Luciano Casarini, Silvio A. Bonometto, Stefano Borgani, Klaus Dolag, Giuseppe Murante, Marino Mezzetti, Luca Tornatore, Giuseppe La Vacca
Forthcoming experiments will enable us to determine tomographic shear spectra at a high precision level. Most predictions on them were based, up to now, on algorithms yielding the expected linear and non-linear spectrum of density fluctuations. Even when simulations were exploited, Halofit prediction on fairly large scales were needed. Here we wish to go beyond this limitation. We perform N-body and hydrodynamical simulations within a large enough cosmological volume to allow a direct connection between simulations and linear spectra. While covering large scales, the simulation resolution is good enough to allow us to explore high-l harmonics of the cosmic shear (up to l ~ 50000), well into the domain where baryon physics becomes important. We then compare shear spectra in the absence and in the presence of various kinds of baryon physics, such as radiative cooling, star formation, and supernova feedback in the form of galactic winds. This allows us to outline several properties of matter fluctuation spectra in the different simulations and to test their impact on shear spectra. We compare our outputs with those obtainable by using approximated expressions for non-linear spectra, and confirm the presence of substantial discrepancies even from purely N-body results. Our simulations and the treatment of their outputs however enable us, for the first time, to obtain shear results fully independent from any approximated expression, also delving in the high-l range where non-linear power spectrum of density perturbations, also including the effect of baryon physics, is required. This will allow us to fully exploit the cosmological information contained in future high-sensitivity cosmic shear surveys, also exploring their physics via weak lensing measures.
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http://arxiv.org/abs/1203.5251
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