ALMA REVEALS WEAK [N ii] EMISSION IN “TYPICAL” GALAXIES AND INTENSE STARBURSTS AT z = 5–6
ALMA REVEALS WEAK [N ii] EMISSION IN “TYPICAL” GALAXIES AND INTENSE STARBURSTS AT z = 5–6
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DOI：
10.3847/0004-637x/832/2/151
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发表时间：
2016-07
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通讯作者：
R. Pavesi;D. Riechers;P. Capak;C. Carilli;C. Sharon;G. Stacey;A. Karim;N. Scoville;V. Smolčić
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文献类型：
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作者：
R. Pavesi;D. Riechers;P. Capak;C. Carilli;C. Sharon;G. Stacey;A. Karim;N. Scoville;V. Smolčić
本文报道了利用阿塔卡马大（亚）毫米波阵列（阿尔马）对三个星系中z = 5-6的代表性样品的[N ii] 205 μm精细结构谱线辐射的干涉测量。这些星系以前在[C ii]和远红外连续辐射中被探测到，并且在星星形成率（SFR）上跨越了几乎两个数量级。我们的结果显示，在宇宙时间的前十亿年中，星系的电离星际介质属性至少有两种不同的状态，按其比例分开。我们发现极低的[N ii]发射相比，[C ii]（）从一个“典型的”恒星形成星系，可能直接或间接（通过其对辐射场的影响）有关的低尘埃丰度和低金属。在我们的样本中，红外发光的适度恒星形成的莱曼break星系（LBG）的特征是电离气体部分（典型的本地恒星形成星系），并显示其电离气体部分在扩展的气体储层中的空间变化的证据。极端的SFR，温暖和紧凑的尘埃星暴阿兹特克-3显示电离分数高于预期的SFR表面密度（），这表明[N ii]主要跟踪弥漫的电离介质，而不是恒星形成H ii地区在这种类型的星系。这个最高的红移样本[N ii]检测提供了一些电离和中性气体建模尝试和星际介质的结构在z = 5-6的“正常”星系和星爆的第一个限制。
We report interferometric measurements of [N ii] 205 μm fine-structure line emission from a representative sample of three galaxies at z = 5–6 using the Atacama Large (sub)Millimeter Array (ALMA). These galaxies were previously detected in [C ii] and far-infrared continuum emission and span almost two orders of magnitude in star formation rate (SFR). Our results show at least two different regimes of ionized interstellar medium properties for galaxies in the first billion years of cosmic time, separated by their ratio. We find extremely low [N ii] emission compared to [C ii] ( ) from a “typical” star-forming galaxy, likely directly or indirectly (by its effect on the radiation field) related to low dust abundance and low metallicity. The infrared-luminous modestly star-forming Lyman-break galaxy (LBG) in our sample is characterized by an ionized-gas fraction ( typical of local star-forming galaxies and shows evidence for spatial variations in its ionized-gas fraction across an extended gas reservoir. The extreme SFR, warm and compact dusty starburst AzTEC-3 shows an ionized fraction higher than expected given its SFR surface density ( ) suggesting that [N ii] dominantly traces a diffuse ionized medium rather than star-forming H ii regions in this type of galaxy. This highest redshift sample of [N ii] detections provides some of the first constraints on ionized and neutral gas modeling attempts and on the structure of the interstellar medium at z = 5–6 in “normal” galaxies and starbursts.