Trigonometric Parallaxes of Maser Sources toward the Far Side of the Milky Way
Abstract
We present trigonometric parallaxes and proper motions for eight maser sources associated with high-mass star-forming regions. Four 22 GHz H2O masers and four 6.7 GHz CH3OH masers were observed over eight epochs between 2024 and 2025. Combining parallax, proper-motion, and radial-velocity information, we determine distances and spiral-arm assignments for these sources. The newly measured far-side masers extend the known distributions of the Sagittarius and Perseus arms toward Galactic longitudes as small as ℓ∼10∘. Their locations and kinematics agree well with recently updated spiral-arm models based on maser astrometry. In particular, the new measurements show that the far-side Sagittarius and Perseus arms tend to converge toward a common spiral feature in the inner Galaxy. This configuration is consistent with the bifurcation scenario proposed for the Milky Way spiral structure, although an unresolved inter-arm structure provides an alternative interpretation that cannot yet be excluded.
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BibTeX
@misc{lin2026trigonometric,
title = {{Trigonometric Parallaxes of Maser Sources toward the Far Side of the Milky Way}},
author = {Z. H. Lin and Y. Xu and M. Reid and J. J. Li and S. B. Bian},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.34219},
eprint = {2609.34219},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.34219},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Trigonometric Parallaxes of Maser Sources toward the Far Side of the Milky Way
AU - Z. H. Lin
AU - Y. Xu
AU - M. Reid
AU - J. J. Li
AU - S. B. Bian
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.34219
UR - https://arxiv.org/abs/2609.34219
AB - We present trigonometric parallaxes and proper motions for eight maser sources associated with high-mass star-forming regions. Four 22 GHz H_2O masers and four 6.7 GHz CH_3OH masers were observed over eight epochs between 2024 and 2025. Combining parallax, proper-motion, and radial-velocity information, we determine distances and spiral-arm assignments for these sources. The newly measured far-side masers extend the known distributions of the Sagittarius and Perseus arms toward Galactic longitudes as small as ℓ∼10^∘. Their locations and kinematics agree well with recently updated spiral-arm models based on maser astrometry. In particular, the new measurements show that the far-side Sagittarius and Perseus arms tend to converge toward a common spiral feature in the inner Galaxy. This configuration is consistent with the bifurcation scenario proposed for the Milky Way spiral structure, although an unresolved inter-arm structure provides an alternative interpretation that cannot yet be excluded.
ER -