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arXiv 1104.3574astro-ph.EP
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从原行星盘到行星系的尘埃矿物学演化

On the Evolution of Dust Mineralogy, From Protoplanetary Disks to Planetary Systems

Isa Oliveira, Johan Olofsson, Klaus M. Pontoppidan, Ewine F. van Dishoeck, Jean-Charles Augereau, Bruno Merin

摘要:

对原行星盘和太阳系天体中尘埃颗粒散发出的硅酸盐特征进行矿物学研究,可以揭示行星形成的过程。彗星、陨石和行星际尘埃颗粒中的晶体物质的重要部分表明,几乎完全无定形的ISM尘埃是由它们形成的。因此,结晶硅酸盐的产生一定发生在原行星盘中,尘埃在那里演化形成行星和星子。人们提出了不同的设想,但仍不清楚这种情况如何以及何时发生。本文介绍了年轻巨蛇座星系团完整的原行星盘样品的尘埃颗粒矿物学。这些结果进行了比较,在年轻的金牛座地区和来源,保留了他们的原行星盘在较老的上天蝎座和Eta Chamaeleontis星团,使用相同的分析技术的所有样本。这种比较允许调查的颗粒矿物学演化与时间的总样本的139个磁盘。平均年龄和磁盘的分数被用来作为指标的不同群体的进化阶段。我们的研究结果表明,在不同地区的磁盘有相似的平均晶粒尺寸和结晶度分数(~10 - 20%)的分布,尽管在平均年龄的蔓延。此外,没有证据表明任何给定的磁盘几何形状的优先晶粒尺寸,也没有平均集群结晶度分数增加的平均年龄在1 - 8百万年的范围内。主要的含义是,在早期(<100万年),在盘表面建立了适度水平的结晶度,达到了一个平衡,这与盘中平面可能发生的事情无关。这些结果在行星形成的背景下进行了讨论,并与我们太阳系中小天体的矿物学结果进行了比较。[摘要]

英文摘要:

Mineralogical studies of silicate features emitted by dust grains in protoplanetary disks and Solar System bodies can shed light on the progress of planet formation. The significant fraction of crystalline material in comets, chondritic meteorites and interplanetary dust particles indicates a modification of the almost completely amorphous ISM dust from which they formed. The production of crystalline silicates thus must happen in protoplanetary disks, where dust evolves to build planets and planetesimals. Different scenarios have been proposed, but it is still unclear how and when this happens. This paper presents dust grain mineralogy of a complete sample of protoplanetary disks in the young Serpens cluster. These results are compared to those in the young Taurus region and to sources that have retained their protoplanetary disks in the older Upper Scorpius and Eta Chamaeleontis stellar clusters, using the same analysis technique for all samples. This comparison allows an investigation of the grain mineralogy evolution with time for a total sample of 139 disks. The mean cluster age and disk fraction are used as indicators of the evolutionary stage of the different populations. Our results show that the disks in the different regions have similar distributions of mean grain sizes and crystallinity fractions (~10-20%) despite the spread in mean ages. Furthermore, there is no evidence of preferential grain sizes for any given disk geometry, nor for the mean cluster crystallinity fraction to increase with mean age in the 1-8 Myr range. The main implication is that a modest level of crystallinity is established in the disk surface early on (< 1 Myr), reaching a equilibrium that is independent of what may be happening in the disk midplane. These results are discussed in the context of planet formation, in comparison with mineralogical results from small bodies in our Solar System. [Abridged]

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