Environmental Effect on the Interstellar Medium in Galaxies across the Cosmic Web at z = 0.73

Abstract

We present new Atacama Large Millimeter Array (ALMA) dust continuum observations of 101 log(M*/M⊙) > 9.5 galaxies in the COSMOS field to study the effect of the environment on the interstellar medium at z ~ 0.7. At this redshift, our targets span a wide range of environments allowing for a diverse sample of galaxies with densities of Σ = 0.16–10.5 Mpc^(−2) (per Δz = 0.024). Using the ALMA observations, we calculate the total interstellar medium (ISM) mass (M_(ISM)) and look for depletion as a function of galaxy density in order to understand the quenching or triggering of star formation in galaxies in different environments. M_(ISM) is found to have a small dependence on the environment, while the depletion timescale remains constant (~200 Myr) across all environments. We find elevated M_(ISM) values at intermediate densities and lower values at high densities compared to low (field) densities. Our observed evolution in gas fraction with density in this single redshift slice is equivalent to the observed evolution with cosmic time over 2–3 Gyr. To explain the change in the gas mass fraction seen in galaxies in intermediate and high densities, these results suggest environmental processes such as mergers and ram pressure stripping are likely playing a role in dense filamentary cluster environments.

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