We derive the total cold gas, atomic hydrogen, and molecular gas masses of approximately 24 000 galaxies covering four decades in stellar mass at redshifts 0.5 < z < 3.0, taken from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey survey. Our inferences are based on the inversion of a molecular hydrogen based star formation law, coupled with a prescription to separate atomic and molecular gas. We find that: (1) there is an increasing trend between the inferred cold gas (H i and H2), H i, and H2 mass and the stellar mass of galaxies down to stellar masses of 108 M already in place at z = 3; (2) the molecular fractions of cold gas increase with increasing stellar mass and look-back time; (3) there is hardly any evolution in the mean H i content of galaxies at fixed stellar mass; (4) the cold gas fraction and relative amount of molecular hydrogen in galaxies decrease at a relatively constant rate with time, independent of stellar mass; (5) there is a large population of low stellar mass galaxies dominated by atomic gas. These galaxies are very gas rich, but only a minor fraction of their gas is molecular; 6) the ratio between star formation rate (SFR) and inferred total cold gas mass (Hi + H2) of galaxies (i.e. star formation efficiency; SFE) increases with star formation at fixed stellar masses. Due to its simplicity, the presented approach is valuable to assess the impact of selection biases on small samples of directly observed gas masses and to extend scaling relations down to stellar mass ranges and redshifts that are currently difficult to probe with direct measurements of gas content.

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Published in Monthly Notices of the Royal Astronomical Society, v. 454, no. 2, p. 2258-2276.

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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This work is based on observations taken by the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. GP acknowledges NOVA (Nederlandse Onderzoekschool voor Astronomie) for funding.