INTEGRAL, eROSITA and Voyager constraints on light bosonic dark matter: ALPs, dark photons, scalars, B − L and L i − L j vectors

The decay of light bosonic dark matter particles can produce a bright electron/positron ( e + e − ) flux that can be strongly constrained by local Voyager observations of the direct e + e − flux, as well as 511 keV line and x-ray continuum observations of e + e − emission. We carefully analyze the e + e − yield and resulting cosmic ray and x-ray spectra from theoretically well-motivated light dark matter models, including (a) electrophilic axion-like particles, (b) dark photons, (c) scalars, and (d) B − L and L i − L j vector bosons. We use the morphology and spectrum of the INTEGRAL 511 keV line data, the eROSITA x-ray continuum spectrum and the Voyager e + e − spectrum to constrain the decay lifetime and coupling of each dark matter model. We find that 511 keV observations typically set world-leading limits on bosonic dark matter decay below masses of ∼ 1 GeV , while eROSITA observations provide the strongest constraints in the range from 1–10 GeV. Finally, we forecast future limits from 21 cm line searches with next-generation HERA data.