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BAHAMAS: new SNIa analysis reveals inconsistencies with standard cosmology

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Title: BAHAMAS: new SNIa analysis reveals inconsistencies with standard cosmology
Authors: Shariff, H
Jiao, X
Trotta, R
Dyk, DAV
Item Type: Journal Article
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 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+/-0.027, 2.8\sigma\ higher than previously reported and w = -0.910+/-0.045, 1.6\sigma\ higher than the standard analysis. We determine the residual scatter to be sigma_res = 0.104+/-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_solar) = 10, differing in mean intrinsic magnitude by 0.055+/-0.022 mag, lower than previously reported. Cosmological parameter constraints are however unaffected by inclusion of host galaxy mass corrections. We find ~4\sigma\ evidence for a sharp drop in the value of the color correction parameter, beta(z), at a redshift z_trans = 0.662+/-0.055. We rule out some possible explanations for this behaviour, which remains unexplained.
Issue Date: 3-Aug-2016
Date of Acceptance: 4-Apr-2016
URI: http://hdl.handle.net/10044/1/32187
DOI: https://dx.doi.org/10.3847/0004-637X/827/1/1
ISSN: 1538-4357
Publisher: American Astronomical Society
Journal / Book Title: Astrophysical Journal
Volume: 827
Copyright Statement: © 2016. The American Astronomical Society. All rights reserved.
Sponsor/Funder: Imperial College Trust
Engineering & Physical Science Research Council (E
Funder's Grant Number: NA
EP/K503733/1
Keywords: Science & Technology
Physical Sciences
Astronomy & Astrophysics
cosmological parameters
dark energy
dark matter
distance scale
methods: statistical
COLLAPSED GIBBS SAMPLERS
HOST-GALAXY PROPERTIES
LIGHT-CURVE SHAPES
STAR-FORMATION
COVARIANCE STRUCTURE
HUBBLE RESIDUALS
DARK-ENERGY
MONTE-CARLO
SN 2011FE
DATA SETS
astro-ph.CO
0201 Astronomical And Space Sciences
0305 Organic Chemistry
0306 Physical Chemistry (Incl. Structural)
Notes: Additional figures showing constraints from sub-samples from JLA. Matches ApJ accepted version
Publication Status: Published
Article Number: 1
Appears in Collections:Physics
Astrophysics
Faculty of Natural Sciences



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