We present results obtained by applying our BAyesian HierArchical Modeling for the Analysis of Supernova cosmology ( BAHAMAS ) software package to the 740 spectroscopically confirmed supernovae type Ia ( SNIa ) from the “ Joint Light-curve Analysis ” ( JLA ) dataset .
We simultaneously determine cosmological parameters and standardization parameters , including host galaxy mass corrections , residual scatter and object-by-object intrinsic magnitudes .
Combining JLA and Planck Cosmic Microwave Background data , we find significant discrepancies in cosmological parameter constraints with respect to the standard analysis : we find \Omega _ { m } = 0.399 \pm 0.027 , 2.8 \sigma higher than previously reported and w = -0.910 \pm 0.045 , 1.6 \sigma higher than the standard analysis .
We determine the residual scatter to be \sigma _ { res } = 0.104 \pm 0.005 .
We confirm ( at the 95 % probability level ) the existence of two sub-populations segregated by host galaxy mass , separated at \log _ { 10 } ( M / M _ { \odot } ) = 10 , differing in mean intrinsic magnitude by 0.055 \pm 0.022 mag , lower than previously reported .
Cosmological parameter constraints are however unaffected by inclusion of host galaxy mass corrections .
We find \sim 4 \sigma evidence for a sharp drop in the value of the color correction parameter , \beta ( z ) , at a redshift z _ { t } = 0.662 \pm 0.055 .
We rule out some possible explanations for this behaviour , which remains unexplained .