Evidence for anisotropy of cosmic acceleration

TY - JOUR

T1 - Evidence for anisotropy of cosmic acceleration

AU - Colin, Jacques

AU - Mohayaee, Roya

AU - Rameez, Mohamed

AU - Sarkar, Subir

PY - 2019/11/1

Y1 - 2019/11/1

N2 - 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.n' 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.

AB - 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.n' 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.

KW - cosmology: observations

KW - dark energy

KW - large-scale structure of Universe

U2 - 10.1051/0004-6361/201936373

DO - 10.1051/0004-6361/201936373

M3 - Journal article

SN - 0004-6361

VL - 631

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

M1 - L13

ER -