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arXiv 1707.07580astro-ph.GA
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第一批恒星在高z DLAs上的金属富集特征

Metal enrichment signatures of the first stars on high-z DLAs

Q. Ma, U. Maio, B. Ciardi, R. Salvaterra

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摘要：

我们使用数值N体流体动力学模拟与不同的波普III恒星模型，以调查的可能性，检测第一个恒星签名与高红移阻尼Ly $α$吸收器（DLAs）的意见。模拟包括原子和分子冷却，恒星形成，能量反馈和金属扩散，由于恒星的质量和金属丰度范围的演变。采用不同的初始质量函数和相应的金属相关的产额和寿命来模拟原始恒星星族。模拟中的DLA根据局部气体温度（所选温度）或主体质量（所选质量）来选择。我们发现，3\%（40\%）的质量（温度）选择高$z$（$z\ge5.5$）的DLAs保留污染的签名，从第一个恒星模型。这类DLAs的晕质量（$<10^{9.6}\,\rm M_{\odot}$）、金属丰度（$<10^{-3}\,\rm Z_{\odot}$）和恒星形成率（$<10^{-1.5}\,\rm M_{\odot}\,yr^{-1}$）都很低。类星体光谱中DLAs的金属丰度比可以作为推断污染恒星产生的性质和限制第一恒星质量范围的有用工具。通过与$z\ge5$观测到的DLAs的丰度比比较，我们发现这些DLAs中的大多数在误差范围内与PopII星主导的富集相一致，并且强烈地反对超大质量第一星（即100~ $\rm M_{\odot}$ -500~ $\rm M_{\odot}$）的污染模式。然而，其中一些仍然可能是由质量范围在[0.1，100]~ $\rm M_{\odot}$的第一颗恒星的污染造成的。特别是，我们发现，从SDSS J1202+3235的丰度比是一致的，预计从PopIII富集为主的大质量（但不是极端）的第一颗恒星。

英文摘要：

We use numerical N-body hydrodynamical simulations with varying PopIII stellar models to investigate the possibility of detecting first star signatures with observations of high-redshift damped Ly$α$ absorbers (DLAs). The simulations include atomic and molecular cooling, star formation, energy feedback and metal spreading due to the evolution of stars with a range of masses and metallicities. Different initial mass functions (IMFs) and corresponding metal-dependent yields and lifetimes are adopted to model primordial stellar populations. The DLAs in the simulations are selected according to either the local gas temperature (temperature selected) or the host mass (mass selected). We find that 3\% (40\%) of mass (temperature) selected high-$z$ ($z\ge5.5$) DLAs retain signatures of pollution from PopIII stars, independently from the first star model. Such DLAs have low halo mass ($<10^{9.6}\,\rm M_{\odot}$), metallicity ($<10^{-3}\,\rm Z_{\odot}$) and star formation rate ($<10^{-1.5}\,\rm M_{\odot}\,yr^{-1}$). { Metal abundance ratios of DLAs imprinted in the spectra of QSO} can be useful tools to infer the properties of the polluting stellar generation and to constrain the first star mass ranges. Comparing the abundance ratios derived from our simulations to those observed in DLAs at $z\ge5$, we find that most of these DLAs are consistent within errors with PopII stars dominated enrichment and strongly disfavor the pollution pattern of very massive first stars (i.e. 100~$\rm M_{\odot}$-500~$\rm M_{\odot}$). However, some of them could still result from the pollution of first stars in the mass range [0.1, 100]~$\rm M_{\odot}$. In particular, we find that the abundance ratios from SDSS J1202+3235 are consistent with those expected from PopIII enrichment dominated by massive (but not extreme) first stars.

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