Issue |
A&A
Volume 643, November 2020
|
|
---|---|---|
Article Number | A5 | |
Number of page(s) | 17 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202038231 | |
Published online | 27 October 2020 |
The ALPINE-ALMA [C II] survey
Molecular gas budget in the early Universe as traced by [C II]
1
Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
e-mail: miroslava.dessauges@unige.ch
2
Università di Bologna – Dipartimento di Fisica e Astronomia, Via Gobetti 93/2, 40129 Bologna, Italy
3
INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
4
Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
5
The Cosmic Dawn Center, University of Copenhagen, Vibenshuset, Lyngbyvej 2, 2100 Copenhagen, Denmark
6
Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, 2100 Copenhagen, Denmark
7
Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo (Kavli IPMU, WPI), 277-8583 Kashiwa, Japan
8
Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033
Japan
9
Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Ave., Cambridge, CB3 0HE
UK
10
Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge, CB3 0HA
UK
11
Leiden Observatory, Leiden University, PO Box 9500, 2300 RA Leiden, The Netherlands
12
IPAC, M/C 314-6, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA, 91125
USA
13
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
14
Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio, 3, 35122 Padova, Italy
15
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
16
The Caltech Optical Observatories, California Institute of Technology, Pasadena, CA, 91125
USA
17
Instituto de Investigación Multidisciplinar en Ciencia y Tecnología, Universidad de La Serena, Raúl Bitrán, 1305 La Serena, Chile
18
Departamento de Astronomía, Universidad de La Serena, Av. Juan Cisternas 1200 Norte, La Serena, Chile
19
Centro de Astronomía (CITEVA), Universidad de Antofagasta, Avenida Angamos 601, Antofagasta, Chile
20
INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
21
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218
USA
22
Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso, Chile
23
Department of Physics, University of California, Davis, One Shields Ave., Davis, CA, 95616
USA
24
Department of Astronomy, University of Florida, 211 Bryant Space Sciences Center, Gainesville, FL, 32611
USA
Received:
22
April
2020
Accepted:
17
July
2020
The molecular gas content of normal galaxies at z > 4 is poorly constrained because the commonly used molecular gas tracers become hard to detect at these high redshifts. We use the [C II] 158 μm luminosity, which was recently proposed as a molecular gas tracer, to estimate the molecular gas content in a large sample of main sequence star-forming galaxies at z = 4.4 − 5.9, with a median stellar mass of 109.7 M⊙, drawn from the ALMA Large Program to INvestigate [C II] at Early times survey. The agreement between the molecular gas masses derived from [C II] luminosities, dynamical masses, and rest-frame 850 μm luminosities extrapolated from the rest-frame 158 μm continuum supports [C II] as a reliable tracer of molecular gas in our sample. We find a continuous decline of the molecular gas depletion timescale from z = 0 to z = 5.9, which reaches a mean value of (4.6 ± 0.8) × 108 yr at z ∼ 5.5, only a factor of between two and three shorter than in present-day galaxies. This suggests a mild enhancement of the star formation efficiency toward high redshifts. Our estimates also show that the previously reported rise in the molecular gas fraction flattens off above z ∼ 3.7 to achieve a mean value of 63%±3% over z = 4.4 − 5.9. This redshift evolution of the gas fraction is in line with that of the specific star formation rate. We use multi-epoch abundance-matching to follow the gas fraction evolution across cosmic time of progenitors of z = 0 Milky Way-like galaxies in ∼1013 M⊙ halos and of more massive z = 0 galaxies in ∼1014 M⊙ halos. Interestingly, the former progenitors show a monotonic increase of the gas fraction with redshift, while the latter show a steep rise from z = 0 to z ∼ 2 followed by a constant gas fraction from z ∼ 2 to z = 5.9. We discuss three possible effects, namely outflows, a pause in gas supply, and over-efficient star formation, which may jointly contribute to the gas fraction plateau of the latter massive galaxies.
Key words: galaxies: evolution / galaxies: high-redshift / galaxies: ISM / ISM: molecules
© ESO 2020
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