Column density distribution and cosmological mass density of neutral gas: Sloan Digital Sky Survey-III Data Release 9^⋆

¹ Institut d’Astrophysique de Paris, CNRS-UPMC, UMR 7095, 98bis bd Arago, 75014 Paris, France
e-mail: noterdaeme@iap.fr
² Lawrence Berkeley National Lab, 1 Cyclotron Rd, Berkeley, CA 94720, USA
³ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
⁴ Institute of Theoretical Physics, University of Zurich, 8057 Zurich, Switzerland
⁵ APC, CNRS UMR 7164, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
⁶ Apache Point Observatory, PO Box 59, Sunspot, NM 88349-0059, USA
⁷ Astronomy Department, University of Florida, 211 Bryant Space Science Center, PO Box 112055, Gainesville, FL 32611-2055, USA
⁸ Institut de Ciències del Cosmos, Universitat de Barcelona, Facultat de Física, Barcelona, Spain
⁹ Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071, USA
¹⁰ Institute of Cosmology and Gravitation, University of Portsmouth, UK
¹¹ Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
¹² Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
¹³ Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
¹⁴ Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA

Received: 19 August 2012
Accepted: 3 October 2012

Abstract

We present the first results from an ongoing survey for damped Lyman-α systems (DLAs) in the spectra of z > 2 quasars observed in the course of the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey (SDSS) III. Our full (non-statistical) sample, based on Data Release 9, comprises 12 081 systems with log N(H   i) ≥ 20, out of which 6839 have log N(H   i) ≥ 20.3. This is the largest DLA sample ever compiled, superseding that from SDSS-II by a factor of seven.

Using a statistical sub-sample and estimating systematics from realistic mock data, we probe the N(H   i) distribution at ⟨z⟩ = 2.5. Contrary to what is generally believed, the distribution extends beyond 10²² cm^-2 with a moderate slope of index  ≈−3.5. This result matches the opacity-corrected distribution observed at z = 0 surprisingly well. The cosmological mass density of neutral gas in DLAs is found to be , evolving only mildly over the past 12 billion years.