English

Stellar Dynamics and Evolution of the Intermediate-Age Open Clusters NGC 2266 and NGC 2324

Astrophysics of Galaxies 2026-07-27 v1 Solar and Stellar Astrophysics

Abstract

We present a refined astrometric and photometric analysis of the well-studied intermediate-age open clusters NGC 2266 and NGC 2324 using high-precision Gaia DR3 data, complemented by 2MASS and LAMOST DR7 catalogs. Probable cluster members are identified using unsupervised machine learning techniques. We apply both Gaussian Mixture Models (GMMs) and \texttt{pyUPMASK}. We find that the GMM-based membership sample yields a cleaner, more coherent cluster sequence in the Gaia CMDs than pyUPMASK. We identified 719 and 852 high-probability members (P0.7P \geq 0.7) for NGC 2266 and NGC 2324, respectively. Using the parallax method, we determine distances of 3.55 ±\pm 0.23~kpc for NGC 2266 and 4.18 ±\pm 0.24~kpc for NGC 2324. The radius estimates for both clusters are 7.23 ±\pm 0.47 pc and 10.94 ±\pm 0.63 pc. Isochrone fitting estimated ages of 1.1±0.11.1 \pm 0.1~Gyr for NGC 2266 and 790±150790 \pm 150~Myr for NGC 2324. These age estimates were derived assuming metallicities of Z=0.0084Z = 0.0084 and Z=0.0038Z = 0.0038, respectively. The King profile fitting indicates that both clusters exhibit compact, well-defined radial structures. Their tidal radii are 8.848.84' (9.13 pc) for NGC 2266 and 10.9710.97' (13.34 pc) for NGC 2324. The slopes of the present-day mass functions are 1.13±0.181.13\pm0.18 for NGC 2266 and 1.24±0.191.24\pm0.19 for NGC 2324, indicating a deficiency of low-mass stars. The derived mass-function slopes are consistent with dynamical evolution in both clusters. The clusters exhibit short relaxation times, while only NGC 2324 shows a mild indication of mass segregation. This study highlights the power of Gaia astrometry to resolve internal structures within open clusters and refine their dynamical parameters.

Keywords

Cite

@article{arxiv.2607.24614,
  title  = {Stellar Dynamics and Evolution of the Intermediate-Age Open Clusters NGC 2266 and NGC 2324},
  author = {Cyrus Raj and D. Bisht and Ashish Raj},
  journal= {arXiv preprint arXiv:2607.24614},
  year   = {2026}
}

Comments

22 pages, 16 figures, 5 tables, accepted for publication in Advances in Space Research