Nulling Baryonic Feedback in Weak Lensing Surveys Using Cross-Correlations with Fast Radio Bursts.

Baryonic feedback is a leading contaminant in studying dark matter using cosmic shear. This has meant omitting much of the data during cosmological inference, or forward modeling the spatial distribution of gas around dark matter halos using models for baryonic feedback, which introduces nuisance parameters and raises questions of potential model misspecification. We propose a novel method of "baryon nulling" using cross-correlations between shear maps and fast radio burst (FRB) dispersion measures. We use the FLAMINGO suite of hydrodynamical simulations, whose power spectra span a wide yet realistic range of feedback variations, to demonstrate that our nulling procedures reduce sensitivity to feedback at k≈1  Mpc^{-1} by a factor of a few, offering a valuable model-independent alternative to standard forward modeling procedures, which often assume a family of feedback models. Sensitive FRB surveys such as CHORD and the DSA-2000, and wide area surveys like Rubin, Roman, and Euclid, may enable the megaparsec-scale clustering of dark matter to be precisely constrained without a baryonic prior.