Significant Molecular Gas Deficiencies in Star-forming Cluster Galaxies at z ∼1.4

Abstract

We present the average gas properties derived from Atacama Large Millimeter Array (ALMA) Band 6 dust continuum imaging of 126 massive (log M ∗/M o˙ ≳ 10.5), star-forming cluster galaxies across 11 galaxy clusters at z = 1-1.75. Using stacking analysis on the ALMA images, combined with UV-far-infrared data, we quantify the average infrared spectral energy distributions (SEDs) and gas properties (molecular gas masses, M mol;gas depletion timescales, τ depl; and gas fractions, fgas) as functions of cluster-centric radius and properties including stellar mass and distance from the main sequence. We find a significant dearth in the ALMA fluxes relative to that expected in the field - with correspondingly low M mol and fgas, and short τ depl - with weak or no dependence on cluster-centric radius out to twice the virial radius. The Herschel+ALMA SEDs indicate warmer dust temperatures (∼36-38 K) than coeval field galaxies (∼30 K). We perform a thorough comparison of the cluster galaxy gas properties to field galaxies, finding deficits of 2-3×, 3-4×, and 2-4× in M mol, τ depl, and fgas compared to coeval field stacks, and larger deficits compared to field scaling relations built primarily on detections. The cluster gas properties derived here are comparable with stacking analyses of (proto-)clusters in the literature, and at odds with findings of field-like τ depl and enhanced fgas reported using CO and dust continuum detections. Our analysis suggests that environment has a considerable impact on gas properties out to large radii, in good agreement with cosmological simulations which project that gas depletion begins beyond the virial radius and largely completes by first passage of the cluster core. © 2022. The Author(s). Published by the American Astronomical Society.