Black holes in nearby nuclear star clusters

Detection of Nuclear Black Holes

The figure shows the radial velocity map of the nuclear cluster in the nearby galaxy NGC4244.

The figure shows the radial velocity map of the nuclear cluster in the nearby galaxy NGC4244.

Using high spatial resolution kinematic data, we are searching for black holes in the nearest nuclear star clusters, by resolving their imprint on the kinematics of stars and gas. These objects are among the best environments to look for massive black holes in low mass galaxies, as nuclear star clusters are the objects with the highest stellar density in the universe. Resolving their internal kinematic structure down to the smallest spatial scales accessible with current instrumentation will unmask hidden black holes dynamically.

For more information, please contact Nadine Neumayer.

A Global Dynamical Model of Omega Centauri

Whether Omega Centauri hosts an intermediate-mass black hole (IMBH) has been debated for nearly two decades. Fast-moving stars near its center point to an IMBH of at least ~8,000 solar masses (Häberle et al. 2024), but a centrally concentrated population of stellar-mass black holes or radially anisotropic orbits could also explain some of the central kinematics, making a definitive mass measurement difficult. Answering this requires a model that fits the full phase-space data without assuming the orbit structure in advance.

A Schwarzschild orbit-superposition model of Omega Centauri fitted to the MUSE velocity distributions. Left: observed and model maps of mean line-of-sight velocity (top) and velocity dispersion (bottom). Right: the full velocity distributions in two regions (A, B). The dashed line is the starting model, and the solid line is the model after the orbit weights have been fitted

A Schwarzschild orbit-superposition model of Omega Centauri fitted to the MUSE velocity distributions. Left: observed and model maps of mean line-of-sight velocity (top) and velocity dispersion (bottom). Right: the full velocity distributions in two regions (A, B). The dashed line is the starting model, and the solid line is the model after the orbit weights have been fitted

I am building a triaxial Schwarzschild orbit-superposition model of Omega Centauri with DYNAMITE. It is fit to the velocities of ~600,000 stars from oMEGACat (MUSE and HST), Gaia DR3, and the SDSS-V Local Volume Mapper, from the cluster center out to about six half-light radii. The dataset is about 100 times larger than those used in earlier models, so this project also involves developing new data-handling techniques.

For more information please contact Peter Smith.