Testing metallicity indicators at z ~ 1.4 with the gravitationally lensed galaxy CASSOWARY 20?
Testing metallicity indicators at z ~ 1.4 with the gravitationally lensed galaxy CASSOWARY 20?
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使用引力透镜星系 CASSOWARY 20 测试 z ~ 1.4 处的金属丰度指标？
DOI：
10.1093/mnras/stu287
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发表时间：
2014
影响因子：
4.8
通讯作者：
James B
中科院分区：
文献类型：
--
作者：
James B
我们展示了对CASSOWARY 20 （CSWA 20）的x -射手观测，这是一个恒星形成（SFR ~ 6 M⊙yr−1）星系，atz= 1.433，被一个巨大的前景星系atz= 0.741产生的引力透镜放大了11.5倍。我们利用温度和密度敏感的发射线分析了cswa20的Hiiregions的综合物理性质。我们发现氧的丰度是太阳的1/7，而碳的丰度是太阳的50倍。异常低的碳氧比可能表明化学富集的时间尺度特别快。x -射手的宽波长覆盖范围使我们能够使用五种不同的方法来确定cswa20的金属丰度，其中三种基于Hiiregions的发射线，两种基于大质量恒星大气中形成的吸收特征。在每种方法的不确定性因子为~ 2的范围内，所有五个估计值都是一致的。从我们的方向看，cswa20的星际介质（ISM）只部分覆盖了恒星形成区；特别是中性离子和第一离子的吸收谱线特别弱。我们发现了ISM大规模流出的证据，其速度高达750 km s - 1，类似于在其他高zz星系中测量到的值，这些星系维持着更高的恒星形成率。
We present X-shooter observations of CASSOWARY 20 (CSWA 20), a star-forming (SFR ∼ 6 M⊙yr−1) galaxy atz= 1.433, magnified by a factor of 11.5 by the gravitational lensing produced by a massive foreground galaxy atz= 0.741. We analysed the integrated physical properties of the Hiiregions of CSWA 20 using temperature- and density-sensitive emission lines. We find the abundance of oxygen to be ∼1/7 of solar, while carbon is ∼50 times less abundant than in the Sun. The unusually low C/O ratio may be an indication of a particularly rapid time-scale of chemical enrichment. The wide wavelength coverage of X-shooter gives us access to five different methods for determining the metallicity of CSWA 20, three based on emission lines from Hiiregions and two on absorption features formed in the atmospheres of massive stars. All five estimates are in agreement, within the factor of ∼2 uncertainty of each method. The interstellar medium (ISM) of CSWA 20 only partially covers the star-forming region as viewed from our direction; in particular, absorption lines from neutrals and first ions are exceptionally weak. We find evidence for large-scale outflows of the ISM with speeds of up 750 km s−1, similar to the values measured in other high-zgalaxies sustaining much higher rates of star formation.