Searching for Black Holes in Globular Clusters

Currently, three detached black hole+star binaries are known in Galactic globular clusters (all in NGC 3201; Giesers et al. 2019). An additional handful of black hole candidates have also been found via X-ray and/or radio observations (e.g., Strader et al. 2012). These black hole candidates are likely just the tip of the observable iceberg. N-body models predict nearly every globular cluster contains a handful of black hole+star binaries observable via measurements of the companion stars' radial velocities (see here). Therefore, I have started a new multi-year observing program to survey Galactic globular clusters for black hole binaries via radial velocity measurements, acquiring data with the Keck Cosmic Web Imager (KCWI) and the Magellan IFU-M. Over the coming years, this program will provide the most robust observational constraints yet on black holes in Galactic globular clusters. 

Our group currently uses three main facilities:

• The Keck Cosmic Web Imager on the 10m Keck II telescope at Keck Observatory
• IFUM on the 6.5m Magellan/Clay telescope at Las Campanas Observatory
• Hubble Space Telescope (10 orbits, Cycle 32: GO-17820)