asymmetry in the left-right symmetric model with dou- blet and singlet fields. In this model, the SM fermions ob- tain masses by integrating out charged singlet fermions. In the neutrino sector, the right(left)-handed neutral fermions, associated with the left(right)-handed Higgs doublet, can generate the left(right)-handed neutrino masses through the seesaw. The mass matrices of the left- and right-handed neutrinos have a same structure as a re- sult of the left-right symmetry. The neutral singlets are also responsible for the baryon asymmetry and the dark matter. Specifically their 2-body decays can produce a desired lepton asymmetry in the left-handed leptons and then the observed baryon asymmetry can be realized by the sphaleron induced lepton-to-baryon conversion. At the same time, the right-handed neutrinos can serve as the dark matter as they have a right relic density from the 3-body decays of the neutral singlets. The decays of these non-thermally produced right-handed neutrinos can easily induce the observed fluxes of 511 keV photons from the Galactic bulge. The attractive feature of our scenario is that the left-right symmetry can connect the properties of the dark matter to the neutrino masses and the baryon asymmetry. Acknowledgement : I thank Manfred Lindner for hospitality at Max-Plank-Institut f¨ ur Kernphysik. This work is supported by the Alexander von Humboldt Foun- dation. In summary we have shown the dark matter can be well determined by the neutrino masses and the baryon It is easy to check that our scenario is consistent with other astrophysical and cosmological constraints [28]. Alternatively, we may explain the observed cosmic positron/electron excess [29–33], which is probably from continuum distribution of pulsars [34, 35], by fine tuning the parameters. With the previous parameter choice, we can determine the mixing angle to be θ 2 i ≃ 10 − $^{22}$. 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