标题： 恒星流出：通往过去的窗口 显示英文标题

标题： Protostellar Outflows: a window to the past

摘要： 在低质量恒星形成的早期阶段，间歇性吸积导致高速喷出物子弹的抛射，这些子弹携带了驱动原恒星吸积历史的化石记录。 我们展示了44个关于$1\,\mathrm{M}_{\odot}$核心的SPH模拟，涵盖了广泛的初始条件，并且跟踪这些核心五个自由落体时间。 单个原恒星由吞噬粒子表示，吞噬粒子使用子网格模型发射间歇性喷流。 Optics算法用于识别喷流中的单个间歇性子弹。 然后利用整体喷流和单个子弹的参数来估算喷流的年龄和能量，以及触发它的吸积事件；并且评估如果忽略观测不确定性及选择效应（如倾角）这些估算的可靠性。 在常用的估算喷流年龄的方法中，在演化早期阶段，基于瓣的长度和前进速度的方法似乎最可靠，而在后期阶段，基于喷流空腔宽度和前进速度的方法则最可靠。 我们描述了一种几乎同样准确且在整个演化过程中可靠的全新方法。 此外，我们还展示了如果每个瓣至少包含两个子弹，可以从子弹的动力学中精确重建原恒星的吸积历史。 喷流携带的大约比原恒星最初抛射的质量多十倍的物质。 显示英文摘要

摘要： During the early phases of low-mass star formation, episodic accretion causes the ejection of high-velocity outflow bullets, which carry a fossil record of the driving protostar's accretion history. We present 44 SPH simulations of $1\,\mathrm{M}_{\odot}$ cores, covering a wide range of initial conditions, and follow the cores for five free-fall times. Individual protostars are represented by sink particles, and the sink particles launch episodic outflows using a subgrid model. The Optics algorithm is used to identify individual episodic bullets within the outflows. The parameters of the overall outflow and the individual bullets are then used to estimate the age and energetics of the outflow, and the accretion events that triggered it; and to evaluate how reliable these estimates are, if observational uncertainties and selection effects (like inclination) are neglected. Of the commonly used methods for estimating outflow ages, it appears that those based on the length and speed of advance of the lobe are the most reliable in the early phases of evolution, and those based on the width of the outflow cavity and the speed of advance are most reliable during the later phases. We describe a new method that is almost as accurate as these methods, and reliable throughout the evolution. In addition we show how the accretion history of the protostar can be accurately reconstructed from the dynamics of the bullets if each lobe contains at least two bullets. The outflows entrain about ten times more mass than originally ejected by the protostar.