Clumpy shocks as the driver of velocity dispersion in molecular clouds: the effects of self-gravity and magnetic fields
| Autor: | Duncan Forgan, Ian A. Bonnell |
|---|---|
| Přispěvatelé: | European Research Council, University of St Andrews. School of Physics and Astronomy, University of St Andrews. St Andrews Centre for Exoplanet Science |
| Rok vydání: | 2018 |
| Předmět: |
Gravity (chemistry)
MHD Astrophysics::High Energy Astrophysical Phenomena NDAS FOS: Physical sciences Astrophysics 01 natural sciences 0103 physical sciences QB Astronomy 010306 general physics 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics QB Physics numerical [Methods] kinematics and dynamic [ISM] Molecular cloud European research Velocity dispersion Astronomy and Astrophysics Astrophysics - Astrophysics of Galaxies Magnetic field Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) Hydrodynamics structure [ISM] Magnetohydrodynamics clouds [ISM] |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 481:4532-4541 |
| ISSN: | 1365-2966 0035-8711 |
| Popis: | We revisit an alternate explanation for the turbulent nature of molecular clouds - namely, that velocity dispersions matching classical predictions of driven turbulence can be generated by the passage of clumpy material through a shock. While previous work suggested this mechanism can reproduce the observed Larson relation between velocity dispersion and size scale ($\sigma \propto L^{\Gamma}$ with $\Gamma \approx 0.5$), the effects of self-gravity and magnetic fields were not considered. We run a series of smoothed particle magnetohydrodynamics experiments, passing clumpy gas through a shock in the presence of a combination of self-gravity and magnetic fields. We find powerlaw relations between $\sigma$ and $L$ throughout, with indices ranging from $\Gamma=0.3-1.2$. These results are relatively insensitive to the strength and geometry of magnetic fields, provided that the shock is relatively strong. $\Gamma$ is strongly sensitive to the angle between the gas' bulk velocity and the shock front, and the shock strength (compared to the gravitational boundness of the pre-shock gas). If the origin of the $\sigma-L$ relation is in clumpy shocks, deviations from the standard Larson relation constrain the strength and behaviour of shocks in spiral galaxies. Comment: 12 pages, 22 figures, accepted to MNRAS |
| Databáze: | OpenAIRE |
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