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, © 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 $\sim$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.