Baryonic feedback measurement from KV450 cosmic shear analysis

TL;DR

This study measures baryonic feedback effects on the matter power spectrum using cosmic shear data from the KV450 survey, providing constraints that suggest a tendency toward positive feedback and implications for cosmological parameters.

Contribution

First direct measurement of baryonic feedback parameter from cosmic shear data, constraining its impact and improving understanding of astrophysical systematics in cosmology.

Findings

Feedback parameter consistent with dark matter-only case within 1.2σ

Measurement of S8 shows only 6% shift from previous results

Feedback exclusion at 2.2σ to 3.1σ when assuming Planck cosmology

Abstract

While baryonic feedback is one of the most important astrophysical systematics that we need to address in order to achieve precision cosmology, few weak lensing studies have directly measured its impact on the matter power spectrum. We report measurement of the baryonic feedback parameter with the constraints on its lower and upper limits from cosmic shear. We use the public data from the Kilo-Degree Survey and the VISTA Kilo-Degree Infrared Galaxy Survey spanning 450 deg$^2$. Estimating both cosmological and feedback parameters simultaneously, we obtain $A_{\rm b}=1.01_{-0.85}^{+0.80}$, which shows a consistency with the dark matter-only (DMO) case at the $\sim1.2~\sigma$ level and a tendency toward positive feedback; the $A_{\rm b}=0$ ($0.81$) value corresponds to the DMO (OWLS AGN) case. Despite this full constraint of the feedback parameter, our $S_8~(\equiv \sigma_8 \sqrt{\Omega_m / 0.3})$ measurement ($0.739^{+0.036}_{- 0.035}$) shifts by only $\sim6$% of the statistical error, compared to the previous measurement. When we assume the flat $\Lambda$CDM cosmology favored by the Nine-Year Wilkinson Microwave Anisotropy Probe (Planck) result, the feedback parameter is constrained to be $A_{\rm b}=1.21_{-0.54}^{+0.61}$ ($1.60_{-0.52}^{+0.53}$), which excludes the DMO case at the $\sim2.2~\sigma$ ($\sim3.1~\sigma$) level.