An Alternative Channel For High-Mass Binary Black Holes-----Dark Matter Accretion Onto Black Hole

TL;DR

This paper models dark matter accretion onto binary black holes and finds it can significantly increase their masses, helping explain observed high-mass mergers, with a slight increase in merger rate.

Contribution

It introduces a population synthesis model including dark matter accretion to explain high-mass binary black hole mergers.

Findings

Dark matter accretion can enhance black hole masses significantly.

The model explains observed high-mass mergers at low metallicity.

Merger rate estimated between 55 and 197 Gpc^{-3} yr^{-1}.

Abstract

By a method of population synthesis we construct a model of dark matter (DM) accretion onto binary black holes (BHs), and investigate the merger rate of the binary BHs. We find that the merger rate can weakly increase (less than 10\%). However, the DM accretion can efficiently enhance the masses of binary BHs. In our model, the result for $Z = 0.01$ without the DM accretion can not explain the GW170104, GW170814, and GW150914, while with the DM accretion, it can cover all observations well. For the higher metallicity ($Z = 0.02$), our model can not explain the mergers of high-mass binary BHs like GW170104, GW170814, and GW150914. We estimate that the merger rate of binary BHs lies between $\rm55Gpc^{-3}yr^{-1}$ to $\rm197Gpc^{-3}yr^{-1}$.