Ongoing hierarchical massive cluster assembly: the LISCA II structure in the Perseus complex

A. Della Croce*, E. Dalessandro, A. Livernois, E. Vesperini, C. Fanelli, L. Origlia, M. Bellazzini, E. Oliva, N. Sanna, A. L. Varri

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We report on the identification of a massive (∼105 M⊙) substructured stellar system in the Galactic Perseus complex likely undergoing hierarchical cluster assembly. This system comprises nine star clusters (including the well-known clusters NGC 654 and NGC 663) and an extended and low-density stellar halo. Gaia-DR3 and available spectroscopic data show that all its components are physically consistent in 6D phase-space (position, parallax, and 3D motion), and homogeneous in age (14–44 Myr) and chemical content (half-solar metallicity). In addition, the system’s global stellar density distribution is that of typical star clusters and shows clear evidence of mass segregation. We find that the hierarchical structure is mostly contracting toward the center with a speed of up to ≃4 − 5 km s−1, while the innermost regions expand at a lower rate (about ≃1 km s−1) and are dominated by random motions. Interestingly, this pattern is dominated by the kinematics of massive stars, while low-mass stars (M 
Original languageEnglish
Article numberA93
Pages (from-to)1-20
Number of pages20
JournalAstronomy and Astrophysics
Publication statusPublished - 6 Jun 2023

Keywords / Materials (for Non-textual outputs)

  • galaxies: star clusters
  • general / open clusters and associations
  • general / astrometry / stars
  • kinematics and dynamics / stars: formation


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