Overview of CO SEST observations: Small Magellanic Cloud

Abstract

We present the results of observations of the ¹²CO(1-0) emission line from the Small Magellanic Cloud done with the 15m SEST telescope. We have fully mapped two areas in the SW region of the SMC bar and have identified several molecular clouds. Molecular clouds in the SMC show different properties than that of Galactic molecular clouds. They follow the same linewidth-size relation (ΔV R^1/2) as Galactic clouds for a large range of radii, but they are undcrluminous in CO. At the smallest scales we can resolve (10 pc), the SMC CO clouds are less luminouds in CO by a factor of 2, while at large scales they are less luminous by a factor of 20. The physical properties derived from two clouds where ¹²CO(2-1), ¹³C0(1-0), and ¹³C0(2-1) observations were done indicate that the CO clouds are clumpy, with a higher kinetic temperature and a smaller filling factor than that of Galactic CO clouds. These properties can be explained as a consequence of a higher photodissociation rate of CO. Assuming virial equilibrium for the CO structures we derive a preliminary estime of the conversion factor to derive total mass of gas from the CO luminosity. This factor is larger that the canonical value adopted for our Galaxy and depends on the size of the molecular cloud.