High velocity outflows from young star-forming galaxies in the UKIDSS
  Ultra-Deep Survey
  We investigate galactic-scale outflows in the redshift range 0.71 < z < 1.63,
using 413 K-band selected galaxies observed in the spectroscopic follow-up of
the UKIDSS Ultra-Deep Survey (UDSz). The galaxies have an average stellar mass
of ~10^9.5 solar masses and span a wide range in rest-frame colours,
representing typical star-forming galaxies at this epoch. We stack the spectra
by various galaxy properties, including stellar mass, [OII] equivalent width,
star-formation rate, specific star-formation rate and rest-frame spectral
indices. We find that outflows are present in virtually all spectral stacks,
with velocities ranging from 100-1000 km s^-1, indicating that large-scale
outflowing winds are a common property at these redshifts. The highest velocity
outflows (>500 km s^-1) are found in galaxies with the highest stellar masses
and the youngest stellar populations. Our findings suggest that high velocity
galactic outflows are mostly driven by star-forming processes rather than AGN,
with implied mass outflow rates comparable to the rates of star formation. Such
behaviour is consistent with models required to reproduce the high-redshift
mass-metallicity relation.
