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arXiv · 2610.27526

A $\wedge$-like metallicity profile in the disk of the Sagittarius dwarf galaxy

Zixi Guo·Xiang-Xiang Xue·Jiang Chang·Chao Liu·Zehao Zhong·Bingqing Zhang·Ruizhi Zhang·Shi Shao·Gang Zhao·Zhuohan Li·Xi Kang·Jie Wang·Jianhui Lian·Haining Li·Ruizheng Jiang
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Abstract

Unveiling the properties of the progenitors that formed the tidal structures of the Milky Way (MW) is essential for exploring the MW's assembly history. Such studies further afford a unique opportunity to dissect the formation and evolution of dwarf galaxies by contrasting surviving and disrupted systems. However, reconstructing the intrinsic structure of progenitors solely from the positions and velocities of their tidal debris remains a formidable challenge. Here, we decode the chemo-kinematic signatures embedded in the stellar streams of the Sagittarius (Sgr) dwarf galaxy through N-body simulations. Our simulation reproduces a vertical metallicity gradient in the Sgr streams. We show that this feature is naturally explained if the stream originated from a disk component with a $\wedge$-like metallicity profile. Remarkably, similar metallicity profiles are identified in MaNGA survey data for a few (3/217) field dwarf galaxies, suggesting this feature is rare but not unique to Sgr. The vertical metallicity gradient of stellar streams preserves extra detailed galactic fossil records, enabling quantitative reconstruction of the peculiar structure of the satellite galaxy. The similar metallicity profiles of Sgr and MW raise the question of a possible special coevolution.

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Zixi Guo, Xiang-Xiang Xue, Jiang Chang, Chao Liu, Zehao Zhong, Bingqing Zhang, Ruizhi Zhang, Shi Shao, Gang Zhao, Zhuohan Li, Xi Kang, Jie Wang, Jianhui Lian, Haining Li, Ruizheng Jiang. 2026-10-20. A $\wedge$-like metallicity profile in the disk of the Sagittarius dwarf galaxy. https://doi.org/10.1038/s41550-026-02996-2

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