On Neutron Star Mergers as the Source of r-process Enhanced Metal Poor Stars in the Milky Way

Understand

We model the history of Galactic r-process enrichment using high-redshift, high-resolution zoom cosmological simulations of a Milky Way (MW) type halo.

• We assume that all r-process sources are neutron star mergers (NSMs) with a power law delay time distribution.
• We model the time to mix pollutants at subgrid scales, which allows us to to better compute the properties of metal poor (MP) and carbon enhanced metal poor (CEMP) stars, along with statistics of their r-process enhanced subclasses.
• Our simulations underpredict the cumulative ratios of r-process enhanced MP and CEMP stars (MP-r, CEMP-r) over MP and CEMP stars by about one order of magnitude, even when the minimum coalescence time of the double neutron stars ($t_{\rm min}$) is set to 1 Myr.