Brief program summary and its significance:

"Structure, velocity field and turbulence in giant HII regions"

    (Gustavo Medina Tanco, Vera Jatenco-Pereira, Reuven Opher IAG/USP)



	Recently, the H_alpha intensity peak, velocity shift and velocity
dispersion maps of NGC604, were obtained by two dimensional high spatial
resolution Fabry-Perot observations with TAURUS II at the 4.2 m William
Herschel Telescope in Spain. The kinematics of this region was studied
in order to show the behavior of the gas at different scales of motion.

	The turbulent movement inside the cloud has been studied by
different authors, and it is different at large and small scales which
led to different interpretations of the mechanisms that play inside
the region covering autogravitation, stellar winds and the
Champagne effect. Nevertheless, the models proposed hitherto to
explain the kinematics of NGC604, based mainly on line profile
analysis, are not conclusive.

	We are concerned with the velocity structure of the cloud
and the character of the turbulence observed. We study the auto-
correlation and second order structure functions of the components
of the velocity field parallel to the line of sight. We domonstrate
that the cloud presents a rich hierarchical velocity structure, and
is made up of fragments with various characteristic scale lengths, the
most notorious having scales of ~10 pc, while the largest may be a
billow-like struture comprising the region as a whole and rotating with
a period of ~ 85 Myr. Besides, we find strong evidences that there is
a Kolmogorov like spectrum at scales > 10 pc, which changes rapidly
to another very well defined power law at smaller scales.

	From this study we show that the autocorrelation and structure
functions have a considerable potential for the study of the dynamics of
intergalactic HII regions where high resolution velocity images are
available. Using this method we intend to study others giant HII regions
(e.g. 30 Dor).


Required minimum field of view (arcmin): 1.8 arcmin

Required psf (FWHM, profile details): 0.26 arcseg

Typical target separation if multiple targets per exposure: 

Signal/noise required per resolution element: 10

Typical exposure time for this S/N & lunar phase:100 images x 36 seg = 3600 seg
of exposure time for each emission line.

Anticipated photometric dynamic range required: 100-1000

What additional photometric calibrations are required? Careful daytime
calibration of filter responses, wavelengths. Flux calibration at
restricted wavelengths on one standart star. Nighttime wavelength checks.

If IR, is tip/tilt feasible (consider isoplanatic patch)? Not IR, but
tip-tilt highly desirable to avoid wind-shake, etc.

Anticipated number of separate pointings to complete program: 1

Can this program execute in a queue? Maybe

Anticipated post-focus instrumentation requirements (filters, gratings,
etc.): Re-imaging optics, etalon, filter, CCD window. 

Required instruments (spectral R, filters, wavelength range): Imaging Fabry
Perot spectrometer.

How soon might you need to revisit this target with another instrument?

Why can't this program execute on the Blanco 4m? Need higher angular
resolution.

References (for non-mainstream applications):

N.S.P. Sabalisck, G. Tenorio-Tagle, H.O. Castaneda, C. Munoz-Tunon,
ApJ, 444, 200 (1995)