Carnegie Postdoctoral Fellow
Galaxy simulations; galactic-scale star formation; short-lived radioisotopes; giant molecular clouds; cloud-scale gas distributions
B.Sc., 2011, Department of Physics, School of Science, Hokkaido University
M.Sc., 2013, Department of Cosmosciences, Graduate School of Science, Hokkaido University
Ph.D., 2016, Department of Cosmosciences, Graduate School of Science, Hokkaido University
Where and how did the early Solar System form in the Galaxy? What is the birth environment of the Solar System? Is our Solar System typical? Are there other planetary systems similar to ours? We have had these fundamental questions for a long time. The existence of daughter products of short-lived radioisotopes (SLRs) such as 26Al and 60Fe in meteorites is an important clue. Most of them are synthesized in the late phases of stellar evolution and injected into the interstellar medium (ISM) by stellar winds and supernovae. While we now understand the nuclear physics of SLR formation, we have no comparable understanding of how newborn SLRs make their way into new generations of stars and planets before decaying. I am passionate about building a comprehensive picture of how the SLRs flow through space and finally reach our early Solar System.
I have been attempting these exciting and challenging problems with chemo-hydrodynamical simulations of the Milky Way galaxy, including element injection from stellar feedback, that allows us to measure for the distribution of abundance ratios of 26Al and 60Fe over all stars in the Galaxy. We show that the SLRs are distributed in kpc-scale structures and that the Solar abundance ratios are well within the normal range (i.e., our Sun is not atypical). That is because star formation is correlated on galactic scales, so that ejecta preferentially enrich atomic gas that will subsequently be accreted onto existing giant molecular clouds (GMCs) or will form new ones. Thus, new generations of stars preferentially form in patches of the Galaxy contaminated by previous generations of stellar winds and supernovae (SNe) [see Fujimoto, Krumholz, and Tachibana 2018].
I plan to expand this work to include a much larger set of elements (not only SLRs but also stable elements which are injected from multiple sources such as AGB stars and neutron star mergers) and to consider more realistic galactic structures such as spiral arms and the galactic bar.
This project as a whole could have a great impact on broad communities, and it will forge links between the disparate astrophysical fields of galaxies, stars, planets, the Solar system, and meteoritics. I, who have been working on large scale galaxy simulations, am very excited to be a part of this Carnegie DTM team, where there are so many great researchers working on planetary science and meteoritics.