Understand
Recent observations of Reticulum II have uncovered an overabundance of r-process elements, compared to similar ultra-faint dwarf spheroidal galaxies (UFDs).
- Because the metallicity and star formation history of Reticulum II appear consistent with all known UFDs, the high r-process abundance of Reticulum II suggests enrichment through a single, rare event, such as a double neutron star (NS) merger.
- However, we note that this scenario is extremely unlikely, as binary stellar evolution models require significant supernova natal kicks to produce NS-NS or NS-black hole mergers, and these kicks would efficiently remove compact binary systems from the weak gravitational potentials of UFDs.
- We examine alternative mechanisms for the production of r-process elements in UFDs, including a novel mechanism wherein NSs in regions of high dark matter density implode after accumulating a black-hole-forming mass of dark matter.