The Lyman α forest flux probability distribution at z>3

Authors

  • F. Calura,

    Corresponding author
    1. INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
    2. INAF, Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34131 Trieste, Italy
    3. Jeremiah Horrocks Institute for Astrophysics and Supercomputing, University of Central Lancashire, Preston PR1 2HE
      E-mail: fcalura@oabo.inaf.it
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  • E. Tescari,

    1. Service d’Astrophysique, CEA-Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France
    2. Dipartimento di Fisica – Sezione di Astronomia, Università di Trieste, Via G. B. Tiepolo 11, 34131 Trieste, Italy
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  • V. D’Odorico,

    1. INAF, Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34131 Trieste, Italy
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  • M. Viel,

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

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

    1. Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany
    2. Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706, USA
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  • J. S. Bolton

    1. School of Physics, University of Melbourne, Parkville, VIC 3010, Australia
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Based on observations collected at the European Southern Observatory Very Large Telescope, Cerro Paranal, Chile – Programs 077.A-0166(A), 075.A-0464(A), 073.B-0787(A), 166.A-0106(A) and 65.O-0296(A).

E-mail: fcalura@oabo.inaf.it

ABSTRACT

We present a measurement of the Lyman α flux probability distribution function (PDF) obtained from a set of eight high-resolution quasar spectra with emission redshifts in the range 3.3 ≤z≤ 3.8. We carefully study the effect of metal absorption lines on the shape of the PDF. Metals have a larger impact on the PDF measurements at lower redshift, where there are relatively fewer Lyman α absorption lines. This may be explained by an increase in the number of metal lines that are blended with Lyman α absorption lines towards higher redshift, but may also be due to the presence of fewer metals in the intergalactic medium (IGM) at earlier times. We also provide a new measurement of the redshift evolution of the effective optical depth, τeff, at 2.8 ≤z≤ 3.6, and find no evidence for a deviation from a power-law evolution in the log (τeff)–log (1 +z) plane. The flux PDF measurements are furthermore of interest for studies of the thermal state of the IGM at z≃ 3. By comparing the PDF to state-of-the-art cosmological hydrodynamical simulations, we place constraints on the temperature of the IGM and compare our results with previous measurements of the PDF at lower redshift. At redshift z= 3, our new PDF measurements are consistent with an isothermal temperature–density relation, T=T0Δγ− 1, with a temperature at the mean density of T0= 19 250 ± 4800 K and a slope γ= 0.90 ± 0.21 (1σ uncertainties). In comparison, joint constraints with existing lower redshift PDF measurements at z < 3 favour an inverted temperature–density relation with T0= 17 900 ± 3500 K and γ= 0.70 ± 0.12, in broad agreement with previous analyses.

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