Structure and origin of velocity fluctuations in the \hii region Sharpless 142
J. R. Roy, G. Joncas;
ApJ, 1985, 288, 142
ABSTRACT:Close to 41,000 H-alpha radial velocities have been measured across most of the evolved H II
region S142 (theta = 25 arcmin), allowing a systematic study of velocity
fluctuations.
Using grids of different mesh size to subdivide the H II region, the mean
velocity dispersion, sigma, is found to be dependent on mesh size L.
A
well-defined correlation in the form of a power law sigma = L exp 0.30 is
found.
Because of ambiguous interpretation of this result in terms of turbulence, the
structure function, B, which tests for velocity correlation at all scales has
also been calculated.
The structure function does not approach zero for r =
3 arcsec-90 arcsec.
A brief qualitative analysis is attempted in terms
of a turbulent energy cascade in a supersonic and compressible
fluid.
Kelvin-Helmholtz instabilities are suggested for the generation and maintenance of
nebular turbulence.
KEYWORDS: h ii regions, nebulae, radial velocity, turbulence, energy transfer, h alpha line, histograms, velocity distribution
PERSOKEY:region hii, turbulence, statistical analysis, halpha, optical, ,
CODE: roy85