The Anisotropic Two-Point Correlation Functions of the Nonlinear Traceless Tidal Field in the Principal-Axis Frame

TL;DR

This paper introduces anisotropic two-point correlation functions of the nonlinear traceless tidal field in the principal-axis frame, measured via N-body simulations, revealing strong correlations and providing analytic fits to aid cosmological analyses.

Contribution

It presents the first measurement and analytic modeling of anisotropic correlation functions of the nonlinear traceless tidal field in the principal-axis frame.

Findings

Correlation length of traceless tidal field ~20 Mpc/h

Correlation length of density field ~5 Mpc/h

Analytic formulas match numerical results well

Abstract

Galaxies on the largest scales of the Universe are observed to be embedded in the filamentary cosmic web which is shaped by the nonlinear tidal field. As an efficient tool to quantitatively describe the statistics of this cosmic web, we present the anisotropic two-point correlation functions of the nonlinear traceless tidal field in the principal-axis frame, which are measured using numerical data from an N-body simulation. We show that both of the nonlinear density and traceless tidal fields are more strongly correlated along the directions perpendicular to the eigenvectors associated with the largest eigenvalues of the local tidal field. The correlation length scale of the traceless tidal field is found to be ~20 Mpc/h, which is much larger than that of the density field ~5 Mpc/h. We also provide analytic fitting formulae for the anisotropic correlation functions of the traceless tidal field, which turn out to be in excellent agreement with the numerical results. We expect that our numerical results and analytic formula are useful to disentangle cosmological information from the filamentary network of the large-scale structures.