The inferred evolution of the cold gas properties of CANDELS galaxies at
  0.5 < z < 3.0
  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 CANDELS 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 (HI and H2), HI,
and H2 mass and the stellar mass of galaxies down to stellar masses of 10^8
Msun 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 HI 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.
