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Peer-reviewedCC BY 4.0The Astrophysical Journal

Impact of Gaia–Sausage–Enceladus Debris on Milky Way Escape-velocity Estimates in TNG50

  • Yin Wu1,2
  • Haining Li1
  • Shi Shao1,2
  • Xiang-Xiang Xue1,3
  • Lan Zhang1
  • Gang Zhao1,2
  1. 1Chinese Academy of Sciences
  2. 2University of Chinese Academy of Sciences
  3. 3Beijing Normal University
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Abstract

The escape velocity is a key probe of the Milky Way (MW) potential, but standard estimates can be biased by unrelaxed substructures. Using MW analogs from the TNG50 cosmological simulation, we investigate the impact of the dominant, highly radial Gaia–Sausage–Enceladus (GSE) debris on escape-velocity measurements. We introduce an adaptive selection strategy that balances statistical reliability with sample size to identify the power-law decline regime of the local halo velocity distribution. Applying this strategy to 16 MW analogs with prominent GSE-like structures and continuous high-velocity tails, we find that retaining GSE-like stars yields a systematic underestimate, with a recovery fraction of 97 . 5 % − 2.9 % + 2.1 % , while removing GSE-like stars alone increases the recovery fraction to 99 . 4 % − 2.5 % + 2.1 % . The ∼2% underestimation of the escape velocity corresponds to an ∼6% underestimation of the total mass. This improvement persists in LAMOST-like magnitude and footprint selection. GSE-like debris is therefore a key contributor to the systematic underestimation of escape-velocity measurements, with direct implications for the inferred MW mass.

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Cite

BibTeXRIS
BibTeX
@article{wu2026impact,
  title = {{Impact of Gaia–Sausage–Enceladus Debris on Milky Way Escape-velocity Estimates in TNG50}},
  author = {Yin Wu and Haining Li and Shi Shao and Xiang-Xiang Xue and Lan Zhang and Gang Zhao},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = nov,
  doi = {10.3847/1538-4357/aeb00d},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aeb00d},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Impact of Gaia–Sausage–Enceladus Debris on Milky Way Escape-velocity Estimates in TNG50
AU  - Yin Wu
AU  - Haining Li
AU  - Shi Shao
AU  - Xiang-Xiang Xue
AU  - Lan Zhang
AU  - Gang Zhao
PY  - 2026
DA  - 2026/11/02
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aeb00d
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aeb00d
AB  - The escape velocity is a key probe of the Milky Way (MW) potential, but standard estimates can be biased by unrelaxed substructures. Using MW analogs from the TNG50 cosmological simulation, we investigate the impact of the dominant, highly radial Gaia–Sausage–Enceladus (GSE) debris on escape-velocity measurements. We introduce an adaptive selection strategy that balances statistical reliability with sample size to identify the power-law decline regime of the local halo velocity distribution. Applying this strategy to 16 MW analogs with prominent GSE-like structures and continuous high-velocity tails, we find that retaining GSE-like stars yields a systematic underestimate, with a recovery fraction of 97 . 5 % − 2.9 % + 2.1 % , while removing GSE-like stars alone increases the recovery fraction to 99 . 4 % − 2.5 % + 2.1 % . The ∼2% underestimation of the escape velocity corresponds to an ∼6% underestimation of the total mass. This improvement persists in LAMOST-like magnitude and footprint selection. GSE-like debris is therefore a key contributor to the systematic underestimation of escape-velocity measurements, with direct implications for the inferred MW mass.
SN  - 1538-4357
SN  - 0004-637X
ER  -