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Title: THE SPATIAL STRUCTURE OF YOUNG STELLAR CLUSTERS. III. PHYSICAL PROPERTIES AND EVOLUTIONARY STATES

We analyze the physical properties of stellar clusters that are detected in massive star-forming regions in the MYStIX project—a comparative, multiwavelength study of young stellar clusters within 3.6 kpc that contain at least one O-type star. Tabulated properties of subclusters in these regions include physical sizes and shapes, intrinsic numbers of stars, absorptions by the molecular clouds, and median subcluster ages. Physical signs of dynamical evolution are present in the relations of these properties, including statistically significant correlations between subcluster size, central density, and age, which are likely the result of cluster expansion after gas removal. We argue that many of the subclusters identified in Paper I are gravitationally bound because their radii are significantly less than what would be expected from freely expanding clumps of stars with a typical initial stellar velocity dispersion of ∼3 km s{sup −1} for star-forming regions. We explore a model for cluster formation in which structurally simpler clusters are built up hierarchically through the mergers of subclusters—subcluster mergers are indicated by an inverse relation between the numbers of stars in a subcluster and their central densities (also seen as a density versus radius relation that is less steep than would be expected from puremore » expansion). We discuss implications of these effects for the dynamical relaxation of young stellar clusters.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4]
  1. Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802 (United States)
  2. Department of Physics, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1 (Canada)
  3. Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, Devon EX4 4SB (United Kingdom)
  4. Instituto de Fisica y Astronomía, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, Valparaíso (Chile)
Publication Date:
OSTI Identifier:
22518767
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 812; 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; CLUSTER EXPANSION; CORRELATIONS; DENSITY; RELAXATION; STAR CLUSTERS; STAR EVOLUTION; STARS; VELOCITY; X RADIATION