Minimally parametric power spectrum reconstruction from the Lyman α forest

Authors

  • Simeon Bird,

    Corresponding author
    1. Institute of Astronomy and Kavli Institute for Cosmology, Madingley Road, Cambridge CB3 0HA
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  • Hiranya V. Peiris,

    1. Institute of Astronomy and Kavli Institute for Cosmology, Madingley Road, Cambridge CB3 0HA
    2. Department of Physics and Astronomy, University College London, London WC1E 6BT
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  • Matteo Viel,

    1. INAF - Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste, Italy
    2. INFN/National Institute for Nuclear Physics, Via Valerio 2, I-34127 Trieste, Italy
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  • Licia Verde

    1. ICREA & Instituto de Ciencias del Cosmos, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona, Spain
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E-mail: spb41@ast.cam.ac.uk

ABSTRACT

Current results from the Lyman α forest assume that the primordial power spectrum of density perturbations follows a simple power-law form. We present the first analysis of Lyman α data to study the effect of relaxing this strong assumption on primordial and astrophysical constraints. We perform a large suite of numerical simulations, using them to calibrate a minimally parametric framework for describing the power spectrum. Combined with cross-validation, a statistical technique which prevents overfitting of the data, this framework allows us to reconstruct the power spectrum shape without strong prior assumptions. We find no evidence for deviation from scale-invariance; our analysis also shows that current Lyman α data do not have sufficient statistical power to robustly probe the shape of the power spectrum at these scales. In contrast, the ongoing Baryon Oscillation Sky Survey will be able to do so with high precision. Furthermore, this near-future data will be able to break degeneracies between the power spectrum shape and astrophysical parameters.

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