Dust Extinction in a Small Molecular Cloud
Dust Extinction in a Small Molecular Cloud
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小分子云中的粉尘消光
DOI：
10.1086/322303
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
S. Pezzuto
中科院分区：
文献类型：
--
作者：
F. Strafella;L. Campeggio;S. Aiello;C. Cecchi;S. Pezzuto
利用尘埃成分引起的恒星光的消光作为示踪剂，观测研究了小暗云中物质的分布。在这里，我们提出了一个光度研究的结果，已经进行了在光学光谱区域通过成像的B，V和I波段。尘埃空间分布的相关信息是通过计数恒星和测量它们的颜色过剩来获得的。网格上的星星计数在局部均匀恒星光度函数的假设下很容易被解释为平均消光Aλ的测量，而在同一网格上平均的颜色过量则是通过比较红化区域和参考位置之间的恒星颜色分布来获得的。通过比较观测到的恒星颜色和双色（V-I）对（B-V）图中未变红恒星的轨迹，也可以得出颜色过量。球状体CB 107的消光图表明，在这个暗云的边界处的尘埃分布可以测量，并与这些物体中的物质分布模型进行比较。通过考虑密度律如n <$（1 +（r/a）α）-β，我们发现我们的观测更倾向于α = 2和β = 1的模型。指示也得到了关于在这个对象的总选择性消光RV的空间变化。在这方面，我们发现RV倾向于向CB 107的最内部区域增加，这表明尘埃颗粒的平均尺寸也增加了。这些意见对分子云边界的建模的影响进行了讨论，并得出一些指示的时间尺度的物理过程负责其结构。还简要讨论了这些物体中星际辐射场的穿透深度，以及它对云化学的可能影响。最后，我们发现的差异，在颜色过剩的地图，这是通过恒星计数和累积分布的颜色，分别获得，建议在CB 107的cluerical分布的物质。
The distribution of matter in a small dark cloud has been investigated observationally by using the extinction of the stellar light that is due to the dust component as a tracer. Here we present the results of a photometric study that has been carried out in the optical spectral region by means of imaging in the B, V, and I bands. The relevant information on the spatial distribution of the dust has been obtained both by counting stars and by measuring their color excesses. While star counts on a reseau grid are easily interpreted as a measurement of the average extinction Aλ under the assumption of a locally uniform stellar luminosity function, the color excesses averaged on the same grid are obtained by a comparison of the stellar color distributions among the reddened regions and a reference position. Color excesses have also been derived by comparing the observed stellar colors with the locus of the unreddened stars in the two-color (V-I) versus (B-V) diagram. The extinction map obtained for the globule CB 107 shows that the dust distribution at the boundary of this dark cloud can be measured and compared with models of matter distribution in these objects. By considering a density law such as n ∝ (1 + (r/a)α)-β, we find that our observations favor models with α = 2 and β = 1. Indications are also obtained about the spatial variation in this object of the total to selective extinction RV. In this respect we find that RV tends to increase toward the innermost regions of CB 107, and this suggests that the mean size of the dust particles also increases. The implications of these observations on the modeling of molecular cloud boundaries are discussed, and some indications on the timescale of the physical processes responsible for their structure are derived. The penetration depth of the interstellar radiation field in these objects is also briefly discussed in the light of its possible consequences on the cloud chemistry. Lastly, the differences that we found in the color excess maps, which were obtained by means of the stellar counts and the cumulative distribution in color, respectively, suggest a clumpy distribution of matter in CB 107.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell