Intrinsic Shape of Star-Forming BzK Galaxies at z~2 in GOODS-N
  We study structure of star-forming galaxies at z~2 in GOODS-N field selected
as sBzK galaxies down to K_{AB} <24.0 mag. Among 1029 sBzK galaxies, 551
galaxies (54%) show a single component in ACS/F850LP image obtained with the
Hubble Space Telescope; the rest show multiple components. We fit the
single-component sBzK galaxies with the single S\'ersic profile using the
ACS/F850LP image and find that a majority of them (64%) show S\'ersic index of
n=0.5-2.5, indicating that they have a disk-like structure. The resulting
effective radii typically range from 1.0 to 3.0 kpc in the rest-frame UV
wavelength. After correcting the effective radii to those in the rest-frame
optical wavelength, we find that the single-component sBzK galaxies locate in
the region where the local and z~1 disk galaxies distribute in the stellar
mass-size diagram, suggesting comparable surface stellar mass density between
the sBzK and z~0-1 disk galaxies. All these properties suggest that the
single-component sBzK galaxies are progenitors of the present-day disk
galaxies. However, by studying their intrinsic shape through comparison between
the observed distribution of apparent axial ratios and the distribution for
triaxial models with axes (A>B>C), we find that the mean B/A ratio is
0.61^{+0.05}_{-0.08} and disk thickness C/A is 0.28^{+0.03}_{-0.04}. This
indicates that the single-component sBzK galaxies at z~2 have a bar-like or
oval shape rather than a round disk shape. The shape seems to resemble to a
bar/oval structure that form through bar instability; if it is the case, the
intrinsic shape may give us a clue to understand dynamical evolution of
baryonic matter in a dark matter halo.
