The energetics of starburst-driven outflows at z=1 from KMOS

Mark Swinbank, Chris Harrison, Alfie Tiley, Helen Johnson, Ian Smail, John Stott, Philip Best, Richard Bower, Martin Bureau, Andy Bunker, Michele Cirasuolo, Matt Jarvis, Georgios Magdis, Ray Sharples, David Sobral

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We present an analysis of the gas outflow energetics from KMOS observations of ∼ 529 main-sequence star-forming galaxies at z ∼ 1 using broad, underlying H α and forbidden lines of [N ii] and [S ii]. Based on the stacked spectra for a sample with median star-formation rates and stellar masses of SFR = 7 M   yr−1 and M = (1.0 ± 0.1) × 1010 M, respectively, we derive a typical mass outflow rate of M˙wind = 1–4 M yr−1 and a mass loading of M˙wind / SFR = 0.2–0.4. By comparing the kinetic energy in the wind with the energy released by supernovae, we estimate a coupling efficiency between the star formation and wind energetics of ϵ ∼  0.03. The mass loading of the wind does not show a strong trend with star-formation rate over the range ∼ 2–20 M yr−1, although we identify a trend with stellar mass such that dM / dt / SFR ∝ M0.26±0.07⋆⁠. Finally, the line width of the broad H α increases with disc circular velocity with a sub-linear scaling relation FWHMbroad ∝ v0.21 ± 0.05. As a result of this behaviour, in the lowest mass galaxies (M ≲ 1010 M), a significant fraction of the outflowing gas should have sufficient velocity to escape the gravitational potential of the halo whilst in the highest mass galaxies (M ≳ 1010 M) most of the gas will be retained, flowing back on to the galaxy disc at later times.
Original languageEnglish
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Early online date9 May 2019
Publication statusPublished - 1 Jul 2019


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