Exposure of details of the formation of massive stars

大质量恒星的诞生过程是目前恒星形成研究中未解之谜之一。大质量恒星的主要形成过程是盘吸积还是合并仍然是一个悬而未决的问题。该项目的目标是在毫米波长范围内的干涉观测中解决这一过程的细节。第一步，我们关注已有的数据。由于最近用VLA和高原de Bure干涉仪的成功测量，我们在8-10M的⊙星（AFGL 490）附近检测到不同的分子种类。对观测数据的初步观察表明，气体正在向一个半径为1500天文单位的盘状结构方向流入。此外，沿高速流出线新发现的弓形激波支持正在进行的非稳态质量吸积的证据。在观测结果的建模方面，我们想要估计探测到的气体的物理性质（温度和密度分布，气体运动）以及质量吸积率。此外，我们打算研究一个密集的20,000 AU大型棒状气体结构的性质，该结构垂直于高速出口并以大质量恒星为中心。我们想要回答这个问题，这个气体棒（或圆盘？）在恒星形成过程中扮演什么角色。在我们项目的第二步中，我们希望扩展我们对更明亮的、非常年轻的恒星周围类似结构的搜索，以找出这些结构是大质量恒星形成过程中的共同特征，还是我们选择的目标的特殊配置。

The birth process of massive stars is one of the unresolved mysteries of present research in star formation. Whether the dominant formation process for massive stars is disk accretion or coalescence is still an open question. The goal of this project is to resolve details of this process in terms of interferometric observations in the mm wavelength range. In a first step, we focus on already available data. Due to successful recent measurements with the VLA and the Plateau de Bure Interferometer, we detected different molecular species in the close vicinity of a 8-10M⊙-star (AFGL 490). A first look at the observational data implies on-going gas infall towards a disk-like structure with a radius of 1500 AU. Additionally newly discovered bow shocks along the line of the high-velocity outflow support evidence for on-going non-steady state mass accretion. In terms of modeling of the observational results, we would like to estimate physical properties of the detected gas (temperature and density profile, gas motion) as well as the mass accretion rate. Furthermore, we intend to study the nature of a dense 20 000 AU large bar-like gas structure perpendicularly located to the high-velocity outflow and centered at the massive star. We want to answer the question which role this gas bar (or disk ?) plays during the star formation. In a second step of our project, we would like to extend our search for comparable structures around more luminous, very young stars to find out whether these structures are common features during massive star formation or a special configuration in case of our selected target.