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Fig. 1


Distribution of HII regions with photometric (blue) or trigonometric (red) distances. Two black stars indicate the location of the Sun (x = 0.0 kpc, y = 8.5 kpc) and the GC (x = 0.0 kpc, y = 0.0 kpc). Q1Q4 indicate the four Galactic quadrants. Position uncertainties are indicated by error bars in X and Y directions.

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