The KMOS³D Survey: design, first results, and the evolution of galaxy kinematics from 0.7<z<2.7

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We present the KMOS³D 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 KMOS³D survey utilizes 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 Halpha emission in 191 M*=3×10⁹-7×10¹¹ Msun 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 vrot/σ>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 Halpha 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 at z 2.3 to 25 km/s at z 0.9 while the rotational velocities at the two redshifts are comparable. Combined with existing results spanning z 0-3, disk velocity dispersions follow an approximate (1+z) evolution that is consistent with the dependence of velocity dispersion on gas fractions predicted by marginally-stable disk theory.