The SINS/zC-SINF survey of z 2 galaxy kinematics: Rest-frame morphology, structure, and colors from near-infrared hubble space telescope imaging

Abstract

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 ∼ 1, with only ∼ 15% requiring a high n > 3 Sérsic index, all more massive than 1010 M⊙. In bulge+disk fits, about 40% of galaxies have a measurable bulge component in the light profiles, with ∼ 15% showing a substantial bulge-to-total ratio (B/T) B/T ≳? 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)rest color gradient and scatter within individual z ∼ 2 massive galaxies with ≳?1011 M⊙ 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.