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Bibliographic Details
Main Authors: Shen, Xianjin, Lin, Zehao, Sakai, Nobuyuki, Xu, Ye, Bian, Shuaibo, Wu, Yuanwei, Sun, Yan, Liu, Dejian, Li, Jingjing, Zhang, Bo, Xu, Shuangjing, Oyama, Tomoaki, Oh, Chungsik, Jiang, Wu, Cui, Lang, Jiang, Pengfei, Li, Guanghui, Honma, Mareki, Oh, Se-Jin, Shen, Zhi-Qiang, Wang, Na
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2604.23963
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Table of Contents:
  • Accurate astrometric measurements for star-forming regions located on the far side of the Milky Way remain scarce. In this work, we present the astrometric results for a 22\,GHz water maser associated with star-forming region G040.96+02.48 located on the far side of the Milky Way, using the East Asian VLBI Network. The target water maser's proper motion was determined to be ($μ_α\cosδ, μ_δ$) = ($-2.06_{-0.51}^{+0.53}$, $-2.95_{-0.44}^{+0.45}$)~mas~yr$^{-1}$. The derived three-dimensional kinematic distance to the star-forming region is 20.2$\pm$3.2\,kpc, placing it slightly outside the Outer Scutum$-$Centaurus Arm. The corresponding vertical height of 872$\pm$139\,pc indicates a significant warp of the outer Galactic disk, which is in good agreement with the latest precessing warp model. Moreover, the resulting peculiar motions reveal a complex kinematic pattern, characterized by a large outward radial velocity of $-32\pm$18\,km~s$^{-1}$. Our observations substantially expand the valuable sample of star-forming regions with accurate astrometric measurements in the Extreme Outer Galaxy.