Far-infrared observations of the galactic star-forming regions associated with IRAS 00338+6312 and RAFGL 5111

Abstract

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 and 185 µm), with ~15 angular resolution, using the Tata Institute of Fundamental Research (TIFR) 100 cm balloon-borne telescope. The HIRES-processed IRAS maps at 12, 25, 60, and 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 three IRAS bands. The neighboring 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 and 185 µm, dust color temperature, T(143/185), and optical depth, τ₁₅₀, maps have been generated for RAFGL 5111. These maps show interesting structural details. Radiative-transfer modeling in spherical geometry has been carried out for individual sources to extract information about the cloud size, the type of the embedded source, the radial density distribution, the optical depth, the 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, and so on. 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 is in reasonable agreement with the measurements for RAFGL 5111. An important conclusion from the present study is that, for all three sources (IRAS 00338+6312, 03595+5110, and 04004+5114, a faint source in the neighborhood of RAFGL 5111), the best fit to the observed SED is obtained for a uniform density [n(r) ~ r⁰] cloud.