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arXiv 1407.5686astro-ph.CO
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Milky Way对宇宙微波背景的畸变

The Distortion of the Cosmic Microwave Background by the Milky Way

Benjamin Czaja, Benjamin C. Bromley

摘要:

银河系可以作为宇宙微波背景(CMB)的大尺度弱引力透镜。我们研究这种效果,使用光子射线跟踪代码和银河系的质量分布与磁盘,凸起和晕组件。对于银河系中位于太阳坐标系的观测者来说,CMB光子路径的弯曲被限制在小于一个角秒,并且仅限于在银河系中心几度范围内通过的光线。然而,整个天空都受到影响,导致CMB在大角度尺度上的全局扭曲。这些失真会导致CMB天空温度球谐展开的低阶多极子泄漏到高阶模中。因此,CMB偶极的分量是由本星系群相对于本星系宇宙静止坐标系的运动产生的,它对太阳系中观测者的高阶矩有贡献。我们的射线跟踪代码,我们表明,这种现象是不敏感的具体选择银河系的潜力。我们还定量排除它作为一个贡献者CMB异常,如功率不对称或相关的排列低阶多极矩。

英文摘要:

The Milky Way can act as a large-scale weak gravitational lens of the cosmic microwave background (CMB). We study this effect using a photon ray-tracing code and a Galactic mass distribution with disk, bulge and halo components. For an observer at the Sun's coordinates in the Galaxy, the bending of CMB photon paths is limited to less than one arcsecond, and only for rays that pass within a few degrees of the Galactic Center. However, the entire sky is affected, resulting in global distortions of the CMB on large angular scales. These distortions can cause the low-order multipoles of a spherical harmonic expansion of the CMB sky temperature to leak into higher-order modes. Thus the component of the CMB dipole that results from the Local Group's motion relative to the local cosmic frame of rest contributes to higher-order moments for an observer in the solar system. With our ray-tracing code we show that the phenomenon is not sensitive to the specific choice of Galactic potential. We also quantitatively rule it out as a contributor to CMB anomalies such as power asymmetry or correlated alignment of low-order multipole moments.

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