2021ApJ...920....5L

Cosmic metals are widely believed to be produced by supernovae (SNe) and compact-object mergers. Here, we discuss the nucleosynthesis of neutrino-dominated accretion flows (NDAFs) with outflows in the centers of core-collapse SNe (CCSNe), and show that the outflows from NDAFs can have a significant contribution to the ⁵⁶Ni abundances of faint explosions if the masses of the progenitor stars are within about 25-50 M_☉. Less-massive progenitor stars can produce more ⁵⁶Ni than their more-massive counterparts in the NDAF outflow nucleosynthesis channel. Therefore, we find that the total (i.e., CCSNe and NDAF outflows) ⁵⁶Ni mass per CCSN depends only weakly upon the mass of the progenitor star. In terms of metallicity evolution, the ratio of ⁵⁶Fe (produced by the decay of ⁵⁶Ni) mass to the initial total gas mass can increase by ∼1.95 times if the upper limits of the nucleosynthesis yields from NDAF outflows and CCSNe are considered. Our results might have significant implications for the chemical evolution of the solar neighborhood, galaxies, and active galactic nuclei.