The Dust-selected Molecular Clouds in the Northeast Region of the Small Magellanic Cloud
Résumé
We present a high-sensitivity (1σ < 1.6 mJy beam-1) continuum observation in a 343 arcmin2 area of the northeast region of the Small Magellanic Cloud at a wavelength of 1.1 mm, conducted using the AzTEC instrument on the ASTE telescope. In the observed region, we identified 20 objects by contouring 10σ emission. Through spectral energy distribution analysis using 1.1 mm, Herschel, and Spitzer data, we estimated gas masses of 5 × 103-7 × 104 M ⊙, assuming a gas-to-dust ratio of 1000. The dust temperature and index of emissivity were also estimated as 18-33 K and 0.9-1.9, respectively, which are consistent with previous low-resolution studies. The dust temperature and the index of emissivity shows a weak negative linear correlation. We also investigated five CO-detected, dust-selected clouds in detail. The total gas masses were comparable to those estimated from the Mopra CO data, indicating that the assumed gas-to-dust ratio of 1000 and the X CO factor of 1 × 1021 cm-2 (K km s-1)-1, with uncertainties of a factor of 2, are reliable for the estimation of the gas masses of molecular or dust-selected clouds. The dust column density showed good spatial correlation with CO emission, except for an object associated with bright young stellar objects. The 8 μm filamentary and clumpy structures also showed a spatial distribution similar to that of the CO emission and dust column density, supporting the fact that polycyclic aromatic hydrocarbon emissions arise from the surfaces of dense gas and dust clouds.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.