Self-calibration of tomographic weak lensing for the physics of baryons to constrain dark energy

Recent numerical studies indicate that uncertainties in the treatment of baryonic physics can affect predictions for weak lensing shear power spectra at a level that is significant for several forthcoming surveys such as the Dark Energy Survey, the SuperNova/Acceleration Probe, and the Large Synoptic Survey Telescope. Correspondingly, we show that baryonic effects can significantly bias dark energy parameter measurements. Elimination of such potential biases by neglecting information in multipoles beyond several hundred leads to weaker parameter constraints by a factor of similar to 2-3 compared with using information out to multipoles of several thousand. Fortunately, the same numerical studies that explore the influence of baryons indicate that they primarily affect power spectra by altering halo structure through the relation between halo mass and mean effective halo concentration. We explore the ability of future weak lensing surveys to constrain both the internal structures of halos and the properties of the dark energy simultaneously as a first step toward self calibrating for the physics of baryons. In this approach, parameter biases are greatly reduced and no parameter constraint is degraded by more than similar to 40% in the case of the Large Synoptic Survey Telescope or 30% in the cases of the SuperNova/Acceleration Probe or the Dark Energy Survey. Modest prior knowledge of the halo concentration relation and its redshift evolution greatly improves even these forecasts. In addition, we find that these surveys can constrain effective halo concentrations themselves usefully with shear power spectra alone. In the most restrictive case of a power-law relation for halo concentration as a function of mass and redshift, the concentrations of halos of mass m similar to 10(14)h(-1)M(circle dot) at z similar to 0.2 can be constrained to better than 10%. Our results suggest that inferring dark energy parameters through shear spectra can be made robust to baryonic physics and that this procedure may even provide useful constraints on galaxy formation models.