An observational method to measure the relative fractions of solenoidal and compressible modes in interstellar clouds
Monthly Notices of the Royal Astronomical Society
Oxford University Press (OUP) / Royal Astronomical Society
We introduce a new method for observationally estimating the fraction of momentum density (ρv) power contained in solenoidal modes (for which ∇ · ρv = 0) in molecular clouds. The method is successfully tested with numerical simulations of supersonic turbulence that produce the full range of possible solenoidal/compressible fractions. At present, the method assumes statistical isotropy, and does not account for anisotropies caused by (e.g.) magnetic fields. We also introduce a framework for statistically describing density-velocity correlations in turbulent clouds. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
A big thanks to Daniel Price for allowing us use of the auxiliary numerical simulations, to Maria Cunningham for allowing us access to the Delta Quadrant Survey data and to Dave Acreman for much-needed help with Figs 1 and 2. CB is funded in part by the UK Science and Technology Facilities Council grant ST/J001627/1 (‘From Molecular Clouds to Exoplanets’) and the ERC grant ERC-2011-StG_20101014 (‘LOCALSTAR’), both held at the University of Exeter. CF acknowledges funding provided by the Australian Research Council under the Discovery Projects scheme (grant DP110102191). Supercomputing time at the Leibniz Rechenzentrum (project pr32lo) and at the Forschungszentrum Jülich (project hhd20) are gratefully acknowledged. The software used in this work was in part developed by the DOE-supported ASC/Alliance Center for Astrophysical Thermonuclear Flashes at the University of Chicago.
This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.
Vol. 442 (2), pp. 1451 - 1469