天の川銀河の衛星銀河はどのようにして誕生したのか？(How did a satellite galaxy of the Milky Way come to be?)

2024-06-11 カリフォルニア大学リバーサイド校(UCR)

＜関連情報＞

• https://news.ucr.edu/articles/2024/06/11/how-did-satellite-galaxy-milky-way-come-be
• https://iopscience.iop.org/article/10.3847/2041-8213/ad50cd

クレーターIIの自己相互作用的ダークマター解釈 Self-interacting Dark Matter Interpretation of Crater II

Xingyu Zhang, Hai-Bo Yu, Daneng Yang, and Haipeng An
The Astrophysical Journal Letters  Published: 2024 June 10
DOI:10.3847/2041-8213/ad50cd

Abstract

The satellite galaxy Crater II of the Milky Way is extremely cold and exceptionally diffuse. These unusual properties are challenging to understand in the standard model of cold dark matter. We use controlled N-body simulations to investigate the formation of Crater II in self-interacting dark matter (SIDM), where dark matter particles can scatter and thermalize. Taking the orbit motivated by the measurements from Gaia Early Data Release 3, we show a strong self-interacting cross section per particle mass of 60 cm² g⁻¹ is favored for Crater II. The simulated SIDM halo, with a 1 kpc core, leads to both a low stellar velocity dispersion and a large half-light radius for Crater II. These characteristics remain robust regardless of the initial stellar distribution.