Interplay of dust alignment, grain growth and magnetic fields in polarization: lessons from the emission-to-extinction ratio
Interplay of dust alignment, grain growth and magnetic fields in polarization: lessons from the emission-to-extinction ratio
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尘埃排列、颗粒生长和极化磁场的相互作用：发射消光比的教训
DOI：
10.1051/0004-6361/201630373
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
A. Jones
中科院分区：
文献类型：
--
作者：
L. Fanciullo;V. Guillet;F. Boulanger;A. Jones
星际介质（ISM）中尘埃的偏振消光和发射很难解释，因为它们与尘埃的光学性质、颗粒排列和磁场方向有着复杂的依赖关系。在分子云中尤其如此。目前的数据尚未充分发挥其潜力。
特别是，发射和消光的组合提供了单独从其中任何一个都无法获得的信息。我们结合联合收割机数据从科学文献中的偏振尘埃消光普朗克数据偏振发射，我们用它们来约束可能的变化，尘埃和分子云内的环境条件，特别是半透明的视线，考虑到磁场方向。
我们专注于\lambda_max -消光中最大偏振的波长-和其他可观测量，如消光偏振，发射偏振和两者之比之间的依赖关系。我们开始使用蒙特-卡罗模拟来重现这些相关性，其中尘埃模型中的相关量-颗粒排列，尺寸分布和磁场方向-变化以模拟分子云内部预期的不同条件。
所选择的量中没有一个能单独解释观测数据：当所有量在云之间和云内都有显著变化时，可以获得最佳结果。然而，一些数据-最值得注意的是具有低发射消光偏振比的恒星-没有被我们的模拟再现。我们的研究结果表明，不仅尘埃演化是必要的，以解释分子云的偏振，但一个简单的尺寸分布的变化是不足以解释的数据，并指出未来和更复杂的模型的方向。
Polarized extinction and emission from dust in the interstellar medium (ISM) are hard to interpret, as they have a complex dependence on dust optical properties, grain alignment and magnetic field orientation. This is particularly true in molecular clouds. The data available today are not yet used to their full potential.
The combination of emission and extinction, in particular, provides information not available from either of them alone. We combine data from the scientific literature on polarized dust extinction with Planck data on polarized emission and we use them to constrain the possible variations in dust and environmental conditions inside molecular clouds, and especially translucent lines of sight, taking into account magnetic field orientation.
We focus on the dependence between \lambda_max -- the wavelength of maximum polarization in extinction -- and other observables such as the extinction polarization, the emission polarization and the ratio of the two. We set out to reproduce these correlations using Monte-Carlo simulations where the relevant quantities in a dust model -- grain alignment, size distribution and magnetic field orientation -- vary to mimic the diverse conditions expected inside molecular clouds.
None of the quantities chosen can explain the observational data on its own: the best results are obtained when all quantities vary significantly across and within clouds. However, some of the data -- most notably the stars with low emission-to-extinction polarization ratio -- are not reproduced by our simulation. Our results suggest not only that dust evolution is necessary to explain polarization in molecular clouds, but that a simple change in size distribution is not sufficient to explain the data, and point the way for future and more sophisticated models.