A decelerating bar in the Galaxy

Chengdong Li (李承东), 2024-03-12

Galaxy & Cosmology Seminar

https://astro.tsinghua.edu.cn/info/1120/2795.htm

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Introduction

About the central bar in the Milky Way.

MW has a psedo-bulge ($1.5$ kpc) and a long bar ($5.0\pm 0.2$ kpc).

The pattern speed of the bar ~ 40 km/s/kpc. Observations prefer it slowing down with time.

Content

• morphology
• origin
• origin of the old disk

morphology

phase space spiral structure, perturbation of the orbits.
ref. Antoja+23 Gaia DR3

Find: two arms inside, one arm outside, cutoff at where the Sun locates.

simulation: two arms structure moves from inner to outside with time

origin of the old disk

thin-disc like metal poor stars

old hypothesis:

1. in-situ formation
2. move from inner

new find: decelerating bar transfers from inner to outer disk