Towards Cosmography of the Local Universe
Abstract
Anisotropies in the distanceredshift relation of cosmological sources are expected due to largescale inhomogeneities in the local Universe. When the observed sources are tracing a largescale matter flow in a general spacetime geometry, the distanceredshift relation with its anisotropies can be described with a geometrical prediction that generalises the wellknown FriedmannLemaîtreRobertsonWalker result. Furthermore, it turns out that a finite set of multipole coefficients contain the full information about a finiteorder truncation of the distanceredshift relation of a given observer. The multipoles of the distanceredshift relation are interesting new cosmological observables that have a direct physical interpretation in terms of kinematical quantities of the underlying matter flow. Using light cones extracted from Nbody simulations we quantify the anisotropies expected in a Λ cold dark matter cosmology by running a Markov chain Monte Carlo analysis on the observed data. In this observational approach the survey selection implements an implicit smoothing scale over which the effective rest frame of matter is fitted. The perceived anisotropy therefore depends significantly on the redshift range and distribution of sources. We find that the multipoles of the expansion rate, as well as the observer's velocity with respect to the largescale matter flow, can be determined robustly with our approach.
 Publication:

The Open Journal of Astrophysics
 Pub Date:
 June 2024
 DOI:
 10.33232/001c.118782
 arXiv:
 arXiv:2402.12165
 Bibcode:
 2024OJAp....7E..44A
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 17 pages, 11 figures