The UC-HII region of MWC 349A is the prototype of an ionized wind driven by a massive star surrounded by a disk. Recent high angular resolution observations of the millimeter recombination lines have shown that the disk rotates with a Keplerian law in its outer parts. However, the kinematics of innermost regions in the UC-HII region of MWC 349A is still unknown, in particular the radius where the wind is launched from the disk. We performed hydrogen recombination line observations with the Heterodyne Instrument for the Far Infrared (HIFI) onboard the Herschel Space Observatory to study the kinematics of its innermost regions by studying their spectral features. In addition to the two laser peaks, we report the first detection of two new components that are blueshifted with respect to the laser peaks for all the recombination lines with principal quantum number n<22. These new spectral features originate from the region where the wind is ejected from the disk. We used our 3D non-LTE radiative transfer model for recombination lines (MORELI) to show that these features are consistent with the wind being ejected at a radius of about 24 AU from the star, which supports magnetohydrodynamic wind models.
翻译:MWC 349A 的 CUC-HII 区域 MWC 349A 是一个由磁盘环绕的巨型恒星驱动的离子化风的原型。最近对毫米再组合线的高角分辨率观测显示,磁盘在其外部部分以开普勒定律旋转。然而,仍然不知道UC-HII 区域最深层区域的动态,特别是从磁盘上发射风的半径。我们与赫歇尔空间观测站的远红外线Heterodyne 仪器进行了氢再组合线观测,以研究其内部区域的动态特征。除了两个激光峰值外,我们还报告首次探测了与激光峰相关的两个新组成部分,这些新部分与所有再组合线的激光峰值有关,主要量号为n < 22。这些新的光谱特征来自从磁盘中喷射风的区域。我们用3D非LTE 热转换模型来研究其内部最深层区域的动态特征,研究其内部区域的动态特征。除了两个激光峰值之外,我们还报告首次探测到所有再组合线的激光峰值为AULIFIFILIFIFL 的这些模型,以显示这些恒度。