Inhomogeneous Enrichment of Radioactive Nuclei in the Galaxy: Deposition of Live 53Mn, 60Fe, 182Hf, and 244Pu into Deep-sea Archives. Surfing the Wave?

Abstract

While modeling the galactic chemical evolution (GCE) of stable elements provides insights to the formation history of the Galaxy and the relative contributions of nucleosynthesis sites, modeling 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 three-dimensional GCE model, we investigated the evolution of four SLRs: ^53 Mn, ^60 Fe, ^182 Hf, and ^244 Pu with the aim of explaining detections of recent (within the last ≈1–20 Myr) deposition of live ^53 Mn, ^60 Fe, and ^244 Pu of extrasolar origin into deep-sea reservoirs. We find that core-collapse supernovae are the dominant propagation mechanism of SLRs in the Galaxy. This results in the simultaneous arrival of these four SLRs on Earth, although they could have been produced in different astrophysical sites, which can explain why live extrasolar ^53 Mn, ^60 Fe, and ^244 Pu are found within the same, or similar, layers of deep-sea sediments. We predict that ^182 Hf should also be found in such sediments at similar depths.

Keywords

• Interstellar medium
• Galactic abundances
• Astrochemistry