New Light on the Search for Low-Metallicity Galaxies
New Light on the Search for Low-Metallicity Galaxies
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DOI：
10.1046/j.1365-8711.2002.05041.x
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发表时间：
2001-10
影响因子：
1
通讯作者：
G. Denicoló;R. Terlevich;Elena Terlevich IoA;Cambridge;UK.;Inaoe;Puebla;Mexico.
中科院分区：
文献类型：
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作者：
G. Denicoló;R. Terlevich;Elena Terlevich IoA;Cambridge;UK.;Inaoe;Puebla;Mexico.
我们提出了一个简单的金属丰度估计的基础上的对数[N ii] λ6584/Hα比，以下N2，我们设想将成为非常有用的排名星系的金属丰度序列从红移测量质量的数据，即使是中等低的光谱分辨率。我们已经校准了N2估计使用汇编H II星系具有准确的氧丰度，加上光电离模型，涵盖了广泛的丰度。模型和观测结果的比较表明，原生氮和次生氮对金属丰度的相关范围都很重要。N2估计值遵循与log（O/H）的线性关系，适用于样本覆盖的整个丰度范围，从大约1/50到太阳值的两倍[7.2<12+log（O/H）<9.1]。我们认为（[Sii] λλ 6717，6731/Hα）比值（以下简称S2）也可以作为一个粗略的金属丰度指标。由于其大的分散性，S2估计值仅在金属丰度非常低的系统中有用，其中[N ii] λ6584未被检测到，或者在[N ii] λ6584与Hα混合的低分辨率光谱中。
We present a simple metallicity estimator based on the logarithmic [N ii] λ6584/Hα ratio, hereafter N2, which we envisage will become very useful for ranking galaxies in a metallicity sequence from redshift survey-quality data even for moderately low spectral resolution. We have calibrated the N2 estimator using a compilation of H ii galaxies having accurate oxygen abundances, plus photoionization models covering a wide range of abundances. The comparison of models and observations indicates that both primary and secondary nitrogen are important for the relevant range of metallicities. The N2 estimator follows a linear relation with log(O/H) that holds for the whole abundance range covered by the sample, from approximately 1/50th to twice the Solar value [7.2<12+log(O/H)<9.1]. We suggest that the ([S ii] λλ6717,6731/Hα) ratio (hereafter S2) can also be used as a rough metallicity indicator. Because of its large scatter the S2 estimator will be useful only in systems with very low metallicity, where [N ii] λ6584 is not detected or in low-resolution spectra where [N ii] λ6584 is blended with Hα.