arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1409.0883astro-ph.HEastro-ph.GA
收藏

俄歇天文台和望远镜阵重建四极矩的偶然纬度

The Fortuitous Latitude of the Pierre Auger Observatory and Telescope Array for Reconstructing the Quadrupole Moment

Peter B. Denton, Thomas J. Weiler

摘要:

确定最高能量宇宙射线到达方向的各向异性是天体物理学中的一项重要任务。将天空划分为球谐函数作为各向异性的度量是常见和有用的。两个最低的非平凡球谐函数,偶极子和四极子,是特别感兴趣的,因为这些分布封装了一个占主导地位的单一源和一个平面的源,以及提供相对较高的统计。目前,探测超高能宇宙射线的最佳实验都是在地面上进行的,由于地球上的固定实验地点,天空中的照射量极不均匀。这种不均匀的曝光增加了推断各向异性的复杂性和误差。事实证明,存在一个实验的最佳纬度,在这个纬度上,非均匀曝光不会削弱四极矩的影响。我们推导出了最佳纬度,并发现(可能是偶然的巧合)这个最佳纬度贯穿了南半球最大的宇宙线实验皮埃尔俄歇天文台(PAO),并接近北半球最大的宇宙线实验望远镜阵列(TA)。因此,假设四极分布,PAO和TA可以重建宇宙线的四极分布,以高精度,而不考虑他们的部分天空曝光。

英文摘要:

Determining anisotropies in the arrival directions of cosmic rays at the highest energy is an important task in astrophysics. It is common and useful to partition the sky into spherical harmonics as a measure of anisotropy. The two lowest nontrivial spherical harmonics, the dipole and the quadrupole, are of particular interest, since these distributions encapsulate a dominant single source and a plane of sources, as well as offering relatively high statistics. The best experiments for the detection of ultra high energy cosmic rays currently are all ground-based, with highly nonuniform exposures on the sky resulting from the fixed experimental locations on the earth. This nonuniform exposure increases the complexity and error in inferring anisotropies. It turns out that there is an optimal latitude for an experiment at which nonuniform exposure does not diminish the inference of the quadrupole moment. We derive the optimal latitude, and find that (presumably by a fortuitous coincidence) this optimal latitude runs through the largest cosmic ray experiment, Pierre Auger Observatory (PAO) in the Southern Hemisphere, and close to the largest cosmic ray experiment in the Northern Hemisphere, Telescope Array (TA). Consequently, assuming a quadrupole distribution, PAO and TA can reconstruct the cosmic ray quadrupole distribution to a high precision, without concern for their partial sky exposure.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑