Sinfoni integral field spectroscopy of z ∼ 2 UV-selected galaxies: Rotation curves and dynamical evolution

We present ∼0″5 resolution near-infrared integral field spectroscopy of the Hα line emission of 14 z ∼ 2 UV-selected BM/BX galaxies, obtained with SINFONI at the ESO Very Large Telescope. The average Hα half-light radius is r_1/2 ≈4 h₇₀^-1 kpc, and line emission is detected over ≳20 h₇₀^-1 kpc in several sources. In nine galaxies, we detect spatially resolved velocity gradients, from 40 to 410 km s^-1 over ∼10 h₇₀ ^-1 kpc. The kinematics of the larger systems are generally consistent with orbital motions. Four galaxies are well described by rotating clumpy disks, and we extracted rotation curves out to radii ≳10 h ₇₀^-1 kpc. One or two galaxies exhibit signatures more consistent with mergers. Analyzing all 14 galaxies in the framework of rotating disks, we infer mean inclination- and beam-corrected maximum circular velocities of v_c ∼ 180 ± 90 km s^-1 and dynamical masses from ∼0.5 to 25 × 10¹⁰ h₇₀^-1 M _⊙ within r_1/2- The specific angular momenta of our BM/BX galaxies are similar to those of local late-type galaxies. Moreover, the specific angular momenta of their baryons are comparable to those of their dark matter halos. Extrapolating from the average v_c at 10 h ₇₀^-1 kpc, the virial mass of the typical halo of a galaxy in our sample is 10^11.7±0.5 h₇₀^-1 M _⊙. Kinematic modeling of the three best cases implies a ratio of v_c to local velocity dispersion v_c/σ ∼ 2-4 and, accordingly, a large geometric thickness. We argue that this suggests a mass accretion (alternatively, gas exhaustion) timescale of ∼500 Myr. We also argue that if our BM/BX galaxies were initially gas-rich, their clumpy disks would subsequently lose their angular momentum and form compact bulges on a timescale of ∼1 Gyr.