Galactic chemical evolution of radioactive isotopes

Côté, Benoit; Lugaro, Maria; Reifarth, Rene; Pignatari, Marco; Világos, Blanka; Yagüe, Andrés; Gibson, Brad K.

Abstract

The presence of short-lived (∼ Myr) radioactive isotopes in meteoritic inclusions at the time of their formation represents a unique opportunity to study the circumstances that led to the formation of the Solar System. To interpret these observations we need to calculate the evolution of radioactive-to-stable isotopic ratios in the Galaxy. We present an extension of the open-source galactic chemical evolution codes NuPyCEE and JINAPyCEE that enables to track the decay of radioactive isotopes in the interstellar medium. We show how the evolution of isotopic ratio depends on the star formation history and efficiency, star-togas mass ratio, and galactic outflows. Given the uncertainties in the observations used to calibrate our model, our predictions for isotopic ratios at the time of formation of the Sun are uncertain by a factor of 3.6. At that time, to recover the actual radioactive-to-stable isotopic ratios predicted by our model, one can multiply the steady-state solution (see Equation 1) by 2.3 +3.4 −0.7. However, in the cases where the radioactive isotope has a half-life longer than ∼ 200 Myr, or the target radioactive or stable isotopes have mass-and/or metallicity-depended production rates, or they originate from different sources with different delay-time distributions, or the reference isotope is radioactive, our codes should be used for more accurate solutions. Our preliminary calculations confirm the dichotomy between radioactive nuclei in the early Solar System with r-and s-process origin, and that 55 Mn and 60 Fe can be explained by galactic chemical evolution, while 26 Al cannot.

Citation

Côté, B., Lugaro, M., Reifarth, R., Pignatari, M., Világos, B., Yagüe, A., & Gibson, B. K. (2019). Galactic chemical evolution of radioactive isotopes. The Astrophysical journal, 878(2), Article 156. https://doi.org/10.3847/1538-4357/ab21d1

• Journal Article Type: Article
• Acceptance Date: May 14, 2019
• Online Publication Date: Jun 25, 2019
• Publication Date: Jun 25, 2019
• Deposit Date: Jun 19, 2019
• Publicly Available Date: Jul 1, 2019
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 878
• Issue: 2
• Article Number: 156
• DOI: https://doi.org/10.3847/1538-4357/ab21d1
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://hull-repository.worktribe.com/output/2012858
• Publisher URL: https://iopscience.iop.org/article/10.3847/1538-4357/ab21d1
• Contract Date: Jun 19, 2019