The most metal-poor damped Ly alpha system at z<3: constraints on early nucleosynthesis
The most metal-poor damped Ly alpha system at z<3: constraints on early nucleosynthesis
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DOI：
10.1051/0004-6361:20054328
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发表时间：
2006-02
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影响因子：
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通讯作者：
P. Erni;P. Richter;C. Ledoux;P. Petitjean
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作者：
P. Erni;P. Richter;C. Ledoux;P. Petitjean
为了约束宇宙中非常早期核合成的条件，我们将极贫金属阻尼Lyman α (DLA)吸收体的化学富集模式与最近爆炸核合成模型计算的预测进行了比较。为此，我们利用公开的UVES/VLT高光谱分辨率数据分析了类星体Q0913+072 (z_em=2.785) z_abs=2.6183处DLA系统中的化学丰度。该吸收塔内的总中性氢柱密度为logN(HI)=20.36。得到了CII、NI、OI、AlII、SiII和FeII的精确柱密度。给出了FeIII和NiII的上限。[C/H]=-2.83, [N/H]=-3.84, [O/H]=-2.47，该体系是迄今为止研究过的金属含量最低的DLA体系之一。它提供了独特的机会来精确测量高红移原星系结构中的CNO丰度。考虑到非常低的总体丰度水平和观测到的丰度模式，数据表明该DLA系统的化学演化主要由一个或最多几个恒星代主导。根据数值模型计算，DLA系统中的化学丰度与单颗零金属丰度大质量恒星（10-50 M_sun）爆炸形成的核心坍缩超新星（SNe）的富集一致，即经典的II型超新星（SNeII），也可能是高能（E>10^51erg）核心坍缩超新星，即所谓的Hypernovae （HNe）。相比之下，使用非零金属丰度祖先或其他爆炸机制的模型，如对不稳定超新星（PISNe）或Ia型超新星（SNeIa），与观测到的丰度模式不匹配。
To constrain the conditions for very early nucleosynthesis in the Universe we compare the chemical enrichment pattern of an extremely metal-poor damped Lyman alpha (DLA) absorber with predictions from recent explosive nucleosynthesis model calculations. For this, we have analyzed chemical abundances in the DLA system at z_abs=2.6183 toward the quasar Q0913+072 (z_em=2.785) using public UVES/VLT high spectral resolution data. The total neutral hydrogen column density in this absorber is logN(HI)=20.36. Accurate column densities are derived for CII, NI, OI, AlII, SiII, and FeII. Upper limits are given for FeIII and NiII. With [C/H]=-2.83, [N/H]=-3.84, and [O/H]=-2.47, this system represents one of the most metal-poor DLA systems investigated so far. It offers the unique opportunity to measure accurate CNO abundances in a protogalactic structure at high redshift. Given the very low overall abundance level and the observed abundance pattern, the data suggest that the chemical evolution of this DLA system is dominated by one or at most a few stellar generations. With reference to numerical model calculations, the chemical abundances in the DLA system are consistent with an enrichment from a single starburst of a zero-metallicity population of massive stars (10-50 M_sun) exploding as core-collapse Supernovae (SNe), i.e., the classical Type II Supernovae (SNeII), and possibly as hyper-energetic (E>10^51erg) core-collapse Supernovae, so-called Hypernovae (HNe), as well. In contrast, models using non-zero metallicity progenitors or other explosion mechanisms, such as pair-instability Supernovae (PISNe) or Type Ia Supernovae (SNeIa), do not match the observed abundance pattern.