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Register a new userInfrared study of the southern Galactic star forming regions associated with IRAS 10049-5657 and IRAS 10031-5632
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S. Vig
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The physical conditions of the interstellar medium and stellar components in the regions of the southern Galactic star forming complexes associated with IRAS 10049-5657 and IRAS 10031-5632 have been investigated. These regions have been mapped simultaneously in two far infrared bands lambda_eff ~ 150 & 210 micron, with ~ 1 angular resolution using the TIFR 1-m balloon borne telescope. Spatial distribution of the temperature of cool dust and optical depth at 200 micron have been obtained. Using the 2MASS sources, the stellar populations of the embedded young clusters have been studied. A rich cluster of OB stars in the IRAS 10049-5657 region has been found with a cluster radius ~ 2 pc. The source in the cluster closest to the IRAS peak, lies above the ZAMS curve of spectral type O5 in the colour-magnitude diagram. Unlike IRAS 10049-5657, a small cluster comprising of a few deeply embedded sources is seen at the location of IRAS 10031-5632. Self consistent radiative transfer modelling aimed at extracting important physical and geometrical details of the two IRAS sources show that the best fit models are in good agreement with the observed spectral energy distributions. The geometric details of the associated cloud and optical depths (at 100 micron) have been estimated. A uniform density distribution of dust and gas is implied for both the sources. In addition, the infrared ionic fine-structure line emission from gas has been modelled for both these regions and compared with data from IRAS-Low Resolution Spectrometer. For IRAS 10049-5657, the observed and modelled luminosities for most lines agree to within a factor of four while for IRAS 10031-5632, we find a discrepancy of a factor of 100.
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A multiwavelength study of the star forming regions associated with IRAS 19111+1048 and IRAS 19110+1045 has been carried out. These have been simultaneously mapped in two far infrared bands at lambda_eff ~ 130 and 200 micron with ~1 angular resolution using the TIFR 1-m balloon borne telescope. The radio emission from the ionised gas of these regions has been imaged at 1280, 610 and 325 MHz using the Giant Metrewave Radio Telescope, India. A total of 20 compact radio sources have been detected from the high resolution radio map of IRAS 19111+1048 at 1280 MHz. Assuming these sources to represent exciting zero age main sequence (ZAMS) stars, the initial mass function is found to be quite steep, with the power law index of 5.3+-0.5 for the mass range 14 < m/M_sun < 33. The spectral types of the ZAMS stars inferred independently from the radio and NIR measurements match very well for a good fraction of the radio sources having NIR counterparts. For IRAS 19110+1045 region, seven radio sources have been detected of which two are associated with deeply embedded 2MASS objects. Self consistent radiative transfer modelling aimed at extracting important physical and geometrical details of the two IRAS sources has been carried out. A uniform density distribution of dust and gas is implied for both the sources. The extents of ionised gas, number of ZAMS stars, presence of deeply embedded sources and lower value of L/M for the cloud, support the youth of IRAS 19110+1045 vis-a-vis its neighbour, IRAS 19111+1048, consistent with earlier studies.
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 at 143 & 185 micron), with about 1.5 arcmin angular resolution, using the TIFR 100 cm balloon borne telescope. The HIRES processed IRAS maps at 12, 25, 60 & 100 micron, 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 micron, dust colour temperature, $T(143/185)$, and optical depth, $tau_{150}$, 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. 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 ($n(r) sim r^0$) cloud.
The Galactic star forming region in the southern sky, associated with IRAS 09002-4732 has been mapped simultaneously in two far infrared bands (148 & 209 um), with ~ 1 angular resolution. Fifteen sources including IRAS 08583-4719, 08589-4714, 09002-4732 and 09014-4736 have been detected, some of which are well resolved. Taking advantage of similar beams in the two bands, a reliable dust temperature [T(148/209)] map has been obtained, which detects colder dust (< 30 K) in this region. The HIRES processed IRAS maps at 12, 25, 60 & 100 um have also been used for comparison. The optical depth maps at 200 um & 100 um, generated from these FIR data quantify the spatial distribution of the dust. The diffuse emission from this entire region has been found to be 35 % of the total FIR luminosity. The slope of the IMF in the mass range 4-16 M_sun has been estimated to be -1.25^+0.75_-0.65 for this star forming complex. Radiative transfer models have been explored to fit available observations of the 4 IRAS sources and extract various physical parameters for corresponding dust-gas clouds. Whereas a constant radial density distribution is favoured in IRAS 08583-4719, 08589-4714 & 09002-4732, the r^-1 law is inferred for IRAS 09014-4736. The dust composition is found to be similar (Silicate dominated) in all the 4 sources. The luminosity per unit mass is found to be in the narrow range of 44-81 L_sun/M_sun for these star forming regions.
A multi-wavelength investigation of the star forming complex IRAS 20286+4105, located in the Cygnus-X region, is presented here. Near-infrared K-band data is used to revisit the cluster / stellar group identified in previous studies. The radio continuum observations, at 610 and 1280 MHz show the presence of a HII region possibly powered by a star of spectral type B0 - B0.5. The cometary morphology of the ionized region is explained by invoking the bow-shock model where the likely association with a nearby supernova remnant is also explored. A compact radio knot with non-thermal spectral index is detected towards the centre of the cloud. Mid-infrared data from the Spitzer Legacy Survey of the Cygnus-X region show the presence of six Class I YSOs inside the cloud. Thermal dust emission in this complex is modelled using Herschel far-infrared data to generate dust temperature and column density maps. Herschel images also show the presence of two clumps in this region, the masses of which are estimated to be {sim} 175 M{sun} and 30 M{sun}. The mass-radius relation and the surface density of the clumps do not qualify them as massive star forming sites. An overall picture of a runaway star ionizing the cloud and a triggered population of intermediate-mass, Class I sources located toward the cloud centre emerges from this multiwavelength study. Variation in the dust emissivity spectral index is shown to exist in this region and is seen to have an inverse relation with the dust temperature.
We present infrared and radio continuum observations of S 201 star forming region. A massive star cluster is observed in this region, which contains different classes of young stellar objects. The near-infrared colour-colour and colour-magnitude diagrams are studied to discuss the nature of these sources. We have discovered the knots of molecular hydrogen emission at 2.122 micron in the central region of S 201. These knots are clearly seen along the diffuse emission in north-west direction which are probably the obscured Herbig-Haro objects. High sensitivity and high resolution radio continuum images from GMRT observations at 610 and 1280 MHz show an interesting arc-shaped structure due to the interaction between the H II region and the adjacent molecular cloud. The ionization front at the interface between the H II region and the molecular cloud is clearly seen by comparing the radio, molecular hydrogen and Br Gamma images. The emission from the carriers of Unidentified Infrared Bands in the mid-infrared 6-9 micron (possibly due to PAHs) as extracted from the Midcourse Space Experiment survey (at 8, 12, 14 and 21 micron) is compared with the radio emission. The HIRES processed IRAS maps at 12, 25, 60, and 100 micron, have also been used for comparison. The spatial distribution of the temperature and the optical depth of the warm dust component around S 201 region, has been generated from the mid-infrared images.
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