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

arXiv:1805.10291 · doi:10.3847/1538-4357/aac836

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 $z$ $\sim$ 3.5. ALMA observations of the dust continuum in the COSMOS field are used to estimate molecular gas masses at $z$ $\approx$ 0.5-3.5. We also use a local universe sample from the ALFALFA HI survey after converting it into molecular masses. The molecular mass ( $M_{I S M}$ ) scaling relation shows a dependence on $z$ , $M_{*}$ , and sSFR relative to the MS, but no dependence on environmental overdensity $Δ$ ( $M_{I S M}$ $\propto$ $Δ^{0.03}$ ). Similarly, gas mass fraction (f $_{g a s}$ ) and depletion timescale ( $τ$ ) show no environmental dependence to $z$ $\sim$ 3.5. At $⟨ z ⟩$ $\sim$ 1.8, the average $⟨ M_{I S M} ⟩$ , $⟨$ f $_{g a s} ⟩$ , and $⟨ τ ⟩$ in densest regions is (1.6 $\pm$ 0.2) $\times$ 10 $^{11}$ $M_{⊙}$ , 55 $\pm$ 2%, and 0.8 $\pm$ 0.1 Gyr, respectively, similar to those in the lowest density bin. Independent of the environment, f $_{g a s}$ decreases and $τ$ increases with increasing cosmic time. Cosmic molecular mass density ( $ρ$ ) in the lowest density bins peaks at $z$ $\sim$ 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 $z$ $\sim$ 3.5.

arXiv commentApJ published

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

Abstract

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