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arXiv 1901.07458astro-ph.GA
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模拟LDN 1780的旋转粉尘排放

Modelling the spinning dust emission from LDN 1780

Matias Vidal, Clive Dickinson, S. E. Harper, Simon Casassus, A. N. Witt

摘要:

我们在两个角尺度上研究了Lynds暗星云(LDN)1780的异常微波辐射(AME)。使用可用的辅助数据在角分辨率为1度,我们构建了一个SED 0.408 GHz至2997 GHz之间。我们发现,有一个显着的量的AME在这些角度尺度和多余的是兼容的物理旋转尘埃模型。我们发现LDN 1780是1度尺度上AME最明显的例子之一。我们检测到AME的显著性> 20 $σ$。我们还发现,在这些角度尺度,在23-70 GHz之间的频率发射的峰值的位置不同于90-3000 GHz的地图上的一个。为了调查AME在这片云的起源,我们使用毫米波天文学研究组合阵列(CARMA)获得的数据,该阵列在30 GHz时提供2弧分分辨率。我们研究了无线电和红外辐射之间的连接使用形态相关性。最好的相关性被发现与MIPS 70 $μ$ m,它跟踪温暖的尘埃(T $\sim$ 50 K)。最后,我们研究了云内两个位置之间的无线电发射率的差异。我们测量了30 GHz发射率差异的因子$\approx 6$。我们表明,这种变化可以解释,使用旋转尘埃模型,通过在整个云的尘埃粒度分布的变化,特别是改变碳的分数,因此多环芳烃的量。

英文摘要:

We study the anomalous microwave emission (AME) in the Lynds Dark Nebula (LDN) 1780 on two angular scales. Using available ancillary data at an angular resolution of 1 degree, we construct an SED between 0.408 GHz to 2997 GHz. We show that there is a significant amount of AME at these angular scales and the excess is compatible with a physical spinning dust model. We find that LDN 1780 is one of the clearest examples of AME on 1 degree scales. We detected AME with a significance > 20$σ$. We also find at these angular scales that the location of the peak of the emission at frequencies between 23-70 GHz differs from the one on the 90-3000 GHz map. In order to investigate the origin of the AME in this cloud, we use data obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) that provides 2 arcmin resolution at 30 GHz. We study the connection between the radio and IR emissions using morphological correlations. The best correlation is found to be with MIPS 70$μ$m, which traces warm dust (T$\sim$50K). Finally, we study the difference in radio emissivity between two locations within the cloud. We measured a factor $\approx 6$ of difference in 30 GHz emissivity. We show that this variation can be explained, using the spinning dust model, by a variation on the dust grain size distribution across the cloud, particularly changing the carbon fraction and hence the amount of PAHs.

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