For different coma areas representative spectra were presented in the
wavelength range from 
. They allow an easy
comparison between the emissions of the cometary head and tail. The spectra
were obtained with the multislit technique, which allowed to record 69
spectra of different coma regions at the same time. The head spectra are
dominated by emissions of the neutral radicals CN, 
, and CH,
whereas the emissions of 
and 
most importantly
contribute to the tail spectra. The ion emissions are not restricted to a
sharp plasma tail, but are also present in the sunward coma.
The results about the distribution of dust and neutral molecules in the
cometary coma mostly agree with the literature. The radial profile of the
overall dust coma is consistent with the 
law expected from the
radial outflow model. The continuum strength is about twice as large as
expected from data published by Neckel & Münch (1987). The
CN profiles clearly show the influence of the solar radiation pressure on
neutral particles as modeled by Combi & Delsemme (1980). The
CN data indicate a relative error of about 10%, and the CN column densities
are larger than those of Combi et al. (1994) by a factor of
1.7. The deviations of the dust continuum and the CN column densities
indicate that our values should be regarded as upper limits for the
abundance of the considered species. The neutral coma model of
Mitchell et al. (1981) is consistent with the relative
abundances of CN, , and CH, but not with the gradients of these
distributions. Concerning the ions we present the first observation of the
two-dimensional spatial distribution of the ion. The
observations are in agreement with the model of Wegmann et al.
(1987) with the exception of a stronger tailward gradient of the ion
as compared to the model. Our abundance is too high which may
be due to observational difficulties or to problems with the (preliminary)
fluorescence emission rate.
The method of multislit spectroscopy in combination with a focal reducer is very well suited to obtain a large number of spectra of an object as extended as a comet. The most important cometary emissions within a wide spectral range are simultaneously observable and their large-scale spatial distribution can be determined.
Acknowledgements
The authors would like to thank S.J. Kim from the Department of Astronomy and
Space Science of the Kyunghee University, Yongin, Kyunggido, South Korea, for
providing fluorescence emission rates for . We also like to express our
thanks to M. Richards from the Max-Planck-Institut für Aeronomie for
discussions and for placing data reduction software at our disposal that was
developed by him. We are grateful for the technical support of P. Grosbøl
from ESO Headquarters while scanning the plates.