Gaia DR3 proper motion anisotropy aligned with l=0°/180° (χ²=457, p<0.001, 18 million stars)

Analysis of 18,000,000 Gaia DR3 stars after applying secular aberration correction (Liu, Zhu & Liu 2024) reveals a statistically significant proper motion anisotropy aligned with the galactic corridor axis at l=0°/180°. Chi-square statistics testing isotropy across 36 galactic longitude bins yield χ²=456.79 (p<0.001) with a +3.5% excess in the corridor zone (±30° of l=0°/180°). The signal strengthens with sample size (χ²=26.20 at 500k stars, χ²=101.01 at 5M stars, χ²=456.79 at 18M stars), indicating a real statistical effect rather than sampling noise. A great circle boundary at l=0°/180° is the best-fit dividing plane.

Assumptions

- The Liu et al. (2024) secular aberration correction adequately removes instrumental systematics
- The anisotropy is corridor-specific and not explained by galactic warp, bar-driven streaming, or spiral arm perturbations
- The ±30° corridor zone definition is physically motivated rather than optimized post-hoc

Open Questions

- Does the same chi-square signal appear when the dividing boundary is placed at other galactic longitudes (l=45°, l=90°)? If so, the signal is not corridor-specific.
- What fraction of the anisotropy can be attributed to known kinematic structures (Hercules stream, bar resonances)?

AI Use Disclosures