We report the internal proper motions of 12 GHz methanol masers in mas-sive star-forming region G35.20-0.74 observed with the Very Long Baseline Array （VLBA） at four epochs spanning about 1.5 yr. Two groups of maser...We report the internal proper motions of 12 GHz methanol masers in mas-sive star-forming region G35.20-0.74 observed with the Very Long Baseline Array （VLBA） at four epochs spanning about 1.5 yr. Two groups of maser features were de-tected, groups A and B, and the latter that had a V-shaped spatial distribution is likely tracing the north outflow in G35.20-0.74. We present a three-dimensional model for the kinematics of these masers, by assuming the interstellar medium was blown by the stellar wind from the driving source （G35.2N） of the outflow. Adopting a position angle of ～ 81° for the main axis of the outflow from previous studies, we estimate an inclination of 35 ° ± 5.5°, a velocity of 8.1 ± 0.7 km s^-1 for the stellar wind along the main axis and an expansion speed gradient of 0.05 ± 0.016 km s^-1 AU^-1. From the model, we derive the age of the north outflow in G35.20-0.74 to be ～ 1.6 × 10^4 yr.展开更多
基金supported by the National Science Foundation of China (Grant Nos.11073046 and 11133008)
文摘We report the internal proper motions of 12 GHz methanol masers in mas-sive star-forming region G35.20-0.74 observed with the Very Long Baseline Array （VLBA） at four epochs spanning about 1.5 yr. Two groups of maser features were de-tected, groups A and B, and the latter that had a V-shaped spatial distribution is likely tracing the north outflow in G35.20-0.74. We present a three-dimensional model for the kinematics of these masers, by assuming the interstellar medium was blown by the stellar wind from the driving source （G35.2N） of the outflow. Adopting a position angle of ～ 81° for the main axis of the outflow from previous studies, we estimate an inclination of 35 ° ± 5.5°, a velocity of 8.1 ± 0.7 km s^-1 for the stellar wind along the main axis and an expansion speed gradient of 0.05 ± 0.016 km s^-1 AU^-1. From the model, we derive the age of the north outflow in G35.20-0.74 to be ～ 1.6 × 10^4 yr.
