Baryonic feedback measurement from KV450 cosmic shear analysis
  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.
