Inhomogeneous enrichment of radioactive nuclei in the Galaxy: Deposition of live Mn-53, Fe-60, Hf-182, and Pu-244 into deep-sea archives. Surfing the wave?

TL;DR

This study models the galactic distribution of short-lived radioactive isotopes to explain their recent deposition in Earth's deep-sea sediments, highlighting core-collapse supernovae as key sources and predicting similar findings for Hf-182.

Contribution

It introduces a 3D galactic chemical evolution model to explain the co-deposition of multiple SLRs and predicts the presence of Hf-182 in deep-sea archives.

Findings

Core-collapse supernovae dominate SLR propagation in the Galaxy.

Multiple SLRs can arrive simultaneously at Earth from different sources.

Hf-182 is predicted to be found in deep-sea sediments at similar depths.

Abstract

While modelling the galactic chemical evolution (GCE) of stable elements provides insights to the formation history of the Galaxy and the relative contributions of nucleosynthesis sites, modelling the evolution of short-lived radioisotopes (SLRs) can provide supplementary timing information on recent nucleosynthesis. To study the evolution of SLRs, we need to understand their spatial distribution. Using a 3-dimensional GCE model, we investigated the evolution of four SLRs: Mn-53, Fe-60, Hf-182, and Pu-244 with the aim of explaining detections of recent (within the last $\approx$1-20 Myr) deposition of live Mn-53, Fe-60, and Pu-244 of extrasolar origin into deep-sea reservoirs. We find that core-collapse supernovae (CCSNe) are the dominant propagation mechanism of SLRs in the Galaxy. This results in the simultaneously arrival of these four SLRs on Earth, although they could have been produced in different astrophysical sites, which can explain why live extrasolar Mn-53, Fe-60, and Pu-244 are found within the same, or similar, layers of deep-sea sediments. We predict that Hf-182 should also be found in such sediments at similar depths.