YOUNG PLANETARY NEBULAE: HUBBLE SPACE TELESCOPE IMAGING AND A NEW MORPHOLOGICAL CLASSIFICATION SYSTEM
YOUNG PLANETARY NEBULAE: HUBBLE SPACE TELESCOPE IMAGING AND A NEW MORPHOLOGICAL CLASSIFICATION SYSTEM
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年轻的行星状星云：哈勃太空望远镜成像和新的形态分类系统
DOI：
10.1088/0004-6256/141/4/134
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
Gregory Villar
中科院分区：
文献类型：
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作者：
R. Sahai;M. Morris;Gregory Villar
利用哈勃太空望远镜拍摄的119个年轻行星状星云（PNs）的图像，其中大部分以前没有发表过，我们为这些天体设计了一个全面的形态分类系统。这个系统概括了最近设计的行星前星云系统，行星前星云是PN的直接祖先。与以前的分类研究不同，我们主要关注年轻的PN，而不是所有的PN，因为前者最好地显示了在形成过程的第一和初级阶段起主导作用的物理过程对它们的影响或对称性。较老的PN会发展出不稳定性，与周围的星际介质相互作用，并受到光电离前沿的影响，所有这些都模糊了早期强加的基本对称性和几何形状。我们的分类系统旨在最大限度地减少对PN样本中不同形状和结构的基本物理原因的偏见，然而，在许多情况下，物理原因很容易由几何形状以及在某些系统中测量的运动学沿着提出。在我们的系统中的次要特征，如ansae，表明射流对移动较慢的，以前的风的影响;腰部是一个强大的赤道物质集中的签名，无论是流出或在绑定开普勒磁盘，和点对称性表明长期的趋势，大概是岁差，在快速，准直流出的中心驱动器的方向。
Using Hubble Space Telescope images of 119 young planetary nebulae (PNs), most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-planetary nebulae, which are the immediate progenitors of PNs. Unlike previous classification studies, we have focused primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many cases, physical causes are readily suggested by the geometry, along with the kinematics that have been measured in some systems. Secondary characteristics in our system, such as ansae, indicate the impact of a jet upon a slower-moving, prior wind; a waist is the signature of a strong equatorial concentration of matter, whether it be outflowing or in a bound Keplerian disk, and point symmetry indicates a secular trend, presumably precession, in the orientation of the central driver of a rapid, collimated outflow.