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

TL;DR

This study uses high-resolution CO observations to analyze molecular clouds in the northern Small Magellanic Cloud, revealing their properties, environmental effects, and relationships with other emissions, highlighting environmental heterogeneity.

Contribution

First high-resolution survey of CO in northern SMC, resolving small clouds and analyzing their properties and environmental interactions.

Findings

Northern SMC CO clouds are under-luminous for their size.

CO clouds lack extended envelopes on scales<30 pc.

CO brightness correlates variably with HI and um emission.

Abstract

We present here the first results from a high-resolution survey of the 12CO(J=1-0) emission across the northern part of the poorly-enriched Small Magellanic Cloud, 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 channel, resolving each complex into 4-7 small clouds of masses in the range of Mvir~10^3-4 Msol 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 HI and um emission; in particular CO is often, but not always, found coincident with peaks of um emission, verifying the need for matching-resolution um and HI data for a complete assessment of the SMC H2 mass.