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 -