Molecular gas in the outflow of the Small Magellanic Cloud

Abstract

We report the first evidence of molecular gas in two atomic hydrogen (HI) clouds associated with gas outflowing from the Small Magellanic Cloud (SMC). We used the Atacama Pathfinder Experiment (APEX) to detect and spatially resolve individual clumps of CO(2-1) emission in both clouds. CO clumps are compact (~ 10 pc) and dynamically cold (linewidths < 1 km/s). Most CO emission appears to be offset from the peaks of the HI emission, some molecular gas lies in regions without a clear HI counterpart. We estimate a total molecular gas mass of 10^3-10^4 Msun in each cloud and molecular gas fractions up to 30% of the total cold gas mass (molecular + neutral). Under the assumption that this gas is escaping the galaxy, we calculated a cold gas outflow rate of 0.3-1.8 Msun/yr and mass loading factors of 3 -12 at a distance larger than 1 kpc. These results show that relatively weak star-formation-driven winds in dwarf galaxies like the SMC are able to accelerate significant amounts of cold and dense matter and inject it into the surrounding environment.

Accepted for publication in ApJ Letters

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• GASKAP-HI Pilot Survey Science I: ASKAP Zoom Observations of HI Emission in the Small Magellanic Cloud
• Shock-multicloud interactions in galactic outflows -- I. Cloud layers with log-normal density distributions
• The in situ formation of molecular and warm ionised gas triggered by hot outflows
• Inflow of low-metallicity cool gas in the halo of the Andromeda galaxy
• Cold HI ejected into the Magellanic Stream
• A detection of H${}_2$ in a high velocity cloud toward the Large Magellanic Cloud
• Molecular Shattering
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