Baryon acoustic oscillations in the Lyα forest of BOSS DR11 quasars^⋆

¹ CEA, Centre de Saclay, IRFU, 91191 Gif-sur-Yvette, France
e-mail: timothee.delubac@epfl.ch
² APC, Université Paris Diderot-Paris 7, CNRS/IN2P3, CEA, Observatoire de Paris, 10 rue A. Domon & L. Duquet, 75205 Paris, France
³ Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
⁴ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
⁵ Brookhaven National Laboratory, 2 Center Road, Upton, NY 11973, USA
⁶ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁷ Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth, PO1 3FX, UK
⁸ Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540, USA
⁹ Apache Point Observatory, PO Box 59, Sunspot, NM 88349, USA
¹⁰ Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Salt Lake City, UT 84112, USA
¹¹ Harvard-Smithsonian Center for Astrophysics, Harvard University, 60 Garden St., Cambridge, MA 02138, USA
¹² Laboratoire d’Astrophysique, École polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
¹³ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
¹⁴ Institució Catalana de Recerca i Estudis Avançats, Barcelona, Catalonia, Spain
¹⁵ Institut de Ciències del Cosmos, Universitat de Barcelona (UB-IEEC), 08028 Barcelona, Catalonia, Spain
¹⁶ Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071, USA
¹⁷ Université Paris 6 et CNRS, Institut d’Astrophysique de Paris, 98bis Bd Arago, 75014 Paris, France
¹⁸ Bruce and Astrid McWilliams Center for Cosmology, Carnegie Mellon University, Pittsburgh, PA 15213, USA
¹⁹ Dept. of Physics, Drexel University, 3141 Chestnut Street, Philiadelphia, PA 19104, USA
²⁰ Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
²¹ Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
²² Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
²³ Department of Astronomy and Astrophysics and the Enrico Fermi Institute, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois, 60615, USA
²⁴ Observatório Nacional, Rua Gal. José Cristino 77, RJ –20921-400 Rio de Janeiro, Brazil
²⁵ Laboratório Interinstitucional de e-Astronomia, – LIneA, Rua Gal. José Cristino 77, RJ –20921-400 Rio de Janeiro, Brazil
²⁶ Department of Astronomy and Space Science, Sejong University, 143-747 Seoul, Korea

Received: 9 April 2014
Accepted: 15 October 2014

Abstract

We report a detection of the baryon acousticoscillation (BAO) feature in the flux-correlation function of the Lyα forest of high-redshift quasars with a statistical significance of five standard deviations. The study uses 137 562 quasars in the redshift range 2.1 ≤ z ≤ 3.5 from the data release 11 (DR11) of the Baryon Oscillation Spectroscopic Survey (BOSS) of SDSS-III. This sample contains three times the number of quasars used in previous studies. The measured position of the BAO peak determines the angular distance, D_A(z = 2.34) and expansion rate, H(z = 2.34), both on a scale set by the sound horizon at the drag epoch, r_d. We find D_A/r_d = 11.28 ± 0.65(1σ)^+2.8_-1.2 (2σ) and D_H/r_d = 9.18 ± 0.28(1σ) ± 0.6(2σ) where D_H = c/H. The optimal combination, ~D_H^0.7D_A^0.3/r_d is determined with a precision of ~2%. For the value r_d = 147.4 Mpc, consistent with the cosmic microwave background power spectrum measured by Planck, we find D_A(z = 2.34) = 1662 ± 96(1σ) Mpc and H(z = 2.34) = 222 ± 7(1σ) km s^-1 Mpc^-1. Tests with mock catalogs and variations of our analysis procedure have revealed no systematic uncertainties comparable to our statistical errors. Our results agree with the previously reported BAO measurement at the same redshift using the quasar-Lyα forest cross-correlation. The autocorrelation and cross-correlation approaches are complementary because of the quite different impact of redshift-space distortion on the two measurements. The combined constraints from the two correlation functions imply values of D_A/r_d that are 7% lower and 7% higher for D_H/r_d than the predictions of a flat ΛCDM cosmological model with the best-fit Planck parameters. With our estimated statistical errors, the significance of this discrepancy is ≈2.5σ.