The Properties of the Star-Forming Interstellar Medium at z=0.84-2.23
  from HiZELS - I: Mapping the Internal Dynamics and Metallicity Gradients in
  High-Redshift Disk Galaxies
  We present adaptive optics assisted, spatially resolved spectroscopy of a
sample of nine H-alpha-selected galaxies at z=0.84--2.23 drawn from the HiZELS
narrow-band survey. These galaxies have star-formation rates of 1-27Mo/yr and
are therefore representative of the typical high-redshift star-forming
population. Our ~kpc-scale resolution observations show that approximately half
of the sample have dynamics suggesting that the ionised gas is in large,
rotating disks. We model their velocity fields to infer the
inclination-corrected, asymptotic rotational velocities. We use the absolute
B-band magnitudes and stellar masses to investigate the evolution of the B-band
and stellar mass Tully-Fisher relationships. By combining our sample with a
number of similar measurements from the literature, we show that, at fixed
circular velocity, the stellar mass of star-forming galaxies has increased by a
factor 2.5 between z=2 and z=0, whilst the rest-frame B-band luminosity has
decreased by a factor ~6 over the same period. Together, these demonstrate a
change in mass-to-light ratio in the B-band of Delta(M/L_B)/(M/L_B)_(z=0) \sim
3.5 between z=1.5 and z=0, with most of the evolution occurring below z=1. We
also use the spatial variation of [NII]/Halpha to show that the metallicity of
the ionised gas in these galaxies declines monotonically with galacto-centric
radius, with an average Delta(log O/H)/DeltaR=-0.027+/-0.005dex/kpc. This
gradient is consistent with predictions for high-redshift disk galaxies from
cosmologically based hydrodynamic simulations.
