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Paper: A Steeper Stellar Mass Spectrum in the Outer Galaxy?
Volume: 287, Galactic Star Formation Across the Stellar Mass Spectrum
Page: 92
Authors: Brand, J.; Wouterloot, J. G. A.; Rudolph, A. L.; de Geus, E. J.
Abstract: We discuss the results of high resolution (∼ 0.1-0.2 pc) BIMA CO observations of the central regions of 3 molecular clouds in the far-outer Galaxy (FOG). We identify clumps and investigate their stability by using the virial theorem, including terms due to gravity, turbulence, magnetic field, and interclump gas pressure, and make a comparison with clumps in local clouds (RMC and Orion B South). While a reasonable combination of these forces can render most clumps stable, an interesting difference between FOG and local clumps emerges when comparing only gravity and turbulence. In the FOG these forces are in equilibrium (virial parameter α ≈ 1) for clumps down to the lowest masses found (a few M), but for local clumps α ≈ 1 only for clumps with masses larger than a few tens of M. Thus it appears that in the FOG gravity is the dominant force down to a much lower mass than in local clouds, implying that gravitational collapse and star formation may occur more readily even in the smallest clumps. This might explain the apparently steeper IMF found in the outer Galaxy.
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