METALLICITY INHOMOGENEITIES IN LOCAL STAR-FORMING GALAXIES AS A SIGN OF RECENT METAL-POOR GAS ACCRETION
METALLICITY INHOMOGENEITIES IN LOCAL STAR-FORMING GALAXIES AS A SIGN OF RECENT METAL-POOR GAS ACCRETION
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DOI：
10.1088/0004-637x/783/1/45
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发表时间：
2014-01
期刊：
影响因子：
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通讯作者：
J. Almeida;A. B. Morales-Luis;C. Muñoz-Tuñón;D. Elmegreen;B. Elmegreen;J. I. D. A. D. Canarias-J.-I.-D.-A.-D.-Canarias-1388340798;La Laguna;Tenerife;Spain.;D. Astrof́isica;U. L. Laguna;D. Physics;Astronomy;Vassar College;Ny;USA.;Ibm Research Division;T. J. W. R. Center;S. O. Physics;U. S. Andrews;UK.
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作者：
J. Almeida;A. B. Morales-Luis;C. Muñoz-Tuñón;D. Elmegreen;B. Elmegreen;J. I. D. A. D. Canarias-J.-I.-D.-A.-D.-Canarias-1388340798;La Laguna;Tenerife;Spain.;D. Astrof́isica;U. L. Laguna;D. Physics;Astronomy;Vassar College;Ny;USA.;Ibm Research Division;T. J. W. R. Center;S. O. Physics;U. S. Andrews;UK.
我们测量了沿着七个矮恒星形成星系长轴的电离气体的氧金属丰度。其中的两个，SDSSJ 1647 +21和SDSSJ 2238 +14，在内部区域表现出超过0.5 dex的金属丰度降低，星星形成活动增强。这种行为类似于Sánchez Almeida等人在一些本地蝌蚪星系中观察到的金属丰度下降，并被解释为显示了盘状星系的早期聚集阶段，星星的形成是由外部贫金属气体吸积维持的。与蝌蚪的一致性有几个含义。(1)它证明了除了本地蝌蚪星系以外的星系也呈现出同样的异常金属丰度模式。(2)我们的金属丰度的不均匀性推断使用直接的方法，从而丢弃系统误差通常归因于其他方法。(3)结合蝌蚪的数据，我们的发现表明，金属丰度下降的阈值大约是太阳值的十分之一。虽然具有明显金属丰度下降的星系是罕见的，但负责它们的物理机制可能维持了本地宇宙中星星形成活动的重要部分。我们认为，星星形成依赖的质量金属丰度的关系，以及其他一般属性其次是大多数本地盘星系，自然被解释为原始气体的副作用。贫金属气体吸积的替代品进行检查。
We measure the oxygen metallicity of the ionized gas along the major axis of seven dwarf star-forming galaxies. Two of them, SDSSJ1647+21 and SDSSJ2238+14, show ≃0.5 dex metallicity decrements in inner regions with enhanced star formation activity. This behavior is similar to the metallicity drop observed in a number of local tadpole galaxies by Sánchez Almeida et al., and was interpreted as showing early stages of assembling in disk galaxies, with the star formation sustained by external metal-poor gas accretion. The agreement with tadpoles has several implications. (1) It proves that galaxies other than the local tadpoles present the same unusual metallicity pattern. (2) Our metallicity inhomogeneities were inferred using the direct method, thus discarding systematic errors usually attributed to other methods. (3) Taken together with the tadpole data, our findings suggest a threshold around one-tenth the solar value for the metallicity drops to show up. Although galaxies with clear metallicity drops are rare, the physical mechanism responsible for them may sustain a significant part of the star formation activity in the local universe. We argue that the star formation dependence of the mass–metallicity relationship, as well as other general properties followed by most local disk galaxies, is naturally interpreted as side effects of pristine gas infall. Alternatives to the metal-poor gas accretion are examined as well.