Similar Scaling Relations for the Gas Content of Galaxies Across Environments to z ~ 3.5

Abstract

We study the effects of the local environment on the molecular gas content of a large sample of log(M*/M⊙) ≳ 10 star-forming and starburst galaxies with specific star formation rates (sSFRs) on and above the main sequence (MS) to z ~ 3.5. ALMA observations of the dust continuum in the COSMOS field are used to estimate molecular gas masses at z ≈ 0.5–3.5. We also use a local universe sample from the ALFALFA H I survey after converting it into molecular masses. The molecular mass (M_(ISM)) scaling relation shows a dependence on z, M *, and sSFR relative to the MS, but no dependence on environmental overdensity Δ(M_(ISM) ∝ Δ^(0.03)). Similarly, gas mass fraction (f_(gas)) and depletion timescale (τ) show no environmental dependence to z ~ 3.5. At〈z〉~ 1.8, the average〈M_(ISM) 〉,〈f_(gas) 〉, and〈τ〉in densest regions is (1.6 ± 0.2) × 10^(11) M⊙, 55 ± 2%, and 0.8 ± 0.1 Gyr, respectively, similar to those in the lowest density bin. Independent of the environment, f_(gas) decreases and τincreases with increasing cosmic time. Cosmic molecular mass density (ρ) in the lowest density bins peaks at z ~ 1–2, and this peak happens at z < 1 in densest bins. This differential evolution of ρ across environments is likely due to the growth of the large-scale structure with cosmic time. Our results suggest that the molecular gas content and the subsequent star formation activity of log(M*/M⊙) ≳ 10 star-forming and starburst galaxies is primarily driven by internal processes, and not by their local environment since z ~ 3.5.

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