The molecular gas contents of z=1.6 (proto)-cluster galaxies and their last gasp of star formation

<p>I will present JVLA CO imaging in the 1-0 transition of a z=1.62 galaxy proto-cluster located in the UKIDSS/UDS. These are the deepest existing data in CO(1-0), corresponding to nearly 100 hours of on-target JVLA observations. With them we gain the powerful ability to study the molecular gas contents of massive cluster galaxies when they were in the last throes of their star formation. We securely detect two spectroscopically confirmed proto-cluster members in CO(1-0), nearly doubling the number of published CO(1-0) detections of normal star-forming galaxies at high redshift. These two proto-cluster members are massive, with log(Mstar~11), and with significant gas reservoirs. We derive star formation rates using Spitzer and Herschel data and find that one galaxy is on the main sequence while the other is a factor of 10 below it. Despite being in a proto-cluster dominated by passive galaxies, our CO sources are broadly consistent with the expected gas fractions from field galaxy scaling relations. I compare these gas fractions to the passive fractions in this same cluster and also to 3 SpARCS clusters with CO measurements and passive fractions. I will discuss the comparison of these two samples and the differences between them. I then discuss what it may imply for cluster-to-cluster variations in the infall histories.