Falling rotation curves of star-forming galaxies at z=0.7-2.6 probed with KMOS-3D and SINS/zC-SINF

I will present the results of a project examining the largely unexplored outer rotation curves of star-forming galaxies at high redshift, exploiting the deep H- alpha IFU kinematic data sets from the KMOS3D and SINS/zCSINF surveys. Through carefully stacking the signal of ~100 massive star-forming disks at z=0.7-2.6, we are able to constrain a representative rotation curve reaching out to 4 effective radii.  Our stacked rotation curve exhibits a turnover with a significant decrease in rotation velocity in the outer regions (~40%). This substantiates the recent evidence for falling outer rotation curves presented for individual massive star-forming disks at high redshift.  Our results are also in good agreement with current studies of the inner ionized gas kinematics of several groups, demonstrating that with increasing redshift star-forming disks are increasingly baryon-dominated. The steep falloff of the stacked outer rotation curve further indicates a significant level of turbulent gas motions at large radii, with important implications on the outer disk structure of massive high-redshift galaxies.