Joint constraints on cosmology and the impact of baryon feedback: Combining KiDS-1000 lensing with the thermal Sunyaev–Zeldovich effect from <i>Planck</i> and ACT

We conduct a pseudo-$C_\ell$ analysis of the tomographic cross-correlation between 1000 deg$^2$ weak lensing data from Kilo-Degree Survey (KiDS-1000) and thermal Sunyaev-Zeldovich (tSZ) effect measured by Planck Atacama Cosmology Telescope (ACT). Using HMx, halo-model-based approach that consistently models gas, star, dark matter components, we are able to derive constraints on both cosmology baryon feedback for first time these data, marginalising over redshift uncertainties, intrinsic alignment galaxies, contamination cosmic infrared background (CIB). find our results be insensitive CIB, while provides small but significant contribution lensing--tSZ cross-correlation. The cosmological consistent with those other low-redshift probes prefer strong feedback. inferred amplitude signal, which scales as $\sigma_8(\Omega_\mathrm{m}/0.3)^{0.2}$, is low $\sim 2\,\sigma$ compared primary microwave Planck. measurements then combined KiDS-1000 shear into novel joint analysis, accounting full cross-covariance probes, providing tight breaking parameter degeneracies inherent probes. gives an improvement 40% constraint $S_8=\sigma_8\sqrt{\Omega_\mathrm{m}/0.3}$ alone, hydrodynamical simulations, demonstrating potential such analyses baryonic tracers tSZ effect. discuss remaining modelling challenges need addressed if included in future precision-cosmology analyses.