Illuminating Black Hole Shadows with Dark Matter Annihilation

Area of Science:

• Astrophysics
• Particle Physics
• Cosmology

Background:

• The Event Horizon Telescope (EHT) provides unprecedented resolution of black hole horizon-scale structures, revealing a dark shadow and bright photon ring.
• Upcoming EHT upgrades will enhance dynamic range, allowing deeper exploration of low-background regions like the inner black hole shadow.

Purpose of the Study:

• To investigate the potential of supermassive black holes as probes for dark matter annihilation.
• To set stringent constraints on dark matter annihilation using EHT observations and simulations.

Main Methods:

• Analysis of black hole image morphology from EHT observations.
• Electron-positron propagation calculations in realistic plasma backgrounds derived from general relativistic magnetohydrodynamic simulations.
• Setting constraints on dark matter annihilation by comparing with astrophysical emission.

Main Results:

• Supermassive black holes can serve as powerful probes for annihilating dark matter accumulating in their vicinity.
• Stringent constraints on dark matter annihilation have been established, requiring contributions below astrophysical emission.
• A substantial region of previously unexplored dark matter parameter space has been excluded.

Conclusions:

• EHT observations, both current and future, provide robust constraints on dark matter annihilation.
• These constraints remain robust against astrophysical uncertainties such as black hole spin and plasma temperature variations.
• The study highlights the synergy between black hole observations and particle physics searches.