半透明云OPH和LDN 1780上尘埃相关厘米波长连续辐射
Dust-correlated cm-wavelength continuum emission on translucent clouds ζ Oph and LDN 1780
摘要：
扩散厘米波红外相关信号，“异常”CMB前景，被认为是出现在卷云的尘埃。我们目前的宇宙背景成像仪（CBI）厘米波数据的两个半透明的云，太阳黑子和LDN 1780的目的是在半透明的云环境中的异常发射的特点。在31 GHz的情况下，测量的亮度比从5 GHz测量的外推高2.4σ，假设在8弧分尺度上的自由-自由光谱。在1{ \odot }角尺度上，这片云的SED主要由cm范围内的自由-自由发射所控制。在LDN 1780中，我们在1{ \odot }的角标度上检测到了3 σ的过量，可以使用旋转尘埃模型进行拟合。在这片云中，CBI数据和跟踪尘埃的红外图像之间存在空间相关性。与近红外模板（IRAS 12和25 μm）的相关性优于IRAS 100 μm，这表明在31 GHz处发射的颗粒非常小。我们计算了这两个云的31 GHz发射率。它们是相似的，并且具有介于卷云和乌云之间的中间值。尽管如此，我们发现了一个指示的发射率和柱密度之间的反比关系，这进一步支持VSG起源的厘米发射，因为大颗粒相对于小颗粒的比例是较小的弥漫云。
英文摘要：
The diffuse cm-wave IR-correlated signal, the "anomalous" CMB foreground, is thought to arise in the dust in cirrus clouds. We present Cosmic Background Imager (CBI) cm-wave data of two translucent clouds, ζ Oph and LDN 1780 with the aim of characterising the anomalous emission in the translucent cloud environment. In ζ Oph, the measured brightness at 31 GHz is 2.4σ higher than an extrapolation from 5 GHz measurements assuming a free-free spectrum on 8 arcmin scales. The SED of this cloud on angular scales of 1{\odot} is dominated by free-free emission in the cm-range. In LDN 1780 we detected a 3 σ excess in the SED on angular scales of 1{\odot} that can be fitted using a spinning dust model. In this cloud, there is a spatial correlation between the CBI data and IR images, which trace dust. The correlation is better with near-IR templates (IRAS 12 and 25 μm) than with IRAS 100 μm, which suggests a very small grain origin for the emission at 31 GHz. We calculated the 31 GHz emissivities in both clouds. They are similar and have intermediate values between that of cirrus clouds and dark clouds. Nevertheless, we found an indication of an inverse relationship between emissivity and column density, which further supports the VSGs origin for the cm-emission since the proportion of big relative to small grains is smaller in diffuse clouds.
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