Baryon acoustic oscillations from the complete SDSS-III Lyα-quasar cross-correlation function at z = 2.4

¹ IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
e-mail: rich@hep.saclay.cea.fr
² Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
³ APC, Université Paris Diderot-Paris 7, CNRS/IN2P3, CEA, Observatoire de Paris, 10 rue A. Domon & L. Duquet, 75014 Paris, France
⁴ LPNHE, CNRS/IN2P3, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, 4 place Jussieu, 75252 Paris Cedex, France
⁵ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
⁶ Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Salt Lake City, UT 84112, USA
⁷ Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
⁸ Department of Physics and Astronomy, University College London, Gower Street, London, UK
⁹ Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
¹⁰ Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Catalonia, Spain
¹¹ Institució de Ciències del Cosmos, Universitat de Barcelona (UB-IEEC), 080028 Barcelona, Catalonia, Spain
¹² Université Paris 6 et CNRS, Institut d’Astrophysique de Paris, 98 bis Blvd. Arago, 75014 Paris, France
¹³ SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ, UK
¹⁴ Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
¹⁵ Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
¹⁶ Brookhaven National Laboratory, 2 Center Road, Upton, NY 11973, USA
¹⁷ Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA

Received: 7 August 2017
Accepted: 25 September 2017

Abstract

We present a measurement of baryon acoustic oscillations (BAO) in the cross-correlation of quasars with the Lyα-forest flux transmission at a mean redshift of z = 2.40. The measurement uses the complete Sloan Digital Sky Survey (SDSS-III) data sample: 168 889 forests and 234 367 quasars from the SDSS data release DR12. In addition to the statistical improvement on our previous study using DR11, we have implemented numerous improvements at the analysis level enabling a more accurate measurement of this cross-correlation. We have also developed the first simulations of the cross-correlation that allow us to test different aspects of our data analysis and to search for potential systematic errors in the determination of the BAO peak position. We measure the two ratios D_H(z = 2.40) /r_d = 9.01 ± 0.36 and D_M(z = 2.40) /r_d = 35.7 ± 1.7, where the errors include marginalization over the non-linear velocity of quasars and the cross-correlation of metals and quasars, among other effects. These results are within 1.8σ of the prediction of the flat-ΛCDM model describing the observed cosmic microwave background anisotropies. We combine this study with the Lyα-forest auto-correlation function, yielding D_H(z = 2.40) /r_d = 8.94 ± 0.22 and D_M(z = 2.40) /r_d = 36.6 ± 1.2, within 2.3σ of the same flat-ΛCDM model.