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Turbulent action at a distance due to stellar feedback in magnetized clouds


A fundamental property of molecular clouds is that they are turbulent1, but how this turbulence is generated and maintained is unknown. One possibility is that stars forming within the cloud regenerate turbulence via their outflows, winds and radiation (‘feedback’)2. However, disentangling motions created by feedback from the initial cloud turbulence is challenging. Here, we confront the relationship between stellar feedback and turbulence by identifying and separating the local and global impact of stellar winds. We analyse magnetohydrodynamic simulations in which we track wind material as it interacts with the ambient cloud. By distinguishing between launched material, gas entrained by the wind and pristine gas we show energy is transferred away from the sources via magnetic waves excited by the expanding wind shells. This action at a distance enhances the fraction of stirring motion compared with compressing motion and produces a flatter velocity power spectrum. We conclude that stellar feedback accounts for significant energy transfer within molecular clouds—an impact enhanced by magnetic waves, which have previously been neglected by observations. Overall, stellar feedback can partially offset global turbulence dissipation.

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Fig. 1: Velocity dispersion, vrms, as a function of time, t.
Fig. 2: Gas density and magnetic field strength (\(B_{\rm{rms}}\) = \(\left( {B_x^2 + B_y^2 + B_z^2} \right)^{1/2}\)).
Fig. 3: Velocity power spectra for the strong-wind run (W1T2) at various times.
Fig. 4: Fraction of turbulence that is solenoidal versus time.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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S.S.R.O. thanks A. Lee, B. Gaches and P. Kumar for helpful comments. S.S.R.O. acknowledges support from NSF Career grant AST-1650486. The data analyses, images and animations were made possible by yt, an open-source Python package for analysing and visualizing volumetric data. Some of the simulations were performed on the Yale University Omega cluster, which is supported in part by the facilities and staff of the Yale University Faculty of Arts and Sciences High Performance Computing Center. The rest of the simulations were carried out on resources at the Massachusetts Green High Performance Computing Center, supported by staff at the University of Massachusetts.

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Authors and Affiliations



S.S.R.O. performed all the simulations without self-gravity, carried out the analyses, produced the figures and wrote the paper. Y.L. carried out the simulations with gravity and performed a preliminary analysis.

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Correspondence to Stella S. R. Offner.

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Supplementary Information

Supplementary Tables 1–2, Supplementary Figures 1–5, Supplementary Video 1 caption

Supplementary Video 1

Slices through the magnetic field strength for two sources in model W2T2

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Offner, S.S.R., Liu, Y. Turbulent action at a distance due to stellar feedback in magnetized clouds. Nat Astron 2, 896–900 (2018).

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