BAHAMAS: NEW ANALYSIS OF TYPE Ia SUPERNOVAE REVEALS INCONSISTENCIES WITH STANDARD COSMOLOGY

Abstract

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 of type Ia (SNe Ia) from the "Joint Light-curve Analysis" (JLA) data set. We simultaneously determine cosmological parameters and standardization parameters, including corrections for host galaxy mass, residual scatter, and object-by-object intrinsic magnitudes. Combining JLA and Planck data on the cosmic microwave background, we find significant discrepancies in cosmological parameter constraints with respect to the standard analysis: we find W =  0.399 0.027 m , s 2.8 higher than previously reported, and = - w 0.910 0.045, s 1.6 higher than the standard analysis. We determine the residual scatter to be s =  0.104 0.005 res . We confirm (at the 95% probability level) the existence of two subpopulations segregated by host galaxy mass, separated at, differing in mean intrinsic magnitude by 0.055 ± 0.022 mag, lower than previously reported. Cosmological parameter constraints, however, are unaffected by the inclusion of corrections for host galaxy mass. We find s4 evidence for a sharp drop in the value of the color correction parameter, ( ) b z , at a redshift =  z 0.662 0.055 t . We rule out some possible explanations for this behavior, which remains unexplained.

Non-parametric reconstruction of cosmological matter perturbations

“…This is clearly seen in Fig. 4c which assumes Ω m0 = 0.399 ± 0.025, as obtained from a recent analysis of type Ia supernova data (assuming the ΛCDM model) [54]. Quantitatively speaking, a fit of the f (z) data to the f (z) reconstructed curves provides χ 2 = 7.51 and χ 2 = 5.20 for the values of Ω m0 displayed in Panels 4a and 4b, respectively, and χ 2 = 25.80 for the SNe Ia value considered in Panel 4c.…”

“…2(a) adopting Ω m0 = 0.308 ± 0.012, as given by the Planck collaboration [51] and in Fig. 2(b) adopting Ω m0 = 0.279 ± 0.025, as given by the WMAP collabora- c) The same as in the previous panels assuming Ωm0 = 0.399 ± 0.027, as obtained from SNe Ia observations [54]. The data points were taken from Table II of Ref.…”

Anisotropic cosmological models in f(R,T) gravity with variable deceleration parameter

“…It is also believed that the universe changed with time from early deceleration phase to late time acceleration phase [16]. Now, a team of scientists led by Professor Subir Sarkar [17] has raised the question on this standard cosmological concept about the acceleration, which is also supported by Shariff et al [18]. The two promising approaches confirmed by the cosmological research community for discussing the cosmic expansion of the universe are: The first one is the introduction of the most exotic entity of mysterious universe dubbed as dark energy, which has positive energy density and negative pressure.…”

Evidence for cosmological particle creation?

“…Apart theoretical motivations, there are also observational reasons to include interactions in the dark sector, as the appearance of observational tensions when the standard model is tested against data of the large-scale clustering of galaxies (LSS), on one hand, and distance measurements of type Ia supernovae (SNe Ia), on the other. Some analyses of the linear mass power spectrum provide a value of Ω m0 ∼ 0.2 − 0.3 [2,3] for the present relative matter density, whereas from SNe Ia data one obtains Ω m0 ∼ 0.3 − 0.4 [4,5] (see also [6] for an analysis of CMB data). With more recent galaxy surveys the value obtained for the matter density in the ΛCDM case presents a better agreement with that derived from distance measurements [7,8].…”