Evolution of the Gas Mass Fraction of Progenitors to Today’s Massive Galaxies: ALMA Observations in the CANDELS GOODS-S Field

We present an Atacama Large Millimeter/submillimeter Array (ALMA) survey of dust continuum emission in a sample of 70 galaxies in the redshift range z = 2-5 selected from the CANDELS GOODS-S field. Multi-epoch abundance matching (MEAM) is used to define potential progenitors of a z = 0 galaxy of stellar mass 1.5 × 10¹¹ M _⊙. Gas masses are derived from the 850 μm luminosity. Ancillary data from the CANDELS GOODS-S survey are used to derive the gas mass fractions. The results at z ≲ 3 are mostly in accord with expectations: The detection rates are 75% for the z = 2 redshift bin, 50% for the z = 3 bin, and 0% for z ≳ 4. The average gas mass fraction for the detected z = 2 galaxies is f _gas = 0.55 ± 0.12 and f _gas = 0.62 ± 0.15 for the z = 3 sample. This agrees with expectations for galaxies on the star-forming main sequence, and shows that gas fractions have decreased at a roughly constant rate from z = 3 to z = 0. Stacked images of the galaxies not detected with ALMA give upper limits to f _gas of <0.08 and <0.15, for the z = 2 and z = 3 redshift bins. None of our galaxies in the z = 4 and z = 5 sample are detected, and the upper limit from stacked images, corrected for low metallicity, is f _gas < 0.66. We do not think that lower gas-phase metallicities can entirely explain the lower dust luminosities. We briefly consider the possibility of accretion of very low-metallicity gas to explain the absence of detectable dust emission in our galaxies at z ≳ 4.