An ALMA Study of Gas-Rich Galaxies in z~1.6 Galaxy Clusters

A comprehensive understanding of galaxy evolution requires a holistic view into the anatomy of a galaxy and the baryonic processes that shape its growth. In particular, this requires a solid understanding of the evolution of the molecular gas content, since the gas provides the necessary raw material to fuel star formation. I will present ALMA CO 2-1 detections in cluster galaxies at z~1.6, including the first spatially-resolved observations of molecular gas in high-redshift clusters. While the majority of these cluster galaxies have main-sequence star formation rates and display evidence of rotating gas disks, I also find potentially important differences from coeval field counterparts, including elevated gas fractions up to 60-80%, slightly smaller CO disks, and asymmetric gas tails—possible signatures of gas stripping in the cluster environment. In the local universe, high-density clusters are devoid of star-forming gas-rich galaxies; with these ALMA data, we are witnessing the first direct evidence that gas-rich galaxies are located in both the field and clusters at high redshift