Cosmic structure and dynamics of the local Universe

Abstract

We present a cosmography analysis of the local Universe based on the recently released Two- Micron All-Sky Redshift Survey catalogue. Our method is based on a Bayesian Networks Machine Learning algorithm (the KIGEN-code) which self-consistently samples the initial den- sity fluctuations compatible with the observed galaxy distribution and a structure formation model given by second-order Lagrangian perturbation theory (2LPT). From the initial con- ditions we obtain an ensemble of reconstructed density and peculiar velocity fields which characterize the local cosmic structure with high accuracy unveiling non-linear structures like filaments and voids in detail. Coherent redshift-space distortions are consistently corrected within 2LPT. From the ensemble of cross-correlations between the reconstructions and the galaxy field and the variance of the recovered density fields, we find that our method is ex- tremely accurate up to k ~ 1 h Mpc -1 and still yields reliable results down to scales of about 3-4 h -1 Mpc. The motion of the Local Group we obtain within ~80 h -1 Mpc (υ LG = 522 ± 86 km s -1, lLG = 291° ± 16°, b LG = 34° ± 8°) is in good agreement with measurements derived from the cosmic microwave background and from direct observations of peculiar motions and is consistent with the predictions of ΛCDM. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS.