电离结构对NGC 7009中ORL和CELs的不一致性动力学的影响
The Discrepant Kinematics of ORLs and CELs in NGC 7009 as a Function of Ionization Structure
摘要：
我们提出了空间和速度分辨阶梯光谱的NGC 7009获得的UVES光谱仪在欧洲南方天文台的甚大望远镜。我们的目标是分析与电子的重组和碰撞激发的发射线的运动学，以确定是否相似或差异可能是有用的，在阐明众所周知的丰度差异来自他们。我们构建重组，荧光，电荷转移和碰撞激发线的位置-速度图。我们发现一个等离子体成分发射的C II，N II，O II和Ne II的复合线的运动学是不一致的：它们是不相容的电离结构来自所有其他证据和运动学来自所有这些线出乎意料地非常相似。我们发现直接证据的重组贡献[N II] 5755。一旦考虑到，来自[N II]、[O III]和[Ne III]的电子温度在给定的位置和速度下一致。从[O II]和[Ar IV]导出的电子密度与直接成像和氢发射的分布一致。C II，N II，O II和Ne II线的运动学与[O III]和[Ne III]禁发射的运动学不一致，表明有一个额外的等离子体成分的复合发射，产生于不同的体积，从NGC 7009内的母离子产生禁发射。因此，从任一类型的线导出的化学丰度仅对于产生它们的血浆组分是正确的。除了[N II] 5755之外，我们没有发现通常用于测定电离星云化学丰度的禁戒线的异常，因此从它们得到的丰度对于它们产生的介质来说应该是可靠的。
英文摘要：
We present spatially- and velocity-resolved echelle spectroscopy for NGC 7009 obtained with the UVES spectrograph at the European Southern Observatory's Very Large Telescope. Our objective is to analyze the kinematics of emission lines excited by recombination and collisions with electrons to determine whether similarities or differences could be useful in elucidating the well-known abundance discrepancy derived from them. We construct position-velocity maps for recombination, fluorescence, charge transfer, and collisionally-excited lines. We find a plasma component emitting in the C II, N II, O II, and Ne II recombination lines whose kinematics are discrepant: They are incompatible with the ionization structure derived from all other evidence and the kinematics derived from all of these lines are unexpectedly very similar. We find direct evidence for a recombination contribution to [N II] 5755. Once taken into account, the electron temperatures from [N II], [O III], and [Ne III] agree at a given position and velocity. The electron densities derived from [O II] and [Ar IV] are consistent with direct imaging and the distribution of hydrogen emission. The kinematics of the C II, N II, O II, and Ne II lines does not coincide with the kinematics of the [O III] and [Ne III] forbidden emission, indicating that there is an additional plasma component to the recombination emission that arises from a different volume from that giving rise to the forbidden emission from the parent ions within NGC 7009. Thus, the chemical abundances derived from either type of line are correct only for the plasma component from which they arise. Apart from [N II] 5755, we find no anomaly with the forbidden lines usually used to determine chemical abundances in ionized nebulae, so the abundances derived from them should be reliable for the medium from which they arise.
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