MASSIV: Mass Assembly Survey with SINFONI in VVDS??? II. Kinematics and close environment classification

Context. Processes driving mass assembly are expected to evolve on different timescales along cosmic time. A transition might happen around z ∼ 1 as the cosmic star formation rate starts its decrease. Aims. We aim to identify the dynamical nature of galaxies in a representative sample to be able to infer and compare the mass assembly mechanisms across cosmic time. Methods. We present an analysis of the kinematics properties of 50 galaxies with redshifts 0.9 < z < 1.6 from the MASSIV sample observed with SINFONI/VLT with a mass range from 4.5 × 109 M to 1.7 × 1011 M and a star formation rate from 6 M yr−1 to 300 M yr−1. This is the largest sample with 2D kinematics in this redshift range. We provide a classification based on kinematics as well as on close galaxy environment. Results. We find that a significant fraction of galaxies in our sample (29%) experience merging or have close companions that may be gravitationally linked. This places a lower limit on the fraction of interacting galaxies because ongoing mergers are probably also present but harder to identify. We find that at least 44 % of the galaxies in our sample display ordered rotation, whereas at least 35 % are non-rotating objects. All rotators except one are compatible with rotation-dominated (Vmax/σ> 1) systems. Non-rotating objects are mainly small objects (Re < 4 kpc). They show a