M. Dessauges-ZavadskyM. GinolfiF. PozziM. BétherminO. Le FèvreS. FujimotoJ. D. SilvermanG. C. JonesL. ValliniD. SchaererA. L. FaisstY. KhusanovaY. FudamotoP. CassataF. LoiaconoP. L. CapakL. YanR. AmorinS. BardelliM. BoquienA. CimattiC. GruppioniN. P. HathiIbar, EduardoEduardoIbarA. M. KoekemoerB. C. LemauxD. NarayananP. A. OeschG. RodighieroM. RomanoM. TaliaS. ToftD. VerganiG. ZamoraniE. Zucca2025-04-132025-04-132020-08-2410.1051/0004-6361/2020382312-s2.0-85095132436https://cris-uv-2.scimago.es/handle/123456789/2049WOS:000588070500005The 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 μ 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 ⊙ , 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 μ m luminosities extrapolated from the rest-frame 158 μ m 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) × 10 8 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 ∼10 13 M ⊙ halos and of more massive z = 0 galaxies in ∼10 14 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.enacceso abiertoAstronomy And AstrophysicsSpace And Planetary Sciencereview