Chemical Composition of Two H II Regions in NGC 6822 Based on VLT Spectroscopy
Chemical Composition of Two H II Regions in NGC 6822 Based on VLT Spectroscopy
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基于 VLT 光谱的 NGC 6822 中两个 H II 区域的化学成分
DOI：
10.1086/444557
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
M. Ruiz
中科院分区：
文献类型：
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作者：
A. Peimbert;M. Peimbert;M. Ruiz
我们给出了本族群不规则星系NGC6822的V区和X区的长缝光谱测量结果。数据由3450-7500ä范围内的VLT FORS观测数据组成。我们用不同的谱线强度比得到了电子的温度和密度。基于复合线，我们得到了氦、碳和氧相对于氢的丰度；这些元素之间的丰度比几乎与星云的温度结构无关。我们还根据碰撞激发谱线测定了N、O、Ne、S、Cl和Ar丰度；这些丰度与H丰度的比值强烈依赖于星云的温度结构。将NGC6822V与太阳、猎户座星云、SMC中的NGC346和LMC中的30个剑鱼座的化学成分进行了比较。从复合线得到的O/H值与Venn和他的同事从NGC6822中的两个A型超巨星得到的值符合得很好。
We present long-slit spectrophotometry of regions V and X of the Local Group irregular galaxy NGC 6822. The data consist of VLT FORS observations in the 3450-7500 Å range. We have obtained electron temperatures and densities using different line intensity ratios. We have derived the He, C, and O abundances relative to H based on recombination lines; the abundance ratios among these elements are almost independent of the temperature structure of the nebulae. We have also determined 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 nebulae. The chemical composition of NGC 6822 V is compared with those of the Sun, the Orion Nebula, NGC 346 in the SMC, and 30 Doradus in the LMC. The value of O/H derived from recombination lines is in good agreement with that derived by Venn and coworkers from two A-type supergiants in NGC 6822.