Journal Article

COLD GASS, an IRAM legacy survey of molecular gas in massive galaxies – II. The non-universality of the molecular gas depletion time-scale

Amélie Saintonge, Guinevere Kauffmann, Jing Wang, Carsten Kramer, Linda J. Tacconi, Christof Buchbender, Barbara Catinella, Javier Graciá-Carpio, Luca Cortese, Silvia Fabello, Jian Fu, Reinhard Genzel, Riccardo Giovanelli, Qi Guo, Martha P. Haynes, Timothy M. Heckman, Mark R. Krumholz, Jenna Lemonias, Cheng Li, Sean Moran, Nemesio Rodriguez-Fernandez, David Schiminovich, Karl Schuster and Albrecht Sievers

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 1, pages 61-76
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18823.x
COLD GASS, an IRAM legacy survey of molecular gas in massive galaxies – II. The non-universality of the molecular gas depletion time-scale

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We study the relation between molecular gas and star formation in a volume-limited sample of 222 galaxies from the COLD GASS survey, with measurements of the CO(1–0) line from the IRAM 30-m telescope. The galaxies are at redshifts 0.025 < z < 0.05 and have stellar masses in the range 10.0 < log M/M < 11.5. The IRAM measurements are complemented by deep Arecibo H i observations and homogeneous Sloan Digital Sky Survey and GALEX photometry. A reference sample that includes both ultraviolet (UV) and far-infrared data is used to calibrate our estimates of star formation rates from the seven optical/UV bands. The mean molecular gas depletion time-scale [] for all the galaxies in our sample is 1 Gyr; however, increases by a factor of 6 from a value of ∼0.5 Gyr for galaxies with stellar masses of ∼1010 M to ∼3 Gyr for galaxies with masses of a few ×1011 M. In contrast, the atomic gas depletion time-scale remains constant at a value of around 3 Gyr. This implies that in high-mass galaxies, molecular and atomic gas depletion time-scales are comparable, but in low-mass galaxies, the molecular gas is being consumed much more quickly than the atomic gas. The strongest dependences of are on the stellar mass of the galaxy [parametrized as ], and on the specific star formation rate (sSFR). A single versus sSFR relation is able to fit both ‘normal’ star-forming galaxies in our COLD GASS sample and more extreme starburst galaxies (luminous infrared galaxies and ultraluminous infrared galaxies), which have yr. Normal galaxies at z = 1–2 are displaced with respect to the local galaxy population in the versus sSFR plane and have molecular gas depletion times that are a factor of 3–5 times longer at a given value of sSFR due to their significantly larger gas fractions.

Keywords: surveys; galaxies: evolution; galaxies: fundamental parameters; galaxies: ISM; radio lines: galaxies

Journal Article.  11761 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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