Program: GN-2012B-Q-93

We propose NIFS AO/NGS observations of eight Halpha-selected galaxies (with SFRs~20Mo/yr) at z=2.23. These are drawn from our panoramic narrow-band Hi-Z Emission Line Survey (HiZELS), and all lie within 25" of bright (R=13.0--14.5) AO guide stars. We will use the data to map the distribution of star formation, dynamics and metallicity on sub-kpc scales to address: (i) what are the dynamical structures and mass of these young galaxies -- what fraction of the mass of L* galaxies is in place by z~2? (ii) Is stellar mass growth dominated via megers or in isolation? (iii) do z~2 galaxies have comparable structural properties (angular momentum per unit mass, reference velocity, scale length) to those at z=0? (iv) what is the evolution of the Tully-Fisher relation (which relates the halo versus stellar mass) with redshift? (iv) Is the distribution and intensity of star-formation within the ISM reflected by the z=0 Kennicutt-Schmidt Law? (v) are the chemical abundance gradients of high-z galaxies stronger or weaker than the thick/thin disks of local spirals? The answers to these questions are critical for developing models of galaxy formation, in particular to determine if stellar mass assembly is dominated by secular isolation or via merger-induced growth.