2011/07/31 by Nikolai Meures, Marco Bruni · 42 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics #Cosmology #Cosmology and Gravitation Theories #Dark energy #Density contrast #Friedmann–Lemaître–Robertson–Walker metric #Galaxies: Formation, Evolution, Phenomena #Galaxy #Hubble volume #Hubble's law #Line-of-sight #Metric expansion of space #Physics #RADIUS #Redshift #Theoretical physics #Universe #astro-ph.CO
paper · pdf · doi:10.1111/j.1365-2966.2011.19850.x
published in Monthly Notices of the Royal Astronomical Society 419(3), 1937-1950 (Oxford University Press) · 15 pages, 12 figures, published in MNRAS. Corrected typos, re-formatted figures, added references and slightly changed notation (r->z)
openalex publication_date 2011/11/17 · arxiv created 2012/01/06 · arxiv updated 2015/03/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Motivated by the dawn of precision cosmology and the wealth of forthcoming high-precision and volume galaxy surveys, in this paper we study the effects of inhomogeneities on light propagation in a flat Λ cold dark matter (ΛCDM) background. To this end we use exact solutions of Einstein’s equations as derived by Meures & Bruni where, starting from small fluctuations, inhomogeneities arise from a standard growing mode and become non-linear. While the matter distribution in these models is necessarily idealized, there is still enough freedom to assume an arbitrary initial density profile along the line of sight. We can therefore model overdensities and voids of various sizes and distributions, e.g. single harmonic sinusoidal modes, coupled modes and more general distributions in a ΛCDM background. Our models allow for an exact treatment of the light-propagation problem, so that the results are unaffected by approximations and unambiguous. Along lines of sight with density inhomogeneities which average out on scales less than the Hubble radius, we find the distance–redshift relation to diverge negligibly from the Friedmann–Lemaitre–Robertson–Walker (FLRW) result. On the contrary, if we observe along lines of sight which do not have the same average density as the background, we find large deviations from the FLRW distance–redshift relation. Hence, a possibly large systematic might be introduced into the analysis of cosmological observations, e.g. supernovae, if we observe along lines of sight which are typically more or less dense than the average density of the Universe. In turn, this could lead to wrong parameter estimation: even if the cosmological principle is valid, the identification of the true FLRW background in an inhomogeneous universe may be more difficult than usually assumed.