[论文解读] Molecules and dust in Cassiopeia A: II - Dust sputtering and diagnosis of dust survival in supernova remnants

Chiara Biscaro, Isabelle Cherchneff|arXiv (Cornell University)|Nov 17, 2015

Gamma-ray bursts and supernovae参考文献 87被引用 29

一句话总结

本研究通过使用致密团块状星云物质模拟仙后座A和II型-P超新星中的尘埃溅射过程，评估超新星遗迹中尘埃的存活情况。结果表明，在致密团块中非热溅射使尘埃质量减少40–80%，仅有6–11%的初始尘埃在遗迹阶段存活；然而，II型-P超新星中的致密星云物质可保留14–45%的尘埃，表明它们是星系中高效尘埃生成源。

ABSTRACT

We study the dust evolution in the supernova remnant Cassiopeia A. We follow the processing of dust grains that formed in the Type II-b supernova by modelling the sputtering of grains. The dust is located in dense ejecta clumps crossed by the reverse shock. Further sputtering in the inter-clump medium once the clumps are disrupted by the reverse shock is investigated. The dust evolution in the dense ejecta clumps of Type II-P supernovae and their remnants is also studied. We study oxygen-rich clumps that describe the ejecta oxygen core, and carbon-rich clumps that correspond to the outermost carbon-rich ejecta zone. We consider the dust components formed in the supernova, several reverse shock velocities and inter-clump gas temperatures, and derive dust grain size distributions and masses as a function of time. We find that non-thermal sputtering in clumps is important and accounts for reducing the grain population by ~ 40% to 80% in mass, depending on the clump gas over-density and the grain type and size. A Type II-b supernova forms small grains that are sputtered within clumps and in the inter-clump medium. For Cas A, silicate grains do not survive thermal sputtering in the inter-clump medium. Our derived masses of currently processed silicate, alumina and carbon grains in Cas A agree well with values derived from observations. Grains produced by Type II-P supernovae better survive the remnant phase. For dense ejecta clumps, dust survival efficiencies range between 42% and 98% in mass. For the SN1987A model, the derived surviving dust mass is in the range ~ 0.06-0.13 Msolar. This type of dense supernovae may efficiently provide galaxies with dust. Specifically, silicate grains over 0.1 micron and other grains over 0,05 micron survive thermal sputtering in the remnant. Therefore, pre-solar grains of supernova origin possibly form in the dense ejecta clumps of Type II-P supernovae.

研究动机与目标

• 研究在超新星遗迹中，由超新星星云物质形成的尘埃颗粒如何在溅射过程中存活。
• 评估团块状星云结构对尘埃处理的影响，特别是非热和热溅射过程的影响。
• 确定不同超新星类型中尘埃的存活比例，特别是II型-b（仙后座A）和II型-P（如SN1987A）超新星。
• 通过随时间建模颗粒演化，将仙后座A和SN1987A等遗迹中观测到的尘埃质量与理论预测相协调。
• 评估超新星对星际尘埃总量的贡献，特别是在高红移星系中的作用。

提出的方法

• 使用随时间变化的尘埃溅射模型，模拟II型-b（仙后座A）和II型-P超新星中致密星云物质团块内的尘埃演化。
• 在团块内部应用非热溅射模型，在团块间介质中应用热溅射模型，变化激波速度和气体温度。
• 使用在非平衡条件下由化学动力学模型推导出的颗粒尺寸分布。
• 考虑多种尘埃成分：硅酸盐、氧化铝、碳化硅（SiC）和碳，其溅射速率随尺寸变化。
• 随时间积分结果，计算团块内和团块间区域中尘埃质量与颗粒尺寸分布的演化。
• 将模拟的尘埃质量与仙后座A和SN1987A中观测到的暖尘埃辐射进行比较，以验证模型预测。

实验结果

研究问题

• RQ1 在仙后座A等II型-b超新星中，致密星云团块内的非热溅射如何影响尘埃质量损失？
• RQ2 在超新星遗迹的团块间介质中，尘埃在热溅射过程中的存活比例是多少？
• RQ3 颗粒尺寸、成分以及团块的过密度如何影响不同超新星类型中尘埃的存活？
• RQ4 与II型-b超新星相比，具有致密星云物质的II型-P超新星在星际尘埃总量中的贡献程度如何？
• RQ5 能否通过团块状星云物质中的溅射模型解释仙后座A和SN1987A等遗迹中观测到的尘埃质量？

主要发现

• 在致密团块中，非热溅射使尘埃质量减少40–80%，具体取决于颗粒类型、尺寸、激波速度和团块过密度。
• 在仙后座A中，硅酸盐颗粒无法在团块间介质中经受热溅射，而氧化铝、SiC和碳质尘埃可能存活。
• 在仙后座A中，初始约0.03 M⊙的尘埃仅有6–11%在遗迹阶段存活，其余部分因溅射而损失。
• 对于具有致密星云物质的II型-P超新星，尘埃存活比例在14%至45%之间，表明其具有显著更高的保存效率。
• 在类似SN1987A的模型中，尘埃质量存活率可达42–98%，存活尘埃质量为0.06–0.13 M⊙，表明其在尘埃生成方面效率极高。
• 尺寸大于0.1 µm（硅酸盐）和0.05 µm（其他成分）的颗粒可经受热溅射，支持其起源于II型-P超新星致密团块的观点。