Supermassive Black Hole Binaries in Ultralight Dark Matter

TL;DR

This paper explores how ultralight dark matter can facilitate the merger of supermassive black hole binaries by forming quasiparticles that extract energy and angular momentum, potentially solving the final parsec problem.

Contribution

It introduces a novel mechanism where ULDM quasiparticles assist SMBH binary mergers and enhance stellar relaxation, addressing the final parsec problem.

Findings

ULDM quasiparticles can extract energy from SMBH binaries.

ULDM enhances stellar relaxation and loss cone replenishment.

Potential solution to the final parsec problem.

Abstract

We investigate the evolution of supermassive black hole (SMBH) binaries and the possibility that their merger is facilitated by ultralight dark matter (ULDM). When ULDM is the main dark matter (DM) constituent of a galaxy, its wave nature enables the formation of massive quasiparticles throughout the galactic halo. Here we show that individual encounters between quasiparticles and a SMBH binary can lead to the efficient extraction of energy and angular momentum from the binary. The relatively short coherence time of ULDM provides a steady-state population of massive quasiparticles, and consequently a potential solution to the final parsec problem. Furthermore, we demonstrate that, in the presence of stars, ULDM quasiparticles can also act as massive perturbers to enhance the stellar relaxation rate locally, replenish the stellar loss cone efficiently, and consequently resolve the final parsec problem.