Gamma-ray emission from dark matter wakes of recoiled black holes

TL;DR

This paper proposes that recoiled black holes moving through dark matter wakes can produce significant gamma-ray emission from neutralino annihilation, contributing to the diffuse gamma-ray background.

Contribution

It introduces a novel scenario where recoiled black holes generate gamma-ray signals via dark matter wakes, a mechanism not previously explored.

Findings

Recoiled black holes create dense dark matter wakes enhancing annihilation signals.

Gamma-ray flashes occur at black hole apapsis, with duration depending on black hole mass and redshift.

The cumulative effect of these black holes can account for a portion of the observed diffuse gamma-ray background.

Abstract

A new scenario for the emission of high-energy gamma-rays from dark matter annihilation around massive black holes is presented. A black hole can leave its parent halo, by means of gravitational radiation recoil, in a merger event or in the asymmetric collapse of its progenitor star. A recoiled black hole which moves on an almost-radial orbit outside the virial radius of its central halo, in the cold dark matter background, reaches its apapsis in a finite time. Near or at the apapsis passage, a high-density wake extending over a large radius of influence, forms around the black hole. It is shown that significant gamma-ray emission can result from the enhancement of neutralino annihilation in these wakes. At its apapsis passage, a black hole is shown to produce a flash of high-energy gamma-rays whose duration is determined by the mass of the black hole and the redshift at which it is ejected. The ensemble of such black holes in the Hubble volume is shown to produce a diffuse high-energy gamma-ray background whose magnitude is compared to the diffuse emission from dark matter haloes alone.