Phibss: Molecular Gas Content and Scaling Relations in z 1-3 Massive, Main-sequence Star-forming Galaxies

L. J. Tacconi, R. Neri, R. Genzel, F. Combes, A. Bolatto, M. C. Cooper, S. Wuyts, F. Bournaud, A. Burkert, J. Comerford, P. Cox, M. Davis, N. M. Förster Schreiber, S. García-Burillo, J. Gracia-Carpio, D. Lutz, T. Naab, S. Newman, A. Omont, A. SaintongeK. Shapiro Griffin, A. Shapley, A. Sternberg, B. Weiner

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We present PHIBSS, the IRAM Plateau de Bure high-z blue sequence CO 3-2 survey of the molecular gas properties in massive, main-sequence star-forming galaxies (SFGs) near the cosmic star formation peak. PHIBSS provides 52 CO detections in two redshift slices at z ~ 1.2 and 2.2, with log(M *(M ☉)) ≥ 10.4 and log(SFR(M ☉/yr)) ≥ 1.5. Including a correction for the incomplete coverage of the M* -SFR plane, and adopting a "Galactic" value for the CO-H2 conversion factor, we infer average gas fractions of ~0.33 at z ~ 1.2 and ~0.47 at z ~ 2.2. Gas fractions drop with stellar mass, in agreement with cosmological simulations including strong star formation feedback. Most of the z ~ 1-3 SFGs are rotationally supported turbulent disks. The sizes of CO and UV/optical emission are comparable. The molecular-gas-star-formation relation for the z = 1-3 SFGs is near-linear, with a ~0.7 Gyr gas depletion timescale; changes in depletion time are only a secondary effect. Since this timescale is much less than the Hubble time in all SFGs between z ~ 0 and 2, fresh gas must be supplied with a fairly high duty cycle over several billion years. At given z and M *, gas fractions correlate strongly with the specific star formation rate (sSFR). The variation of sSFR between z ~ 0 and 3 is mainly controlled by the fraction of baryonic mass that resides in cold gas.
Original languageEnglish
Number of pages22
JournalAstrophysical Journal
Issue number1
Early online date16 Apr 2013
Publication statusPublished - 1 May 2013


  • galaxies: evolution
  • galaxies: high redshift
  • galaxies ISM
  • ISM: molecules


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