Clumpy shocks as the driver of velocity dispersion in molecular clouds : the effects of self-gravity and magnetic fields
Abstract
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 (σ ∝ LΓ with Γ ≈ 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 power-law relations between σ and L throughout, with indices ranging from Γ = 0.3-1.2. These results are relatively insensitive to the strength and geometry of magnetic fields, provided that the shock is relatively strong. Γ 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 σ-L relation is in clumpy shocks, deviations from the standard Larson relation constrain the strength and behaviour of shocks in spiral galaxies.
Citation
Forgan , D H & Bonnell , I A 2018 , ' Clumpy shocks as the driver of velocity dispersion in molecular clouds : the effects of self-gravity and magnetic fields ' , Monthly Notices of the Royal Astronomical Society , vol. 481 , no. 4 , pp. 4532-4541 . https://doi.org/10.1093/mnras/sty2580
Publication
Monthly Notices of the Royal Astronomical Society
Status
Peer reviewed
ISSN
0035-8711Type
Journal article
Rights
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at: https://doi.org/10.1093/mnras/sty2580
Description
DHF and IAB gratefully acknowledge support from the ECOGAL project, grant agreement 291227, funded by the European Research Council under ERC-2011-ADG.Collections
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