The Spatial Structure of Young Stellar Clusters. I. Subclusters

Abstract

The clusters of young stars in massive star-forming regions show a wide range of sizes, morphologies, and numbers of stars. Their highly subclustered structures are revealed by the MYStIX project's sample of 31,754 young stars in nearby sites of star formation (regions at distances <3.6 kpc that contain at least one O-type star.) In 17 of the regions surveyed by MYStIX, we identify subclusters of young stars using finite mixture models -- collections of isothermal ellipsoids that model individual subclusters. Maximum likelihood estimation is used to estimate the model parameters, and the Akaike Information Criterion is used to determine the number of subclusters. This procedure often successfully finds famous subclusters, such as the BN/KL complex behind the Orion Nebula Cluster and the KW-object complex in M17. A catalog of 142 subclusters is presented, with 1 to 20 subclusters per region. The subcluster core radius distribution for this sample is peaked at 0.17 pc with a standard deviation of 0.43 dex, and subcluster core radius is negatively correlated with gas/dust absorption of the stars -- a possible age effect. Based on the morphological arrangements of subclusters, we identify four classes of spatial structure: long chains of subclusters, clumpy structures, isolated clusters with a core-halo structure, and isolated clusters well fit by a single isothermal ellipsoid.

Accepted for publication in The Astrophysical Journal; 67 pages, 9 figures, and 4 tables. Supplemental materials from the online-version of this article, including machine-readable tables and source code in R are available at the public MYStIX website (http://astro.psu.edu/mystix/)

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Cited by in corpus (9)

• The formation of NGC 3603 young starburst cluster: "prompt" hierarchical assembly or monolithic starburst?
• The Structure, Dynamics and Star Formation Rate of the Orion Nebula Cluster
• The state of globular clusters at birth II: primordial binaries
• The Spatial Structure of Young Stellar Clusters. II. Total Young Stellar Populations
• The evolutionary tracks of young massive star clusters
• The Structural Evolution of Forming and Early Stage Star Clusters
• Young open clusters in the galactic star forming region NGC 6357
• The Herschel/PACS view of the Cep OB2 region: Global protoplanetary disk evolution and clumpy star formation
• The Gaia-ESO Survey: N-body modelling of the Gamma Velorum cluster