INTEGRAL, eROSITA and Voyager constraints on light bosonic dark matter: ALPs, dark photons, scalars, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>B</mml:mi> <mml:mo>−</mml:mo> <mml:mi>L</mml:mi> </mml:math> and <

The decay of light bosonic dark matter particles can produce a bright electron/positron ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mi>e</a:mi> <a:mo>+</a:mo> </a:msup> <a:msup> <a:mi>e</a:mi> <a:mo>−</a:mo> </a:msup> </a:math> ) flux that can be strongly constrained by local Voyager observations of the direct <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msup> <c:mi>e</c:mi> <c:mo>+</c:mo> </c:msup> <c:msup> <c:mi>e</c:mi> <c:mo>−</c:mo> </c:msup> </c:math> flux, as well as 511 keV line and x-ray continuum observations of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msup> <e:mi>e</e:mi> <e:mo>+</e:mo> </e:msup> <e:msup> <e:mi>e</e:mi> <e:mo>−</e:mo> </e:msup> </e:math> emission. We carefully analyze the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:msup> <g:mi>e</g:mi> <g:mo>+</g:mo> </g:msup> <g:msup> <g:mi>e</g:mi> <g:mo>−</g:mo> </g:msup> </g:math> 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) <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mi>B</i:mi> <i:mo>−</i:mo> <i:mi>L</i:mi> </i:math> and <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msub> <k:mi>L</k:mi> <k:mi>i</k:mi> </k:msub> <k:mo>−</k:mo> <k:msub> <k:mi>L</k:mi> <k:mi>j</k:mi> </k:msub> </k:math> vector bosons. We use the morphology and spectrum of the INTEGRAL 511 keV line data, the eROSITA x-ray continuum spectrum and the Voyager <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:msup> <m:mi>e</m:mi> <m:mo>+</m:mo> </m:msup> <m:msup> <m:mi>e</m:mi> <m:mo>−</m:mo> </m:msup> </m:math> 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 <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:mo>∼</o:mo> <o:mn>1</o:mn> <o:mtext> </o:mtext> <o:mtext> </o:mtext> <o:mi>GeV</o:mi> </o:math> , 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.