Journal Article

The initial conditions of the Universe from constrained simulations

Francisco-Shu Kitaura

in Monthly Notices of the Royal Astronomical Society: Letters

Published on behalf of The Royal Astronomical Society

Volume 429, issue 1, pages L84-L88
Published in print February 2013 |
Published online November 2012 | e-ISSN: 1745-3933 | DOI: http://dx.doi.org/10.1093/mnrasl/sls029

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I present a new approach to recover the primordial density fluctuations and the cosmic web structure underlying a galaxy distribution. The method is based on sampling Gaussian fields which are compatible with a galaxy distribution and a structure formation model. This is achieved by splitting the inversion problem into two Gibbs-sampling steps: the first being a Gaussianization step transforming a distribution of point sources at Lagrangian positions – which are not a priori given– into a linear alias-free Gaussian field. This step is based on Hamiltonian sampling with a Gaussian–Poisson model. The second step consists on a likelihood comparison in which the set of matter tracers at the initial conditions is constrained on the galaxy distribution and the assumed structure formation model. For computational reasons second-order Lagrangian perturbation theory is used. However, the presented approach is flexible to adopt any structure formation model. A semi-analytic halo-model-based galaxy mock catalogue is taken to demonstrate that the recovered initial conditions are closely unbiased with respect to the actual ones from the corresponding N-body simulation down to scales of a ∼5 Mpc h−1. The cross-correlation between them shows a substantial gain of information, being at k ∼ 0.3 h Mpc−1 more than doubled. In addition the initial conditions are extremely well Gaussian distributed and the power spectra follow the shape of the linear power spectrum being very close to the actual one from the simulation down to scales of k ∼ 1 h Mpc−1.

Keywords: catalogues; galaxies: clusters: general; galaxies: statistics; large-scale structure of Universe; dark matter

Journal Article.  3722 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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