The Dust-Selected Molecular Clouds in the Northeast Region of the Small Magellanic Cloud

Abstract

We present a high-sensitivity ($1\sigma <1.6\mathrm{mJy}\mathrm{bea}{\mathrm{m}}^{-1}$) continuum observation in a 343 arcmin${}^2$ area of the northeast region in 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 $10\sigma$ emission. Through spectral energy distribution (SED) analysis using 1.1 mm, $Herschel$, and $Spitzer$ data, we estimated the gas masses of $5\times 10^3-7\times 10^4{\mathrm{M}}_{\odot }$, assuming a gas-to-dust ratio of 1000. Dust temperature and the 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 relation between 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 $X_{\mathrm{CO}}$ factor of $1\times 10^{21}\mathrm{c}{\mathrm{m}}^{-2}(\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}{)}^{-1}$, with uncertainties of a factor of 2, are reliable for the estimation of the gas masses of molecular or dust-selected clouds. Dust column density showed good spatial correlation with CO emission, except for an object that associates with bright young stellar objects. The $8\mu \mathrm{m}$ filamentary and clumpy structures also showed similar spatial distribution with 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.

21 pages, 11 figures, accepted for publication by ApJ

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Cited by in corpus (2)

• An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. I. Overview: CO Cloud Distributions
• ALMA 0.1 pc View of Molecular Clouds Associated with High-Mass Protostellar Systems in the Small Magellanic Cloud: Are Low-Metallicity Clouds Filamentary or Not?