[论文解读] Origin of central abundances in the hot intra-cluster medium - II. Chemical enrichment and supernova yield models

François Mernier, J. de Plaa+8 more|UvA-DARE (University of Amsterdam)|Aug 12, 2016

Gamma-ray bursts and supernovae参考文献 105被引用 27

一句话总结

本研究将44个星系团热星系间介质（ICM）中观测到的X射线元素丰度比与超新星核合成模型进行比较，发现标准SNIa和SNcc模型无法再现Ca/Fe与Ni/Fe比值。研究结论指出，混合了燃烧与延迟爆轰机制的SNIa，或Ca-rich gap爆发天体的贡献，更能匹配观测结果，暗示ICM富集过程中SNIa的贡献比例为29–45%，高于原始太阳系中的比例。

ABSTRACT

The hot intra-cluster medium (ICM) is rich in metals, which are synthesised by supernovae (SNe) and accumulate over time into the deep gravitational potential well of clusters of galaxies. Since most of the elements visible in X-rays are formed by type Ia (SNIa) and/or core-collapse (SNcc) supernovae, measuring their abundances gives us direct information on the nucleosynthesis products of billions of SNe since the epoch of the star formation peak (z~2-3). In this study, we compare the most accurate average X/Fe abundance ratios (compiled in a previous work from XMM-Newton EPIC and RGS observations of 44 galaxy clusters, groups, and ellipticals), representative of the chemical enrichment in the nearby ICM, to various SNIa and SNcc nucleosynthesis models found in the literature. The use of a SNcc model combined to any favoured standard SNIa model (deflagration or delayed-detonation) fails to reproduce our abundance pattern. In particular, the Ca/Fe and Ni/Fe ratios are significantly underestimated by the models. We show that the Ca/Fe ratio can be reproduced better, either by taking a SNIa delayed-detonation model that matches the observations of the Tycho supernova remnant, or by adding a contribution from the Ca-rich gap transient SNe, whose material should easily mix into the hot ICM. On the other hand, the Ni/Fe ratio can be reproduced better by assuming that both deflagration and delayed-detonation SNIa contribute in similar proportions to the ICM enrichment. In either case, the fraction of SNIa over the total number of SNe (SNIa+SNcc) contributing to the ICM enrichment ranges within 29-45%. This fraction is found to be systematically higher than the corresponding SNIa/SNe fraction contributing to the enrichment of the proto-solar environnement (15-25%). We also discuss and quantify two useful constraints on both SNIa and SNcc that can be inferred from the ICM abundance ratios.

研究动机与目标

• 确定主导星系团中热星系间介质（ICM）化学富集的超新星类型。
• 检验标准Ia型（SNIa）与核心塌缩型（SNcc）超新星产物模型是否能再现观测到的ICM元素丰度模式。
• 量化不同SNIa爆发模型（如燃烧与延迟爆轰）以及替代超新星类型（如Ca-rich gap爆发天体）对ICM金属富集的相对贡献。
• 推导对关键天体物理参数（如SNcc前身星的初始金属丰度、初始分光函数（IMF）以及形成SNIa的低质量恒星星族比例）的约束。
• 评估白矮星在亚钱德拉塞卡尔质量下发生爆轰是否可作为星系团中SNIa的主要爆发通道。

提出的方法

• 利用XMM-Newton EPIC与RGS对44个星系团、星系群及椭圆星系的高精度X/Fe丰度比作为观测约束。
• 将观测到的丰度模式与文献中列出的SNIa与SNcc核合成产物模型进行比较，包括燃烧与延迟爆轰SNIa模型。
• 通过分析关键丰度比（尤其是对SNIa爆发物理最敏感的Ca/Fe与Ni/Fe）来评估模型拟合效果。
• 引入原始太阳系丰度的约束，以比较ICM富集与本地太阳系成分的异同。
• 评估替代超新星通道（如Ca-rich gap爆发天体）对再现观测到的Ca/Fe比值的影响。
• 量化原子数据、仪器校准与产物模型中的不确定性，以评估其对模型解释的影响。

实验结果

研究问题

• RQ1 标准SNIa与SNcc产物模型能否再现热星系间介质中观测到的X/Fe丰度比？
• RQ2 对ICM富集有贡献的超新星中，Ia型的比例是多少？与原始太阳系中SNIa的比例相比如何？
• RQ3 ICM中观测到的高Ca/Fe比是否能由已知的SNIa爆发模型解释，还是需要额外的超新星通道（如Ca-rich gap爆发天体）？
• RQ4 ICM丰度模式对SNcc前身星的初始金属丰度与初始分光函数（IMF）有何约束？
• RQ5 白矮星在亚钱德拉塞卡尔质量下发生爆轰的模型是否可作为星系团中SNIa的主导爆发通道？

主要发现

• 标准SNIa与SNcc模型无法再现ICM中观测到的Ca/Fe与Ni/Fe比值，两种比值均被显著低估。
• Ca/Fe比值更符合延迟爆轰SNIa模型（与Tycho遗迹匹配）或包含Ca-rich gap爆发天体贡献的模型。
• 当燃烧与延迟爆轰SNIa对ICM富集的贡献相当时，Ni/Fe比值的匹配度最佳。
• 估计对ICM富集有贡献的SNIa比例为29–45%，显著高于原始太阳系中15–25%的比例。
• SNcc前身星的初始金属丰度必须非零，因为零金属丰度的SNcc模型被数据排除。
• 基于丰度约束，可以合理排除大质量恒星对ICM富集有显著贡献（如对超新星PISNe的贡献）。