A determination of the spectra of Galactic components observed by the Wilkinson Microwave Anisotropy Probe
A determination of the spectra of Galactic components observed by the Wilkinson Microwave Anisotropy Probe
复制标题
威尔金森微波各向异性探测器观测到的星系成分光谱的测定
DOI：
10.1111/j.1365-2966.2006.10572.x
复制
发表时间：
2006
影响因子：
4.8
通讯作者：
R. Davis
中科院分区：
文献类型：
--
作者：
R. Davies;C. Dickinson;C. Dickinson;A. Banday;T. Jaffe;K. Gorski;K. Gorski;K. Gorski;R. Davis
威尔金森微波各向异性探针 (WMAP) 数据与自由、同步加速器和灰尘的辅助数据相结合，可以更好地了解这些组件的发射光谱。在这里，我们使用互相关技术检查中纬度地区的天空变化。特别是，我们将 15 个选定天空区域中观测到的发射与三个“标准”模板进行了比较。
扩散电离气体的自由-自由发射由众所周知的 K 和 Ka 波段光谱拟合，但导出的发射率对应于类似于 4000-5000 K 的平均电子温度。这与银河 H II 区域的估计不一致，尽管在不同区域也发现 H α 与自由-自由强度的导出比率存在类似于 2 的变化。差异的根源尚不清楚。
在所研究的 15 个领域中，大多数领域都清楚地检测到了与灰尘相关的异常排放。异常发射与 94 GHz 下的 Finkbeiner、Davis & Schlegel 模型 8 预测 (FDS8) 密切相关，有效频谱指数在 20 至 60 GHz 之间，β 值类似于 -2.85。此外，云与云之间的发射率变化大约为 2。通过估计灰尘色温（特别是 FDS8 x T^n）来调制模板，可以适度改进对 K 波段异常灰尘的拟合。我们发现首选值 n 类似于 1.6，尽管区域之间存在分散。然而，在热粉尘排放占主导地位的较高频率下，优选指数降至零。
同步加速器发射在 GHz 频率和 WMAP 频段之间变陡。有迹象表明天空中的光谱指数存在变化，但当前数据不够精确，无法准确量化各个区域的光谱指数变化。
我们对 WMAP 数据的分析强烈表明，低 WMAP 频率下与灰尘相关的发射具有与旋转灰尘兼容的频谱；我们没有发现同步加速器成分与尘埃相关的证据。讨论了这些结果对于校正银河系前景发射的宇宙微波背景数据的重要性。
Wilkinson Microwave Anisotropy Probe (WMAP) data when combined with ancillary data on free-free, synchrotron and dust allow an improved understanding of the spectrum of emission from each of these components. Here, we examine the sky variation at intermediate latitudes using a cross-correlation technique. In particular, we compare the observed emission in 15 selected sky regions to three 'standard' templates.
The free-free emission of the diffuse ionized gas is fitted by a well-known spectrum at K and Ka band, but the derived emissivity corresponds to a mean electron temperature of similar to 4000-5000 K. This is inconsistent with estimates from Galactic H II regions although a variation in the derived ratio of H alpha to free-free intensity by a factor of similar to 2 is also found from region to region. The origin of the discrepancy is unclear.
The anomalous emission associated with dust is clearly detected in most of the 15 fields studied. The anomalous emission correlates well with the Finkbeiner, Davis & Schlegel model 8 predictions (FDS8) at 94 GHz, with an effective spectral index between 20 and 60 GHz, of beta similar to -2.85. Furthermore, the emissivity varies by a factor of similar to 2 from cloud to cloud. A modestly improved fit to the anomalous dust at K band is provided by modulating the template by an estimate of the dust colour temperature, specifically FDS8 x T^n. We find a preferred value n similar to 1.6, although there is a scatter from region to region. Nevertheless, the preferred index drops to zero at higher frequencies where the thermal dust emission dominates.
The synchrotron emission steepens between GHz frequencies and the WMAP bands. There are indications of spectral index variations across the sky but the current data are not precise enough to accurately quantify this from region to region.
Our analysis of the WMAP data indicates strongly that the dust-correlated emission at the low WMAP frequencies has a spectrum which is compatible with spinning dust; we find no evidence for a synchrotron component correlated with dust. The importance of these results for the correction of cosmic microwave background data for Galactic foreground emission is discussed.