Article Dans Une Revue Astronomy & Astrophysics - A&A Année : 2019

Evidence for anisotropy of cosmic acceleration

Roya Mohayaee
Mohamed Rameez
  • Fonction : Auteur
Subir Sarkar
  • Fonction : Auteur

Résumé

Observations reveal a “bulk flow” in the local Universe which is faster and extends to much larger scales than are expected around a typical observer in the standard ΛCDM cosmology. This is expected to result in a scale-dependent dipolar modulation of the acceleration of the expansion rate inferred from observations of objects within the bulk flow. From a maximum-likelihood analysis of the Joint Light-curve Analysis catalogue of Type Ia supernovae, we find that the deceleration parameter, in addition to a small monopole, indeed has a much bigger dipole component aligned with the cosmic microwave background dipole, which falls exponentially with redshift z: q0 = qm + qd.n̂ exp(-z/S). The best fit to data yields qd = −8.03 and S = 0.0262 (⇒d ∼ 100 Mpc), rejecting isotropy (qd = 0) with 3.9σ statistical significance, while qm = −0.157 and consistent with no acceleration (qm = 0) at 1.4σ. Thus the cosmic acceleration deduced from supernovae may be an artefact of our being non-Copernican observers, rather than evidence for a dominant component of “dark energy” in the Universe.Key words: cosmology: observations / dark energy / large-scale structure of Universe⋆ The code used here is available at: https://github.com/rameez3333/Dipole_JLA

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hal-01867250 , version 1 (05-07-2023)

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Jacques Colin, Roya Mohayaee, Mohamed Rameez, Subir Sarkar. Evidence for anisotropy of cosmic acceleration. Astronomy & Astrophysics - A&A, 2019, 631, pp.L13. ⟨10.1051/0004-6361/201936373⟩. ⟨hal-01867250⟩
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