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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:53Mn,60Fe,182Hf, and244Pu with the aim of explaining detections of recent (within the last ≈1–20 Myr) deposition of live53Mn,60Fe, and244Pu 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 extrasolar53Mn,60Fe, and244Pu are found within the same, or similar, layers of deep-sea sediments. We predict that182Hf should also be found in such sediments at similar depths.
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Galactic Chemical Evolution of Radioactive Isotopes with an s-process Contribution
Abstract Analysis of inclusions in primitive meteorites reveals that several short-lived radionuclides (SLRs) with half-lives of 0.1–100 Myr existed in the early solar system (ESS). We investigate the ESS origin of107Pd,135Cs, and182Hf, which are produced byslowneutron captures (thes-process) in asymptotic giant branch (AGB) stars. We modeled the Galactic abundances of these SLRs using theOMEGA+galactic chemical evolution (GCE) code and two sets of mass- and metallicity-dependent AGB nucleosynthesis yields (Monash and FRUITY). Depending on the ratio of the mean-lifeτof the SLR to the average length of time between the formations of AGB progenitorsγ, we calculate timescales relevant for the birth of the Sun. Ifτ/γ≳ 2, we predict self-consistent isolation times between 9 and 26 Myr by decaying the GCE predicted107Pd/108Pd,135Cs/133Cs, and182Hf/180Hf ratios to their respective ESS ratios. The predicted107Pd/182Hf ratio indicates that our GCE models are missing 9%–73% of107Pd and108Pd in the ESS. This missing component may have come from AGB stars of higher metallicity than those that contributed to the ESS in our GCE code. Ifτ/γ≲ 0.3, we calculate instead the time (TLE) from the last nucleosynthesis event that added the SLRs into the presolar matter to the formation of the oldest solids in the ESS. For the 2M⊙,Z= 0.01 Monash model we find a self-consistent solution ofTLE= 25.5 Myr.
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- Award ID(s):
- 1927130
- PAR ID:
- 10361566
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 924
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 10
- Size(s):
- Article No. 10
- Sponsoring Org:
- National Science Foundation
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