The effect of inhomogeneities on dark energy constraints

Abstract

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 correlated with $w$. The best fit values $w=-0.933\pm 0.065$ and $\eta =0.61\pm 0.37$ are consistent with homogeneity at $<2\sigma$ level. Assuming homogeneity ($\eta =1$), we find $w=-0.961\pm 0.055$, indicating only a small change in $w$. For a time-dependent dark energy equation of state, $w_0=-0.951\pm 0.112$ and $w_a=0.059\pm 0.418$, to be compared with $w_0=-0.983\pm 0.127$ and $w_a=0.07\pm 0.432$ in the homogeneous case, which is also a very small change. Current data are not sufficient to constrain the fraction of dark matter (DM) in compact objects, $f_p$ at the 95$\%$ C.L., however at 68$\%$ C.L. $f_p<0.73$. Future supernova surveys will improve the constraints on $\eta$, and $f_p$, by a factor of $\sim$ 10.

16 pages, 4 figures, accepted by JCAP

References in corpus (13)

• Dynamics of dark energy
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Cosmology and the Fate of Dilatation Symmetry
• Primordial Black Holes as Dark Matter
• Supernova Constraints and Systematic Uncertainties from the First 3 Years of the Supernova Legacy Survey
• SNLS3: Constraints on Dark Energy Combining the Supernova Legacy Survey Three Year Data with Other Probes
• Do stochastic inhomogeneities affect dark-energy precision measurements?
• Extending the supernova Hubble diagram to z~1.5 with the Euclid space mission
• New Constraints on Macroscopic Compact Objects as a Dark Matter Candidate from Gravitational Lensing of Type Ia Supernovae
• Narrowing down the possible explanations of cosmic acceleration with geometric probes
• Measuring weak lensing correlations of Type Ia Supernovae
• Observational constraints from SNe Ia and Gamma-Ray Bursts on a clumpy universe
• Unbiased constraints on the clumpiness of universe from standard candles

Cited by in corpus (9)

• Does the Hubble constant tension call for new physics?
• Limits on stellar-mass compact objects as dark matter from gravitational lensing of type Ia supernovae
• Lens modelling of the strongly lensed Type Ia supernova iPTF16geu
• Mapping the inhomogeneous Universe with Standard Sirens: Degeneracy between inhomogeneity and modified gravity theories
• Understanding the Dyer-Roeder approximation as a consequence of local cancellations of projected shear and expansion rate fluctuations
• Constraining Temporal Oscillations of Cosmological Parameters Using Type Ia Supernovae
• Type Ia supernova constraints on compact object dark matter
• Accurate modelling of extragalactic microlensing by compact objects
• White dwarfs as a probe of dark energy