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arXiv 0906.0280astro-ph.HE
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绘制最具能量的宇宙射线

Mapping the most energetic cosmic rays

A. M. Hillas

摘要:

使用均匀曝光图和一种不需要选择关联窗口半径的赤经共振形式,研究了2007年8月俄歇合作组探测到的75 Mpc以内活动星系核的光学探测方向与57 EeV以上宇宙射线到达方向之间的相关性。使用后者,即使不使用3.2度窗口,偶然相关的几率也远低于1/10^5;与Nagar和Matulich列出的75 Mpc以内的FRI类射电星系(它们位于活动星系团中)的相关性也同样显著;在其他能量较低的数据中也可以发现相关性。Cen A目前在这个能量下不活跃,因为更遥远的射电星系如此突出。57 EeV切割选择俄歇数据的该启示性(质子)样本的功效可能几乎是偶然的并且不稳健。俄歇样品中的宇宙射线似乎在途中从大约50 Mpc散射了3-4度,在一个相对较好探测的天空区域,星系晕中磁场的Bz分量可能有4度的系统偏转。源似乎大多在120 Mpc以内。这与GZK的生存视界是一致的,但前提是:(a)俄歇能量被低估了~25%;(b)能谱的突然下降不仅仅是GZK效应,而是本质上反映了源的能量截止。

英文摘要:

The correlation between the directions of optically-detected AGNs within 75 Mpc and the arrival directions of cosmic rays above 57 EeV detected by the Auger collaboration up to August 2007 is examined using uniform-exposure plots and a form of right ascension resonance which does not require choice of an association window radius. Using the latter, the chance of accidental correlation is found to be well below 1 in 10^5 even without using 3.2 degree windows; the correlation with FRI-like radio galaxies within 75 Mpc, listed by Nagar & Matulich (which are in AGN clusters), is separately just as significant; and a correlation can also be found in other data at a lower energy. Cen A is currently inactive at this energy, as more distant radio galaxies are so prominent. The efficacy of a 57 EeV cut to select this revelatory (proton) sample of the Auger data may be almost accidental and not robust. The cosmic rays in the Auger sample seem to be scattered by ~3-4 degrees en route, from about 50 Mpc, and in one relatively well probed sky region there may be a 4 degree systematic deflection in a Bz component of the magnetic field in the galactic halo. The sources appear to be mostly within 120 Mpc. This is compatible with a GZK survival horizon, but only if (a) the Auger energies are underestimated by ~25% and (b) the sudden fall in the energy spectrum is not simply a GZK effect but essentially reflects an energy cut-off in the sources.

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