English

GULP II: Hierarchical Distribution and Evolution of Young Stellar Structures in NGC 4449

Astrophysics of Galaxies 2025-05-07 v1

Abstract

We investigate the hierarchical distribution and evolution of young stellar structures in the dwarf starburst galaxy NGC 4449 using data from the GULP survey. By analyzing the spatial distribution of field stars younger than 100 Myr, we identify large-scale stellar complexes and substructures using HDBSCAN -- a density-based clustering algorithm -- and trace their evolution over time. While comparing these stellar structures in different regions of the galaxy, we find that the central bar-like region shows a clear expansion of the structures within the first \sim 60 Myrs, while the arm-like structure in the NE shows no discernible trend, possibly due to external perturbations from tidal interactions with a neighboring galaxy. An age-dependent two point correlation function (TPCF) analysis shows that young stars exhibit a strong hierarchical distribution, with clustering strength decreasing over time. The power-law slope of the TPCF, which starts at α0.65\alpha \sim 0.65 for stars younger than 5 Myr, shows a slight decline to α0.4\alpha \sim 0.4 for stars older than 50 Myr, though it does not reach a completely flat (random) distribution. This trend indicates a subtle weakening of structural hierarchy among young (<<100 Myr) stars, which is primarily driven by internal stellar motions. Future work will extend this analysis to the remaining 26 galaxies in the GULP survey to better constrain the role of the galactic environment in shaping the hierarchical evolution of young stellar populations.

Keywords

Cite

@article{arxiv.2505.02890,
  title  = {GULP II: Hierarchical Distribution and Evolution of Young Stellar Structures in NGC 4449},
  author = {Beena Meena and Elena Sabbi and Peter Zeidler and Bruce G. Elmegreen and Jan J. Eldridge and Varun Bajaj and Mario Gennaro and Anna Pasquali and Debra M. Elmegreen and Ralf S. Klessen and Linda J. Smith and Luciana Bianchi and Aida Wofford and Pietro Facchini and John S. Gallagher and Daniela Calzetti and Eva K. Grebel and Angela Adamo},
  journal= {arXiv preprint arXiv:2505.02890},
  year   = {2025}
}

Comments

23 Pages, 11 Figures, 2 Tables, Accepted for publication in ApJ