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Wide-field Infrared Survey Explorer Observations of Young Stellar Objects in the Western Circinus Molecular Cloud

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The Wide-field Infrared Survey Explorer has uncovered a population of young stellar objects in the Western Circinus molecular cloud. Images show the YSOs to be clustered into two main groups that are coincident with dark filamentary structure in the nebulosity. Analysis of photometry shows numerous Class I and II objects. The locations of several of these objects are found to correspond to known dense cores and CO outflows. Class I objects tend to be concentrated in dense aggregates, and Class II objects more evenly distributed throughout the region.
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... Reipurth et al. (1996) presented four distinct millimeter sources, Cir-MMSs 1-4, in their 1300 μm map in the Circinus Cloud Complex, which is hereafter referred to as the Cir-MMS field. Following this discovery, Liu et al. (2011) presented Wide-field Infrared Survey Explorer (WISE) observations of YSOs in the western part of the complex. Cir-MMSs 1-4 are all low-mass YSOs. ...
... Later, using a parameterized rate of turbulence decay and a time-dependent form of the virial theorem, which deals with the cloud as a whole, Matzner & McKee (2000) examined their effects on cluster formation. Reipurth et al. (1996) discovered four millimeter sources in the Cir-MMS field, and Liu et al. (2011) presented a three-color WISE image that highlights YSO populations in the same field. Figure 13 shows a false-color image of the Cir-MMS field, combined with SIRPOL+WISE image data that include sources that are very red and rather bright. ...
... From north to south, the orientations of two CO outflow sources, IRAS 14563-6250 and IRAS 14564-6254, are wellaligned with the magnetic field direction (approximately 70°) in this field. Note that the source position of IRAS 14564-6254 is not associated with that indicated by Liu et al. (2011). ...
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We present the results of near-infrared (NIR) linear imaging polarimetry in the J, H, and K s bands of the low-mass star cluster-forming region in the Circinus Molecular Cloud Complex. Using aperture polarimetry of point-like sources, positive detection of 314, 421, and 164 sources in the J, H, and K s bands, respectively, was determined from among 749 sources whose photometric magnitudes were measured. For the source classification of the 133 point-like sources whose polarization could be measured in all 3 bands, a color–color diagram was used. While most of the NIR polarizations of point-like sources are well-aligned and can be explained by dichroic polarization produced by aligned interstellar dust grains in the cloud, 123 highly polarized sources have also been identified with some criteria. The projected direction on the sky of the magnetic field in the Cir-MMS region is indicated by the mean polarization position angles (70°) of the point-like sources in the observed region, corresponding to approximately pc². In addition, the magnetic field direction is compared with the outflow orientations associated with Infrared Astronomy Satellite sources, in which two sources were found to be aligned with each other and one source was not. We also show prominent polarization nebulosities over the Cir-MMS region for the first time. Our polarization data have revealed one clear infrared reflection nebula (IRN) and several candidate IRNe in the Cir-MMS field. In addition, the illuminating sources of the IRNe are identified with near- and mid-infrared sources.
... The numerical factors are a combination of the conversion factors between magnitude and flux density at the appropriate wavelengths and the weighting factors. Alternatively, the slope can be quantified by simply measuring the slope between w1 and w4: To compare these two techniques, we use a sample of eight YSOs, which have α values calculated from 2MASS K s and w4 photometry, from the Liu et al. (2011) study of the Western Circinus molecular cloud. These eight YSOs span a range of YSO types, and they also allow us to compare our WISE-only α values with those derived using 2MASS and WISE data. ...
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