Collaborative Research: RUI: The disintegration of clusters and their contribution to the metal-poor bulge

Globular clusters are spherical groups of thousands of stars, bound together by gravity. The clusters contain some of the first stars formed in the Galaxy. As a globular cluster moves through space, it will fall toward the center of the Galaxy. Stars will become disrupted and some stars will leave the cluster and become part of the Milky Way. The team of investigators are from four primarily undergraduate universities. They seek to confirm which stars came from clusters by spectroscopically measuring the abundances of elements in stars that are moving in the same directions in the Milky Way. The stars with similar composition are likely members of the same original cluster. The location of stripped cluster stars depends on the mass distribution of the Galaxy. In this way, the Galaxy’s gravitational potential can be probed. During the course of the research, the team will publish their successes in student research projects and share opportunities with other faculty at small Universities. The team hopes to attract other researchers to pursue similar, cutting-edge projects. Each of the team members will also fund undergraduate students in this research, involving students from minority serving institutions. The researchers will obtain new, detailed observations of 3000 stars. These will be carefully selected as candidate globular cluster tidal debris or members of eroded low-luminosity globular clusters. Measuring the radial velocities and metallicities will give a probability for these stars having originated from a globular cluster. In this way, the team can establish a connection between the stars in the inner Galaxy and those that have been stripped from clusters. The location of stripped stars gives direct insight into the fraction of globular clusters that have contributed to the bulge field. Stripped globular cluster stars further allow the initial properties of the early globular clusters to be probed. Identifying stars from globular cluster stars that are now part of the inner Galaxy is essential for understanding the assembly history of the Milky Way. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.