Infrared Observations of the Galactic Star Forming Regions associated with IRAS 00338 + 6312 & RAFGL 5111

Two Galactic star forming regions, one in a very early phase of evolution and another evolved one, associated with the IRAS sources 00338+6312 and 03595+5110 (RAFGL 5111) respectively have been studied in detail. These sources have been mapped simultaneously in two far infrared bands (λ eff = 143 & 185 µm), with ∼ 1. ′ 5 angular resolution, using the TIFR 100 cm balloon borne telescope. The HIRES processed IRAS maps at 12, 25, 60 & 100 µm, have been used for comparison. Whereas IRAS 00338+6312 is resolved only in the TIFR bands, RAFGL 5111 is very well resolved in both the TIFR bands, as well as in at least 3 IRAS bands. The neighbouring fainter source IRAS 04004+5114 has also been resolved in the TIFR bands. Taking advantage of the identical beams in the two TIFR bands at 143 & 185 µm, dust colour temperature, T (143/185), and optical depth, τ 150 , maps have been generated for RAFGL 5111. These maps show interesting structural details. Radiative transfer modelling in spherical geometry has been carried out for individual sources to extract information about: the cloud size, type of the embedded source, radial density distribution, optical depth, gas to dust ratio, and the dust grain composition. The best fit models are in good agreement with the observed spectral energy distribution (SED), radio continuum data etc. Another scheme of radiative transfer through the interstellar dust-gas cloud including the heavier elements has been used to predict ionic nebular line emission, which are in reasonable agreement with the measurements for RAFGL 5111. An important conclusion from the present study is that, for all the three sources (IRAS 00338+6312; 03595+5110; and 04004+5114, a faint source in the neighbourhood of RAFGL 5111), the best fit to the observed SED is obtained for a uniform density (n(r) ∼ r 0) cloud.