On the α/Fe Bimodality of the M31 Disks
An outstanding question is whether the α /Fe bimodality exists in disk galaxies other than in the Milky Way. Here we present a bimodality using our state-of-the-art galactic chemical evolution models that can explain various observations in the Andromeda galaxy (M31) disks, namely, elemental abundan...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/2041-8213/acf7c7 |
| _version_ | 1797662284327157760 |
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| author | Chiaki Kobayashi Souradeep Bhattacharya Magda Arnaboldi Ortwin Gerhard |
| author_facet | Chiaki Kobayashi Souradeep Bhattacharya Magda Arnaboldi Ortwin Gerhard |
| author_sort | Chiaki Kobayashi |
| collection | DOAJ |
| description | An outstanding question is whether the α /Fe bimodality exists in disk galaxies other than in the Milky Way. Here we present a bimodality using our state-of-the-art galactic chemical evolution models that can explain various observations in the Andromeda galaxy (M31) disks, namely, elemental abundances both of planetary nebulae and of red giant branch stars recently observed with the James Webb Space Telescope. We find that in M31 a high- α thicker-disk population out to 30 kpc formed by a more intense initial starburst than that in the Milky Way. We also find a young low- α thin disk within 14 kpc, which is formed by a secondary star formation M31 underwent about 2–4.5 Gyr ago, probably triggered by a wet merger. In the outer disk, however, the planetary nebula observations indicate a slightly higher- α young (∼2.5 Gyr) population at a given metallicity, possibly formed by secondary star formation from almost pristine gas. Therefore, an α /Fe bimodality is seen in the inner disk (≲14 kpc), while only a slight α /Fe offset of the young population is seen in the outer disk (≳18 kpc). The appearance of the α /Fe bimodality depends on the merging history at various galactocentric radii, and wide-field multiobject spectroscopy is required for unveiling the history of M31. |
| first_indexed | 2024-03-11T18:57:54Z |
| format | Article |
| id | doaj.art-cf36960b1a764b488b095fb4c9bc8d2d |
| institution | Directory Open Access Journal |
| issn | 2041-8205 |
| language | English |
| last_indexed | 2024-03-11T18:57:54Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj.art-cf36960b1a764b488b095fb4c9bc8d2d2023-10-10T15:34:20ZengIOP PublishingThe Astrophysical Journal Letters2041-82052023-01-019561L1410.3847/2041-8213/acf7c7On the α/Fe Bimodality of the M31 DisksChiaki Kobayashi0https://orcid.org/0000-0002-4343-0487Souradeep Bhattacharya1https://orcid.org/0000-0003-4594-6943Magda Arnaboldi2https://orcid.org/0000-0001-7214-3009Ortwin Gerhard3https://orcid.org/0000-0003-3333-0033Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire , Hatfield AL10 9AB, UK ; c.kobayashi@herts.ac.ukInter University Centre for Astronomy and Astrophysics , Ganeshkhind, Post Bag 4, Pune 411007, IndiaEuropean Southern Observatory , Karl-Schwarzschild-Str. 2, D-85748 Garching, GermanyMax-Planck-Institut für extraterrestrische Physik , Giessenbachstrae, D-85748 Garching, GermanyAn outstanding question is whether the α /Fe bimodality exists in disk galaxies other than in the Milky Way. Here we present a bimodality using our state-of-the-art galactic chemical evolution models that can explain various observations in the Andromeda galaxy (M31) disks, namely, elemental abundances both of planetary nebulae and of red giant branch stars recently observed with the James Webb Space Telescope. We find that in M31 a high- α thicker-disk population out to 30 kpc formed by a more intense initial starburst than that in the Milky Way. We also find a young low- α thin disk within 14 kpc, which is formed by a secondary star formation M31 underwent about 2–4.5 Gyr ago, probably triggered by a wet merger. In the outer disk, however, the planetary nebula observations indicate a slightly higher- α young (∼2.5 Gyr) population at a given metallicity, possibly formed by secondary star formation from almost pristine gas. Therefore, an α /Fe bimodality is seen in the inner disk (≲14 kpc), while only a slight α /Fe offset of the young population is seen in the outer disk (≳18 kpc). The appearance of the α /Fe bimodality depends on the merging history at various galactocentric radii, and wide-field multiobject spectroscopy is required for unveiling the history of M31.https://doi.org/10.3847/2041-8213/acf7c7Andromeda GalaxyMilky Way GalaxyChemical abundancesPlanetary nebulaeGalaxy formationGalaxy chemical evolution |
| spellingShingle | Chiaki Kobayashi Souradeep Bhattacharya Magda Arnaboldi Ortwin Gerhard On the α/Fe Bimodality of the M31 Disks The Astrophysical Journal Letters Andromeda Galaxy Milky Way Galaxy Chemical abundances Planetary nebulae Galaxy formation Galaxy chemical evolution |
| title | On the α/Fe Bimodality of the M31 Disks |
| title_full | On the α/Fe Bimodality of the M31 Disks |
| title_fullStr | On the α/Fe Bimodality of the M31 Disks |
| title_full_unstemmed | On the α/Fe Bimodality of the M31 Disks |
| title_short | On the α/Fe Bimodality of the M31 Disks |
| title_sort | on the α fe bimodality of the m31 disks |
| topic | Andromeda Galaxy Milky Way Galaxy Chemical abundances Planetary nebulae Galaxy formation Galaxy chemical evolution |
| url | https://doi.org/10.3847/2041-8213/acf7c7 |
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