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On the Dynamical Evolution of Young Stellar Aggregates

Wiśniowski T., Rickman H., Wajer P.

Acta Astronomica

2021

Vol. 71, No. 3

243--260

We report on N-body simulations of embedded stellar clusters over a time span of 10 Myr from inception until several crossing times after gas expulsion. We focus our attention on the survivability of bound stellar clusters following gas expulsion. The final values of the bound fraction are significantly larger in case the initial structure is relatively open with a Plummer radius of ≈1 pc than for a much stronger degree of concentration. However, only one of 12 simulated clusters shows any promise of leaving behind a long-lived, bound system. We tentatively conclude that the predictions of our model are in rough agreement with the observed "infant mortality" of newborn stellar aggregates. We also find that relaxation effects due to close encounters, while present, are significantly curtailed by the rapid expansion of the clusters.

Open Clusters in 2MASS Photometry. II. Mass Function and Mass Segregation

Bukowiecki Ł., Maciejewski G., Konorski P., Niedzielski A.

Acta Astronomica

2012

Vol. 62, No. 3

281--296

This is a continuation of our study of open clusters based on the 2-Micron All Sky Survey photometry. Here we present the results of the mass function analysis for 599 known open clusters in the Milky Way. The main goal of this project is a study of the dynamical state of open clusters, the mass segregation effect and an estimate of the total mass and the number of cluster members. We noticed that the cluster size (core and overall radii) decreases along dynamical evolution of clusters. The cluster cores evolve faster than the halo regions and contain proportionally less low-mass stars from the beginning of the cluster dynamical evolution. We also noticed, that the star density decreases for the larger clusters. Finally, we found an empirical relation describing the exponential decrease of the mass function slope with the dynamical evolution of clusters.