6x2pt: Forecasting gains from joint weak lensing and galaxy clustering analyses with spectroscopic-photometric galaxy cross-correlations
astro-ph.CO
/ Authors
Harry Johnston, Nora Elisa Chisari, Shahab Joudaki, Robert Reischke, Benjamin Stölzner, Arthur Loureiro, Constance Mahony, Sandra Unruh, Angus H. Wright, Marika Asgari
and 18 more authors
Maciej Bilicki, Pierre Burger, Andrej Dvornik, Christos Georgiou, Benjamin Giblin, Catherine Heymans, Hendrik Hildebrandt, Benjamin Joachimi, Konrad Kuijken, Shun-Sheng Li, Laila Linke, Lucas Porth, HuanYuan Shan, Tilman Tröster, Jan Luca van den Busch, Maximilian von Wietersheim-Kramsta, Ziang Yan, Yun-Hao Zhang
/ Abstract
We explore the enhanced self-calibration of photometric galaxy redshift distributions, $n(z)$, through the combination of up to six two-point functions. Our $\rm 3\times2pt$ configuration is comprised of photometric shear, spectroscopic galaxy clustering, and spectroscopic-photometric galaxy-galaxy lensing (GGL). We further include spectroscopic-photometric cross-clustering; photometric GGL; and photometric auto-clustering, using the photometric shear sample as density tracer. We perform simulated likelihood forecasts of the cosmological and nuisance parameter constraints for Stage-III- and Stage-IV-like surveys. For the Stage-III-like case, we employ realistic but perturbed redshift distributions, and distinguish between "coherent" shifting in one direction, versus more internal scattering and full-shape errors. For perfectly known $n(z)$, a $\rm 6\times2pt$ analysis gains $\sim40\%$ in Figure of Merit (FoM) in the $S_8\equivσ_8\sqrt{Ω_{\rm m}/0.3}$ and $Ω_{\rm m}$ plane relative to the $\rm 3\times2pt$ analysis. If untreated, coherent and incoherent redshift errors lead to inaccurate inferences of $S_8$ and $Ω_{\rm m}$, respectively. Employing bin-wise scalar shifts $δ{z}_i$ in the tomographic mean redshifts reduces cosmological parameter biases, with a $\rm 6x2pt$ analysis constraining the shift parameters with $2-4$ times the precision of a photometric $\rm 3^{ph}\times2pt$ analysis. For the Stage-IV-like survey, a $\rm 6\times2pt$ analysis doubles the FoM($σ_8{-}Ω_{\rm m}$) compared to any $\rm 3\times2pt$ or $\rm 3^{ph}\times2pt$ analysis, and is only $8\%$ less constraining than if the $n(z)$ were perfectly known. A Gaussian mixture model for the $n(z)$ reduces mean-redshift errors and preserves the $n(z)$ shape. It also yields the most accurate and precise cosmological constraints for any $N\rm\times2pt$ configuration given $n(z)$ biases.