# Dynamics around supermassive black holes

**Authors:** Alessia Gualandris, David Merritt  
**arXiv:** [0708.3083](https://arxiv.org/abs/0708.3083)  
**Date:** 2007-08-23  
**Summary page:** https://www.summarizepaper.com/en/paper/0708.3083v1/

## Key points

- The paper "Dynamics around Supermassive Black Holes" explores the various ways in which the presence of supermassive black holes (SBHs) affects the dynamics of galactic nuclei.
- Single SBHs act as sinks, destroying a mass in stars equal to their own mass in roughly one relaxation time and causing nuclei to expand.
- The formation of binary SBHs displaces a mass in stars roughly equal to the binary mass, creating low-density cores and ejecting hyper-velocity stars.
- Gravitational radiation recoil can eject coalescing binary SBHs from nuclei, resulting in offset SBHs and lopsided cores.
- Studying the dynamics of galactic nuclei can provide important insights into the properties of SBHs such as their masses and spins.
- Observations of hyper-velocity stars ejected by binary SBH systems can help constrain the masses of individual black holes.
- These mechanisms may contribute to the evolution of galaxies over cosmic time scales.
- Mergers between galaxies hosting SBHs may lead to the formation of larger black hole systems which could have significant implications for our understanding of galaxy formation and evolution.

## Summary

In their paper "Dynamics around Supermassive Black Holes," Alessia Gualandris and David Merritt explore the various ways in which the presence of supermassive black holes (SBHs) affects the dynamics of galactic nuclei. They explain that single SBHs act as sinks, destroying a mass in stars equal to their own mass in roughly one relaxation time and causing nuclei to expand. The formation of binary SBHs displaces a mass in stars roughly equal to the binary mass, creating low-density cores and ejecting hyper-velocity stars. Additionally, gravitational radiation recoil can eject coalescing binary SBHs from nuclei, resulting in offset SBHs and lopsided cores. The authors review recent work on these mechanisms and discuss their observable consequences. They note that studying the dynamics of galactic nuclei can provide important insights into the properties of SBHs such as their masses and spins. For example, observations of hyper-velocity stars ejected by binary SBH systems can help constrain the masses of individual black holes. Gualandris and Merritt also discuss how these mechanisms may contribute to the evolution of galaxies over cosmic time scales. They suggest that mergers between galaxies hosting SBHs may lead to the formation of larger black hole systems which could have significant implications for our understanding of galaxy formation and evolution. Overall, this paper provides a comprehensive overview of how SBHs influence galactic dynamics at various scales, highlighting both theoretical predictions and observational evidence. It emphasizes how studying these phenomena can help us gain insight into properties such as masses and spins of supermassive black holes as well as understand galaxy formation and evolution over cosmic timescales.