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arXiv 2206.08613astro-ph.HEastro-ph.GA
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中微子吸积流对活动星系核化学演化的贡献

Nucleosynthesis Contribution of Neutrino-dominated Accretion Flows to the Chemical Evolution of Active Galactic Nuclei

Yan-Qing Qi, Tong Liu, Zhen-Yi Cai, Mouyuan Sun

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6 pages, 2 figures, accepted for publication in ApJ
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摘要：

最近对类星体的观测显示，在它们的宽发射线中有很高的线通量比，并且这个比似乎与红移无关，直到$z \gtrsim 6$，这表明这些早期类星体的宽线区域是惊人的富含金属。在这里，我们通过添加一个新的成分，即，中微子主导的吸积流（NDAF）与流出，在传统的核心坍缩超新星（CCSNe）的顶部。在存在来自具有流出物的NDAF的化学贡献的情况下，总金属质量（即，如果祖星的质量在$\sim 25-55~M_{\odot}$的范围内，则每个CCSN的常规CCSN和具有流出的NDAF的总和与祖星的质量的依赖性很弱。我们采用改进的开箱模型，采用三种典型的初始质量函数（IMF）来模拟化学演化。我们发现，与额外的化学贡献，从NDAF流出，类星体的金属丰度可以更迅速地富集在非常早期的宇宙（$z \sim 10$），并达到更高的饱和度比没有NH3的情况下，在$z \sim 8$，之后，他们慢慢地演变红移。在\citet{Toyouchi2022}的“头重脚轻”IMF模型下，类星体的金属丰度可以达到$\sim 20~Z_{\odot}$（$Z_\odot$表示太阳的金属丰度，而$\sim 20\%$是由海王星的流出产生的），这很好地解释了类星体观测到的超太阳金属丰度和红移无关的演化。

英文摘要：

Recent observations of quasars show high line-flux ratios in their broad emission lines and the ratios appear to be independent of redshift up to $z \gtrsim 6$, which indicate that the broad-line regions of these early quasars are surprisingly metal-rich. Here, we revisit the chemical evolution of high-redshift quasars by adding a new ingredient, i.e., the neutrino-dominated accretion flows (NDAFs) with outflows, on top of the conventional core-collapse supernovae (CCSNe). In the presence of the chemical contribution from NDAFs with outflows, the total metal mass (i.e., the summation of the conventional CCSN and NDAFs with outflows) per CCSN depends weakly upon the mass of the progenitor star if the mass is in the range of $\sim 25-55~M_{\odot}$. We model the chemical evolution by adopting a improved open-box model with three typical initial mass functions (IMFs). We find that, with the additional chemical contribution from NDAFs with outflows, the quasar metallicity can be enriched more rapidly in the very early Universe ($z \sim 10$) and reaches higher saturation than the no-NDAF case at $z \sim 8$, after which they evolve slowly with redshift. The quasar metallicity can reach $\sim 20~Z_{\odot}$ ($Z_\odot$ denotes the metallicity of the Sun; and $\sim 20\%$ of which is produced by NDAF outflows) at $z \sim 8$ for the ``top-heavy'' IMF model in \citet{Toyouchi2022}, which readily explains the quasar observations on the super-solar metal abundance and redshift-independent evolution.

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