• Understanding the spectral energy distributions of the galactic star forming regions IRAS 18314-0720, 18355-0532 and 18316-0602

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      https://www.ias.ac.in/article/fulltext/joaa/020/01-02/0001-0022

    • Keywords

       

      Infrared SED; HII regions; radiative transfer; IRAS 18314-0720; IRAS 18355-0532; IRAS 18316-0602

    • Abstract

       

      Embedded Young Stellar Objects (YSO) in dense interstellar clouds are treated self-consistently to understand their spectral energy distributions (SED). Radiative transfer calculations in spherical geometry involving the dust as well as the gas component, have been carried out to explain observations covering a wide spectral range encompassing near-infrared to radio continuum wavelengths. Various geometric and physical details of the YSOs are determined from this modelling scheme.

      In order to assess the effectiveness of this self-consistent scheme, three young Galactic star forming regions associated with IRAS 18314-0720, 18355-0532 and 18316-0602 have been modelled as test cases. They cover a large range of luminosity (≈ 40). The modelling of their SEDs has led to information about various details of these sources, e.g. embedded energy source, cloud structure and size, density distribution, composition and abundance of dust grains etc. In all three cases, the best fit model corresponds to the uniform density distribution. Two types of dust have been considered, viz., Draine & Lee (DL) and the Mezger, Mathis & Panagia (MMP). Models with MMP type dust explain the dust continuum and radio continuum emission from IRAS 18314-0720 and 18355-0532 self-consistently. These models predict much lower intensities for the fine structure lines of ionized heavy elements, than those observed for IRAS 18314-0720 and 18355-0532. This discrepancy has been resolved by invoking clumpiness in the interstellar medium. For IRAS 18316-0602, the model with DL type dust grains is preferred.

    • Author Affiliations

       

      Bhaswati Mookerjea1 S. K. Ghosh1

      1. Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai (Bombay) - 400 005, India
    • Dates

       
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