The impact of baryons on the sensitivity of dark energy measurements

TL;DR

This paper investigates how baryonic physics affect dark energy measurements from weak lensing surveys, using a halo model to quantify biases and uncertainties, and explores methods to mitigate these effects.

Contribution

It introduces a halo model with analytic modifications to account for baryonic effects and assesses their impact on dark energy constraints in upcoming surveys.

Findings

Baryonic effects can degrade dark energy parameter constraints by up to 80%.

Including external baryon information and CMB priors significantly reduces uncertainties.

Probing non-linear scales offers limited improvement in constraining baryonic effects.

Abstract

Baryonic effects on large-scale structure, if not accounted for, can significantly bias dark energy constraints. As the detailed physics of the baryons is not yet well-understood, correcting for baryon effects introduces additional parameters which must be marginalized over, increasing the uncertainties on the inferred cosmological parameters. Forthcoming weak lensing surveys are aiming for percent-level precision on the dark energy equation of state, so the problem must be thoroughly examined. We use a halo model with analytic modifications which capture the impact of adiabatic contraction of baryons and feedback on the matter power spectrum, and generalize the Navarro-Frenk-White profile to account for a possible inner core. A Fisher analysis predicts degradations of 40% in the $w_0$-$w_a$ Figure of Merit for a Euclid-like survey, and up to 80% for other cosmological parameters. We forecast potential inner core constraints of a few $\mathrm{kpc}$, while for a fixed inner core, adiabatic concentration and feedback parameters are constrained to a few percent. We explore the scales where baryons and dark energy contribute most to the Fisher information, finding that probing to increasingly non-linear scales does little to reduce degradation. Including external baryon information improves our forecasts, but limiting degradation to 1% requires strong priors. Adding Planck cosmic microwave background priors improves the Figure of Merit by a factor of 2.7 and almost completely recovers the individual marginalized errors on $w_0$ and $w_a$. We also quantify the calibration of baryon modelling required to reduce biases of dark energy forecasts to acceptable levels for forthcoming lensing surveys.