An HST/WFC3-IR Morphological Survey of Galaxies at z = 1.5-3.6: I.
  Survey Description and Morphological Properties of Star Forming Galaxies
  We present the results of a 42-orbit HST/WFC3 survey of the rest-frame
optical morphologies of star forming galaxies with spectroscopic redshifts in
the range z=1.5-3.6. The survey consists of 42 orbits of F160W imaging covering
~65 arcmin^2 distributed widely across the sky and reaching a depth of 27.9 AB
for a 5 sigma detection within a 0.2 arcsec radius aperture. Focusing on an
optically selected sample of 306 star forming galaxies with stellar masses in
the range M* = 10^9 - 10^11 Msun, we find that typical circularized effective
half-light radii range from ~ 0.7 - 3.0 kpc and describe a stellar mass -
radius relation as early as z ~ 3. While these galaxies are best described by
an exponential surface brightness profile, their distribution of axis ratios is
strongly inconsistent with a population of inclined exponential disks and is
better reproduced by triaxial stellar systems with minor/major and
intermediate/major axis ratios ~ 0.3 and 0.7 respectively. While rest-UV and
rest-optical morphologies are generally similar for a subset of galaxies with
HST/ACS imaging data, differences are more pronounced at higher masses M* > 3 x
10^10 Msun. Finally, we discuss galaxy morphology in the context of efforts to
constrain the merger fraction, finding that morphologically-identified
mergers/non-mergers generally have insignificant differences in terms of
physical observables such as stellar mass and star formation rate, although
merger-like galaxies selected according to some criteria have statistically
smaller effective radii and correspondingly larger SFR surface density.
