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arXiv 1707.09650astro-ph.SRastro-ph.GA
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南行星状星云V的IFU光谱学:低电离结构

IFU spectroscopy of Southern Planetary Nebulae V: Low-ionization structures

A. Ali, M. A. Dopita

摘要:

在本系列的第5篇论文中,我们使用新的积分场光谱学数据研究了四个南银河系行星状星云Hen 2-141,NGC 5307,IC 2553和PB 6的光谱学和形态学。给出了样品的形貌和电离结构的发射谱线图。此外,这些对象的物理条件,化学成分,和运动学特性的推导。结果表明,PB 6和Hen 2-141为很高激发类,IC 2553和NGC 5307为中高激发类。元素丰度表明,PB 6属Ⅰ型,Hen 2-141和IC 2553属Ⅱ a型,NGC 5307属Ⅱ b/Ⅲ型。这些观测揭示了所有天体中存在定义明确的低电离结构或“\knots“。诊断图显示,这些结的激发机制可能是由星云中心恒星的致密物质的光电离。对其中六个结的物理分析显示,除了它们较低的电子密度外,它们与周围的星云气体没有显着差异。尽管这些节点的低电离发射线增强了,但它们的化学丰度几乎与周围的星云相当,除了NGC 5307节点的氮丰度可能略高。IC 2553的综合光谱显示,几乎所有导致研究人员将其中心恒星描述为弱发射线恒星类型的关键线实际上都是星云起源。

英文摘要:

In this 5th paper of the series, we examine the spectroscopy and morphology of four southern Galactic planetary nebulae Hen 2-141, NGC5307, IC 2553, and PB6 using new integral field spectroscopy data. The morphologies and ionization structures of the sample are given as a set of emission-line maps. In addition, the physical conditions, chemical compositions, and kinematical characteristics of these objects are derived. The results show that PB6 and Hen 2-141 are of very high excitation classes and IC 2553 and NGC5307 are mid to high excitation objects. The elemental abundances reveal that PB6 is of Type I, Hen 2-141 and IC 2553 are of Type IIa, and NGC5307 of Type IIb/III. The observations unveil the presence of well- defined low-ionization structures or \knots" in all objects. The diagnostic diagrams reveal that the excitation mechanism of these knots is probably by photo-ionization of dense material by the nebular central stars. The physical analysis of six of these knots show no significant differences with their surrounding nebular gas, except their lower electron densities. In spite of the enhancement of the low-ionization emission lines of these knots, their chemical abundances are nearly comparable to their surrounding nebulae, with the exception of perhaps slightly higher nitrogen abundances in the NGC5307 knots. The integrated spectrum of IC 2553 reveals that nearly all key lines that have led researchers to characterize its central star as a weak-emission line star type are in fact of nebular origin.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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