Mergers of Supermassive Black Holes in Astrophysical Environments

TL;DR

This paper uses advanced simulations to explore electromagnetic signals from merging supermassive black holes, revealing how these signals depend on spins, mass ratios, and environment, with implications for detection.

Contribution

It provides new insights into electromagnetic signatures during black hole mergers using fully relativistic hydrodynamics simulations, highlighting environmental effects.

Findings

Characteristic electromagnetic variability depends on spins and mass ratios.

Hot accretion flows produce flares and quasi-periodic oscillations.

Circumbinary disks show low luminosity, complicating detection.

Abstract

Modeling the late inspiral and merger of supermassive black holes is central to understanding accretion processes and the conditions under which electromagnetic emission accompanies gravitational waves. We use fully general relativistic, hydrodynamics simulations to investigate how electromagnetic signatures correlate with black hole spins, mass ratios, and the gaseous environment in this final phase of binary evolution. In all scenarios, we find some form of characteristic electromagnetic variability whose pattern depends on the spins and binary mass ratios. Binaries in hot accretion flows exhibit a flare followed by a sudden drop in luminosity associated with the plunge and merger, as well as quasi-periodic oscillations correlated with the gravitational waves during the inspiral. Conversely, circumbinary disk systems are characterized by a low luminosity of variable emission, suggesting challenging prospects for their detection.