Fuzzy Dark Matter and the Dark Energy Survey Year 1 Data
  Gravitational weak lensing by dark matter halos leads to a measurable imprint
in the shear correlation function of galaxies. Fuzzy dark matter (FDM),
composed of ultralight axion-like particles of mass $m\sim 10^{-22}\text{ eV}$,
suppresses the matter power spectrum and shear correlation with respect to
standard cold dark matter. We model the effect of FDM on cosmic shear using the
optimised halo model HMCode, accounting for additional suppression of the mass
function and halo concentration in FDM as observed in $N$-body simulations. We
combine Dark Energy Survey year 1 (DES-Y1) data with the Planck cosmic
microwave background anisotropies to search for shear correlation suppression
caused by FDM. We find no evidence of suppression compared to the preferred
cold DM model, and thus set a new lower limit to the FDM particle mass. Using a
log-flat prior and marginalising over uncertainties related to the non-linear
model of FDM, we find a new, independent 95\% C.L. lower limit $\log_{10}m>-23$
combining Planck and DES-Y1 shear, an improvement of almost two orders of
magnitude on the mass bound relative to CMB-only constraints. Our analysis is
largely independent of baryonic modelling, and of previous limits to FDM
covering this mass range. Our analysis highlights the most important aspects of
the FDM non-linear model for future investigation. The limit to FDM from weak
lensing could be improved by up to three orders of magnitude with
$\mathcal{O}(0.1)$ arcmin cosmic shear angular resolution, if FDM and baryonic
feedback can be simultaneously modelled to high precision in the halo model.
