Analytic prediction of baryonic effects from the EFT of large scale structures

Abstract

The large scale structures of the universe will likely be the next leading\nsource of cosmological information. It is therefore crucial to understand their\nbehavior. The Effective Field Theory of Large Scale Structures provides a\nconsistent way to perturbatively predict the clustering of dark matter at large\ndistances. The fact that baryons move distances comparable to dark matter\nallows us to infer that baryons at large distances can be described in a\nsimilar formalism: the backreaction of short-distance non-linearities and of\nstar-formation physics at long distances can be encapsulated in an effective\nstress tensor, characterized by a few parameters. The functional form of\nbaryonic effects can therefore be predicted. In the power spectrum the leading\ncontribution goes as $\\propto k^2 P(k)$, with $P(k)$ being the linear power\nspectrum and with the numerical prefactor depending on the details of the\nstar-formation physics. We also perform the resummation of the contribution of\nthe long-wavelength displacements, allowing us to consistently predict the\neffect of the relative motion of baryons and dark matter. We compare our\npredictions with simulations that contain several implementations of baryonic\nphysics, finding percent agreement up to relatively high wavenumbers such as\n$k\\simeq 0.3\\,h\\, Mpc^{-1}$ or $k\\simeq 0.6\\, h\\, Mpc^{-1}$, depending on the\norder of the calculation. Our results open a novel way to understand baryonic\neffects analytically, as well as to interface with simulations.\n