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arXiv 0801.0547astro-ph
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银河系同步辐射对CMB各向异性测量的影响。I.全天巡天总强度的角功率谱分析

The impact of Galactic synchrotron emission on CMB anisotropy measurements. I. Angular power spectrum analysis of total intensity all-sky surveys

L. La Porta, C. Burigana, W. Reich, P. Reich

摘要:

银河系前景辐射是精确测量宇宙微波背景(CMB)各向异性的一个限制因素。我们进行角功率谱分析(APS)的全天空总强度图在408 MHz和1420 MHz,这是占主导地位的同步辐射出银河系平面。我们从地图中减去较亮的光源。我们研究的APS作为银河系纬度的函数,通过考虑各种削减和作为天空位置的函数,通过将天空分成大小约为15度x 15度的补丁。银河系射电漫射同步辐射的APS最好用幂律$C_{\ell} \sim k \ell^α$和$α\in [-3.0,-2.6]$拟合,其中较低的$α$值通常对应于较高的纬度。然而,对斑块的分析表明,存在强烈的局部变化。$\ell \in [20,40]$的平均APS用于确定408 MHz和1420 MHz之间的平均光谱指数,然后将同步加速器APS结果外推到微波范围。一个简单的外推到23 GHz的同步辐射APS发现在408和1420 MHz并不能解释所有的功率在WMAP同步组件,即使在中/高银河系纬度。这表明其他成分(例如自由或旋转灰尘排放)的显著微波贡献(约为信号的50%)。外推的同步加速器APS和CMB APS之间的比较表明,一个掩模排除与$|b_{gal}| \lesssim 5^{\circ}$的区域将减少前景波动的宇宙学的在70 GHz,即使在最低的多极。我们讨论了我们的分析微波温度各向异性地图的宇宙学开发的主要影响。

英文摘要:

Galactic foreground emission is a limiting factor for precise cosmic microwave background (CMB) anisotropy measurements. We perform an angular power spectrum analysis (APS) of all-sky total intensity maps at 408 MHz and 1420 MHz, which are dominated by synchrotron emission out of the Galactic plane. We subtract the brighter sources from the maps. We study the APS as a function of Galactic latitude by considering various cuts and as a function of sky position by dividing the sky into patches of about 15 deg x 15 deg in size. The APS of the Galactic radio diffuse synchrotron emission is best fitted by a power law, $C_{\ell} \sim k \ell^α$, with $α\in [-3.0,-2.6]$, where the lower values of $α$ typically correspond to the higher latitudes. Nevertheless, the analysis of the patches reveals that strong local variations exist. The mean APS for $\ell \in [20,40]$ is used to determine the mean spectral index between 408 MHz and 1420 MHz, which is then adopted to extrapolate the synchrotron APS results to the microwave range. A simple extrapolation to 23 GHz of the synchrotron emission APS found at 408 and 1420 MHz does not explain all the power in the WMAP synchrotron component even at middle/high Galactic latitudes. This suggests a significant microwave contribution (of about 50% of the signal) by other components such as free-free or spinning dust emission. The comparison between the extrapolated synchrotron APS and the CMB APS shows that a mask excluding the regions with $|b_{gal}| \lesssim 5^{\circ}$ would reduce the foreground fluctuations to about half of the cosmological ones at 70 GHz even at the lowest multipoles. We discuss the main implications of our analysis for the cosmological exploitation of microwave temperature anisotropy maps.

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