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.