Tracing the W3/W4/W5 and Perseus complex dynamical evolution with star clusters

¹ Department of Physics and Astronomy ‘Augusto Righi’, University of Bologna, via Gobetti 93/2, 40129 Bologna, Italy
² INAF – Astrophysics and Space Science Observatory of Bologna, via Gobetti 93/3, 40129 Bologna, Italy
³ Department of Astronomy, Indiana University, Swain West, 727 E. 3rd Street, IN 47405 Bloomington, USA
⁴ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Florence, Italy

^★ Corresponding author: alessandro.dellacroce@inaf.it

Received: 21 January 2025
Accepted: 14 April 2025

Abstract

The Perseus complex offers an ideal testbed to study cluster formation and early evolution as it hosts two major hierarchical structures (namely LISCA I and LISCA II) and the W3/W4/W5 (W345) region characterized by recent star formation. The aim of this work was to provide a full characterization of the population of star clusters in the W345 region, in terms of their structural, photometric, and kinematic properties. The clusters were then used to probe the dynamical properties of the W345 region and, on a larger scale, to investigate the evolution of the Perseus complex. We used Gaia DR3 data to search for star clusters in the W345 region and characterize them in terms of their density structure, ellipticity, internal dynamical state, and ages. We also used young stellar object (YSO) catalogs from near-infrared surveys cross-matched with Gaia data to probe their kinematics in the region. We identified five stellar clusters belonging to the W345 complex. The three younger clusters are still partially embedded in the gas and show evidence of expansion, while the older clusters cleared the surrounding gas. We also found that YSOs trace the parent gas structure and possibly its kinematics. Thanks to the 6D information available for star clusters, we followed their orbital evolution to assess the formation conditions and evolution of the complex. When accounting for the Galactic potential, we find that the Perseus complex is not dispersing. The observed expansion might be a projection effect due to stars orbiting the Galaxy at different velocities. In addition, we find that the LISCA I and W345 systems formed some 20–30 Myr ago just a few hundred parsecs away, while LISCA II was originally ≃0.75–1 kpc apart. Finally, we also assessed the impact of spiral arm perturbations by constructing a tailored Galactic potential that matches the observed Galactic spiral arm structure. We find that spiral structures drag star clusters toward higher-density regions, possibly keeping clusters closer for longer than the unperturbed, axisymmetric case.