Joint constraints on cosmology and the impact of baryon feedback: combining KiDS-1000 lensing with the thermal Sunyaev-Zeldovich effect from Planck and ACT

Abstract

We conduct a pseudo-C analysis of the tomographic cross-correlation between 1000 deg 2 of weak lensing data from the Kilo-Degree Survey (KiDS-1000) and the thermal Sunyaev-Zeldovich (tSZ) effect measured by Planck and the Atacama Cosmology Telescope (ACT). Using HMX, a halo-model-based approach that consistently models the gas, star, and dark matter components, we are able to derive constraints on both cosmology and baryon feedback for the first time from this data, marginalising over redshift uncertainties, intrinsic alignment of galaxies, and contamination by the cosmic infrared background (CIB). We find our results to be insensitive to the CIB, while intrinsic alignment provides a small but significant contribution to the lensing-tSZ cross-correlation. The cosmological constraints are consistent with those of other low-redshift probes and prefer strong baryon feedback. The inferred amplitude of the lensing-tSZ cross-correlation signal, which scales as σ 8 (Ω m /0.3) 0.2 , is low by ∼ 2 σ compared to the primary cosmic microwave background constraints by Planck. The lensing-tSZ measurements are then combined with pseudo-C measurements of KiDS-1000 cosmic shear into a novel joint analysis, accounting for the full cross-covariance between the probes, providing tight cosmological constraints by breaking parameter degeneracies inherent to both probes. The joint analysis gives an improvement of 40 % on the constraint of S 8 = σ 8 Ω m /0.3 over cosmic shear alone, while providing constraints on baryon feedback consistent with hydrodynamical simulations, demonstrating the potential of such joint analyses with baryonic tracers like the tSZ effect. We discuss remaining modelling challenges that need to be addressed if these baryonic probes are to be included in future precision-cosmology analyses.

The halo model with beyond-linear halo bias: unbiasing cosmological constraints from galaxy-galaxy lensing and clustering

“…Importantly the halo model allows for the marginalisation over nuisance parameters that can account for uncertainty on the impact of baryon feedback on the simulated dark matter distribution (Debackere et al 2021). This approach also facilitates straightforward extensions to simultaneously model multiple large-scale structure probes and constrain baryon feedback models (see for example Mead et al 2020;Acuto et al 2021;Tröster et al 2021). In addition a halo model approach permits the study of an essentially unlimited range of exotic cosmological models (Cataneo et al 2019;Bose et al 2020).…”

Snowmass2021: Opportunities from Cross-survey Analyses of Static Probes

“…Cross-correlations are essential to this program, since the tSZ and kSZ by themselves provide only a line-of-sight integral of the ionized gas properties. By cross-correlating tSZ measurements with low-redshift structure, gas properties at different redshifts can be extracted, enabling powerful tests of feedback models [39][40][41][42]. The kSZ effect, on the other hand, depends on both the gas density and its velocity.…”

Large-scale dark matter simulations

“…Perhaps, more interestingly will be the comparison with observational data. Although current constraint are able to only marginally rule out the most extreme feedback scenarios (Huang et al 2021), new prospects for estimating the magnitude of baryonic effects in the real Universe will open with the imminent improvement in weak lensing surveys and in the joint analysis of gas observables (kinetic and thermal Sunyaev-Zeldovich effects, and X-ray gas fractions; Schneider et al 2021;Tröster et al 2021).…”