The Velocity Statistics of Turbulent Clouds in the Presence of Gravity, Magnetic fields, Radiation, and Outflow Feedback

Yue Hu, Christoph Federrath, Siyao Xu, Sajay Sunny Mathew

Published 2022-03-03Version 1

The interaction of turbulence, magnetic fields, self-gravity, and stellar feedback within molecular clouds is crucial for understanding star formation. We study the effects of self-gravity and outflow feedback on the properties of the turbulent velocity via the structure function over length scales from $\sim$ 0.01 pc to 2 pc. We analyze a series of three-dimensional, magnetohydrodynamical (MHD) simulations of star cluster formation, including self-gravity, turbulence, magnetic fields, stellar radiative heating, and outflow feedback. We observe that self-gravity and protostellar outflows increase the velocity fluctuations over all length scales. In particular, outflows can amplify the velocity fluctuations by up to a factor of $\sim$7 on scales $\sim$ 0.01 - 0.2 pc and drive turbulence up to a scale of $\sim$ 1 pc. The amplified velocity fluctuations provide more support against gravity and enhance fragmentation on small scales. The role of self-gravity is more significant on smaller dense clumps and it increases the fraction of the compressive velocity component up to a scale of $\sim$ 0.2 pc. However, outflow feedback drives both solenoidal and compressive modes, but it induces a higher fraction of solenoidal modes relative to compressive modes. Thus, with outflows, the dense core ends up with a slightly higher fraction of solenoidal modes. We find that the compressible fraction is fairly constant with about 1/3 on scales $\sim$ 0.1 - 0.2 pc. The combined effect of enhanced velocity dispersion and reduced compressive fraction contributes to a reduction in the star formation rate compared to when outflow feedback is not included.