Star Formation Patterns and Hierarchies

Abstract

Star formation occurs in hierarchical patterns in both space and time. Galaxies form large regions on the scale of the interstellar Jeans length and these large regions apparently fragment into giant molecular clouds and cloud cores in a sequence of decreasing size and increasing density. Young stars follow this pattern, producing star complexes on the largest scales, OB associations on smaller scales, and so on down to star clusters and individual stars. Inside each scale and during the lifetime of the cloud on that scale, smaller regions come and go in a hierarchy of time. As a result, cluster positions are correlated with power law functions, and so are their ages. At the lowest level in the hierarchy, clusters are observed to form in pairs. For any hierarchy like this, the efficiency is automatically highest in the densest regions. This high efficiency promotes bound cluster formation. Also for any hierarchy, the mass function of the components is a power law with a slope of around -2, as observed for clusters.

16 pages, 2 figures, Ecole Evry Schatzman 2010: Star Formation in the Local Universe. Lecture 3 of 5

References in corpus (16)

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• The structures of embedded clusters in the Perseus, Serpens and Ophiuchus molecular clouds
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Cited by in corpus (13)

• Molecular Gas and Star Formation in Nearby Disk Galaxies
• Nonthermal particles and photons in starburst regions and superbubbles
• Expanding associations in the Vela-Puppis region: 3D structure and kinematics of the young population
• High resolution study of the cluster complexes in a lensed spiral at redshift ~1.5; constraints on the bulge formation and disk evolution
• Short-lived radioactivity in the early Solar System: the Super-AGB star hypothesis
• The challenge of simulating the star cluster population of dwarf galaxies with resolved interstellar medium
• Revealing a Ring-like Cluster Complex in a Tidal Tail of the Starburst Galaxy NGC 2146
• The VMC Survey. XXIX. Turbulence-Controlled Hierarchical Star Formation in the Small Magellanic Cloud
• The properties, origin and evolution of stellar clusters in galaxy simulations and observations
• The physics governing the upper truncation mass of the globular cluster mass function
• A starburst in the core of a galaxy cluster: The dwarf irregular NGC 1427A in Fornax
• Topography of the Young Galactic Disk: Spatial and Kinematic Patterns of the Clustered Star Formation in the Solar Neighborhood
• The Panchromatic Hubble Andromeda Treasury. Progression of Large-Scale Star Formation across Space and Time in M31