多极行星状星云中错位角的分布
The distribution of misalignment angles in multipolar planetary nebulae
AI总结：
本研究测量数十个多极行星状星云相邻对称轴的投影错位角，发现其符合20至60度范围内的有限随机三维角分布，并指出该分布可能源于双星轨道角动量与巨星包层对流提供的随机角动量共同塑造吸积盘喷流。
摘要：
我们测量了数十个多极行星状星云相邻对称轴在天球平面上的投影角，发现这些错位角的分布意味着一个限制在<60度的随机三维角分布。我们将对称轴定义为连接两个相反瓣（气泡）或团块的直线。我们构建了投影角alpha的累积分布函数，发现相邻对称轴之间三维角delta的完全随机分布，即不相关方向，不符合观测分布。对观测分布的良好拟合是相邻对称轴之间三维角的有限随机分布，即在20<delta<60度范围内的随机分布。我们假设沿伴星周围吸积盘角动量轴的一对喷流塑造了每个对称轴。这种有限的随机分布可能源于向吸积盘提供角动量的两个量级相当的来源：一个具有固定方向，另一个具有随机方向变化。我们讨论了一种情景，其中固定轴的角动量源是双星轨道角动量，而随机角动量源是由于失质量巨星前身星的剧烈包层对流。
英文摘要：
We measure the projected angle on the plane of the sky between adjacent symmetry axes of tens of multipolar planetary nebulae and find that the distribution of these misalignment angles implies a random three-dimensional angle distribution limited to <60 degrees. We identify a symmetry axis as a line connecting two opposite lobes (bubbles) or clumps. We build a cumulative distribution function of the projected angles alpha and find that an entirely random distribution of the three-dimensional angles delta between adjacent symmetry axes, namely, uncorrelated directions, does not fit the observed one. A good fit to the observed distribution is a limited random distribution of the three-dimensional angle between adjacent symmetry axes, i.e., random distribution in the range of 20<delta<60 degrees. We assume that a pair of jets along the angular momentum axis of an accretion disk around the companion shape each symmetry axis. The limited random distribution might result from two sources of angular momentum to the accretion disks with comparable magnitude: one with a fixed direction and one with a stochastic direction variation. We discuss a scenario where the fixed-axis angular momentum source is the binary orbital angular momentum, while the stochastic source of angular momentum is due to the vigorous envelope convection of the mass-losing giant progenitor.
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