标题： 巴纳德68中芯-芯碰撞的证据 显示英文标题

标题： Evidence for Core-Core Collision in Barnard 68

摘要： 预恒星核Barnard 68（B68）是研究恒星形成初始条件和化学过程的典型源。先前的数值模拟表明东南子弹正在撞击B68的主要部分。为了获得更多的观测证据，在30 GHz处使用Effelsberg 100米望远镜进行了基态SO（$1_0-0_1$）发射线的测绘观测。基于从SO推导出的速度场和通道图，清楚地检测到了三个速度分量。主体的速度场表明存在旋转，并且可以用刚体旋转模型很好地拟合。子弹与主核心之间的测量径向速度差异约为0.4 km s$^{-1}$，这几乎等于先前数值模拟得到的速度。因此，子弹很可能正在撞击B68的旋转主体部分。进行了1D球形非局部热平衡蒙特卡洛辐射转移RATRAN代码以通过分析观测的速度积分强度来推导SO的径向丰度分布。在距核心60$^{\prime\prime}$（0.02 pc）半径内，SO被耗尽。在主核心中心以外大于60$^{\prime\prime}$的半径上，丰度保持恒定，为2.0$\times$10$^{-9}$。在子弹与主核心界面处，丰度增强，表明子弹与主核心碰撞产生了冲击波。总之，根据动力学和化学分析，我们的观测结果支持了先前提出的B68中的核心-核心碰撞场景。 显示英文摘要

摘要： The prestellar core Barnard 68 (B68) is a prototypical source to study the initial conditions and chemical processes of star formation. A previous numerical simulation suggested the southeastern bullet is impacting on the main body of B68. In order to obtain more observational evidence, mapping observations of the ground state SO ($1_0-0_1$) emission line at 30 GHz were made with the Effelsberg 100 m telescope. Based on the velocity field and channel maps derived from SO, three velocity components were clearly detected. The velocity field of the main body indicates rotation and is well fitted by a solid-body rotation model. The measured radial velocity difference between the bullet and the main core is about 0.4 km s$^{-1}$, which is almost equal to the velocity obtained by the previous numerical simulation. Therefore, the bullet is most likely impacting onto the rotating main body of B68. A 1D spherical non-LTE Monte-Carlo radiation transfer RATRAN code is performed to derive the radial abundance profile of SO by analyzing the observed velocity-integrated intensity. SO is depleted inside a 60$^{\prime\prime}$ (0.02 pc) radius from the core. The abundance stays constant at 2.0$\times$10$^{-9}$ for radii larger than 60$^{\prime\prime}$ from the center of the main core. The abundance is enhanced at the interface of the bullet and the main core indicating that shock waves were produced by the collision between the bullet and the main core. In conclusion, based on the kinematical and chemical analysis, our observational results support the previously proposed core-core collision scenario in B68.