THE KMOS^3DSURVEY: DESIGN, FIRST RESULTS, AND THE EVOLUTION OF GALAXY KINEMATICS FROM 0.7 ⩽<i>z</i>⩽ 2.7

Abstract

We present the KMOS 3D survey, a new integral field survey of over 600 galaxies at 0.7 < z < 2.7 using KMOS at the Very Large Telescope (VLT). The KMOS 3D survey utilises synergies with multi-wavelength ground and space-based surveys to trace the evolution of spatially-resolved kinematics and star formation from a homogeneous sample over 5 Gyrs of cosmic history. Targets, drawn from a mass-selected parent sample from the 3D-HST survey, cover the star formation-stellar mass (M * ) and rest-frame (U -V ) -M * planes uniformly. We describe the selection of targets, the observations, and the data reduction. In the first year of data we detect H emission in 191 M * = 3 10 9 -7 10 11 M galaxies at z = 0.7 -1.1 and z = 1.9 -2.7. In the current sample 83% of the resolved galaxies are rotation-dominated, determined from a continuous velocity gradient and v rot / 0 > 1, implying that the star-forming 'main sequence' (MS) is primarily composed of rotating galaxies at both redshift regimes. When considering additional stricter criteria, the H kinematic maps indicate at least 70% of the resolved galaxies are disk-like systems. Our high-quality KMOS data confirm the elevated velocity dispersions reported in previous IFS studies at z 0.7. For rotation-dominated disks, the average intrinsic velocity dispersion decreases by a factor of two from 50 km s -1 at z 2.3 to 25 km s -1 at z 0.9. Combined with existing results spanning z 0 -3, we show that disk velocity dispersions follow an evolution that is consistent with the dependence of velocity dispersion on gas fractions predicted by marginally-stable disk theory.