Electron-positron pair production near the Galactic Centre and the 511 keV emission line

TL;DR

This paper proposes that 40 GeV dark matter annihilation near the Galactic Centre, combined with historical high-density gas, can explain both the observed positron annihilation line and gamma-ray excess.

Contribution

It introduces a novel scenario linking dark matter annihilation and past high-density gas to account for the 511 keV line.

Findings

Dark matter annihilation can produce sufficient positrons for the 511 keV line.

High-density gas near the Galactic Centre enhances positron production.

The model simultaneously explains gamma-ray excess and positron emission.

Abstract

Recent observations indicate that a high production rate of positrons (strong 511 keV line) and a significant amount of excess GeV gamma-ray exist in our Galactic bulge. The latter issue can be explained by $\sim 40$ GeV dark matter annihilation through $b \bar{b}$ channel while the former one remains a mystery. On the other hand, recent studies reveal that a large amount of high density gas might exist near the Galactic Centre million years ago to account for the young, massive stars extending from 0.04 pc - 7 pc. In this article, I propose a new scenario and show that the 40 GeV dark matter annihilation model can also explain the required positron production rate (511 keV line) in the bulge due to the existence of the high density gas cloud near the supermassive black hole long time ago.