Abstract
We investigate potential gains in cosmological constraints from the combination of galaxy clustering and galaxygalaxy lensing by optimizing the lens galaxy sample selection using information from Dark Energy Survey (DES) Year 3 data and assuming the DES Year 1 metacalibration sample for the sources. We explore easily reproducible selections based on magnitude cuts in iband as a function of (photometric) redshift, z_{phot}, and benchmark the potential gains against those using the wellestablished redMaGiC [E. Rozo et al., Mon. Not. R. Astron. Soc. 461, 1431 (2016)] sample. We focus on the balance between density and photometric redshift accuracy, while marginalizing over a realistic set of cosmological and systematic parameters. Our optimal selection, the MagLim sample, satisfies i < 4z_{phot }+ 18 and has ∼30% wider redshift distributions but ∼3.5 times more galaxies than redMaGiC. Assuming a wCDM model (i.e. with a free parameter for the dark energy equation of state) and equivalent scale cuts to mitigate nonlinear effects, this leads to 40% increase in the figure of merit for the pair combinations of Ω_{m}, w, and σ_{8}, and gains of 16% in σ_{8}, 10% in Ωm, and 12% in w. Similarly, in ΛCDM, we find an improvement of 19% and 27% on σ_{8} and Ωm, respectively. We also explore fluxlimited samples with a flat magnitude cut finding that the optimal selection, i < 22.2, has ∼7 times more galaxies and ∼20% wider redshift distributions compared to MagLim, but slightly worse constraints. We show that our results are robust with respect to the assumed galaxy bias and photometric redshift uncertainties with only moderate further gains from increased number of tomographic bins or the inclusion of bin crosscorrelations, except in the case of the fluxlimited sample, for which these gains are more significant.
Original language  English 

Article number  043503 
Pages (fromto)  125 
Number of pages  25 
Journal  Physical Review D 
Volume  103 
Issue number  4 
Early online date  1 Feb 2021 
DOIs  
Publication status  Published  15 Feb 2021 
Keywords
 dark energy
 dark matter
 cosmology
 observations
 cosmological parameters
 UKRI
 STFC
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Collaboration, D. (Creator), Avila Perez, S. (Creator) & Bacon, D. (Creator), American Physical Society, 15 Feb 2021
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