Search for gamma-ray line signals around the black hole at the galactic center with DAMPE observation

TL;DR

This study uses DAMPE gamma-ray data to search for potential dark matter annihilation signals near the galactic center's black hole, setting constraints on annihilation cross sections despite no detection of line signals.

Contribution

First analysis of DAMPE data targeting gamma-ray lines from dark matter spikes around the galactic center's black hole, providing new upper limits on annihilation cross sections.

Findings

No significant gamma-ray line signals detected.

Established upper limits on dark matter annihilation cross section.

Constraints suggest either no spike or different annihilation channels.

Abstract

The adiabatic growth of a black hole (BH) may enhance the dark matter (DM) density surrounding it, causing a spike in the DM density profile. The spike around the supermassive BH at the center of the Milky Way may lead to a dramatic enhancement of the gamma-ray flux of DM annihilation from the galactic center (GC). In this work, we analyze the gamma-ray data of the innermost region (i.e., the inner 1$^\circ$) of the GC to search for potential line-like signals from the BH spike. Such line-like signals could be generated in the process of DM particles annihilating into double photons. We adopt the gamma-ray data from the Dark Matter Particle Explorer (DAMPE). Although the DAMPE has a much smaller effective area than the Fermi-LAT, the gamma-ray line search can benefit from its unprecedented high energy resolution. No significant line-like signals are found in our analysis. We derive upper limits on the cross section of the annihilation based on this non-detection. We find that despite the DAMPE's small effective area for photon detection, we can still place strong constraints on the cross section ($\left<\sigma v\right>\lesssim10^{-27}\,{\rm cm^3\,s^{-1}}$) in the spike scenario due to the very bright model-expected flux from the spike. Our results indicate that either DM does not annihilate primarily through the $\gamma\gamma$ channel in the mass range we considered or no sharp density spike is present at the GC.