The History of R-Process Enrichment in the Milky Way
  We investigate the production sites and the enrichment history of $r$-process
elements in the Galaxy, as traced by the [Eu/Fe] ratio, using the high
resolution, cosmological zoom-in simulation `Eris'. At $z=0$, Eris represents a
close analog to the Milky Way, making it the ideal laboratory to understand the
chemical evolution of our Galaxy. Eris formally traces the production of oxygen
and iron due to Type-Ia and Type-II supernovae. We include in post-processing
the production of $r$-process elements from compact binary mergers. Unlike
previous studies, we find that the nucleosynthetic products from compact binary
mergers can be incorporated into stars of very low metallicity and at early
times, even with a minimum delay time of 100 Myr. This conclusion is relatively
insensitive to modest variations in the merger rate, minimum delay time, and
the delay time distribution. By implementing a first-order prescription for
metal-mixing, we can further improve the agreement between our model and the
data for the chemical evolution of both [$\alpha$/Fe] and [Eu/Fe].We argue that
compact binary mergers could be the dominant source of $r$-process
nucleosynthesis in the Galaxy.
