R. Klein 1 Th. Henning 1& D. Cesarsky 2
1 Astrophysikalisches Institut und Universitäts-Sternwarte (AIU) Jena, Schillergäßchen 2-3, D-07745 Jena, Germany
2 Institut d'Astrophysique Spatiale (IAS), Paris, France
M17 is one of the best-studied regions of massive star formation in
our galaxy. It is located in the Carina spiral arm at a distance of
2.2kpc. The region is associated with an optically bright H II
region which is partially surrounded by the bowl-shaped
molecular cloud M17-SW. The cloud core M17-North is located
10
north of the exciting stars of M17 and was hardly studied
in detail up to now.
The detection of the compact dust core M17-North at millimetre
wavelengths made the object an extremely interesting target for the
study of star formation and the properties of the dust and molecule
population in a cloud core. Therefore, M17-North was observed with
all four instruments of the Infrared Space Observatory (ISO). The
spectrometers detected a strong rising continuum starting at about
20
superimposed with fine structure lines and the unidentified
infrared bands (UIBs) (Cesarsky et al. 1998, Henning et al. 1998).
Here we present spectro-imaging data of the molecular cloud core. The
data were obtained with the ISOCAM camera using the circular variable
filters (CVF). The observations led to the detection of a new source
north-east of the mm core with a very strongly rising continuum. We
rate this detection as a further sign of on-going star formation.
Inside the mm core we might see the counterparts of embedded NIR
sources. Furthermore, the spatial variation in the intensity of the
fine structure lines and UIBs are studied. The single spectra have a
spectral resolution of about 40. They are dominated by the UIBs. The
UIB around 16.6
only recently reported is also detected. The
carriers of the UIBs are believed to be small polycyclic aromatic
hydrocarbon clusters (PAH). The reason is that the bands can be fitted
with Lorentzians line profiles and almost no continuum remains when
the bands are subtracted from the continuum. The plateaus under the
UIBs can be explained as the broad wings of Lorentzians. If the bands
would be radiated by very small carbon grains one would expect an
underlying continuum.