The Doppler effect on indirect detection of dark matter using dark matter only simulations

TL;DR

This paper demonstrates that dark matter velocity spectroscopy can distinguish dark matter signals from baryonic backgrounds using simulations, with potential detection prospects for the 3.5 keV line by high-resolution X-ray instruments.

Contribution

The study introduces a robust velocity spectroscopy technique using dark matter only simulations, highlighting its effectiveness in identifying dark matter signals amidst backgrounds.

Findings

Velocity dependence of dark matter signals is opposite to baryonic signals.

Micro-X can detect the 3.5 keV line at ≥3σ with six pointings.

Halo triaxiality reduces the significance of the velocity signature.

Abstract

Indirect detection of dark matter is a major avenue for discovery. However, baryonic backgrounds are diverse enough to mimic many possible signatures of dark matter. In this work, we study the newly proposed technique of dark matter velocity spectroscopy\,\cite{speckhard2016}. The non-rotating dark matter halo and the Solar motion produce a distinct longitudinal dependence of the signal which is opposite in direction to that produced by baryons. Using collisionless dark matter only simulations of Milky Way like halos, we show that this new signature is robust and holds great promise. We develop mock observations by high energy resolution X-ray spectrometer on a sounding rocket, the Micro-X experiment, to our test case, the 3.5 keV line. We show that by using six different pointings, Micro-X can exclude a constant line energy over various longitudes at $\geq$ 3$\sigma$. The halo triaxiality is an important effect and it will typically reduce the significance of this signal. We emphasize that this new {\it smoking gun in motion} signature of dark matter is general, and is applicable to any dark matter candidate which produces a sharp photon feature in annihilation or decay.