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 _ { 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 .