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    • Keywords


      Quasar: absorption lines; galaxies: intergalactic medium.

    • Abstract


      In recent years, the Lyman-𝛼 forest in quasar spectra has been used, together with 𝑁-body simulations, to determine the underlying matter distribution in the intergalactic medium (IGM). One of the key parameters to be known in order to compare observations and numerical simulations is the mean HI absorption in the IGM. To derive the latter, one has first to fit the quasar continuum.We have observed 20 high redshift and highly luminous QSOs (𝑚V ≤ 17.5 and 2.40 ≤ 𝑧em ≤ 3.91) at intermediate spectral resolution, with either EMMI (ESO Multi-Mode Instrument) on the ESO-NTT telescope or CARELEC at the OHP (Observatoire de Haute-Provence), and applied different methods of determining the QSO continuum to this QSO sample. We have measured the amount of absorption, known as the flux decrement, 𝐷𝐴, in the Lyman-𝛼 forest for these different methods and compared the results. In addition, we have compared 𝐷𝐴 values measured along the same lines of sight observed at high and intermediate spectral resolutions.We discuss the systematics resulting from the use of automatic continuum fitting methods.

    • Author Affiliations


      A. Aghaee1 2 P. Petitjean3 R. Srianand4 C. S. Stalin5 R. Guimarães6

      1. Department of Physics, University of Sistan and Baluchestan, Zahedan 98135-674, Iran.
      2. School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P. O. Box 19395-5531, Tehran, Iran.
      3. Institut d’Astrophysique de Paris, Université Paris 06 & CNRS, UMR7095, 98bis Bd Arago, 75014 Paris, France.
      4. Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007, India.
      5. Indian Institute of Astrophysics, Koramangala, Bangalore 560 034, India.
      6. Universidade de Feira de Santana, Av. Transnordestinam S/N, 40036-900, Feira de Santana, BA - Brasil.
    • Dates

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