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 h^-1₇₀ kpc, and line emission is detected over >~20 h^-1₇₀ kpc in several sources. In nine galaxies, we detect spatially resolved velocity gradients, from 40 to 410 km s^-1 over ~10 h^-1₇₀ 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^-1₇₀ 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 h^-1₇₀ M_solar 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^-1₇₀ kpc, the virial mass of the typical halo of a galaxy in our sample is 10^11.7+/-0.5 h^-1₇₀ M_solar. 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.

Based on observations obtained at the Very Large Telescope (VLT) of the European Southern Observatory, Paranal, Chile (ESO program IDs 073.B-9018, 074.A-9011, 075.A-0466, and 076.A-0527).