Turbulence in giant molecular clouds: The effect of photoionization feedback

Abstract

Giant molecular clouds (GMCs) are observed to be turbulent, but theory shows that without a driving mechanism turbulence should quickly decay. The question arises by which mechanisms turbulence is driven or sustained. It has been shown that photoionizing feedback from massive stars has an impact on the surrounding GMC and can for example create vast HII bubbles. We therefore address the question of whether turbulence is a consequence of this effect of feedback on the cloud. To investigate this, we analyse the velocity field of simulations of high-mass star-forming regions by studying velocity structure functions and power spectra. We find that clouds whose morphology is strongly affected by photoionizing feedback also show evidence of driving of turbulence by preserving or recovering a Kolmogorov-type velocity field. On the contrary, control run simulations without photoionizing feedback have a velocity distribution that bears the signature of gravitational collapse and of the dissipation of energy, where the initial Kolmogorov-type structure function is erased.