  We present a study of the kinematic properties of the ionized gas in the
dominant giant HII region of the well known HII galaxy: II Zw 40. High spatial
and spectral resolution spectroscopy has been obtained using IFU mode on the
GMOS instrument at Gemini-North telescope. We have used a set of kinematics
diagnostic diagrams, such as the intensity vs. velocity dispersion intensity
vs. radial velocity, for global and individual analysis in sub-regions of the
nebula. We aim to separate the main line broadening mechanisms responsible for
producing a smooth supersonic integrated line profile for the giant HII region.
The brightest central region (R ~ 50 pc) is responsible for sigma derived from
a single fit to the integrated line profile. The dominant action of gravity,
and possibly unresolved winds of young (<10 Myr) massive stars, in this small
region should be responsible for the characteristic Halpha velocity profile of
the starburst region as a whole. Our observations show that the complex
structure of the interstellar medium of this galactic scale star-forming region
is very similar to that of nearby extragalactic giant HII regions in the Local
Group galaxies.
