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arXiv 0907.1354astro-ph.HEastro-ph.CO
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超高能下各向异性与化学成分

Anisotropy vs chemical composition at ultra-high energies

Martin Lemoine, Eli Waxman

摘要:

本文提出并讨论了超高能宇宙射线的化学成分的测试,依赖于作为能量的函数测量的各向异性图案。特别是,我们表明,如果一个记录的各向异性信号产生的重核的电荷Z以上的能量E_{thr},应该记录一个更强(可能更强)的各向异性能量> E_{thr} /Z由于质子组件,预计将与重核的源。这一结论仍然是强大的参数方面的特点来源,它并不依赖于在所有的天体物理磁场的建模。作为一个具体的例子,我们应用这个测试的皮埃尔俄歇天文台的最新数据。假设在55 EeV以上所报道的各向异性不是统计上的偶然,并且在能量<10 EeV时没有观察到显著的各向异性,我们表明,向Cen A的明显聚集不能归因于重核。关于与附近活动星系核的明显过度相关,也得出了类似的结论。然后我们讨论了一个磁光强度的鲁棒下限,这个下限是一个源必须具有的,以便能够将电荷Z的粒子加速到100 EeV,L_B>10^{45}Z^{-2}erg/s。结合上述结论,我们认为,目前的PAO数据不支持宇宙线起源于活动射电安静甚至射电大声星系的模型。最后,我们证明,在Cen A方向的明显集群可以解释的贡献,最后几个伽马射线暴或磁星在宿主星系由于散射的宇宙射线的磁化叶。

英文摘要:

This paper proposes and discusses a test of the chemical composition of ultra-high energy cosmic rays that relies on the anisotropy patterns measured as a function of energy. In particular, we show that if one records an anisotropy signal produced by heavy nuclei of charge Z above an energy E_{thr}, one should record an even stronger (possibly much stronger) anisotropy at energies >E_{thr}/Z due to the proton component that is expected to be associated with the sources of the heavy nuclei. This conclusion remains robust with respect to the parameters characterizing the sources and it does not depend at all on the modelling of astrophysical magnetic fields. As a concrete example, we apply this test to the most recent data of the Pierre Auger Observatory. Assuming that the anisotropy reported above 55EeV is not a statistical accident, and that no significant anisotropy has been observed at energies <10EeV, we show that the apparent clustering toward Cen A cannot be attributed to heavy nuclei. Similar conclusions are drawn regarding the apparent excess correlation with nearby active galactic nuclei. We then discuss a robust lower bound to the magnetic luminosity that a source must possess in order to be able to accelerate particles of charge Z up to 100EeV, L_B>10^{45}Z^{-2}erg/s. Using this bound in conjunction with the above conclusions, we argue that the current PAO data does not support the model of cosmic ray origin in active radio-quiet or even radio-loud galaxies. Finally, we demonstrate that the apparent clustering in the direction of Cen A can be explained by the contribution of the last few gamma-ray bursts or magnetars in the host galaxy thanks to the scattering of the cosmic rays on the magnetized lobes.

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