Probing deviations from general relativity with the Euclid spectroscopic survey

Authors

  • E. Majerotto,

    Corresponding author
    1. INAF – Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (LC), Italy
    2. Instituto de Física Teórica (UAM/CSIC), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
    3. Departamento de Física Teórica (UAM), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
      E-mail: elisabetta.majerotto@uam.es
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  • L. Guzzo,

    1. INAF – Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (LC), Italy
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  • L. Samushia,

    1. Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama building, Portsmouth PO1 3FX
    2. National Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, GE-0160 Tbilisi, Georgia
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  • W. J. Percival,

    1. Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama building, Portsmouth PO1 3FX
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  • Y. Wang,

    1. Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, USA
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  • S. de la Torre,

    1. INAF – Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (LC), Italy
    2. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ
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  • B. Garilli,

    1. IASF-Milano, INAF, Via Bassini 15, I-20133 Milano, Italy
    2. Laboratoire d’Astrophysique de Marseille, UMR 6110 CNRS-Université de Provence, 38 rue Frederic Joliot-Curie, F-13388 Marseille Cedex 13, France
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  • P. Franzetti,

    1. IASF-Milano, INAF, Via Bassini 15, I-20133 Milano, Italy
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  • E. Rossetti,

    1. Dipartimento di Astronomia, Alma Mater Studiorum-Università di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
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  • A. Cimatti,

    1. Dipartimento di Astronomia, Alma Mater Studiorum-Università di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
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  • C. Carbone,

    1. Dipartimento di Astronomia, Alma Mater Studiorum-Università di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
    2. INAF – Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
    3. INFN, Sezione di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna, Italy
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  • N. Roche,

    1. INAF – Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
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  • G. Zamorani

    1. INAF – Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
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E-mail: elisabetta.majerotto@uam.es

ABSTRACT

We discuss the ability of the planned Euclid mission to detect deviations from general relativity (GR) using its extensive redshift survey of more than 50 million galaxies. Constraints on the gravity theory are placed measuring the growth rate of structure within 14 redshift bins between z= 0.7 and 2. The growth rate is measured from redshift-space distortions, i.e. the anisotropy of the clustering pattern induced by coherent peculiar motions. This is performed in the overall context of the Euclid spectroscopic survey, which will simultaneously measure the expansion history of the Universe, using the power spectrum and its baryonic features as a standard ruler, accounting for the relative degeneracies of expansion and growth parameters. The resulting expected errors on the growth rate in the different redshift bins, expressed through the quantity fσ8, range between 1.3 and 4.4 per cent. We discuss the optimization of the survey configuration and investigate the important dependence on the growth parametrization and the assumed cosmological model. We show how a specific parametrization could actually drive the design towards artificially restricted regions of the parameter space. Finally, in the framework of the popular ‘γ parametrization’, we show that the Euclid spectroscopic survey alone will already be able to provide substantial evidence (in Bayesian terms) if the growth index differs from the GR value γ= 0.55 by at least ∼0.13. This will combine with the comparable inference power provided by the Euclid weak lensing survey, resulting in Euclid’s unique ability to provide a decisive test of modified gravity.

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