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

Mookerjea, B Ghosh, SK

B. Mookerjea et Sk. Ghosh, Understanding the spectral energy distributions of the Galactic star forming regions IRAS 18314-0720, 18355-0532 and 18316-0602, J ASTROPHYS, 20(1-2), 1999, pp. 1-22

45

INGLESE

Article

Space Sciences

JOURNAL OF ASTROPHYSICS AND ASTRONOMY

0250-6335 → ACNP

20

1-2

1999

1 - 22

ISI

0250-6335(199906)20:1-2<1:UTSEDO>2.0.ZU;2-S

Embedded Young Stellar Objects (YSO) in dense interstellar clouds are treat ed 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 observation s covering a wide spectral range encompassing near-infrared to radio contin uum wavelengths. Various geometric and physical details of the YSOs are det ermined from this modelling scheme. In order to assess the effectiveness of this self-consistent scheme, three young Galactic star forming regions ass ociated with IRAS 18314-0720, 18355-0532 and 18316-0602 have been modelled as test cases. They cover a large range of luminosity (approximate to 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, dens ity distribution, composition and abundance of dust grains etc. In all thre e cases, the best fit model corresponds to the uniform density distribution . Two types of dust have been considered, viz., Draine gr 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 18 313-0720 and 18355-0532. This discrepancy has been resolved by invoking clu mpiness in the interstellar medium. For IRAS 18316-0602, the model with DL type dust grains is preferred.