Molecular gas reservoirs in cluster galaxies at z=1.46

Abstract

We present molecular gas reservoirs of eighteen galaxies associated with the XMMXCS J2215.9-1738 cluster at z=1.46. From Band 7 and Band 3 data of the Atacama Large Millimeter/submillimeter Array (ALMA), we detect dust continuum emission at 870 um and CO J=2-1 emission line from 8 and 17 member galaxies respectively within a cluster-centric radius of $R_{200}$. The molecular gas masses derived from the CO and/or dust continuum luminosities show that the fraction of molecular gas mass and the depletion time scale for the cluster galaxies are larger than expected from the scaling relations of molecular gas on stellar mass and offset from the main sequence of star-forming galaxies in general fields. The galaxies closer to the cluster center in terms of both projected position and accretion phase seem to show a larger deviation from the scaling relations. We speculate that the environment of galaxy cluster helps feed the gas through inflow to the member galaxies and also reduce the efficiency of star formation. The stacked Band 3 spectrum of 12 quiescent galaxies with stellar mass $\sim10^{11}$ M$_\odot$ within 0.5$R_{200}$ shows no detection of CO emission line, giving the upper limit of molecular gas mass and molecular gas fraction to be $<10^{10}$ M$_\odot$ and $<10$%, respectively. Therefore, the massive galaxies in the cluster core quench the star formation activity while consuming most of the gas reservoirs.