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arXiv 1608.04781astro-ph.GA
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用多相非均匀ISM模拟Galerkin中的尘埃演化

Modelling Dust Evolution in Galaxies with a Multiphase, Inhomogeneous ISM

Svitlana Zhukovska, Clare Dobbs, Edward B. Jenkins, Ralf Klessen

摘要:

我们开发了一个多相,非均匀ISM中的尘埃演化模型,包括尘埃的生长和破坏过程。颗粒演化的物理条件取自类银河系旋涡星系中巨分子云的流体动力学模拟。我们改进了ISM中的尘埃增长的处理方法,以研究温度依赖的粘附系数和离子-颗粒相互作用的作用。本文根据在本星系中测量的气相Si丰度[Si/H]_{gas}的详细观测数据,导出了平均[Si/H]_{gas}与本星系气体密度n(H)之间的关系,并以此作为模型的临界约束。该关系式要求粘附系数随气体温度而减小。由尘埃空间分布建立的综合关系式再现了冷云中观测关系式的-0.5斜率。这个斜率比暖介质的斜率更陡,这可以用尘埃的增长来解释。我们发现,它发生在所有采用的最小晶粒尺寸a_{min}的值从1到5 nm。对于经典的截止值a_{min} =5 nm,离子-颗粒相互作用导致了比观测值更长的生长时间尺度和更高的[Si/H]_{gas}。对于小于3 nm的a_{min},离子-颗粒相互作用提高了生长速率,使[Si/H]_{gas}-n(H)关系的斜率变陡,与观测结果有较好的吻合。ISM中尘埃再形成的速率远远超过了简单演化模型所预期的恒星源产生尘埃的速率。在物质进出尘埃的循环达到稳定状态后,尘埃的增长平衡了在类似的3.5亿年时间尺度上运行的破坏。

英文摘要:

We develop a model of dust evolution in a multiphase, inhomogeneous ISM including dust growth and destruction processes. The physical conditions for grain evolution are taken from hydrodynamical simulations of giant molecular clouds in a Milky Way-like spiral galaxy. We improve the treatment of dust growth by accretion in the ISM to investigate the role of the temperature-dependent sticking coefficient and ion-grain interactions. From detailed observational data on the gas-phase Si abundances [Si/H]_{gas} measured in the local Galaxy, we derive a relation between the average [Si/H]_{gas} and the local gas density n(H) which we use as a critical constraint for the models. This relation requires a sticking coefficient that decreases with the gas temperature. The synthetic relation constructed from the spatial dust distribution reproduces the slope of -0.5 of the observed relation in cold clouds. This slope is steeper than that for the warm medium and is explained by the dust growth. We find that it occurs for all adopted values of the minimum grain size a_{min} from 1 to 5nm. For the classical cut-off of a_{min}=5 nm, the ion-grain interactions result in longer growth timescales and higher [Si/H]_{gas} than the observed values. For a_{min} below 3 nm, the ion-grain interactions enhance the growth rates, steepen the slope of [Si/H]_{gas}-n(H) relation and provide a better match to observations. The rates of dust re-formation in the ISM by far exceed the rates of dust production by stellar sources as expected from simple evolution models. After the cycle of matter in and out of dust reaches a steady state, the dust growth balances the destruction operating on similar timescales of 350 Myr.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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