On the α /Fe Bimodality of the M31 Disks

Chiaki Kobayashi, Souradeep Bhattacharya, Magda Arnaboldi, Ortwin Gerhard

Research output: Contribution to journalArticlepeer-review

2 Downloads (Pure)

Abstract

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.
Original languageEnglish
Article numberL14
Pages (from-to)1-5
Number of pages5
JournalAstrophysical Journal Letters
Volume956
Issue number1
DOIs
Publication statusPublished - 10 Oct 2023

Keywords

  • Chemical abundances
  • Galaxy chemical evolution
  • Planetary nebulae
  • Andromeda Galaxy
  • James Webb Space Telescope
  • Galaxy formation
  • Milky Way Galaxy

Fingerprint

Dive into the research topics of 'On the α /Fe Bimodality of the M31 Disks'. Together they form a unique fingerprint.

Cite this