Friday, March 27, 2026 at 3:30 pm

JILA Foothills Room

Lucy Walton, CU Boulder

"The combined influence of mass segregation and Counter-rotation on eccentric nuclear disks"

Abstract:

Black hole mergers produce gravitational wave recoil kicks, and these kicks can redistribute the orbits of surrounding stars to produce an aligned, eccentric nuclear disk (END) of stars. Understanding the dynamics of these structures is increasingly important as growing observational evidence, particularly from the James Webb Space Telescope (JWST), points to their presence in galactic nuclei (Tahmasebzadeh et al., 2025). N-body simulations commonly assume a single-mass population. In efforts to study more realistic dynamical properties observed in our universe, we investigate and present results from N-body simulations to explore the effects of mass segregation from including a heavy stellar population. We also investigate the impacts of including a counter-rotating population in eccentric nuclear disks. The results of the conjunction of the impacts of these two properties are presented here for the first time. This is motivated by previous work that has shown that these recoil kicks create a counter-rotating population in eccentric nuclear disks. Subsequently, we investigate whether mass segregation still exists under these conditions. We find that radial mass segregation occurs regardless of the inclusion of a retrograde population of stars. While both co-rotating and counter-rotating disks exhibit vertical mass segregation with rotation about the minor axis, only co-rotating disks display vertical mass segregation with rotation about the major axis. Heavy stars move to higher eccentricities as the system evolves, an effect that is exacerbated by the inclusion of a counter-rotating stellar population via secular torques. Counter-rotation also strengthens alignment within each mass population. The result of mass segregation and increased eccentricity is that tidal disruption event (TDE) rates are preferentially enhanced for heavy stars, and this is further amplified when a counter-rotating population is present. These results demonstrate the complex interplay between stellar demographics and orbital dynamics in shaping the evolution and tidal disruption activity of ENDs.

Back to Speakers