Outer Rotation Curve of the Galaxy with VERA II: Annual Parallax and Proper Motion of the Star-Forming Region IRAS21379+5106

الأصل · EN

We conducted astrometric VLBI observations of water-vapor maser emission in the massive star forming region IRAS 21379+5106 to measure the annual parallax and proper motion, using VERA. The annual parallax was measured to be 0.262 ± 0.031 mas corresponding to a trigonometric distance of 3.82⁺⁰.⁵¹₋₀.₄₁ kpc. The proper motion was (μαδ, μδ)=(-2.74 ± 0.08, -2.87 ± 0.18) mas yr⁻¹. Using this result, the Galactic rotational velocity was estimated to be Vθ=218± 19 km s⁻¹ at the Galactocentric distance R=9.22±0.43 kpc, when we adopted the Galactic constants R₀=8.05± 0.45 kpc and V₀=238± 14 km s⁻¹. With newly determined distance, the bolometric luminosity of the central young stellar object was re-evaluated to (2.15± 0.54)× 10³ L, which corresponds to spectral type of B2--B3. Maser features were found to be distributed along a straight line from south-west to north-east. In addition, a vector map of the internal motions constructed from the residual proper motions implies that maser features trace a bipolar flow and that it cannot be explained by simple ballistic motion.