The H-alpha velocity field of the Omega nebula (M 17)
G. Joncas, J. R. Roy;
ApJ, 1986, 307, 649
ABSTRACT:Using a Fabry-Perot camera, 9054 H-alpha radial velocities were measured across the H II region M 17.
The mean
v(LSR) = 18.6 + or - 0.1 km/s, which is 1.4 km/s blueshifted with respect to the
mean velocity of the associated molecular cloud M 17 SW.
The dispersion of
the velocity histogram is slightly skewed to the blue.
A gradient in
radial velocity is observed from west to east, with the most blueshifted
velocities appearing closest to the molecular cloud.
The velocity field can be
explained as a flow of ionized gas approximatively in the plane of the sky.
There
is a relation between random velocity and size, with velocity
fluctuations increasing as some power of size; the power index depends on the
sampling method of the velocity field.
An interpretation of the relation is
suggested in terms of turbulence, and a brief discussion of mechanisms for
turbulent kinetic energy input is presented.
KEYWORDS: h alpha line, molecular clouds, nebulae, radial velocity, velocity distribution, astronomical maps, gas dynamics, h ii regions, histograms, ionized gases
PERSOKEY:region hii, turbulence, optical, halpha, statistical analysis, ,
CODE: joncas86