We present the serendipitous discovery of a galaxy group in the XMM-LSS field with MIGHTEE Early Science observations. 20 galaxies are detected in H i in this z ∼ 0.044 group, with a 3σ column density sensitivity of $N_{\rm H\, \small {I}} = 1.6\times 10^{20}\, \mathrm{cm}^{-2}$. This group has not been previously identified, despite residing in a well-studied extragalactic legacy field. We present spatially resolved H i total intensity and velocity maps for each of the objects which reveal environmental influence through disturbed morphologies. The group has a dynamical mass of $\log_{10} (M_{\rm dyn}/\mathrm{M}_\odot) = 12.32$, and is unusually gas-rich, with an H i-to-stellar mass ratio of $\log _{10}(f_{\rm H\, \small {I}}^\mathrm{*}) = -0.2$, which is 0.7 dex greater than expected. The group’s high H i content, spatial, velocity, and identified galaxy type distributions strongly suggest that it is in the early stages of its assembly. The discovery of this galaxy group is an example of the importance of mapping spatially resolved H i in a wide range of environments, including galaxy groups. This scientific goal has been dramatically enhanced by the high sensitivity, large field-of-view, and wide instantaneous bandwidth of the MeerKAT telescope.

中文翻译：

---

MIGHTEE-HI：与 MeerKAT 在 z = 0.044 发现一个富含 H i 的星系群

我们通过 MIGHTEE 早期科学观测展示了在 XMM-LSS 领域偶然发现的一个星系群。在这个 z ∼ 0.044 组的 H i 中检测到 20 个星系，3σ 柱密度灵敏度为 $N_{\rm H\, \small {I}} = 1.6\times 10^{20}\, \mathrm{cm }^{-2}$。尽管居住在一个经过充分研究的河外传统领域，但这个群体以前没有被发现。我们为每个对象呈现空间分辨的 H i 总强度和速度图，这些图通过受干扰的形态揭示环境影响。该组的动态质量为 $\log_{10} (M_{\rm dyn}/\mathrm{M}_\odot) = 12.32$，并且异常富含气体，具有 H i 到恒星的质量$\log _{10}(f_{\rm H\, \small {I}}^\mathrm{*}) = -0.2$ 的比率，比预期大 0.7 dex。该组的高 H i 含量、空间、速度、并且确定的星系类型分布强烈表明它处于组装的早期阶段。这个星系群的发现是在包括星系群在内的广泛环境中映射空间分辨的 H i 重要性的一个例子。MeerKAT 望远镜的高灵敏度、大视场和宽瞬时带宽极大地增强了这一科学目标。