R.P. Verma , S.K. Ghosh , A.D. Karnik , B. Mookerjea & T.N. Rengarajan
Tata Institute of Fundamental Research, Mumbai 400005 Homi Bhabha Road, Mumbai (Bombay) 400005 India
Three compact HII regions/ molecular clumps (IRAS 19181+1349,
20286+4105 and 20178+ 4046) have been observed at mid infrared wave-
lengths using ISO and at far infrared wavelengths using the TIFR 1 m
balloon-borne telescope. ISO observations have been made in seven spectral
bands (3.3, 3.7, 6.0, 6.75, 9.6 and 11.4 
m) using the ISOCAM
instrument. Four of these bands (3.3, 6.0, 7.7 and 11.4 micron) cover the
emission from Polycyclic Aromatic Hydrocarbon (PAH) molecules; the
remaining three serve as comparison bands. An area of
around each
source has been imaged with a pixel size of
.
Far infrared
observations have been made simultaneously in two bands with effective
wavelengths of 
130 and 200 m, using liquid 3He
cooled bolometer arrays. Areas of
around each source
have been mapped. The far
infrared data have been deconvolved using a Maximum Entropy Method and the
angular resolution in the deconvolved maps is about 1'. In addition, IRAS
survey data for these sources in the four IRAS bands (12, 25, 60 and 100
m) have also been processed using the HIRES routine.
Results of these observations will be presented in this paper. In the high resolution mid infrared maps multiple embeded energy sources have been resolved. There are structural similarities between the images in the mid infrared bands and the large scale maps in the far infrared bands despite very different angular resolutions of the two. A comparison of the flux densities in different ISO bands clearly shows the importance of PAH emission. Spectral energy distributions for these sources have been constructed by combining data from all these observations. Radiation transfer calculations through dust cloud have been made to understand these spectral energy distributions as well as the infrared morphologies of these sources.