ALMA reveals the molecular gas properties of 5 star-forming galaxies across the main sequence at 3 < z < 3.5

Abstract

We present the detection of CO(5-4) with S/N> 7 - 13 and a lower CO transition with S/N > 3 (CO(4-3) for 4 galaxies, and CO(3-2) for one) with ALMA in band 3 and 4 in five main sequence star-forming galaxies with stellar masses 3-6x10^10 M/M_sun at 3 < z < 3.5. We find a good correlation between the total far-infrared luminosity LFIR and the luminosity of the CO(5-4) transition L'CO(5-4), where L'CO(5-4) increases with SFR, indicating that CO(5-4) is a good tracer of the obscured SFR in these galaxies. The two galaxies that lie closer to the star-forming main sequence have CO SLED slopes that are comparable to other star-forming populations, such as local SMGs and BzK star-forming galaxies; the three objects with higher specific star formation rates (sSFR) have far steeper CO SLEDs, which possibly indicates a more concentrated episode of star formation. By exploiting the CO SLED slopes to extrapolate the luminosity of the CO(1-0) transition, and using a classical conversion factor for main sequence galaxies of alpha_CO = 3.8 M_sun(K km s^-1 pc^-2)^-1, we find that these galaxies are very gas rich, with molecular gas fractions between 60 and 80%, and quite long depletion times, between 0.2 and 1 Gyr. Finally, we obtain dynamical masses that are comparable with the sum of stellar and gas mass (at least for four out of five galaxies), allowing us to put a first constraint on the alpha_CO parameter for main sequence galaxies at an unprecedented redshift.

17 pages, 8 figures; accepted for publication in The Astrophysical Journal

References in corpus (20)

• Cosmic Star Formation History
• The Cosmic Evolution Survey (COSMOS) -- Overview
• Star Formation in AEGIS Field Galaxies since z=1.1 : The Dominance of Gradually Declining Star Formation, and the Main Sequence of Star-Forming Galaxies
• A simple model to interpret the ultraviolet, optical and infrared emission from galaxies
• zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
• The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
• UltraVISTA: a new ultra-deep near-infrared survey in COSMOS
• Combined CO & Dust Scaling Relations of Depletion Time and Molecular Gas Fractions with Cosmic Time, Specific Star Formation Rate and Stellar Mass
• COLD GASS, an IRAM Legacy Survey of Molecular Gas in Massive Galaxies: II. The non-universality of the Molecular Gas Depletion Timescale
• The VIMOS Ultra-Deep Survey: ~10,000 galaxies with spectroscopic redshifts to study galaxy assembly at early epochs 2<z<~6
• Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago
• CO excitation of normal star forming galaxies out to z=1.5 as regulated by the properties of their interstellar medium
• Vigorous star formation with low efficiency in massive disk galaxies at z=1.5
• The Ly-alpha Properties of Faint Galaxies at z2-3 with Systemic Redshifts and Velocity Dispersions from Keck-MOSFIRE
• Automated Mining of the ALMA Archive in the COSMOS Field (A3COSMOS): II. Cold Molecular Gas Evolution out to Redshift 6
• A Multiwavelength Consensus on the Main Sequence of Star-Forming Galaxies at z~2
• Dust continuum emission as a tracer of gas mass in galaxies
• Gas Fraction and Depletion Time of Massive Star Forming Galaxies at z~3.2: No Change in Global Star Formation Process out to z>3
• Molecular gas content in strongly-lensed z~1.5-3 star-forming galaxies with low IR luminosities
• VALES: I. The molecular gas content in star-forming dusty H-ATLAS galaxies up to z=0.35

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