TAPIR Seminar

In person and online -- to Join via Zoom

https://caltech.zoom.us/j/89695722750

In recent years, the first detections of gravitational wave signals emanating from merging compact binaries have generated great interest in the origins of these systems. Dynamical formation in dense stellar environments like globular clusters (GCs) has emerged as an important formation channel, especially for black hole (BH) binaries. While this understanding is supported by numerical simulations and observational findings, there remain numerous uncertainties. Observationally constraining the mere size of black hole (BH) populations––much less BH merger rates––in GCs is a challenging endeavor. Uncertainties in the stellar initial mass function (IMF) and high-mass binary fraction in GCs greatly influence the strength of this formation channel, particularly with regards to especially-massive mergers like GW190521. In this talk, I first summarize simulated BH dynamics in GCs and the observational evidence for BH populations in these clusters, before discussing recent and ongoing efforts to understand the impact of the uncertain stellar IMF and high-mass binary fraction on BH merger rates. I examine how binary-rich clusters and those born with top-heavy IMFs generate more BH mergers than standard clusters, especially enhancing the production of upper-mass gap and intermediate-mass BHs. I conclude with a discussion of how current research into stellar ejecta from globular clusters may provide another potential handle to constrain BH populations (and resultant merger rates) in these dense stellar environments.