• DOI:10.1038/nature08773
• Corpus ID: 4322787

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

@article{Tacconi2010HighMG,
  title={High molecular gas fractions in normal massive star-forming galaxies in the young Universe},
  author={Linda J. Tacconi and Reinhard Genzel and Roberto Neri and Pierre Cox and Michael C. Cooper and Kristen Leah Shapiro and Alberto D. Bolatto and Nicolas Bouch{\'e} and Fr{\'e}d{\'e}ric Bournaud and Andreas Burkert and Françoise Combes and Julia M. Comerford and Marc Davis and Natascha M. Forster Schreiber and Santiago Garc{\'i}a-Burillo and Javier Graci{\'a}-Carpio and Dieter Lutz and Thorsten Naab and Alain Omont and Alice E. Shapley and Amiel Sternberg and Benjamin J. Weiner},
  journal={Nature},
  year={2010},
  volume={463},
  pages={781-784}
}

• L. Tacconi, R. Genzel, +19 authors B. Weiner
• Published 10 February 2010
• Physics
• Nature

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 rapidly. 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 quasars, 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 galaxies. The slow decrease between z ≈ 2 and z ≈ 1 probably requires a mechanism of semi-continuous replenishment of fresh gas to the young galaxies.