Rubin-LSST

Abstract:

We conduct a pseudo-C_ℓ analysis of the tomographic cross-correlation between 1000 deg² 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 these 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 σ₈(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_ℓ 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 S₈ = σ₈Ω_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 such as 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.

Abstract:

We explore a sample of 1492 galaxies with measurements of the mean stellar population properties and the spin parameter proxy, λRe⁠, drawn from the SAMI Galaxy Survey. We fit a global [α/Fe]–σ relation, finding that [α/Fe]=(0.395±0.010)log10(σ)−(0.627±0.002)⁠. We observe an anti-correlation between the residuals Δ[α/Fe] and the inclination-corrected λeoRe⁠, which can be expressed as Δ[α/Fe]=(−0.057±0.008)λeoRe+(0.020±0.003)⁠. The anti-correlation appears to be driven by star-forming galaxies, with a gradient of Δ[α/Fe]∼(−0.121±0.015)λeoRe⁠, although a weak relationship persists for the subsample of galaxies for which star formation has been quenched. We take this to be confirmation that disc-dominated galaxies have an extended duration of star formation. At a reference velocity dispersion of 200 km s−1, we estimate an increase in half-mass formation time from ∼0.5 Gyr to ∼1.2 Gyr from low- to high-λeoRe galaxies. Slow rotators do not appear to fit these trends. Their residual α-enhancement is indistinguishable from other galaxies with λeoRe⪅0.4⁠, despite being both larger and more massive. This result shows that galaxies with λeoRe⪅0.4 experience a similar range of star formation histories, despite their different physical structure and angular momentum.