Work

Dynamical Origin of the Vertical Metallicity Gradient of the Milky Way Bulge

Year: 2024

Type: article

Abstract: A vertical metallicity gradient (VMG) in the Milky Way bulge is well-established. Yet, its origin has not been fully understood under the Galactic secular evolution scenario. We construct single-disk and triple-disk N-body models with an initial radial metallicity gradient (RMG) for each disk. These models generate a VMG through a “two-step heating” mechanism: the outer, metal-poor particles move inward via the bar instability and subsequently undergo more significant vertical heating during the buckling instability, so they end up at greater vertical height. The “two-step heating” mechanism nearly linearly transforms the RMGs in precursor disks into VMGs. Comparing the models with a triple-disk model tagged with radially independent Gaussian metallicity, we find that, despite certain limitations, the “two-step heating” mechanism is still important in shaping the Galactic VMG. If the bar and buckling instabilities contributed to the formation of boxy/peanut-shaped bulges, then the “two-step heating” mechanism is inevitable in the secular evolution of a boxy/peanut-shaped bulge.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/ad8640

Authors: Bin-Hui Chen, Juntai Shen, Zhong Liu

Language: English

Topic: Stellar, planetary, and galactic studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,499

Funders: National Natural Science Foundation of China, National Key Research and Development Program of China

Awards: G7169562915, G8777153063