CHAOS. VI. Direct Abundances in NGC 2403
CHAOS. VI. Direct Abundances in NGC 2403
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DOI：
10.3847/1538-4357/abf8b9
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发表时间：
2021-05
期刊：
影响因子：
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通讯作者：
N. Rogers;E. Skillman;R. Pogge;D. Berg;J. Moustakas;K. Croxall;Jiayi Sun
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文献类型：
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作者：
N. Rogers;E. Skillman;R. Pogge;D. Berg;J. Moustakas;K. Croxall;Jiayi Sun
我们报告了星系NGC 2403的直接丰度，这是由螺旋的化学丰度（CHAOS）项目观测到的。利用大型双筒望远镜上的多目标双摄谱仪，我们观测到两个H区，其R g /R e范围为0.18-2.31。32个H区包含至少一个极光线检测，我们共检测到122个温度敏感的极光线。在这里，我们第一次使用T - e -T - e图中的本征散射，加上测量温度的不确定度的正交，来确定从不同电离区的测量推断出的一个电离区的电子温度的不确定度。然后，我们使用所有可用的温度数据在H ii区域内，以获得每个电离区内的加权平均温度。我们使用这种新的温度优先排序方法重新推导了所有混沌星系的氧丰度，我们发现梯度与Berg等人最近的研究结果一致。NGC 2403的直接氧丰度梯度为- 0.09（±0.03）dex/R e，固有色散为0.037（±0.017）index； N/O丰度梯度为- 0.17（±0.03）dex/R e，固有色散为0.060（±0.018）index。为了进行直接比较，我们使用Berg等人早期研究NGC 2403的谱线强度，发现他们重新计算的O/H和N/O梯度值与我们的结果一致。
We report the direct abundances for the galaxy NGC 2403 as observed by the CHemical Abundances Of Spirals (CHAOS) project. Using the Multi-Object Double Spectrograph on the Large Binocular Telescope, we observe two fields with H ii regions that cover an R g /R e range of 0.18–2.31. Thirty-two H ii regions contain at least one auroral line detection, and we detect a total of 122 temperature-sensitive auroral lines. Here, for the first time, we use the intrinsic scatter in the T e –T e diagrams, added in quadrature to the uncertainty on the measured temperature, to determine the uncertainty on an electron temperature inferred for one ionization zone from a measurement in a different ionization zone. We then use all available temperature data within a H ii region to obtain a weighted-average temperature within each ionization zone. We rederive the oxygen abundances of all CHAOS galaxies using this new temperature prioritization method, and we find that the gradients are consistent with the results of a recent study of Berg et al. For NGC 2403, we measure a direct oxygen abundance gradient of −0.09(±0.03) dex/R e , with an intrinsic dispersion of 0.037(±0.017) dex and a N/O abundance gradient of −0.17(±0.03) dex/R e with an intrinsic dispersion of 0.060(±0.018) dex. For direct comparison, we use the line intensities from an earlier study of NGC 2403 by Berg et al. and find their recomputed values for the O/H and N/O gradients are consistent with ours.