Cold gas outflows from the Small Magellanic Cloud traced with ASKAP

N. M. McClure-Griffiths, H. Dénes, J. M. Dickey, S. Stanimirović, L. Staveley-Smith, Katherine Jameson, Enrico Di Teodoro, James R. Allison, J. D. Collier, A. P. Chippendale, T. Franzen, Gülay Gürkan, G. Heald, A. Hotan, D. Kleiner, K. Lee-Waddell, D. McConnell, A. Popping, Jonghwan Rhee, C. J. Riseley, M. A. Voronkov, M. Whiting

Published 2018-11-05Version 1

Feedback from massive stars plays a critical role in the evolution of the Universe by driving powerful outflows from galaxies that enrich the intergalactic medium and regulate star formation. 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 feedback. Here, we show that the nearby dwarf galaxy, the Small Magellanic Cloud (SMC), has atomic hydrogen outflows extending at least 2 kiloparsecs (kpc) from the star-forming bar of the galaxy. The outflows are cold, $T<400~{\rm K}$, and may have formed during a period of active star formation $25 - 60$ million years (Myr) ago. The total mass of atomic gas in the outflow is $\sim 10^7$ solar masses, ${\rm M_{\odot}}$, or $\sim 3$% of the total atomic gas of the galaxy. The inferred mass flux in atomic gas alone, $\dot{M}_{HI}\sim 0.2 - 1.0~{\rm M_{\odot}~yr^{-1}}$, is up to an order of magnitude greater than the star formation rate. We suggest that most of the observed outflow will be stripped from the SMC through its interaction with its companion, the Large Magellanic Cloud (LMC), and the Milky Way, feeding the Magellanic Stream of hydrogen encircling the Milky Way.