Signatures of supermassive black hole binaries on maser systems

TL;DR

This paper proposes a new method to identify supermassive black hole binaries by analyzing their effects on water maser emission kinematics, revealing distinctive spectral signatures that differ from single black hole systems.

Contribution

It introduces a simulation-based approach to detect binary black holes through maser kinematic and spectral signatures, including deviations from Keplerian rotation.

Findings

Redshifted masers deviate from Keplerian rotation

Masers show double-peaked spectral structures

Binary systems influence maser velocity distributions

Abstract

We illustrate a novel signature of black hole binaries from their effect on the kinematics of water maser emission in their environments. With the help of simulations, we establish the condition for clumps to mase based on their coherence lengths calibrated to those of the known maser galaxy NGC 4258. This is then used to identify masing clumps around a binary black hole system, and quantify the kinematic and spectral differences relative to the single black hole case. For some generic circumstances, blue-shifted masers around a binary black hole are found to preferentially follow the Keplerian rotation curve observed in the single black hole case. The redshifted ones, however, are found to visibly deviate from this relation, and also display more scatter with a tendency towards lower absolute values of the velocity along the line-of-sight. The spectrum of the masers as a function of line-of-sight velocity also shows a double peaked structure, reminiscent of recent observations of systems such as Mrk 1. Our results motivate future prospects for identifying binary black hole candidates with the help of water maser emissions.