Statistical Properties of Line Centroid Velocity Increments in the rho Ophiuchi Cloud
D. C. Lis, J. Keene, Y. Li, T. G. Phillips, J. Pety;
ApJ, 1998, 504, 889
ABSTRACT:We present a comparison of histograms of CO (2-1) line centroid velocity increments in the rho Ophiuchi molecular cloud with those computed for
spectra synthesized from a three-dimensional, compressible, but
non-star-forming and nongravitating, hydrodynamic simulation.
Histograms of
centroid velocity increments in the rho Oph cloud clearly show non-Gaussian
wings similar to those found in histograms of velocity increments and
derivatives in experimental studies of laboratory and atmospheric flows, as well
as numerical simulations of turbulence.
The magnitude of these wings
increases monotonically with decreasing separation, down to the angular
resolution of the data.
This behavior is consistent with that found in the phase of
the simulation that has most of the properties of incompressible
turbulence.
The time evolution of the magnitude of the non-Gaussian wings in the
histograms of centroid velocity increments in the simulation is consistent with
the evolution of the vorticity in the flow.
We cannot exclude, however,
the possibility that the wings are associated with the shock interaction
regions.
Moreover, the effects of shocks may be more important in an active star-forming
region like the rho Oph cloud than in the simulation; however, being able to
identify shock interaction regions in the interstellar medium is also
important, since numerical simulations show that vorticity is generated in shock
interactions.
KEYWORDS: hydrodynamics, ism: clouds, ism: individual name: rho ophiuchi cloud, ism: kinematics and dynamics, turbulence
PERSOKEY:turbulence, ,
CODE: lis98