The R-Process Alliance: Enrichment of R-process Elements in Simulated Milky Way-like Galaxies

ORAL

Abstract

The R-Process Alliance (RPA) has largely increased the number of measured stars with heavy elements synthesized by the rapid neutron-capture process (r-process). The next step of RPA is to understand the enrichment of r-process elements in the Milky Way using a large set of observed and simulated data. In this talk, I will review simulation studies on the enrichment of r-process elements. We study the formation of stars with varying amounts of r-process elements with our detailed cosmological zoom-in simulation of a Milky Way-like galaxy. Most stars with no overabundance in r-process elements, as well as the strongly r-process enhanced r-II stars ([Eu/Fe] >+0.7), are formed in dwarf galaxies accreted by the Milky Way within the 6 Gyr after the Big Bang. In contrast, over half of the moderately enhanced r-I stars (+0.3 < [Eu/Fe] <= +0.7) are formed in the main in-situ disk after 6 Gyr. We compare our findings with high-resolution spectroscopic observations of r-process-enhanced metal-poor stars in the halo and dwarf galaxies, including those collected by the RPA. We conclude that observed [Eu/Fe] and [Eu/Mg] ratios can be employed in chemical tagging of the Milky Way's accretion history.

*This work was supported in part by JSPS KAKENHI Grant Numbers JP22KJ0157, JP21H04499, JP21K03614, JP22H01259, JP21H04997, JP23H00127, JP23H05432, JP23H04894, JP23H04891, JP24H00027, JP24K00669, JP22K03688, JP24K07095, MEXT Grant Number JPMXP1020230406, JICFuS, NSF grants OISE-1927130, AST-2205847, 2206263, 2307436, the NRF of Korea, ICT (RS-2024-00333766), NASA Astrophysics Data Analysis Program grant 80NSSC21K0627, NOIRLab, which is managed by the Association of Universities for Research in Astronomy under a cooperative agreement with the U.S. NSF, the Swedish Research Council (VR 2021-05556), NASA Astrophysics Theory Program grant 80NSSC24K089. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

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Publication: 10.48550/arXiv.2410.11943
10.1093/mnras/stac2489

Presenters

  • Yutaka Hirai

    • Tohoku University

Authors

  • Yutaka Hirai

    • Tohoku University

  • Timothy C Beers

    • University of Notre Dame

  • Young Sun Lee

    • Chungnam National University

  • Shinya Wanajo

    • Max Planck Institute for Gravitational Physics

  • Ian U Roederer

    • North Carolina State University

  • Masaomi Tanaka

    • Tohoku University

  • Masashi Chiba

    • Tohoku University

  • Takayuki R Saitoh

    • Kobe University

  • Vinicius M Placco

    • NSF NOIRLab

  • Terese T Hansen

    • Stockholm University

  • Rana Ezzeddine

    • University of Florida

  • Anna Frebel

    • Massachusetts Institute of Technology

  • Erika M Holmbeck

    • Lawrence Livermore National Laboratory

  • Charli M Sakari

    • San Francisco State University