TY - JOUR

T1 - The ALPINE-ALMA [CII] survey

T2 - Molecular gas budget in the early Universe as traced by [CII]

AU - Dessauges-Zavadsky, M.

AU - Ginolfi, M.

AU - Pozzi, F.

AU - Bethermin, M.

AU - Le Fevre, O.

AU - Fujimoto, S.

AU - Silverman, J. D.

AU - Jones, G. C.

AU - Vallini, L.

AU - Schaerer, D.

AU - Faisst, A. L.

AU - Khusanova, Y.

AU - Fudamoto, Y.

AU - Cassata, P.

AU - Loiacono, F.

AU - Capak, P. L.

AU - Yan, L.

AU - Amorin, R.

AU - Bardelli, S.

AU - Boquien, M.

AU - Cimatti, A.

AU - Gruppioni, C.

AU - Hathi, N. P.

AU - Ibar, E.

AU - Koekemoer, A. M.

AU - Lemaux, B. C.

AU - Narayanan, D.

AU - Oesch, P. A.

AU - Rodighiero, G.

AU - Romano, M.

AU - Talia, M.

AU - Toft, S.

AU - Vergani, D.

AU - Zamorani, G.

AU - Zucca, E.

PY - 2020/10/27

Y1 - 2020/10/27

N2 - 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 [CII] 158 mu m 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 10(9.7) M-circle dot, drawn from the ALMA Large Program to INvestigate [CII] at Early times survey. The agreement between the molecular gas masses derived from [CII] luminosities, dynamical masses, and rest-frame 850 mu m luminosities extrapolated from the rest-frame 158 mu m continuum supports [CII] 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) x 10(8) yr at z similar to 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 similar to 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 similar to 10(13) M-circle dot halos and of more massive z=0 galaxies in similar to 10(14) M-circle dot 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 similar to 2 followed by a constant gas fraction from z similar to 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.

AB - 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 [CII] 158 mu m 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 10(9.7) M-circle dot, drawn from the ALMA Large Program to INvestigate [CII] at Early times survey. The agreement between the molecular gas masses derived from [CII] luminosities, dynamical masses, and rest-frame 850 mu m luminosities extrapolated from the rest-frame 158 mu m continuum supports [CII] 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) x 10(8) yr at z similar to 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 similar to 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 similar to 10(13) M-circle dot halos and of more massive z=0 galaxies in similar to 10(14) M-circle dot 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 similar to 2 followed by a constant gas fraction from z similar to 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.

KW - galaxies: evolution

KW - galaxies: high-redshift

KW - galaxies: ISM

KW - ISM: molecules

KW - STAR-FORMING GALAXIES

KW - MASS-METALLICITY RELATION

KW - C-II

KW - MAIN-SEQUENCE

KW - SCALING RELATIONS

KW - CONVERSION FACTOR

KW - LEGACY SURVEY

KW - EVOLUTION

KW - MODEL

KW - DUST

U2 - 10.1051/0004-6361/202038231

DO - 10.1051/0004-6361/202038231

M3 - Journal article

VL - 643

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - A5

ER -