SINS/zC-SINF Survey of z sim 2 Galaxy Kinematics: Rest-frame Morphology, Structure, and Colors from Near-infrared Hubble Space Telescope Imaging

We present the analysis of Hubble Space Telescope (HST) J- and H-band imaging for 29 galaxies on the star-forming main sequence at z ~ 2, which have adaptive optics Very Large Telescope SINFONI integral field spectroscopy from our SINS/zC-SINF program. The SINFONI Hα data resolve the ongoing star formation and the ionized gas kinematics on scales of 1–2 kpc; the near-IR images trace the galaxies' rest-frame optical morphologies and distributions of stellar mass in old stellar populations at a similar resolution. The global light profiles of most galaxies show disk-like properties well described by a single Sérsic profile with $n\sim 1$, with only $\sim 15\%$ requiring a high $n\gt 3$ Sérsic index, all more massive than ${{10}^{10}}\;{{M}_{\odot }}$. In bulge+disk fits, about 40% of galaxies have a measurable bulge component in the light profiles, with $\sim 15\%$ showing a substantial bulge-to-total ratio (B/T) $B/T\gtrsim 0.3$. This is a lower limit to the frequency of z ~ 2 massive galaxies with a developed bulge component in stellar mass because it could be hidden by dust and/or outshined by a thick actively star-forming disk component. The galaxies' rest-optical half-light radii range between 1 and 7 kpc, with a median of 2.1 kpc, and lie slightly above the size–mass relation at these epochs reported in the literature. This is attributed to differences in sample selection and definitions of size and/or mass measurements. The ${{(u-g)}_{{\rm rest}}}$ color gradient and scatter within individual z ~ 2 massive galaxies with $\gtrsim {{10}^{11}}\;{{M}_{\odot }}$ are as high as in z = 0 low-mass, late-type galaxies and are consistent with the high star formation rates of massive z ~ 2 galaxies being sustained at large galactocentric distances.