Metal enrichment in the Fermi bubbles as a probe of their origin

Yoshiyuki Inoue, Shinya Nakashima, Masaya Tahara, Jun Kataoka, Tomonori Totani, Yutaka Fujita, Yoshiaki Sofue

    Research output: Contribution to journalArticlepeer-review

    8 Citations (Scopus)


    The Fermi bubbles are gigantic gamma-ray structures in our Galaxy. The physical origin of the bubbles is still under debate. The leading scenarios can be divided into two categories. One is nuclear star-forming activity similar to extragalactic starburst galaxies and the other is past active galactic nucleus (AGN)-like activity of the Galactic center supermassive black hole. In this letter, we propose that metal abundance measurements will provide an important clue to probe their origin. Based on a simple spherically symmetric bubble model, we find that the generated metallicity and abundance patterns of the bubbles' gas strongly depend on assumed star formation or AGN activities. Star formation scenarios predict higher metallicities and abundance ratios of [O/Fe] and [Ne/Fe] than AGN scenarios do because of supernovae ejecta. Furthermore, the resultant abundance depends on the gamma-ray emission process because different mass injection histories are required for the different gamma-ray emission processes due to the acceleration and cooling time scales of non-thermal particles. Future X-ray missions such as ASTRO-H and Athena will give a clue to probe the origin of the bubbles through abundance measurements with their high energy resolution instruments.

    Original languageEnglish
    Article number56
    JournalPublications of the Astronomical Society of Japan
    Issue number3
    Publication statusPublished - 2015 Apr 8


    • Galaxy
    • ISM
    • abundances-Galaxy
    • center-Galaxy
    • halo-X-rays

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science


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