Dark Matter Velocity Spectroscopy

TL;DR

Velocity spectroscopy can distinguish dark matter signals from astrophysical or instrumental effects by measuring energy shifts, with upcoming experiments like Astro-H reaching the necessary resolution to implement this method effectively.

Contribution

The paper introduces velocity spectroscopy as a novel technique to identify dark matter signals and demonstrates its feasibility with upcoming high-resolution X-ray observations.

Findings

Upcoming experiments will achieve 0.1% energy resolution.

Velocity shifts can differentiate dark matter signals from other causes.

Astro-H can separate causes of the 3.5-keV line in the Milky Way.

Abstract

Dark matter decays or annihilations that produce line-like spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will reach the required 0.1% level. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.