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首页> 外文期刊>The Astrophysical Journal. Letters >Lower bounds on magnetic fields in intergalactic voids from long-term GeV-TeV light curves of the blazar MRK 421
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Lower bounds on magnetic fields in intergalactic voids from long-term GeV-TeV light curves of the blazar MRK 421

机译：Blazar MRK 421的长期GeV-TeV光曲线对银河系空隙中磁场的下界

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摘要

Lower bounds are derived on the amplitude B of intergalactic magnetic fields (IGMFs) in the region between Galaxy and the blazar Mrk 421, from constraints on the delayed GeV pair-echo flux that are emitted by secondary e ~- e ~+ produced in γγ interactions between primary TeV gamma rays and the cosmic infrared background. The distribution of galaxies mapped by the Sloan Digital Sky Survey shows that this region is dominated by a large intergalactic void. We utilize data from long-term, simultaneous GeV-TeV observations by the Fermi Large Area Telescope and the ARGO-YBJ experiment extending over 850 days. For an assumed value of B, we evaluate the daily GeV pair-echo flux expected from the TeV data, select the dates where this exceeds the Fermi 2σ sensitivity, compute the probability that this flux is excluded by the Fermi data for each date, and then combine the probabilities using the inverse normal method. Consequently, we exclude B < 10~(-20.5) G for a field coherence length of 1 kpc at ～4σ level, as long as plasma instabilities are unimportant for cooling of the pair beam. This is much more significant than the 2σ bounds we obtained previously from observations of Mrk 501, by virtue of more extensive data from the ARGO-YBJ, as well as improved statistical analysis. Compared with most other studies of IGMF bounds, the evidence we present here for a non-zero IGMF is more robust as it does not rely on unproven assumptions on the primary TeV emission during unobserved periods.
机译：下界是由银河系和blazar Mrk 421之间区域中的星际磁场（IGMF）的振幅B得出的，这是由对γγ中产生的次级e〜-e〜+发射的延迟GeV对回波通量的约束得出的TeV伽马射线与宇宙红外背景之间的相互作用。斯隆数字天空调查所绘制的星系分布表明，该区域主要由较大的星际空隙所主导。我们利用来自费米大面积望远镜的长期GeV-TeV同步观测数据以及850天以上的ARGO-YBJ实验数据。对于B的假定值，我们评估从TeV数据获得的每日GeV对回波通量，选择超出费米2σ灵敏度的日期，计算每个日期费米数据排除该通量的概率，以及然后使用逆法线法合并概率。因此，只要等离子不稳定性对于冷却双束光束不重要，我们就可以在〜4σ的水平上将场长1 kpc的场相干长度排除为B <10〜（-20.5）G。由于来自ARGO-YBJ的更广泛的数据以及经过改进的统计分析，这比我们先前从Mrk 501的观测中获得的2σ边界要重要得多。与大多数其他关于IGMF边界的研究相比，我们在这里提出的非零IGMF的证据更为可靠，因为它不依赖未经观察期间未证明的关于主要TeV发射的假设。

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