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arXiv · 1503.07273

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

Hiroyuki Nakanishi·Nobuyuki Sakai·Tomoharu Kurayama·Mitsuhiro Matsuo·Hiroshi Imai·Ross A. Burns·Takeaki Ozawa·Mareki Honma·Katsunori Shibata·Noriyuki Kawaguchi
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Abstract

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 $0.262 \pm 0.031$ mas corresponding to a trigonometric distance of $3.82^{+0.51}_{-0.41}$ kpc. The proper motion was $(μ_α\cosδ, μ_δ)=(-2.74 \pm 0.08, -2.87 \pm 0.18)$ mas yr$^{-1}$. Using this result, the Galactic rotational velocity was estimated to be $V_θ=218\pm 19$ km s$^{-1}$ at the Galactocentric distance $R=9.22\pm0.43$ kpc, when we adopted the Galactic constants $R_0=8.05\pm 0.45$ kpc and $V_0=238\pm 14$ km s$^{-1}$. With newly determined distance, {the bolometric luminosity of the central young stellar object was re-evaluated to $(2.15\pm 0.54)\times 10^3 L_\odot$, 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.

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Hiroyuki Nakanishi, Nobuyuki Sakai, Tomoharu Kurayama, Mitsuhiro Matsuo, Hiroshi Imai, Ross A. Burns, Takeaki Ozawa, Mareki Honma, Katsunori Shibata, Noriyuki Kawaguchi. 2015-03-25. Outer Rotation Curve of the Galaxy with VERA II: Annual Parallax and Proper Motion of the Star-Forming Region IRAS21379+5106. https://doi.org/10.1093/pasj%2Fpsv012

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