Imperial College London
Portrait Picture

Professor David van Dyk

Faculty of Natural Sciences, Department of Mathematics

Chair in Statistics
 
 
 
//

Contact

 

+44 (0)20 7594 8574d.van-dyk Website

 
 
//

Assistant

 

Mr David Whittaker +44 (0)20 7594 8481

 
//

Location

 

539Huxley BuildingSouth Kensington Campus

//

Summary

 

Publications

Citation

BibTex format

@article{Shariff:2016:1/1,
author = {Shariff, H and Jiao, X and Trotta, R and van, Dyk D},
doi = {1/1},
journal = {The Astrophysical Journal},
title = {Bahamas: new analysis of type Ia supernovae reveals inconsistencies with standard cosmology},
url = {http://dx.doi.org/10.3847/0004-637X/827/1/1},
volume = {827},
year = {2016}
}
Download

RIS format (EndNote, RefMan)

TY  - JOUR
AB  - 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 ${{\rm{\Omega }}}_{{\rm{m}}}=0.399\pm 0.027$, $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 ${\sigma }_{{\rm{res}}}=0.104\pm 0.005$. We confirm (at the 95% probability level) the existence of two subpopulations segregated by host galaxy mass, separated at ${\mathrm{log}}_{10}(M/{M}_{\odot })=10$, 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 $\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 behavior, which remains unexplained.
AU  - Shariff,H
AU  - Jiao,X
AU  - Trotta,R
AU  - van,Dyk D
DO  - 1/1
PY  - 2016///
SN  - 1538-4357
TI  - Bahamas: new analysis of type Ia supernovae reveals inconsistencies with standard cosmology
T2  - The Astrophysical Journal
UR  - http://dx.doi.org/10.3847/0004-637X/827/1/1
UR  - http://arxiv.org/abs/1510.05954v2
UR  - http://hdl.handle.net/10044/1/32187
VL  - 827
ER  -
Download