AI 中文总结
本研究通过ALMA观测S255N SMA3的SiO与CS发射，发现该源的高速准直双极喷流，证实密集星团环境中也能形成有序盘驱动喷流。
AI 中文摘要
我们呈现了对S255IR区域致密源SMA3的ALMA Band 6观测结果，分析了SiO（J = 5-4、6-5）和CS（J = 5-4）的发射线，以表征其外流的结构与运动学特征。数据揭示了由SiO示踪的高度准直双极喷流，其视线方向速度高达±60 km s⁻¹，去投影速度约±80 km s⁻¹，在约5800 au的空间范围内准直比约为4.7，推断的动力学年龄为343年。位置-速度图显示出连续的三角形速度结构，与稳态盘风而非偶发或X风驱动的流一致。激发分析得出SiO的特征温度约为42 K，我们还推导了喷流的质量、动量和动能，表明这是一个致密、质量加载的分子外流。发射线呈现出明显的化学和运动学分化：SiO示踪高速喷流的核心，而CS在原恒星附近以较低速度被观测到，仅在更大距离处达到高速。尽管形成于大质量恒星形成的密集星团区域，该喷流仍表现出高度的对称性、准直性和动力学连贯性，这通常与孤立或较不拥挤区域形成的原恒星相关。这表明，即使在大质量恒星形成特有的密集竞争环境中，也能启动并维持有序、窄准直的盘驱动喷流。
英文摘要
We present ALMA Band 6 observations of the compact source SMA3 in the S255IR region, analysing both SiO (J = 5-4, 6-5) and CS (J = 5-4) emission to characterise the structure and kinematics of its outflow. The data reveal a highly collimated bipolar jet traced by SiO, reaching line-of-sight velocities of up to $\pm$60 km s$^{-1}$ and de-projected velocities of $\pm$~80 km s$^{-1}$, with a collimation ratio of ~4.7 over a spatial extent of ~5800 au. The inferred dynamical age is 343 yr. Position-velocity diagrams exhibit a continuous velocity structure with triangular morphology, consistent with a steady disk wind rather than an episodic or X-wind-driven flow. Excitation analysis yields a characteristic SiO temperature of ~42 K, and we derive the jet mass, momentum, and kinetic energy which are indicative of a dense, mass-loaded molecular outflow. The emission shows clear chemical and kinematic differentiation: SiO traces the high-velocity jet spine, while CS is observed at lower velocities close to the protostar, and only reaches high velocities at larger distances. Despite forming within a clustered high-mass star-forming region, the jet exhibits a high degree of symmetry, collimation, and dynamical coherence more commonly associated with protostars forming in isolation or less crowded star-forming regions. This demonstrates that well-ordered, narrowly collimated, disk-driven jets can be launched and maintained even in the dense, competitive environments characteristic of high-mass star formation.
Comments11 pages, 9 figures. Accepted for publication by MNRAS
