Hypervelocity intracluster stars ejected by supermassive black hole binaries

TL;DR

This paper investigates how supermassive black hole binaries can eject hypervelocity stars and planetary nebulae, using simulations to match observed fast intracluster objects in the Virgo Cluster, revealing insights into black hole properties.

Contribution

It demonstrates that the observed hypervelocity intracluster planetary nebulae can be explained by three-body interactions with a supermassive black hole binary, providing constraints on its parameters.

Findings

Number and kinematic signature of ICPNe consistent with SMBBH scattering

Supports a 10:1 mass ratio for the SMBH binary in M87

Simulation results align with observed hypervelocity stars in Virgo

Abstract

Hypervelocity stars have been recently discovered in the outskirts of galaxies, such as the unbound star in the Milky Way halo, or the three anomalously fast intracluster planetary nebulae (ICPNe) in the Virgo Cluster. These may have been ejected by close 3-body interactions with a binary supermassive black hole (SMBBH), where a star which passes within the semimajor axis of the SMBBH can receive enough energy to eject it from the system. Stars ejected by SMBBHs may form a significant sub-population with very different kinematics and mean metallicity than the bulk of the intracluster stars. The number, kinematics, and orientation of the ejected stars may constrain the mass ratio, semimajor axis, and even the orbital plane of the SMBBH. We investigate the evolution of the ejected debris from a SMBBH within a clumpy and time-dependent cluster potential using a high resolution, self-consistent cosmological N-body simulation of a galaxy cluster. We show that the predicted number and kinematic signature of the fast Virgo ICPNe is consistent with 3-body scattering by a SMBBH with a mass ratio $10:1$ at the center of M87.