The chemical properties of the Milky Way's on-bar and off-bar regions: evidence for inhomogeneous star formation history in the bulge

Jianhui Lian, Gail Zasowski, Sten Hasselquist, Justus Neumann, Steven R. Majewski, Roger E. Cohen, José G. Fernández-Trincado, Richard R. Lane, Peélope Longa-Peña, Alexandre Roman-Lopes

Research output: Contribution to journalArticlepeer-review

34 Downloads (Pure)

Abstract

Numerous studies of integrated starlight, stellar counts, and kinematics have confirmed that the Milky Way is a barred galaxy. However, far fewer studies have investigated the bar’s stellar population properties, which carry valuable independent information regarding the bar’s formation history. Here we conduct a detailed analysis of chemical abundance distributions ([Fe/H] and [Mg/Fe]) in the on-bar and off-bar regions to study the azimuthal variation of star formation history (SFH) in the inner Galaxy. We find that the on-bar and off-bar stars at Galactocentric radii 3 < rGC < 5 kpc have remarkably consistent [Fe/H] and [Mg/Fe] distribution functions and [Mg/Fe]–[Fe/H] relation, suggesting a common SFH shared by the long bar and the disc. In contrast, the bar and disc at smaller radii (2 < rGC < 3 kpc) show noticeable differences, with relatively more very metal-rich (⁠[Fe/H] ∼ 0.4) stars but fewer solar abundance stars in the bar. Given the three-phase star formation history proposed for the inner Galaxy in Lian et al. (2020c), these differences could be explained by the off-bar disc having experienced either a faster early quenching process or recent metal-poor gas accretion. Vertical variations of the abundance distributions at small rGC suggest a wider vertical distribution of low-α stars in the bar, which may serve as chemical evidence for vertical heating through the bar buckling process. The lack of such vertical variations outside the bulge may then suggest a lack of vertical heating in the long bar.
Original languageEnglish
Pages (from-to)282-290
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume500
Issue number1
Early online date24 Oct 2020
DOIs
Publication statusPublished - 1 Jan 2021

Keywords

  • RCUK
  • STFC
  • ST/S000550/1
  • The Galaxy: abundances
  • The Galaxy: bulge
  • The Galaxy: formation
  • The Galaxy: evolution
  • The Galaxy: stellar content
  • The Galaxy: structure

Fingerprint

Dive into the research topics of 'The chemical properties of the Milky Way's on-bar and off-bar regions: evidence for inhomogeneous star formation history in the bulge'. Together they form a unique fingerprint.

Cite this