%0 Generic %1 rahman2021constraints %A Rahman, W. %A Trotta, R. %A Boruah, S. S. %A Hudson, M. J. %A van Dyk, D. A. %D 2021 %K tifr %T New Constraints on Anisotropic Expansion from Supernovae Type Ia %U http://arxiv.org/abs/2108.12497 %X We re-examine the contentious question of constraints on anisotropic expansion from Type Ia supernovae (SNIa) in the light of a novel determination of peculiar velocities, which are crucial to test isotropy with supernovae out to distances $200/h$ Mpc. We re-analyze the Joint Light-Curve Analysis (JLA) Supernovae (SNe) data, improving on previous treatments of peculiar velocity corrections and their uncertainties (both statistical and systematic) by adopting state-of-the-art flow models constrained independently via the 2M$++$ galaxy redshift compilation. We also introduce a novel procedure to account for colour-based selection effects, and adjust the redshift of low-$z$ SNe self-consistently in the light of our improved peculiar velocity model. We adopt the Bayesian hierarchical model BAHAMAS to constrain a dipole in the distance modulus in the context of the $Łambda$CDM model and the deceleration parameter in a phenomenological Cosmographic expansion. We do not find any evidence for anisotropic expansion, and place a tight upper bound on the amplitude of a dipole, $|D_\mu| < 5.93 10^-4$ (95\% credible interval) in a $Łambda$CDM setting, and $|D_q_0| < 6.29 10^-2$ in the Cosmographic expansion approach. Using Bayesian model comparison, we obtain posterior odds in excess of 900:1 (640:1) against a constant-in-redshift dipole for $Łambda$CDM (the Cosmographic expansion). In the isotropic case, an accelerating universe is favoured with odds of $1100:1$ with respect to a decelerating one.

@misc{rahman2021constraints, abstract = {We re-examine the contentious question of constraints on anisotropic expansion from Type Ia supernovae (SNIa) in the light of a novel determination of peculiar velocities, which are crucial to test isotropy with supernovae out to distances $\lesssim 200/h$ Mpc. We re-analyze the Joint Light-Curve Analysis (JLA) Supernovae (SNe) data, improving on previous treatments of peculiar velocity corrections and their uncertainties (both statistical and systematic) by adopting state-of-the-art flow models constrained independently via the 2M$++$ galaxy redshift compilation. We also introduce a novel procedure to account for colour-based selection effects, and adjust the redshift of low-$z$ SNe self-consistently in the light of our improved peculiar velocity model. We adopt the Bayesian hierarchical model \texttt{BAHAMAS} to constrain a dipole in the distance modulus in the context of the $\Lambda$CDM model and the deceleration parameter in a phenomenological Cosmographic expansion. We do not find any evidence for anisotropic expansion, and place a tight upper bound on the amplitude of a dipole, $|D_\mu| < 5.93 \times 10^{-4}$ (95\% credible interval) in a $\Lambda$CDM setting, and $|D_{q_0}| < 6.29 \times 10^{-2}$ in the Cosmographic expansion approach. Using Bayesian model comparison, we obtain posterior odds in excess of 900:1 (640:1) against a constant-in-redshift dipole for $\Lambda$CDM (the Cosmographic expansion). In the isotropic case, an accelerating universe is favoured with odds of $\sim 1100:1$ with respect to a decelerating one.}, added-at = {2021-08-31T08:00:49.000+0200}, author = {Rahman, W. and Trotta, R. and Boruah, S. S. and Hudson, M. J. and van Dyk, D. A.}, biburl = {https://www.bibsonomy.org/bibtex/2218c5938fb7ed091599de07198a7fcc4/citekhatri}, description = {New Constraints on Anisotropic Expansion from Supernovae Type Ia}, interhash = {ec546d57f7337cd7cfb4d0203cfc7c5b}, intrahash = {218c5938fb7ed091599de07198a7fcc4}, keywords = {tifr}, note = {cite arxiv:2108.12497Comment: 24 Pages, 14 figures, submitted to MNRAS}, timestamp = {2021-08-31T08:00:49.000+0200}, title = {New Constraints on Anisotropic Expansion from Supernovae Type Ia}, url = {http://arxiv.org/abs/2108.12497}, year = 2021 }