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arXiv 0910.2702astro-ph.HEastro-ph.CO
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在局域体积中UHECRs与邻近星系的相关性

The correlation of UHECRs with nearby galaxies in the Local Volume

Antonio J. Cuesta, Francisco Prada

摘要:

我们探讨了超高能宇宙射线(UHECRs)局部起源的可能性。使用Karachentsev等人的目录。包括距离小于10 Mpc(本地体积)的邻近星系,我们搜索与皮埃尔俄歇合作迄今为止发布的UHECR事件样本的相关性。对应样本的选择是用可变的距离和光度切割来进行的,这些切割提取了目录中最可能的源。在对扫描进行惩罚之后的机会相关的概率为0.96%,其对应于2.6σ的相关信号。我们发现,对于宇宙射线与星系源的最大角距、到源的最大距离和亮于B波段绝对星等的源,使信号最大化的参数分别为:θ = 3.0度、D_{max} = 4 Mpc和M_B=-15。这意味着一个偏好的UHECRs的到达方向与最近的和最明亮的星系在本地体积。我们注意到D<10 Mpc的邻近星系与UHECR的相关性与Pierre Auger合作组织使用70- 100 Mpc的活动星系核(AGN)而不是本地星系发现的相似,尽管在我们的研究中只有不到20%的宇宙线事件与源相关。然而,在宇宙射线光谱的高能端混合成分的观测证据支持UHECR的本地起源的可能性,因为CNO核可以旅行只有几个Mpc没有强烈的衰减GZK效应,而观察到的抑制能谱将需要更远的来源的情况下,纯质子成分与CMB相互作用。

英文摘要:

We explore the possibility of a local origin for ultra high energy cosmic rays (UHECRs). Using the catalogue of Karachentsev et al. including nearby galaxies with distances less than 10Mpc (Local Volume), we search for a correlation with the sample of UHECR events released so far by the Pierre Auger collaboration. The counterpart sample selection is performed with variable distance and luminosity cuts which extract the most likely sources in the catalogue. The probability of chance correlation after penalizing for scans is 0.96%, which corresponds to a correlation signal of 2.6σ. We find that the parameters that maximize the signal are ψ=3.0deg, D_{max}=4Mpc and M_B=-15 for the maximum angular separation between cosmic rays and galaxy sources, maximum distance to the source, and sources brighter than B-band absolute magnitude respectively. This implies a preference for the UHECRs arrival directions to be correlated with the nearest and most luminous galaxies in the Local Volume. We note that nearby galaxies with D<10Mpc show a similar correlation with UHECRs as compared to that found by The Pierre Auger Collaboration using active galactic nuclei (AGNs) within 70-100Mpc instead of local galaxies, although less than 20% of cosmic ray events are correlated to a source in our study. However, the observational evidence for mixed composition in the high-energy end of the cosmic ray spectrum supports the possibility of a local origin for UHECRs, as CNO nuclei can travel only few Mpc without strong attenuation by the GZK effect, whereas the observed suppression in the energy spectrum would require more distant sources in the case of pure proton composition interacting with the CMB.

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