obtain colour-complete spectroscopic samples matching the depth of weak lensing catalogs means that the analyses of different cosmic shear datasets often use the same samples for redshift calibration. This introduces a source of statistical and systematic uncertainty that is highly correlated across different weak lensing datasets, and which must be accurately characterised and propagated in order to obtain robust cosmological constraints from their combination. In this paper we introduce a method to quantify and propagate the uncertainties on the source redshift distribution in two different surveys sharing the same calibrating sample. The method is based on an approximate analytical marginalisation of the p(z) statistical uncertainties and the correlated marginalisation of residual systematics. We apply this method to the combined analysis of cosmic shear data from the DESY1 data release and the HSC-DR1 data, using the COSMOS 30-band catalog as a common redshift calibration sample. We find that, although there is significant correlation in the uncertainties on the redshift distributions of both samples, this does not change the final constraints on cosmological parameters significantly. The same is true also for the impact of residual systematic uncertainties from the errors in the COSMOS 30-band photometric redshifts. Additionally, we show that these effects will still be negligible in Stage-IV datasets. Finally, the combination of DESY1 and HSC-DR1 allows us to constrain the “clumpiness” parameter to S 8 = 0.768+0.021 -0.017. This corresponds to a ∼√(2) improvement in uncertainties with respect to either DES or HSC alone.

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