Regular magnetic fields are frequently found within and in the outskirts of galaxies, but their presence, properties, and origin has not yet been established for galaxy groups. On the basis of broadband radio polarimetric imaging with the Westerbork Synthesis Radio Telescope (WSRT), we made use of Rotation Measure Synthesis to disentangle contributions from magnetic fields on various scales for several polarised radio sources inside, behind, or in the vicinity of the Stephan's Quintet (HCG92, SQ). We recognise the signature of a large-scale, genuinely regular, magnetised screen, seemingly constrained to the Quintet itself. Although we cannot exclude a contribution from the Milky Way, our analysis favours a magnetic structure within the SQ system. If indeed associated with the galaxy group in question, it would span a volume of at least $60\,\times\,40\,\times\,20\,\mathrm{kpc}$ and have a strength at least as high as that previously detected within large spiral galaxies. This field would then surpass the extent of any other known galactic, regular magnetic fields, have a considerable strength of a few microgauss, and would be the first known example of such a structure in a galaxy system other than a galaxy pair. Several other explanations are also presented and evaluated.

中文翻译：

---

与斯蒂芬五重奏相关的大规模、规则的星系际磁场？

在星系内部和外围经常发现规则磁场，但尚未确定星系群的存在、性质和起源。在 Westerbork 合成射电望远镜 (WSRT) 的宽带射电极化成像的基础上，我们利用旋转测量合成来解开 Stephan 内部、后面或附近的几个极化射电源的各种尺度的磁场贡献。五重奏（HCG92，SQ）。我们认识到一个大型的、真正规则的、磁化的屏幕的特征，似乎仅限于五重奏本身。虽然我们不能排除银河系的贡献，但我们的分析倾向于 SQ 系统内的磁结构。如果确实与所讨论的星系群相关联，它的体积至少为 60 美元\，\times\,40\,\times\,20\,\mathrm{kpc}$ 并且具有至少与先前在大型螺旋星系中检测到的强度一样高的强度。然后，该磁场将超过任何其他已知的银河系规则磁场的范围，具有几微高斯的相当大的强度，并且将是除星系对之外的星系系统中此类结构的第一个已知示例。还提出和评估了其他几种解释。