SINFONI Integral Field Spectroscopy of<i>z</i>∼ 2 UV‐selected Galaxies: Rotation Curves and Dynamical Evolution

Abstract

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^(-1)_(70) kpc, and line emission is detected over ≳20 h^(-1)_(70)kpc in several sources. In nine galaxies, we detect spatially resolved velocity gradients, from 40 to 410 km s^(-1) over ~10 h^(-1)_(70) 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^(-1)_(70) 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 × 10^(10) h^(-1)_(70) 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 vc at 10 himg1.gif kpc, the virial mass of the typical halo of a galaxy in our sample is 10^(11.7±0.5) h^(-1)_(70) 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.