Properties of nuclear star clusters in Little Red Dots

Determine the mass, size, density profile, and composition of putative nuclear star clusters in Little Red Dots (LRDs) at redshifts z≈4–6 in order to reduce the dominant astrophysical uncertainties in predicted tidal disruption event and extreme-mass-ratio inspiral rates.

Background

Rate predictions for tidal disruption events and captured extreme-mass-ratio inspirals in LRDs depend sensitively on the structure and content of their nuclear star clusters (e.g., total stellar mass, the fraction and distribution of stellar-mass black holes, break radii, and central density).

Because these nuclear star cluster properties at high redshift are not yet measured, the paper adopts reasonable assumptions guided by observations of high-z compact clusters and local scaling relations. The authors explicitly identify the lack of direct knowledge of these properties as the dominant source of uncertainty in their rate estimates.