Presentation #208.05 in the session The Proposed STAR-X Explorer Mission: Opportunities for the HEAD Community to Explore the Fast, Furious and Forming Universe with Simultaneous UV and X-ray Observations.
In the past decade, the number of known galaxy clusters at z > 1 has increased rapidly, from tens to hundreds. Ongoing and planned surveys by mm-wave telescopes like SPT-3G and CMB-S4 will increase these numbers to thousands, and provide the first complete samples of galaxy clusters at z > 2. However, despite these rapid advances, our understanding of the assembly and evolution of these massive structures is limited due to the lack of follow-up capabilities in the X-ray, which probes the dominant baryonic component: the intracluster medium. STAR-X will transform our understanding of galaxy clusters through the discovery of thousands of new clusters in the wide and medium surveys, alongside the pointed follow-up of both the most nearby and the most distant known clusters. These surveys aim to understand the assembly history of the most massive structures in the universe, by studying the three most critical phases in cluster growth: (i) the initial formation of the intracluster medium, as it “lights up” in the protocluster phase (z>3); (ii) the relaxation and metal enrichment of the intracluster medium as it becomes polluted by metals from early starburst-driven winds (z>2), and (iii) the continued accretion of material onto the cluster from the cosmic web (z~0). In this talk I will summarize the science goals in each of these areas, as well as demonstrate how the combination of STAR-X’s high angular resolution, wide field of view, and soft sensitivity are optimal for studies of the faintest intracluster plasma in both the early and late universe.