NEAR IR IMAGING AND SPECTROSCOPY OF OPTICALLY OBSCURED GALACTIC GIANT HII 
REGIONS:  DISCOVERY OF YOUNG CLUSTERS.

Peter S. Conti 
JILA and APS, University of Colorado, Boulder

Many HII and Giant HII regions in our Galaxy are partially or totally
obscured in the visible by the absorbing effects of interstellar dust. 
Near infrared imaging (and spectroscopy) can be used to ascertain the
stellar populations of these star-forming regions. JHK photometry of a 
sample of GHII regions will be presented.  Aside from W49, all of them 
show the presence of a compact stellar cluster.  

K band spectroscopy has been obtained for a few of the exciting stars
of these clusters.  In M17, early O type stars have been identified by
absorption and emission lines in the K band. Other hot stars are
featureless at this wavelength. The absence of stellar lines in the latter
stars is due to local dust emission, very likely from circumstellar
material in a disc as in a YSO.  Shorter wavelength observations reveal
the presence of late O - early B stellar spectra in these latter objects.
By contrast, in W43 (which is totally obscured optically) the brightest
exciting star is a Wolf-Rayet object; two other bright objects are early
O-type.  The brightest star in W42 is an early O type; two other bright
hot objects have spectral similarities to the YSOs in M17. In W31, the 
brightest star in the K band is featureless, but the next four brightest 
are early O types.

JHK color-color diagrams of several clusters indicate color excesses of
some members, suggesting the presence of stellar discs. This is a little
curious given that these GHII regions were radio selected as being the
brightest in our Galaxy. Why should they also be so young? Additional near
IR observations and analyses are planned.  In W49 there is NO cluster is
visible in the near IR, yet one is clearly visible in VLA radio images. 
In this object, the massive stars are at an even earlier star formation
stage, analogous to and scaled up from UCHII regions. W49 is intermediate 
in luminosity between these newly born objects and the recently discovered 
UDHII regions in starburst galaxies (buried SSCs)