THE MASS–METALLICITY RELATION WITH THE DIRECT METHOD ON STACKED SPECTRA OF SDSS GALAXIES
THE MASS–METALLICITY RELATION WITH THE DIRECT METHOD ON STACKED SPECTRA OF SDSS GALAXIES
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DOI：
10.1088/0004-637x/765/2/140
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发表时间：
2012-11
期刊：
影响因子：
--
通讯作者：
B. Andrews;P. Martini
中科院分区：
文献类型：
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作者：
B. Andrews;P. Martini
星系恒星质量和气相金属丰度之间的关系是驱动星系演化的主要过程的敏感诊断，即宇宙学气体流入，恒星中的金属生产，以及通过星系风的气体流出。我们采用直接方法测量了Sloan数字巡天的200，000个恒星形成星系的金属丰度，这些星系被堆叠在（1）恒星质量和（2）恒星质量和星星形成率（SFR）的箱中，以显着提高弱[O iii] λ4363和[O ii] λ7320的信噪比，应用直接法需要7330条极光线。这些金属丰度测量跨越了30年的恒星质量，log（M/M）= 7.4-10.5，这使得直接方法质量-金属丰度关系能够同时捕获高质量周转，并比以前采用更不确定的强线方法的研究延长了整整10年的质量。直接法的质量-金属丰度关系在低质量（O/H <$M 12）时急剧上升，直到log（M/M）= 8.9时翻转，在高质量时渐近线为12 + log（O/H）= 8.8。直接方法的质量金属丰度关系有一个陡峭的斜率，较低的周转质量，和一个因素的两到三个更大的依赖SFR比强线质量金属丰度关系。此外，SFR的依赖性似乎单调的恒星质量，不像强线质量金属丰度的关系。我们还测量了星星形成历史的重要示踪物--N/O丰度比，发现了明显的原生和次生氮富集特征。N/O与氧丰度密切相关，与恒星质量的关系更是如此。
The relation between galaxy stellar mass and gas-phase metallicity is a sensitive diagnostic of the main processes that drive galaxy evolution, namely cosmological gas inflow, metal production in stars, and gas outflow via galactic winds. We employed the direct method to measure the metallicities of ∼200,000 star-forming galaxies from the Sloan Digital Sky Survey that were stacked in bins of (1) stellar mass and (2) both stellar mass and star formation rate (SFR) to significantly enhance the signal-to-noise ratio of the weak [O iii] λ4363 and [O ii] λλ7320, 7330 auroral lines required to apply the direct method. These metallicity measurements span three decades in stellar mass from log(M⋆/M☉) = 7.4–10.5, which allows the direct method mass–metallicity relation to simultaneously capture the high-mass turnover and extend a full decade lower in mass than previous studies that employed more uncertain strong line methods. The direct method mass–metallicity relation rises steeply at low mass (O/H ∝ M⋆1/2) until it turns over at log(M⋆/M☉) = 8.9 and asymptotes to 12 + log(O/H) = 8.8 at high mass. The direct method mass–metallicity relation has a steeper slope, a lower turnover mass, and a factor of two to three greater dependence on SFR than strong line mass–metallicity relations. Furthermore, the SFR-dependence appears monotonic with stellar mass, unlike strong line mass–metallicity relations. We also measure the N/O abundance ratio, an important tracer of star formation history, and find the clear signature of primary and secondary nitrogen enrichment. N/O correlates tightly with oxygen abundance, and even more so with stellar mass.