Characterizing the Low-Mass Molecular Component in the Northern Small Magellanic Cloud

Abstract

We present here the first results from a high-resolution survey of the ^(12)CO(J = 1-0) emission across the northern part of the poorly enriched Small Magellanic Cloud (SMC), made with the ATNF Mopra telescope. Three molecular complexes detected in the lower resolution NANTEN survey are mapped with a beam FWHM of ~42", to sensitivities of approximately 210 mK per 0.9 km s^(–1) channel, resolving each complex into 4-7 small clouds of masses in the range of M_(vir) ~ 10^(3)-10^(4) M_☉ and with radii no larger than 16 pc. The northern SMC CO clouds follow similar empirical relationships to the southern SMC population, yet they appear relatively under-luminous for their size, suggesting that the star-forming environment in the SMC is not homogeneous. Our data also suggests that the CO cloud population has little or no extended CO envelope on scales ≳30 pc, further evidence that the weak CO component in the north SMC is being disassociated by penetrating UV radiation. The new high-resolution data provide evidence for a variable correlation of the CO integrated brightness with integrated H I and 160 μm emission; in particular CO is often, but not always, found coincident with peaks of 160 μm emission, verifying the need for matching-resolution 160 μm and H I data for a complete assessment of the SMC H_2 mass.

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