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Title: The spatial structure of young stellar clusters. I. Subclusters

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 M 17. A catalog of 142 subclusters is presented, with 1-20 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, andmore » isolated clusters well fit by a single isothermal ellipsoid.« less
Authors:
; ; ; ; ;  [1] ;  [2] ;  [3] ; ; ;  [4] ;  [5]
  1. Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
  2. School of Mathematics and Statistics, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)
  3. Department of Physics, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1 (Canada)
  4. Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, Devon EX4 4SB (United Kingdom)
  5. Department of Physics and Astronomy, California State Polytechnic University, 3801 West Temple Avenue, Pomona, CA 91768 (United States)
Publication Date:
OSTI Identifier:
22356780
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 787; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; BORON NITRIDES; CATALOGS; DISTRIBUTION; DUSTS; MAXIMUM-LIKELIHOOD FIT; MIXTURES; NEBULAE; STAR CLUSTERS; STARS