A hydrodynamical halo model for weak-lensing cross correlations
  On the scale of galactic haloes, the distribution of matter in the cosmos is
affected by energetic, non-gravitational processes; so-called baryonic
feedback. A lack of knowledge about the details of how feedback processes
redistribute matter is a source of uncertainty for weak-lensing surveys, which
accurately probe the clustering of matter in the Universe over a wide range of
scales. We develop a cosmology-dependent model for the matter distribution that
simultaneously accounts for the clustering of dark matter, gas and stars. We
inform our model by comparing it to power spectra measured from the BAHAMAS
suite of hydrodynamical simulations. As well as considering matter power
spectra, we also consider spectra involving the electron-pressure field, which
directly relates to the thermal Sunyaev-Zel'dovich (tSZ) effect. We fit
parameters in our model so that it can simultaneously model both matter and
pressure data and such that the distribution of gas as inferred from tSZ has
influence on the matter spectrum predicted by our model. We present two
variants; one that matches the feedback-induced suppression seen in the
matter-matter power spectrum at the per-cent level and a second that matches
the matter-matter data slightly less well (~2 per cent), but that is able to
simultaneously model the matter-electron pressure spectrum at the ~15 per-cent
level. We envisage our models being used to simultaneously learn about
cosmological parameters and the strength of baryonic feedback using a
combination of tSZ and lensing auto- and cross-correlation data.
