IRON: A KEY ELEMENT FOR UNDERSTANDING THE ORIGIN AND EVOLUTION OF INTERSTELLAR DUST
IRON: A KEY ELEMENT FOR UNDERSTANDING THE ORIGIN AND EVOLUTION OF INTERSTELLAR DUST
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DOI：
10.3847/0004-637x/825/2/136
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发表时间：
2016-07-10
影响因子：
4.9
通讯作者：
Dwek, Eli
中科院分区：
文献类型：
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作者：
Dwek, Eli
铁的起源和消耗不同于构成星际尘埃的所有其他丰富的难熔元素。铁主要在Ia型超新星（SNe Ia）和核心坍缩超新星（CCSN）中合成，并存在于AGB恒星的流出物中。只有后两者被观测到是星际尘埃的来源，因为对Ia超新星尘埃的搜索提供了强有力的证据，证明它们的喷出物中没有任何大量的尘埃。因此，超过65%的铁以气态形式注入ISM中。然而，沿着ISM中的许多视线进行的紫外线和X射线观测表明，与预期的太阳丰度相比，铁在气相中严重耗尽。丢失的铁，占总量的90%左右，被认为被锁定在星际尘埃中。这表明，大部分缺失的铁必须通过冷吸积从ISM气体中沉淀到预先存在的硅酸盐，碳或复合颗粒上。因此，铁是唯一一种需要大部分生长发生在传统恒星凝聚源之外的元素。这是一个强有力的声明，不依赖于我们对ISM中粉尘破坏效率的不断发展的理解。将这些复合颗粒的物理、光学和化学性质与它们的许多观测表现结合起来，是理解星际尘埃的性质和起源的一个重大挑战。
The origin and depletion of iron differ from all other abundant refractory elements that make up the composition of interstellar dust. Iron is primarily synthesized in Type Ia supernovae (SNe Ia) and in core collapse supernovae (CCSN), and is present in the outflows from AGB stars. Only the latter two are observed to be sources of interstellar dust since searches for dust in SN Ia have provided strong evidence for the absence of any significant mass of dust in their ejecta. Consequently, more than 65% of the iron is injected into the ISM in gaseous form. Yet ultraviolet and X-ray observations along many lines of sight in the ISM show that iron is severely depleted in the gas phase as compared to expected solar abundances. The missing iron, comprising about 90% of the total, is believed to be locked up in interstellar dust. This suggests that most of the missing iron must have precipitated from the ISM gas by a cold accretion onto preexisting silicate, carbon, or composite grains. Iron is thus the only element that requires most of its growth to occur outside the traditional stellar condensation sources. This is a robust statement that does not depend on our evolving understanding of the dust destruction efficiency in the ISM. Reconciling the physical, optical, and chemical properties of such composite grains with their many observational manifestations is a major challenge for understanding the nature and origin of interstellar dust.