Effect of gas accretion on $α$-element bimodality in Milky Way-mass galaxies in the FIRE-2 simulations
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arXiv
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| Format: | Preprint |
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2025
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| author | Parul, Hanna Bailin, Jeremy Loebman, Sarah R. Wetzel, Andrew Barry, Megan Bhattarai, Binod |
| author_facet | Parul, Hanna Bailin, Jeremy Loebman, Sarah R. Wetzel, Andrew Barry, Megan Bhattarai, Binod |
| contents | We analyse the stellar distributions on the [Fe/H]-[Mg/Fe] plane for 11 Milky Way-mass galaxies from the FIRE-2 cosmological baryonic zoom-in simulations. Alpha-element bimodality, in the form of two separate sequences on the [Fe/H]-[Mg/Fe] plane, is not a universal feature of disk galaxies. Five galaxies demonstrate double sequences with the $α$-enriched one being older and kinematically hotter, in qualitative agreement with the high-$α$ and low-$α$ populations in the Milky Way disk; three galaxies have unimodal distribution, two show weakly-bimodal features where low-$α$ sequence is visible only over a short range of metallicities, and one show strong bimodality with a different slope of high-$α$ population. We examine the galaxies' gas accretion history over the last 8 Gyr, when bimodal sequences emerge, and demonstrate that the presence of the low-$α$ sequence in the bimodal galaxies is related to the recent infall of metal-poor gas from the circumgalactic medium that joins the galaxy in the outskirts and induces significant growth of the gas disks compared to their non-bimodal counterparts. We also analyse the sources of the accreted gas and illustrate that both gas-rich mergers and smooth accretion of ambient gas can be the source of the accreted gas, and create slightly different bimodal patterns. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_12342 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Effect of gas accretion on $α$-element bimodality in Milky Way-mass galaxies in the FIRE-2 simulations Parul, Hanna Bailin, Jeremy Loebman, Sarah R. Wetzel, Andrew Barry, Megan Bhattarai, Binod Astrophysics of Galaxies We analyse the stellar distributions on the [Fe/H]-[Mg/Fe] plane for 11 Milky Way-mass galaxies from the FIRE-2 cosmological baryonic zoom-in simulations. Alpha-element bimodality, in the form of two separate sequences on the [Fe/H]-[Mg/Fe] plane, is not a universal feature of disk galaxies. Five galaxies demonstrate double sequences with the $α$-enriched one being older and kinematically hotter, in qualitative agreement with the high-$α$ and low-$α$ populations in the Milky Way disk; three galaxies have unimodal distribution, two show weakly-bimodal features where low-$α$ sequence is visible only over a short range of metallicities, and one show strong bimodality with a different slope of high-$α$ population. We examine the galaxies' gas accretion history over the last 8 Gyr, when bimodal sequences emerge, and demonstrate that the presence of the low-$α$ sequence in the bimodal galaxies is related to the recent infall of metal-poor gas from the circumgalactic medium that joins the galaxy in the outskirts and induces significant growth of the gas disks compared to their non-bimodal counterparts. We also analyse the sources of the accreted gas and illustrate that both gas-rich mergers and smooth accretion of ambient gas can be the source of the accreted gas, and create slightly different bimodal patterns. |
| title | Effect of gas accretion on $α$-element bimodality in Milky Way-mass galaxies in the FIRE-2 simulations |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2501.12342 |