ALMA Reveals the Molecular Gas Properties of Five Star-forming Galaxies across the Main Sequence at 3

Scientific paper - Original scientific paper

• Author: Paolo Cassata
• Author: Daizhong Liu
• Author: Brent Groves
• Author: Eva Schinnerer
• Author: Eduardo Ibar
• Author: Mark Sargent
• Author: Alexander Karim
• Author: Margherita Talia
• Author: Olivier Le Fèvre
• Author: Lidia Tasca
• Author: Brian C. Lemaux
• Author: Bruno Ribeiro
• Author: Stefano Fiore
• Author: Michael Romano
• Author: Chiara Mancini
• Author: Laura Morselli
• Author: Giulia Rodighiero
• Author: Lucía Rodríguez-Muñoz
• Author: Andrea Enia
• Author: Vernesa Smolčić
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics; Astronomy and Astrophysics

Abstract (english)

We present the detection of CO (5−4) with signal-to-noise ratio (S/N) > 7–13 and a lower CO transition with S/N > 3 (CO (4−3) for four galaxies, and CO (3−2) for one) with the Atacama Large Millimeter/submillimeter Array in bands 3 and 4 in five main-sequence (MS) star-forming galaxies with stellar masses (3– 6) × 10^10M_⊙ at 3 < z < 3.5. We find a good correlation between the total far-infrared luminosity L_FIR and the luminosity of the CO (5−4) transition ( ) L'_CO(5-4), where L'_CO(5-4) - increases with star formation rate (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 MS have CO spectral line energy distribution (SLED) slopes that are comparable to other star-forming populations, such as local submillimeter galaxies and BzK star- forming galaxies ; the three objects with higher specific star formation rates 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 MS galaxies of α_CO = 3.8 M_⊙ (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 to the sum of stellar and gas mass (at least for four out of five galaxies), allowing us to put a first constraint on the α_CO parameter for MS galaxies at an unprecedented redshift.

• Keywords (english): molecular gas properties
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Astrophysical Journal
• Numbering: vol. 891, no. 1, 83
• p-ISSN: 0004-637X
• e-ISSN: 1538-4357
• DOI: https://doi.org/10.3847/1538-4357/ab7452
• URN:NBN: urn:nbn:hr:217:953449
• Publication: 2020
• Document URL: https://iopscience.iop.org/article/10.3847/1538-4357/ab7452
• Type of resource: Text
• Access conditions: Open access
• Public note: © 2020. The American Astronomical Society. All rights reserved. Received 2019 July 26. Accepted 2020 February 8. Published 2020 March 6.
• Created on: 2020-08-27 20:16:52