New calibrations for abundance determinations in H ii regions
New calibrations for abundance determinations in H ii regions
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DOI：
10.1093/mnras/stw238
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发表时间：
2016-01
影响因子：
4.8
通讯作者：
L. Pilyugin;L. Pilyugin;L. Pilyugin;E. Grebel
中科院分区：
文献类型：
--
作者：
L. Pilyugin;L. Pilyugin;L. Pilyugin;E. Grebel
本文提出了计算HII区氧丰度与三条强发射线R_2，R_3，N_2（R校准）或S_2，R_3，N_2（S校准）强度的简单关系式。使用对应方法的313个参考HII区域的样本作为校准数据点。氮丰度的测定，R校准，关系也被构建。我们发现，仅用R_2和N_2（或S_2和N_2对氧）两条强线的强度，就可以估算高金属丰度HII区的氧和氮丰度。给出了相应的二维关系。与现有的校准关系相比，建议的校准关系具有相当大的优点。首先，在整个金属丰度范围内，通过建议的校准估计的氧和氮丰度与Te基丰度在~0.1 dex内一致，即，基于校准的丰度的相对准确度为0.1 dex。虽然我们为高金属丰度和低金属丰度天体构建了不同的关系，但这两者之间的分离可以简单地从N_2线的强度获得。此外，高和低金属丰度关系的适用范围对于相邻金属丰度重叠，即，过渡区消失。其次，两种建议校准产生的氧气丰度彼此非常一致。事实上，R基和S基氧丰度在大多数情况下在约0.05 dex内一致，超过3000个HII区光谱。
Simple relations for deriving the oxygen abundance in HII regions with intensities of the three strong emission lines R_2, R_3, and N_2 (R calibration) or S_2, R_3, and N_2 (S calibration) in their spectra are suggested. A sample of 313 reference HII regions of the counterpart method is used as calibrating data points. Relations for the determination of nitrogen abundances, the R calibration, are also constructed. We find that the oxygen and nitrogen abundances in high-metallicity HII regions can be estimated using the intensities of the two strong lines R_2 and N_2 (or S_2 and N_2 for oxygen) only. The corresponding two-dimensional relations are provided. There are considerable advantages of the suggested calibration relations as compared to the existing ones. First, the oxygen and nitrogen abundances estimated through the suggested calibrations agree with the Te-based abundances within ~0.1 dex over the whole metallicity range, i.e., the relative accuracy of the calibration-based abundances is 0.1 dex. Although we constructed distinct relations for high- and low-metallicity objects, the separation between these two can be simply obtained from the intensity of the N_2 line. Moreover, the applicability ranges of the high- and low-metallicity relations overlap for adjacent metallicities, i.e., the transition zone disappears. Second, the oxygen abundances produced by the two suggested calibrations are in remarkable agreement with each other. In fact, the R-based and S-based oxygen abundances agree within ~0.05 dex in the majority of cases for more than three thousand HII region spectra.