Improved constraints on cosmological parameters from Type Ia supernova data

Authors

  • M. C. March,

    Corresponding author
    1. Imperial College London, Astrophysics Group, Blackett Laboratory, Prince Consort Road, London SW7 2AZ
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  • R. Trotta,

    1. Imperial College London, Astrophysics Group, Blackett Laboratory, Prince Consort Road, London SW7 2AZ
    2. African Institute for Mathematical Sciences, 6 Melrose Road, Muizenberg, 7945 Cape Town, South Africa
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  • P. Berkes,

    1. Brandeis University, Volen Center for Complex Systems, 415 South Street, Waltham, MA 02454-9110, USA
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  • G. D. Starkman,

    1. CERCA, Department of Physics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA
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  • P. M. Vaudrevange

    1. CERCA, Department of Physics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA
    2. DESY, Notkestrasse 85, 22607 Hamburg, Germany
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E-mail: marisa.march06@imperial.ac.uk

ABSTRACT

We present a new method based on a Bayesian hierarchical model to extract constraints on cosmological parameters from Type Ia supernova (SNIa) data obtained with the SALT-II light-curve fitter. We demonstrate with simulated data sets that our method delivers tighter statistical constraints on the cosmological parameters over 90 per cent of the time, that it reduces statistical bias typically by a factor of ∼2–3 and that it has better coverage properties than the usual χ2 approach. As a further benefit, a full posterior probability distribution for the dispersion of the intrinsic magnitude of SNe is obtained. We apply this method to recent SNIa data, and by combining them with cosmic microwave background and baryonic acoustic oscillations data, we obtain Ωm= 0.28 ± 0.02,  ΩΛ= 0.73 ± 0.01 (assuming w=−1) and Ωm= 0.28 ± 0.01, w=−0.90 ± 0.05 (assuming flatness; statistical uncertainties only). We constrain the intrinsic dispersion of the B-band magnitude of the SNIa population, obtaining σintμ= 0.13 ± 0.01 mag. Applications to systematic uncertainties will be discussed in a forthcoming paper.

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