Rising from the Ashes. II. The Bar-driven Abundance Bimodality of the Milky Way
The Milky Way hosts at least two modes in its present-day distribution of Fe and α -elements. The exact cause of this bimodality is disputed, but one class of explanations involves the merger between the Milky Way and a relatively massive satellite (Gaia-Sausage-Enceladus) at z ∼ 2. However, reprod...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/adceab |
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| author | Angus Beane James W. Johnson Vadim A. Semenov Lars Hernquist Vedant Chandra Charlie Conroy |
| author_facet | Angus Beane James W. Johnson Vadim A. Semenov Lars Hernquist Vedant Chandra Charlie Conroy |
| author_sort | Angus Beane |
| collection | DOAJ |
| description | The Milky Way hosts at least two modes in its present-day distribution of Fe and α -elements. The exact cause of this bimodality is disputed, but one class of explanations involves the merger between the Milky Way and a relatively massive satellite (Gaia-Sausage-Enceladus) at z ∼ 2. However, reproducing this bimodality in simulations is not straightforward, with conflicting results on the prevalence, morphology, and mechanism behind multimodality. We present a case study of a galaxy in the Illustris TNG50 simulation that undergoes sequential phases of starburst, brief quiescence, and then rejuvenation. This scenario results in a pronounced abundance bimodality after a post-processing adjustment of the [ α /Fe] of old stars designed to mimic a higher star formation efficiency in dense gas. The high- and low- α sequences are separated in time by the brief quiescent period, which is associated not with a merger but with the formation of a bar followed by active galactic nucleus (AGN) activity. This galaxy indicates a novel scenario in which the α -bimodality in the Milky Way is caused by the formation of the bar via AGN-induced quenching. In addition to a stellar age gap in the Milky Way, we predict that abundance bimodalities should be more common in barred as opposed to unbarred galaxies. |
| format | Article |
| id | doaj-art-71cd3dfd2bd841dc89dcc4d496459d4e |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-71cd3dfd2bd841dc89dcc4d496459d4e2025-08-20T03:48:13ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01985222110.3847/1538-4357/adceabRising from the Ashes. II. The Bar-driven Abundance Bimodality of the Milky WayAngus Beane0https://orcid.org/0000-0002-8658-1453James W. Johnson1https://orcid.org/0000-0002-6534-8783Vadim A. Semenov2https://orcid.org/0000-0002-6648-7136Lars Hernquist3https://orcid.org/0000-0001-6950-1629Vedant Chandra4https://orcid.org/0000-0002-0572-8012Charlie Conroy5https://orcid.org/0000-0002-1590-8551Center for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USACarnegie Science Observatories , 813 Santa Barbara Street, Pasadena, CA 91101, USACenter for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USACenter for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USACenter for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USACenter for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USAThe Milky Way hosts at least two modes in its present-day distribution of Fe and α -elements. The exact cause of this bimodality is disputed, but one class of explanations involves the merger between the Milky Way and a relatively massive satellite (Gaia-Sausage-Enceladus) at z ∼ 2. However, reproducing this bimodality in simulations is not straightforward, with conflicting results on the prevalence, morphology, and mechanism behind multimodality. We present a case study of a galaxy in the Illustris TNG50 simulation that undergoes sequential phases of starburst, brief quiescence, and then rejuvenation. This scenario results in a pronounced abundance bimodality after a post-processing adjustment of the [ α /Fe] of old stars designed to mimic a higher star formation efficiency in dense gas. The high- and low- α sequences are separated in time by the brief quiescent period, which is associated not with a merger but with the formation of a bar followed by active galactic nucleus (AGN) activity. This galaxy indicates a novel scenario in which the α -bimodality in the Milky Way is caused by the formation of the bar via AGN-induced quenching. In addition to a stellar age gap in the Milky Way, we predict that abundance bimodalities should be more common in barred as opposed to unbarred galaxies.https://doi.org/10.3847/1538-4357/adceabthe Milky WayGalactic barActive galactic nucleiPost-starburst galaxiesMagnetohydrodynamical simulations |
| spellingShingle | Angus Beane James W. Johnson Vadim A. Semenov Lars Hernquist Vedant Chandra Charlie Conroy Rising from the Ashes. II. The Bar-driven Abundance Bimodality of the Milky Way The Astrophysical Journal the Milky Way Galactic bar Active galactic nuclei Post-starburst galaxies Magnetohydrodynamical simulations |
| title | Rising from the Ashes. II. The Bar-driven Abundance Bimodality of the Milky Way |
| title_full | Rising from the Ashes. II. The Bar-driven Abundance Bimodality of the Milky Way |
| title_fullStr | Rising from the Ashes. II. The Bar-driven Abundance Bimodality of the Milky Way |
| title_full_unstemmed | Rising from the Ashes. II. The Bar-driven Abundance Bimodality of the Milky Way |
| title_short | Rising from the Ashes. II. The Bar-driven Abundance Bimodality of the Milky Way |
| title_sort | rising from the ashes ii the bar driven abundance bimodality of the milky way |
| topic | the Milky Way Galactic bar Active galactic nuclei Post-starburst galaxies Magnetohydrodynamical simulations |
| url | https://doi.org/10.3847/1538-4357/adceab |
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