Measuring the gas reservoirs in 108 < M⋆ < 1011 M⊙ galaxies at 1 ≤ z ≤ 3

Abstract

Context. Understanding the gas content in galaxies, along with its consumption and replenishment, is vital to our grasp of the evolution of the Universe. Numerous studies have addressed this notion, utilizing various observational tools and analytical methods. These include examining low-transition 12CO millimeter rotational lines and exploring the far-infrared and the (sub-)millimeter emission of galaxies. With the capabilities of present-day facilities, much of this research has been centered on relatively bright galaxies. Aims. This study is aimed at exploring the gas reservoirs of a more general type of galaxy population at 1.0 < z < 3.0 that is not restricted to bright (sub-)millimeter objects. We strive to obtain a measurement that will help to constrain our knowledge of the gas content at 1010 − 11 M⊙, with upper limits at ∼108 − 10 M⊙. Methods. We stacked ALMA 1.1 mm data to measure the gas content of a mass-complete sample of galaxies down to ∼108.6 M⊙ at z = 1 (∼109.2 M⊙ at z = 3) extracted from the HST/CANDELS sample in GOODS-S. The selected sample is composed of 5530 predominantly blue (⟨b − i⟩∼0.12 mag, ⟨i − H⟩∼0.81 mag), star-forming main sequence (MS) objects (ΔMS = log SFR−log SFRMS ∼ −0.03 dex). Results. At 1010 − 11 M⊙, our gas fractions (fgas = Mgas/(Mgas + M⋆)), ranging from 0.32 to 0.48 at these redshifts, are in good agreement with other studies based on mass-complete samples down to 1010 M⊙. These values are, however, lower than expected, according to other works more biased to individual detections. At 109 − 10 M⊙, we obtained 3σ upper limits for the fgas values ranging from 0.69 to 0.77. At 108 − 9 M⊙, these upper limits rise to ∼0.97. The upper limits at 109 − 10 M⊙ are on the level of the extrapolations of scaling relations based on mass-complete samples and below those based on individual detections. As such, these results suggest that the gas content of low-mass galaxies is, at most, equivalent to what has been extrapolated from the literature scaling relations based on mass-complete samples down to 1010 M⊙. Overall, the comparison of our results with the literature reflects how the inclusion of bluer, less obscured, and more MS-like objects progressively pushes the gas content down to lower values.