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Wang, Tao; Elbaz, David; Daddi, Emanuele; Liu, Daizhong; Kodama, Tadayuki; Tanaka, Ichi; Schreiber, Corentin; Zanella, Anita; Valentino, Francesco; Sargent, Mark; Kohno, Kotaro; Xiao, Mengyuan; Pannella, Maurilio; Ciesla, Laure; Gobat, Raphael; Koyama, Yusei (2018): Revealing the Environmental Dependence of Molecular Gas Content in a Distant X-Ray Cluster at z=2.51. In: Astrophysical Journal Letters, Vol. 867, No. 2, L29
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Abstract

We present a census of the molecular gas properties of galaxies in the most distant known X-ray cluster, CLJ1001, at z = 2.51, using deep observations of CO(1-0) with the Karl G. Jansky Very Large Array. In total, 14 cluster members with M-* > 10(10.5) M-circle dot are detected, including all of the massive star-forming members within the virial radius, providing the largest galaxy sample in a single cluster at z > 2 with CO(1-0) measurements. We find a large variety in the gas content of these cluster galaxies, which is correlated with their relative positions (or accretion states), with those closer to the cluster core being increasingly gas-poor. Moreover, despite their low gas content, the galaxies in the cluster center exhibit an elevated star formation efficiency (SFE;SFE = SFR/M-gas) compared to field galaxies, suggesting that the suppression on the SFR is likely delayed compared to that on the gas content. Their gas depletion time is around t(dep) similar to 400 Myr, which is comparable to the cluster dynamical time. This implies that they will consume all of their gas within a single orbit around the cluster center, and form a passive cluster core by z similar to 2. This result is one of the first direct pieces of evidence for the influence of environment on the gas reservoirs and SFE of z > 2 cluster galaxies, thereby providing new insights into the rapid formation and quenching of the most massive galaxies in the early universe.