Observational constraints from supernovae Ia and gamma-ray bursts on a clumpy universe

Bretón, Nora; Montiel, Ariadna

doi:10.1103/physrevd.87.063527

Cited by 10 publications

(15 citation statements)

References 41 publications

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“…It is suggested that a Universe composed only by homogeneously distributed matter is strongly favored by GRB observations. This is greatly different from what was obtained in previous works [32,33].…”

Section: B Long Gamma-ray Burstscontrasting

confidence: 99%

“…This is completely different from what was obtained in Ref. [33]. Finally, we perform a joint analysis which provides good constraints on both model parameters.…”

Section: Conclusion and Discussioncontrasting

confidence: 57%

“…In the past few years, there has been a rich literature concerning the constraints on the smoothness parameter from observations of standard candles [30,[32][33][34]50]. However, we should keep in mind that distances of SNe Ia applied to test the inhomogeneity were estimated from the global fit in the context of a standard homogeneous dark energy model, i.e., the flat ΛCDM or wCDM model.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…[33]). However, so far, confrontations of the ZKDR luminosity distance with observations have not led to conclusive results in the sense of totally excluding this model.…”

Section: The Zkdr Luminosity Distancementioning

confidence: 99%

“…More recently, this issue was also studied by using Union2.1 SN Ia [40] plus nine long GRBs in 1.55 ≤ z ≤ 3.57 [41] and the constrained value of the smoothness parameter indicated a clumped Universe [33]. On the other hand, as concluded in their work, this result may be an indication that the ZKDR approximation is not a precise form of describing the effects of clumpiness in the expanding Universe.…”

Section: Introductionmentioning

confidence: 97%

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Unbiased constraints on the clumpiness of the Universe from standard candles

Ding

Zhu

2015

Phys. Rev. D

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We perform unbiased tests for the clumpiness of the Universe by confronting the Zel'dovichKantowski-Dyer-Roeder luminosity distance, which describes the effect of local inhomogeneities on the propagation of light with the observational one estimated from measurements of standard candles, i.e., type Ia supernovae (SNe Ia) and gamma-ray bursts (GRBs). Methodologically, we first determine the light-curve fitting parameters which account for distance estimation in SNe Ia observations and the luminosity/energy relations which are responsible for distance estimation of GRBs in the global fit to reconstruct the Hubble diagrams in the context of a clumpy Universe.Subsequently, these Hubble diagrams allow us to achieve unbiased constraints on the matter density parameter Ω m , as well as the clumpiness parameter η which quantifies the fraction of homogeneously distributed matter within a given light cone. At a 1σ confidence level, the constraints are Ω m = 0.34 ± 0.02 and η = 1.00 +0.00 −0.02 from the joint analysis. The results suggest that the Universe full of Friedman-Lemaître-Robertson-Walker fluid is favored by observations of standard candles with very high statistical significance. On the other hand, they may also indicate that the Zel'dovich-Kantowski-Dyer-Roeder approximation is a sufficiently accurate form to describe the effects of local homogeneity on the expanding Universe.

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Section: B Long Gamma-ray Burstscontrasting

confidence: 99%

“…This is completely different from what was obtained in Ref. [33]. Finally, we perform a joint analysis which provides good constraints on both model parameters.…”

Section: Conclusion and Discussioncontrasting

confidence: 57%

Section: Conclusion and Discussionmentioning

confidence: 99%

“…[33]). However, so far, confrontations of the ZKDR luminosity distance with observations have not led to conclusive results in the sense of totally excluding this model.…”

Section: The Zkdr Luminosity Distancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Unbiased constraints on the clumpiness of the Universe from standard candles

Ding

Zhu

2015

Phys. Rev. D

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Supernovae as probes of cosmic parameters: estimating the bias from under-dense lines of sight

Busti

Holanda

Clarkson

2013

J. Cosmol. Astropart. Phys.

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Correctly interpreting observations of sources such as type Ia supernovae (SNe Ia) require knowledge of the power spectrum of matter on AU scales -which is very hard to model accurately. Because under-dense regions account for much of the volume of the universe, light from a typical source probes a mean density significantly below the cosmic mean. The relative sparsity of sources implies that there could be a significant bias when inferring distances of SNe Ia, and consequently a bias in cosmological parameter estimation. While the weak lensing approximation should in principle give the correct prediction for this, linear perturbation theory predicts an effectively infinite variance in the convergence for ultra-narrow beams. We attempt to quantify the effect typically under-dense lines of sight might have in parameter estimation by considering three alternative methods for estimating distances, in addition to the usual weak lensing approximation. We find in each case this not only increases the errors in the inferred density parameters, but also introduces a bias in the posterior value.PACS numbers:

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The effect of inhomogeneities on dark energy constraints

Dhawan

Goobar

Mörtsell

2018

J. Cosmol. Astropart. Phys.

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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 (η) is weakly correlated with w. The best fit values w = −0.933 ± 0.065 and η = 0.61 ± 0.37 are consistent with homogeneity at < 2σ level. Assuming homogeneity (η = 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 η, and hence, f p , by a factor of ∼ 10.

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Observational constraints from supernovae Ia and gamma-ray bursts on a clumpy universe

Cited by 10 publications

References 41 publications

Unbiased constraints on the clumpiness of the Universe from standard candles

Unbiased constraints on the clumpiness of the Universe from standard candles

Supernovae as probes of cosmic parameters: estimating the bias from under-dense lines of sight

The effect of inhomogeneities on dark energy constraints

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