Only the Special Survive: Evolution of Long-Lived Star Clusters in Galaxy Simulations

Abstract

In this work, we aim to answer one crucial question behind the discrepancy between chemical trends of field stars and clusters in the Galactic disk: is the chemical gradient mismatch driven by cluster migration and differential survivability as a function of galactic location? To answer this question, we explored the evolution of long-lived (> 1 Gyr) star clusters in Milky Way-galaxy simulations. In particular, we investigated why some star clusters remain bound over billions of years. We have traced the unique trajectories for a sample of open clusters around two FIRE galaxies throughout cosmic time. Additionally, we characterized the small-scale environment surrounding these clusters over their orbital history. We see that clusters across both FIRE galaxies spend the majority of their lives in under-dense regions of gas, except for brief passages where they interact with gas clouds, causing their orbits to be altered.