# Cold gas outflows from the Small Magellanic Cloud traced with ASKAP

## Abstract

Feedback from massive stars plays a critical part in the evolution of the Universe by driving powerful outflows from galaxies that enrich the intergalactic medium and regulate star formation1. An important source of outflows may be the most numerous galaxies in the Universe: dwarf galaxies. With small gravitational potential wells, these galaxies easily lose their star-forming material in the presence of intense stellar feedback1,2. Here, we show that a nearby dwarf galaxy—the Small Magellanic Cloud—has atomic hydrogen outflows extending at least 2 kiloparsecs from the star-forming bar of the galaxy. The outflows are cold (< 400 K) and may have formed during a period of active star formation 25–60 Myr ago3,4. The total mass of atomic gas in the outflow is about 107 solar masses (that is, about 3 per cent of the total atomic gas of the galaxy). The inferred mass flux in atomic gas alone, $$\dot M_{{\mathrm{H}}\;{\textsc{{I}}}}$$  ≈ 0.2–1.0 solar masses per year, is up to one order of magnitude greater than the star-formation rate. We suggest that most of the observed outflow will be stripped from the Small Magellanic Cloud through its interaction with its companion, the Large Magellanic Cloud, and the Milky Way, feeding the Magellanic Stream of hydrogen encircling the Milky Way.

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## Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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## Acknowledgements

ASKAP is part of the Australia Telescope National Facility, which is managed by CSIRO. Operation of the ASKAP is funded by the Australian Government with support from the National Collaborative Research Infrastructure Strategy. The ASKAP uses the resources of the Pawsey Supercomputing Centre. The ASKAP, Murchison Radio-astronomy Observatory and Pawsey Supercomputing Centre were established as initiatives of the Australian Government, with support from the Government of Western Australia and Science and Industry Endowment Fund. We acknowledge the Wajarri Yamatji people as the traditional owners of the observatory site. The MCELS data were provided by R. C. Smith, P. F. Winkler and S. D. Points. The MCELS project has been supported in part by NSF grants AST-9540747 and AST-0307613, and through the generous support of the Dean B. McLaughlin Fund at the University of Michigan—a bequest from the family of D. B. McLaughlin in memory of his lasting impact on astronomy. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions, through project number CE170100013. N.M.M.-G. acknowledges funding from the Australian Research Council via grant FT150100024. We gratefully acknowledge contributions by W. Raja and K. Bannister to ASKAP commissioning.

## Author information

Authors

### Contributions

N.M.M.-G., J.M.D., S.S. and L.S.-S. developed the idea for the project. H.D. calibrated the ASKAP data. N.M.M.-G. and H.D. produced the ASKAP plus Parkes H i data cube. J.R.A., J.D.C, A.P.C., T.F, G.H, A.H., D.K., K.L.-W., D.M., A.P., J.R., C.J.R., M.A.V. and M.W. are members of the ASKAP Early Science and Commissioning team, with responsibility for delivery of ASKAP data. N.M.M.-G. wrote the paper with direct contributions from H.D., J.M.D., S.S., L.S.-S., K.J. and E.D.T. All authors reviewed the manuscript.

### Corresponding author

Correspondence to N. M. McClure-Griffiths.

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## Supplementary information

### Supplementary Information

Supplementary Figure 1

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McClure-Griffiths, N.M., Dénes, H., Dickey, J.M. et al. Cold gas outflows from the Small Magellanic Cloud traced with ASKAP. Nat Astron 2, 901–906 (2018). https://doi.org/10.1038/s41550-018-0608-8

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