A new probe of dark matter properties: gravitational waves from an intermediate mass black hole embedded in a dark matter mini-spike

TL;DR

This paper proposes that gravitational wave observations from stellar objects captured by intermediate mass black holes with dark matter mini-halos can reveal detailed properties of dark matter distribution and the evolutionary history of the black holes.

Contribution

It introduces a novel method to probe dark matter properties using gravitational waves from IMBH-stellar object interactions, sensitive to the dark matter density profile.

Findings

GW detectability depends on the DM density profile.

Detection can precisely determine the DM power index.

This method can distinguish IMBH formation and merger history.

Abstract

An intermediate mass black hole (IMBH) may have a dark matter (DM) mini-halo around it and develop a spiky structure within less than a parsec from the IMBH. When a stellar mass object is captured by the mini-halo, it eventually infalls into such an IMBH due to gravitational wave back reaction which in turn could be observed directly by future space-borne gravitational wave experiments such as eLISA/NGO. In this paper, we show that the GW detectability strongly depends on the radial profile of the DM distribution. So if the GW is detected, the power index, that is, the DM density distribution would be determined very accurately. The DM density distribution obtained would make it clear how the IMBH has evolved from a seed BH and whether the IMBH has experienced major mergers in the past. Unlike the gamma ray observations of DM annihilation, GW is just sensitive to the radial profile of the DM distribution and even to non-interacting DM. Hence the effect we demonstrate here can be used as a new and powerful probe into DM properties.