Being KLEVER at cosmic noon: ionised gas outflows are inconspicuous in
  low-mass star-forming galaxies but prominent in massive AGN hosts
  We investigate the presence of ionised gas outflows in a sample of 141
main-sequence star-forming galaxies at $1.2<z<2.6$ from the KLEVER (KMOS Lensed
Emission Lines and VElocity Review) survey. Our sample covers an exceptionally
wide range of stellar masses, $8.1<\log(M_\star/M_{\odot})<11.3$, pushing
outflow studies into the dwarf regime thanks to gravitationally lensed objects.
We stack optical rest-frame emission lines (H$\beta$, [OIII], H$\alpha$ and
[NII]) in different mass bins and seek for tracers of gas outflows by using a
novel, physically motivated method that improves over the widely used,
simplistic double Gaussian fitting. We compare the observed emission lines with
the expectations from a rotating disc (disc+bulge for the most massive
galaxies) model, whereby significant deviations are interpreted as a signature
of outflows. We find clear evidence for outflows in the most massive,
$\log(M_\star/M_{\odot}) > 10.8$, AGN-dominated galaxies, suggesting that AGNs
may be the primary drivers of these gas flows. Surprisingly, at
$\log(M_\star/M_{\odot})\leq 9.6$, the observed line profiles are fully
consistent with a rotating disc model, indicating that ionised gas outflows in
dwarf galaxies might play a negligible role even during the peak of cosmic
star-formation activity. Finally, we find that the observed mass loading factor
scales with stellar mass as expected from the TNG50 cosmological simulation,
but the ionised gas mass accounts for only 2$\%$ of the predicted value. This
suggests that either the bulk of the outflowing mass is in other gaseous phases
or the current feedback models implemented in cosmological simulations need to
be revised.
