High‐resolution far‐infrared observations of a large area of the star‐forming complex RCW 106 obtained using the TIFR 1‐m balloon‐borne telescope are presented. Intensity maps have been obtained simultaneously in two bands centred around 150 and 210 μm. Intensity maps have also been obtained in the four IRAS bands using HIRES‐processed IRAS data. From the 150‐ and 210‐μm maps, reliable maps of dust temperature and optical depth have been generated. The star formation in this complex has occurred in five linear sub‐clumps. Using the map at 210 μm, which has a spatial resolution superior to that of IRAS at 100 μm, 23 sources have been identified. The spectral energy distribution (SED) and luminosity of these sources have been determined using the associations with the IRAS maps. The luminosity distribution of these sources has been obtained. Assuming these embedded sources to be zero‐age main‐sequence stars and using the mass–luminosity relation for these, the power‐law slope of the initial mass function is found to be −1.73±0.5. This index for this very young complex is about the same as that for more evolved complexes and clusters. Radiation transfer calculations in spherically symmetric geometry have been undertaken to fit the SEDs of 13 sources with fluxes in both the TIFR and the IRAS bands. From this, the r−2 density distribution in the envelopes is ruled out. Finally, a correlation is seen between the luminosity of embedded sources and the computed dust masses of the envelopes.
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.Subject Headings: IRAS 00338+6312 -RAFGL 5111 -IRAS 03595+5110 -IRAS 04004+5114 -Far Infrared Mapping -Radiative Transfer -H II region
Mid and far infrared maps of many Galactic star forming regions show multiple peaks in close proximity , implying more than one embedded energy sources. With the aim of understanding such interstellar clouds better, the present study models the case of two embedded sources. A radiative transfer scheme has been developed to deal with an uniform density dust cloud in a cylindrical geometry, which includes isotropic scattering in addition to the emission and absorption processes. This scheme has been applied to the Galactic star forming region associated with IRAS 19181+1349, which shows observational evidence for two embedded energy sources. Two independent modelling approaches have been adopted, viz., to fit the observed spectral energy distribution (SED) best; or to fit the various radial profiles best, as a function of wavelength. Both the models imply remarkably similar physical parameters.
We developed a method of acquiring high-resolution MRI for the generation of Quantitative Susceptibility Mapping (QSM) using Ultra-short echo time (UTE) MRI with a novel 3D rosette k-space trajectory. This method was used to generate high-resolution (0.94 mm3 isotropic) magnetic susceptibility maps in an Iron-Chloride phantom and the human brain. Generated maps were then compared with the susceptibility maps reconstructed from low-resolution data acquired using multi-echo UTE acquisition. Susceptibility values were comparable with current literature demonstrating the promise of this novel method in the generation of QSM.
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