Stellar Escape from Globular Clusters I: Escape Mechanisms and Properties at Ejection by Newlin C. Weatherford et al. on Wednesday 30 November

The theory of stellar escape from globular clusters (GCs) dates back nearly a

century, especially the gradual evaporation of GCs via two-body relaxation

coupled with external tides. More violent ejection can also occur via strong

gravitational scattering, supernovae, gravitational wave-driven mergers, tidal

disruption events, and physical collisions, but comprehensive study of the many

escape mechanisms has been limited. Recent exquisite kinematic data from the

Gaia space telescope has revealed numerous stellar streams in the Milky Way

(MW) and traced the origin of many to specific MWGCs, highlighting the need for

further examination of stellar escape from these clusters. In this study, the

first of a series, we lay groundwork for detailed follow-up comparisons between

Cluster Monte Carlo (CMC) GC models and the latest Gaia data on the outskirts

of MWGCs, their tidal tails, and associated streams. We thoroughly review

escape mechanisms from GCs and examine their relative contributions to the

escape rate, ejection velocities, and escaper demographics. We show for the

first time that three-body binary formation may dominate high-speed ejection

from typical MWGCs, potentially explaining some of the hypervelocity stars in

the MW. Due to their mass, black holes strongly catalyze this process, and

their loss at the onset of observable core collapse, characterized by a steep

central brightness profile, dramatically curtails three-body binary formation,

despite the increased post-collapse density. We also demonstrate that even when

born from a thermal eccentricity distribution, escaping binaries have

significantly non-thermal eccentricities consistent with the roughly uniform

distribution observed in the Galactic field.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16523v1