A 3.55 keV line from $\text{DM}\rightarrow a \rightarrow \gamma$: predictions for cool-core and non-cool-core clusters

TL;DR

This paper investigates a 3.55 keV X-ray line from dark matter decay involving an axion-like particle converting to photons in galaxy clusters, using simulations to predict signal morphology and strength.

Contribution

It provides detailed numerical simulations of magnetic field effects on the 3.55 keV line in both cool-core and non-cool-core clusters, offering new predictions for future observations.

Findings

Good agreement with current data on signal strength and morphology

Predictions for future observations considering various observational setups

Quantitative analysis of magnetic field effects on X-ray line signals

Abstract

We further study a scenario in which a 3.55 keV X-ray line arises from decay of dark matter to an axion-like particle (ALP), that subsequently converts to a photon in astrophysical magnetic fields. We perform numerical simulations of Gaussian random magnetic fields with radial scaling of the magnetic field magnitude with the electron density, for both cool-core `Perseus' and non-cool-core `Coma' electron density profiles. Using these, we quantitatively study the resulting signal strength and morphology for cool-core and non-cool-core clusters. Our study includes the effects of fields of view that cover only the central part of the cluster, the effects of offset pointings on the radial decline of signal strength and the effects of dividing clusters into annuli. We find good agreement with current data and make predictions for future analyses and observations.