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High molecular gas fractions in normal massive star-forming galaxies in the young Universe

Nature volume 463, pages 781–784 (2010)Cite this article

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Abstract

Stars form from cold molecular interstellar gas. As this is relatively rare in the local Universe, galaxies like the Milky Way form only a few new stars per year. Typical massive galaxies in the distant Universe formed stars an order of magnitude more rapidly1,2. Unless star formation was significantly more efficient, this difference suggests that young galaxies were much more molecular-gas rich. Molecular gas observations in the distant Universe have so far largely been restricted to very luminous, rare objects, including mergers and quasars3,4,5, and accordingly we do not yet have a clear idea about the gas content of more normal (albeit massive) galaxies. Here we report the results of a survey of molecular gas in samples of typical massive-star-forming galaxies at mean redshifts <z> of about 1.2 and 2.3, when the Universe was respectively 40% and 24% of its current age. Our measurements reveal that distant star forming galaxies were indeed gas rich, and that the star formation efficiency is not strongly dependent on cosmic epoch. The average fraction of cold gas relative to total galaxy baryonic mass at z = 2.3 and z = 1.2 is respectively about 44% and 34%, three to ten times higher than in today’s massive spiral galaxies6. The slow decrease between z ≈ 2 and z ≈ 1 probably requires a mechanism of semi-continuous replenishment of fresh gas to the young galaxies.

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Figure 1: Integrated CO spectra.
Figure 2: CO maps in EGS 1305123.
Figure 3: High molecular gas fractions in SFGs at high z.

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Acknowledgements

This work is based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). We thank B. Lazareff and the IRAM staff for their work in developing the new PdBI receiver systems, which made these technically difficult observations feasible. We are grateful to J. Blaizot, L.-M. Dansac, R. Davé, D. Kereŝ, P. Ocvirk, C. Pichon and R. Teyssier for communicating unpublished results of their simulations and for discussions. A.B. and T.N. thank the Cluster of Excellence "Origin and Structure of the Universe" for support. M.C.C. is a Spitzer Fellow; A.B. is a Max Planck Fellow.

Author Contributions All authors have contributed extensively to this manuscript.

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Authors and Affiliations

  1. Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstr. 1, 85748 Garching, Germany ,

    L. J. Tacconi, R. Genzel, N. Bouché, N. M. Förster Schreiber, J. Gracia-Carpio & D. Lutz

  2. Department of Physics, Le Conte Hall, University of California, Berkeley, California 94720, USA,

    R. Genzel

  3. IRAM, 300 Rue de la Piscine, 38406 St Martin d’Heres, Grenoble, France ,

    R. Neri & P. Cox

  4. Steward Observatory, 933 N. Cherry Ave., University of Arizona, Tucson, Arizona 85721-0065, USA ,

    M. C. Cooper & B. Weiner

  5. Department of Astronomy, Campbell Hall, University of California, Berkeley, California 94720, USA,

    K. Shapiro, J. Comerford & M. Davis

  6. Department of Astronomy, University of Maryland, College Park, Maryland 20742-2421, USA,

    A. Bolatto

  7. Service d'Astrophysique, DAPNIA, CEA/Saclay, F-91191 Gif-sur-Yvette Cedex, France ,

    F. Bournaud

  8. Universitätssternwarte der Ludwig-Maximiliansuniversität, Scheinerstr. 1, D-81679 München, Germany ,

    A. Burkert & T. Naab

  9. LERMA, Observatoire de Paris, 61 Av. de l'Observatoire, F-75 014 Paris, France ,

    F. Combes

  10. Observatorio Astronómico Nacional-OAN, Apartado 1143, 28800 Alcalá de Henares-Madrid, Spain ,

    S. Garcia-Burillo

  11. Institut d’Astrophysique de Paris, CNRS and Université Pierre and Marie Curie, 98 bis boulevard Arago, 75014 Paris, France ,

    A. Omont

  12. Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547, USA,

    A. Shapley

  13. School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel

    A. Sternberg

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  1. L. J. Tacconi
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  2. R. Genzel
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Correspondence to L. J. Tacconi.

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Tacconi, L., Genzel, R., Neri, R. et al. High molecular gas fractions in normal massive star-forming galaxies in the young Universe. Nature 463, 781–784 (2010). https://doi.org/10.1038/nature08773

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