The assembly history of NGC 1365 through chemical archaeology
Abstract
Galaxies build through infalling gas and galaxy mergers. Tracking the dynamical history of a galaxy from a single snapshot in time is notoriously difficult. We show that the dynamical history of a galaxy can be tracked using oxygen abundances as archeological tracers. We derive the gas-phase oxygen abundances for 4546 spaxels across the face-on spiral galaxy NGC~1365 at a spatial resolution of 175 pc, providing 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 main disk oxygen abundance gradient formed earliest, 11.9-12.5 billion years ago via mergers with multiple 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 was assembled more recently (5.9-8.6 billion years ago) through a minor merger. This work indicates that cosmological simulations and ultra-high spatial resolution oxygen abundances together can provide an archaeological probe of the star formation and merger histories of spiral galaxies.
Versions
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BibTeX
@misc{kewley2026assembly,
title = {{The assembly history of NGC 1365 through chemical archaeology}},
author = {Lisa J. Kewley and Kathryn Grasha and Alex Garcia and Paul Torrey and Jeff Rich and Z. S. Hemler and Qian-hui Chen and Peixin Zhu and Mark Seibert and Lars Hernquist and Barry Madore},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.40160},
eprint = {2609.40160},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.40160},
}
RIS
TY - UNPB
TI - The assembly history of NGC 1365 through chemical archaeology
AU - Lisa J. Kewley
AU - Kathryn Grasha
AU - Alex Garcia
AU - Paul Torrey
AU - Jeff Rich
AU - Z. S. Hemler
AU - Qian-hui Chen
AU - Peixin Zhu
AU - Mark Seibert
AU - Lars Hernquist
AU - Barry Madore
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.40160
UR - https://arxiv.org/abs/2609.40160
AB - Galaxies build through infalling gas and galaxy mergers. Tracking the dynamical history of a galaxy from a single snapshot in time is notoriously difficult. We show that the dynamical history of a galaxy can be tracked using oxygen abundances as archeological tracers. We derive the gas-phase oxygen abundances for 4546 spaxels across the face-on spiral galaxy NGC~1365 at a spatial resolution of 175 pc, providing 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 main disk oxygen abundance gradient formed earliest, 11.9-12.5 billion years ago via mergers with multiple 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 was assembled more recently (5.9-8.6 billion years ago) through a minor merger. This work indicates that cosmological simulations and ultra-high spatial resolution oxygen abundances together can provide an archaeological probe of the star formation and merger histories of spiral galaxies.
ER -