The dark matter interpretation of the 511 keV line

The 511 keV high-precision map obtained by the INTEGRAL/SPI experiment suggested a surprisingly large amount of positrons in our galaxy with respect to 'naive' astrophysical expectations. Although an astrophysical origin is not excluded, this signal may shed light on dark matter. Here we discuss a possible MeV dark matter interpretation of the 511 keV line and point out a possible way of validating the MeV dark matter scenario. In particular, we show that the number of electrons generated by MeV annihilating particles would be large enough to lead to a visible Sunyaev-Zel'dovich (SZ) effect signature in clusters of galaxies if their dark matter halo profile behaves as ρ(r)~1/r^γ with γ>1 in the inner part (i.e. on distances corresponding to a sub-arcsecond resolution for an experiment dedicated to SZ measurement).