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首页> 外文期刊>The Astrophysical journal >VERY LARGE TELESCOPE ECHELLE SPECTROPHOTOMETRY OF THE PLANETARY NEBULA NGC 5307 AND TEMPERATURE VARIATIONS
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VERY LARGE TELESCOPE ECHELLE SPECTROPHOTOMETRY OF THE PLANETARY NEBULA NGC 5307 AND TEMPERATURE VARIATIONS

机译：行星状星云NGC 5307的非常大的遥镜分光光度法和温度变化

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摘要

Echelle spectrophotometry of the planetary nebula NGC 5307 is presented. The data consist of Very Large Telescope Ultraviolet Visual Echelle Spectrograph observations in the 3100-10360 A range. Electron temperatures and densities have been determined using different line intensity ratios. We determine the H, He, C, and O abundances based on recombination lines; these abundances are almost independent of the temperature structure of the nebula. We also determine the N, O, Ne, S, Cl, and Ar abundances based on collisionally excited lines; the ratios of these abundances relative to that of H depend strongly on the temperature structure of the nebula. From the O Ⅱ/[O Ⅲ] line intensity ratios we find a t~2 = 0.056 +- 0.005. The chemical composition of NGC 5307 is compared with those of the Sun and the Orion Nebula. From the study of the relative intensities of the O Ⅱ recombination lines of multiplet 1 in this and other nebulae, it is found that for electron densities smaller than about 5000 cm~(-3) collisional redistribution is not complete; this effect has to be taken into account to derive the O abundances for those cases in which not all the lines of the multiplet are observed. From the O Ⅱ λ4649 versus N_e(Cl Ⅲ) diagram we find a critical electron density of 1325 cm~(-3) for collisional redistribution of the O Ⅱ lines of multiplet 1. Based on this diagram, we also argue that the O Ⅱ and the [O Ⅲ] lines originate in the same regions. We also find that the radial velocities and the FWHM of the O Ⅱ and [O Ⅲ] lines in NGC 5307 are similar, supporting the previous result. These two results imply that for NGC 5307 and probably for many other gaseous nebulae chemical inhomogeneities are not responsible for the large temperature fluctuations observed.
机译：介绍了星云NGC 5307的Echelle分光光度法。数据由3100-10360 A范围内的超大型望远镜紫外可见埃歇尔光谱仪观测值组成。已经使用不同的线强度比来确定电子温度和密度。我们根据重组线确定H，He，C和O的丰度;这些丰度几乎与星云的温度结构无关。我们还根据碰撞激发线确定N，O，Ne，S，Cl和Ar的丰度;这些丰度相对于H的比率在很大程度上取决于星云的温度结构。从OⅡ/ [OⅢ]线强度比，我们发现t〜2 = 0.056 +-0.005。将NGC 5307的化学成分与太阳和猎户星云的化学成分进行了比较。通过对该多重和多重星云中多重态1的OⅡ重组线的相对强度的研究，发现对于小于约5000 cm〜（-3）的电子密度，碰撞重新分布是不完整的。对于未观察到多重线的所有线的情况，必须考虑这种影响才能得出O丰度。从OⅡλ4649与N_e（ClⅢ）的关系图中，我们可以发现多重电子1的OⅡ线的碰撞重分布的临界电子密度为1325 cm〜（-3）。基于该图，我们还认为OⅡ [OⅢ]线起源于同一地区。我们还发现NGC 5307中OⅡ和[OⅢ]线的径向速度和FWHM相似，支持了先前的结果。这两个结果表明，对于NGC 5307以及可能对于许多其他气态星云，化学不均匀性与观察到的较大温度波动无关。

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