The heavy elements (Z > 30) are created in neutron (n)-capture processes that are predicted to happen at vastly different nucleosynthetic sites. Using ESO VLT/FLAMES spectra, we measured the chemical abundances of the n-capture elements Y, Ba, La, Nd, and Eu in 98 red giant branch stars with -2.4 < [Fe/H] < -0.9 in the Sculptor dwarf spheroidal galaxy. From the abundances of the s-process element Ba and the r-process element Eu, it is clear that the r-process enrichment occurred throughout the entire chemical evolution history of Sculptor. Furthermore, there is no evidence for the r-process to be significantly delayed in time relative to core-collapse supernovae. Neutron star mergers are unlikely the dominant (or only) nucleosynthetic site of the r-process. For the first time we probe the use of [Y/Mg] and [Ba/Mg] as chemical clocks in a galaxy different from the Milky Way. These abundance ratios have a strong correlation with age in Sculptor, making them useful as chemical clocks. However, this trend is significantly offset from those observed in the Milky Way and the Fornax dSph galaxy (see Figure). Thus we conclude that chemical clocks based on the delayed timescale of the s-process are not Universal but depend on both metallicity and environment.
Skuladottir, Hansen, Salvadori, Choplin 2019, A&A, 631, A171
