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arXiv 2107.01043astro-ph.GA
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猎户座A分子云周围Interstellar Dust的光学性质

Optical Properties of Interstellar Dust around the Orion A Molecular Cloud

Hayato Uehara, Kazuhito Dobashi, Shingo Nishiura, Tomomi Shimoikura, Takahiro Naoi

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Accepted by The Astrophysical Journal, 21 pages, 11 figures, 6 tables
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摘要：

我们研究了猎户座A分子云周围星际尘埃的光学性质，以研究尘埃颗粒的粒度分布和组成。猎户座A是太阳附近研究最多的分子云之一（$d \simeq 400\ \rm{pc}$）。在本文中，我们使用光学和近红外光度数据。光学数据由$BVRI$带成像观测获得。由$JHK_{S}$谱带组成的近红外数据取自2 MASS点源星表。我们在猎户座A周围制作了一些彩色多余图，并测量了它们的比率，如$E(R-I)/E(B-V)$。为了研究尘埃的性质，我们将观测到的比率与Naoi T.等人（2021年），他们基于标准尘埃模型计算了光学至近红外波长的消光;他们假设了具有上限截止半径的幂律粒度分布，并假设$graphite$和$silicate$为主要成分。结果发现猎户座A周围的上截止半径为$\simeq 0.3$ $\rmμ$ m，与$graphite$相比，$silicate$占优势（其中$silicate$的分数大于$93$ %）。此外，我们还从观测到的$A_{V}$和色余$E(B-V)$的消光率进一步导出了总消光率与选择消光率的比值$R_{V}$，并与模型计算结果进行了比较。粉尘特性（即，从$R_{V}$导出的上限截止半径和$graphite/silicate$的比率）与从颜色过量比率导出的那些几乎一致。

英文摘要：

We have studied optical properties of interstellar dust around the Orion A molecular cloud to investigate the size distribution and the composition of dust grains. Orion A is one of the most studied molecular clouds in the solar vicinity ($d \simeq 400\ \rm{pc}$). In this paper, we used optical and near-infrared photometric data. The optical data were obtained by $BVRI$ bands imaging observations. The near-infrared data consisting of $JHK_{S}$ bands were taken from 2MASS point source catalog. We produced some color excess maps around Orion A, and measured their ratios such as $E(R-I)/E(B-V)$. In order to investigate dust properties, we compared the observed ratios with results of simulation performed by Naoi T. et al. (2021) who calculated the extinction in the optical to near-infrared wavelengths based on a standard dust model; they assumed a power-law grain-size distribution with an upper cutoff radius and assumed $graphite$ and $silicate$ as dominant components. As a result, we found that the upper cutoff radius around Orion A is $\simeq 0.3$ $\rmμ$m, and $silicate$ predominates compared with $graphite$ (with the fraction of $silicate$ grater than $93$ %). In addition, we further derived the total-to-selective extinction ratio $R_{V}$ from the observed extinction of $A_{V}$ and the color excess $E(B-V)$, and compared it with the model calculations. Dust properties (i.e., the upper cutoff radius and the ratio of $graphite/silicate$) derived from $R_{V}$ is almost consistent with those derived from the color excess ratios.

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