ANISOTROPY IN THE MATTER DISTRIBUTION BEYOND THE BARYONIC ACOUSTIC OSCILLATION SCALE

Tracing the cosmic evolution of the baryonic acoustic oscillation (BAO) scale with galaxy two-point correlation functions is currently the most promising approach to detect dark energy at early times. A number of ongoing and future experiments will measure the BAO peak with unprecedented accuracy. We show based on a set of N-body simulations that the matter distribution is anisotropic out to ∼150 h–1 Mpc, far beyond the BAO scale of ∼100 h–1 Mpc, and discuss implications for the measurement of the BAO. To that purpose we use alignment correlation functions, i.e., cross-correlation functions between high density peaks and the overall matter distribution measured along the orientation of the peaks and perpendicular to it. The correlation function measured along (perpendicular to) the orientation of high density peaks is enhanced (reduced) by a factor of two compared to the conventional correlation function and the location of the BAO peak shifts toward smaller (larger) scales if measured along (perpendicular to) the orientation of the high density peaks. Similar effects are expected to shape observed galaxy correlation functions at BAO scales.