The sins survey: Modeling the dynamics of z 2 galaxies and the high-z tully-fisher relation

We present the modeling of SINFONI integral field dynamics of 18 star-forming galaxies at z 2 from Hα line emission. The galaxies are selected from the larger sample of the SINS survey, based on the prominence of ordered rotational motions with respect to more complex merger-induced dynamics. The quality of the data allows us to carefully select systems with kinematics dominated by rotation, and to model the gas dynamics across the whole galaxy using suitable exponential disk models. We obtain a good correlation between the dynamical mass and the stellar mass, finding that large gas fractions (M _gas M _*) are required to explain the difference between the two quantities. We use the derived stellar mass and maximum rotational velocity V _max from the modeling to construct for the first time the stellar mass Tully-Fisher relation at z 2.2. The relation obtained shows a slope similar to what is observed at lower redshift, but we detect an evolution of the zero point. We find that at z 2.2 there is an offset in log(M _*) for a given rotational velocity of 0.41 0.11 with respect to the local universe. This result is consistent with the predictions of the latest N-body/hydrodynamical simulations of disk formation and evolution, which invoke gas accretion onto the forming disk in filaments and cooling flows. This scenario is in agreement with other dynamical evidence from SINS, where gas accretion from the halo is required to reproduce the observed properties of a large fraction of the z 2 galaxies.