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<p>Galaxies build through infalling gas and galaxy mergers. Tracking the dynamical history of a galaxy from a single snapshot in time is notoriously difficult. Here we show that the dynamical history of a galaxy can be tracked using oxygen abundances as archaeological tracers. We derive the gas-phase oxygen abundances for 4,546 spaxels across the face-on spiral galaxy NGC 1365 at a spatial resolution of 175 pc, thus obtaining one of the most detailed chemical fossil records of a spiral galaxy outside our Milky Way. We apply IllustrisTNG cosmological simulations to analyse the chemical abundance distribution in a theoretical model for NGC 1365. In the model, the oxygen-abundance gradient of the main disk formed earliest, 11.9–12.5 billion years ago via mergers with several dwarf galaxies. A steep inner-bar gradient formed slowly over the last 12 billion years through enrichment from star formation triggered by the infall of gas into the nuclear regions. An extended ionized gas disk with flat oxygen abundances assembled more recently (5.9–8.6 billion years ago) through a minor merger. This work indicates that cosmological simulations and ultrahigh-spatial-resolution oxygen abundances can together provide an archaeological probe of the star-formation and merger histories of spiral galaxies.</p>

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The assembly history of NGC 1365 through chemical archaeology

  • 期刊论文

  • 发表日期：

    2026年3月23日

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  • Lisa J. Kewley,
  • Kathryn Grasha,
  • Alex Garcia,
  • Paul Torrey,
  • Jeff Rich,
  • Z. S. Hemler,
  • Qian-Hui Chen,
  • Peixin Zhu,
  • Mark Seibert,
  • Lars Hernquist,
  • Barry Madore

摘要

Galaxies build through infalling gas and galaxy mergers. Tracking the dynamical history of a galaxy from a single snapshot in time is notoriously difficult. Here we show that the dynamical history of a galaxy can be tracked using oxygen abundances as archaeological tracers. We derive the gas-phase oxygen abundances for 4,546 spaxels across the face-on spiral galaxy NGC 1365 at a spatial resolution of 175 pc, thus obtaining one of the most detailed chemical fossil records of a spiral galaxy outside our Milky Way. We apply IllustrisTNG cosmological simulations to analyse the chemical abundance distribution in a theoretical model for NGC 1365. In the model, the oxygen-abundance gradient of the main disk formed earliest, 11.9–12.5 billion years ago via mergers with several dwarf galaxies. A steep inner-bar gradient formed slowly over the last 12 billion years through enrichment from star formation triggered by the infall of gas into the nuclear regions. An extended ionized gas disk with flat oxygen abundances assembled more recently (5.9–8.6 billion years ago) through a minor merger. This work indicates that cosmological simulations and ultrahigh-spatial-resolution oxygen abundances can together provide an archaeological probe of the star-formation and merger histories of spiral galaxies.