Speaker
Description
Stage IV surveys such as LSST will probe deeply into the nonlinear regime, where systematic effects from galaxy bias and baryonic feedback become dominant and poorly constrained nuisance parameters can lead to degeneracies.
We perform a $3\times2$pt analysis for LSST Y1 and Y10 to investigate how modelling choices impact cosmological constraints. In particular, we explore the balance between model complexity and scale cuts, focusing on parameter degeneracies and baryonic feedback effects on the galaxy–matter and galaxy-galaxy power spectrum.
In this talk, I will show that a linear bias model delivers percent-level, unbiased constraints on $\Omega_{\rm m}$ and $\sigma_8$ only up to $k_{\rm max}=0.1\,h/$Mpc, while pushing to smaller scales requires a perturbative approach. Comparing HEFT with a minimal bias variant with fixed higher-order terms, we find that the latter is unbiased in $\Lambda$CDM even at small scales.
We show that higher-order bias can closely mimic baryonic suppression, while baryonic effects cannot reproduce the full range of higher-order bias behaviour.
We also show that modelling choices significantly affect the precision of neutrino mass measurements. While a detection is possible for both Y1 and Y10 at $k \sim 0.3\, h/$Mpc, the inferred value depends sensitively on the assumed model.
| Other topic / keywords: | baryonic feedback, galaxy bias |
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