Dissecting the thermal Sunyaev-Zeldovich-gravitational lensing
  cross-correlation with hydrodynamical simulations
  We use the cosmo-OWLS suite of cosmological hydrodynamical simulations, which
includes different galactic feedback models, to predict the cross-correlation
signal between weak gravitational lensing and the thermal Sunyaev-Zeldovich
(tSZ) $y$-parameter. The predictions are compared to the recent detection
reported by van Waerbeke and collaborators. The simulations reproduce the weak
lensing-tSZ cross-correlation, $\xi_{y\kappa}(\theta)$, well. The uncertainty
arising from different possible feedback models appears to be important on
small scales only ($\theta \lesssim 10$ arcmin), while the amplitude of the
correlation on all scales is sensitive to cosmological parameters that control
the growth rate of structure (such as $\sigma_8$, $\Omega_m$ and $\Omega_b$).
This study confirms our previous claim (in Ma et al.) that a significant
proportion of the signal originates from the diffuse gas component in low-mass
($M_{\rm{halo}} \lesssim 10^{14} M_{\odot}$) clusters as well as from the
region beyond the virial radius. We estimate that approximately 20$\%$ of the
detected signal comes from low-mass clusters, which corresponds to about 30$\%$
of the baryon density of the Universe. The simulations also suggest that more
than half of the baryons in the Universe are in the form of diffuse gas outside
halos ($\gtrsim 5$ times the virial radius) which is not hot or dense enough to
produce a significant tSZ signal or be observed by X-ray experiments. Finally,
we show that future high-resolution tSZ-lensing cross-correlation observations
will serve as a powerful tool for discriminating between different galactic
feedback models.
