Orateur
Description
Galaxy clustering and weak lensing on small scales hold much of the cosmological information in the coming surveys of large scale structure. They also carry the imprint of baryons: gas expelled from haloes by feedback suppresses the matter power spectrum at the level of the statistical errors, and this effect is degenerate with . The same gas is observed directly, in X-rays, through the thermal Sunyaev–Zel'dovich effect and in 21-cm emission, and galaxies and active nuclei trace the haloes that hold it. We use a differentiable halo model that describes galaxies, AGN, hot and neutral gas and matter within one population of haloes and one baryon budget. With it we predict every auto- and cross-spectrum among these tracers, together with their joint covariance. Because each prediction is differentiable with respect to cosmological and astrophysical parameters, we compute Fisher forecasts by automatic differentiation. The gain comes from constraining feedback with the data instead of marginalising over it.