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The effect of inhomogeneities on dark energy constraints
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Number of Authors: 32018 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 7, article id 024Article in journal (Refereed) Published
Abstract [en]

Constraints on models of the late time acceleration of the universe assume the cosmological principle of homogeneity and isotropy on large scales. However, small scale inhomogeneities can alter observational and dynamical relations, affecting the inferred cosmological parameters. For precision constraints on the properties of dark energy, it is important to assess the potential systematic effects arising from these inhomogeneities. In this study, we use the Type Ia supernova magnitude-redshift relation to constrain the inhomogeneities as described by the Dyer-Roeder distance relation and the effect they have on the dark energy equation of state (w), together with priors derived from the most recent results of the measurements of the power spectrum of the Cosmic Microwave Background and Baryon Acoustic Oscillations. We find that the parameter describing the inhomogeneities (eta) is weakly correlated with w. The best fit values w = -0.933 +/- 0.065 and eta = 0.61 +/- 0.37 are consistent with homogeneity at < 2 sigma level. Assuming homogeneity (eta = 1), we find w = -0.961 +/- 0.055, indicating only a small change in w. For a time-dependent dark energy equation of state, w(0) = -0.951 +/- 0.112 and w(a) = 0.059 +/- 0.418, to be compared with w(0) = -0.983 +/- 0.127 and w(a) = 0.07 +/- 0.432 in the homogeneous case, which is also a very small change. We do not obtain constraints on the fraction of dark matter in compact objects, f(p), at the 95% C.L. with conservative corrections to the distance formalism. Future supernova surveys will improve the constraints on eta, and hence, f(p), by a factor of similar to 10.

Place, publisher, year, edition, pages
2018. no 7, article id 024
Keywords [en]
dark energy experiments, supernova type Ia, standard candles
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-158930DOI: 10.1088/1475-7516/2018/07/024ISI: 000438670000002OAI: oai:DiVA.org:su-158930DiVA, id: diva2:1240113
Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2018-08-20Bibliographically approved

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Dhawan, SuhailGoobar, ArielMörtsell, Edvard
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