High Resolution Studies of Lensed z~2 Galaxies: Kinematics and Metal Gradients

We use the OSIRIS integral field unit (IFU) spectograph to secure spatially-resolved   strong   emission   lines   of   15   gravitationally-lensed   star-forming galaxies at redshift z~2. With the aid of gravitational lensing and Keck laser-assisted adaptive optics, the spatial resolution of these sub-luminous galaxies is at a few hundred parsecs. First, we demonstrate that high spatial resolution is crucial in diagnosing the kinematic properties and dynamical maturity of z~2 galaxies.  We  observe  a  significantly  lower  fraction  of  rotationally-supported systems  than  what  has  been  claimed  in  lower  spatial  resolution  surveys. Second, we find a much larger fraction of z~2 galaxies with weak metallicity gradients, contrary to the simple picture suggested by earlier studies that well-ordered rotation develops concurrently with established steep metal gradients in all but merging systems. Comparing our observations with the predictions of  hydronamical  simulations,  strong  feedback  is  likely  to  play  a  key  role  in flattening metal gradients in early star-forming galaxies.