芬兰奥卢大学Mélina Poulain团队研究了矮星系中星团迁移和合并的证据。2025年4月9日，《自然》杂志发表了这一成果。

核星团（NSC）是宇宙中密度最大的恒星系统。这些星团可以在所有星系类型的中心找到，但往往有利于中等恒星质量在10⁹M⊙左右的星系。目前，有两个主要过程正在争论中，以解释它们的形成：气体流入的原位恒星形成和动力摩擦引起的球状星团（GC）的迁移和合并。对NSC恒星群的研究表明，前者在大质量星系中占主导地位，而后者在矮星系中占优势，两者在中等质量时贡献相等。然而，到目前为止，还没有观察到GC的持续合并来证实这一情况。

研究组使用哈勃太空望远镜的高分辨率图像，偶然发现了五个具有复杂核区的矮星系，其特征是多个核和潮汐尾。这些结构在互补的N体模拟中得到了再现，支持了它们是由星团迁移和合并引起的解释。该过程的小检测率和短模拟时间尺度（低于100 Myr）可以解释为什么以前没有观察到这一点。该研究强调，需要进行高分辨率的大型调查，以全面绘制迁移场景步骤。

附：英文原文

Title: Evidence of star cluster migration and merger in dwarf galaxies

Author: Poulain, Mlina, Smith, Rory, Duc, Pierre-Alain, Marleau, Francine R., Habas, Rebecca, Durrell, Patrick R., Fensch, Jrmy, Lim, Sungsoon, Mller, Oliver, Paudel, Sanjaya, Snchez-Janssen, Rubn

Issue&Volume: 2025-04-09

Abstract: Nuclear star clusters (NSCs) are the densest stellar systems in the Universe. These clusters can be found at the centre of all galaxy types but tend to favour galaxies of intermediate stellar mass around 109M⊙ (refs.1,2). At present, two main processes are under debate to explain their formation: in situ star formation from gas infall3 and migration and merging of globular clusters (GCs) caused by dynamical friction4. Studies5,6,7,8,9 of NSC stellar populations suggest that the former predominates in massive galaxies, whereas the latter prevails in dwarf galaxies, and both contribute equally at intermediate mass. However, until now, no ongoing merger of GCs has been observed to confirm this scenario. Here we report the serendipitous discovery of five dwarf galaxies with complex nuclear regions, characterized by multiple nuclei and tidal tails, using high-resolution images from the Hubble Space Telescope. These structures have been reproduced in complementary N-body simulations, supporting the interpretation that they result from migrating and merging of star clusters. The small detection rate and short simulated timescales (below 100Myr) of this process may explain why this has not been observed previously. This study highlights the need for large surveys with high resolution to fully map the migration scenario steps.

DOI: 10.1038/s41586-025-08783-9

Source: https://www.nature.com/articles/s41586-025-08783-9