4.6 Article

THE IMPACT OF THERMODYNAMICS ON GRAVITATIONAL COLLAPSE: FILAMENT FORMATION AND MAGNETIC FIELD AMPLIFICATION

期刊

ASTROPHYSICAL JOURNAL LETTERS
卷 760, 期 2, 页码 -

出版社

IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/760/2/L28

关键词

ISM: general; ISM: kinematics and dynamics; ISM: magnetic fields; stars: formation

资金

  1. Fellow of the Baden-Wurttemberg Stiftung
  2. program International Collaboration II via contract research [P-LS-SPII/18]
  3. SNF grant [200020_137896]
  4. Deutsche Forschungsgemeinschaft (DFG) through the SPP 1573 Physics of the Interstellar Medium [SCHL 1964/1-1]
  5. SFB 963 Astrophysical Flow Instabilities and Turbulence
  6. DFG via the SPP 1573 [1358/14-1, SM 321/1-1]
  7. SFB 881 The Milky Way System [B1, B2, B3]
  8. DFG [BA 3706/1-1]
  9. Australian Research Council under the Discovery Projects scheme [DP110102191]
  10. Swiss National Science Foundation (SNF) [200020_137896] Funding Source: Swiss National Science Foundation (SNF)

向作者/读者索取更多资源

Stars form by the gravitational collapse of interstellar gas. The thermodynamic response of the gas can be characterized by an effective equation of state. It determines how gas heats up or cools as it gets compressed, and hence plays a key role in regulating the process of stellar birth on virtually all scales, ranging from individual star clusters up to the galaxy as a whole. We present a systematic study of the impact of thermodynamics on gravitational collapse in the context of high-redshift star formation, but argue that our findings are also relevant for present-day star formation in molecular clouds. We consider a polytropic equation of state, P = k rho Gamma, with both sub-isothermal exponents Gamma < 1 and super-isothermal exponents Gamma > 1. We find significant differences between these two cases. For Gamma > 1, pressure gradients slow down the contraction and lead to the formation of a virialized, turbulent core. Weak magnetic fields are strongly tangled and efficiently amplified via the small-scale turbulent dynamo on timescales corresponding to the eddy-turnover time at the viscous scale. For Gamma < 1, on the other hand, pressure support is not sufficient for the formation of such a core. Gravitational contraction proceeds much more rapidly and the flow develops very strong shocks, creating a network of intersecting sheets and extended filaments. The resulting magnetic field lines are very coherent and exhibit a considerable degree of order. Nevertheless, even under these conditions we still find exponential growth of the magnetic energy density in the kinematic regime.

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