Morphologies of ~190,000 Galaxies at z=0-10 Revealed with HST Legacy
  Data I. Size Evolution
  We present redshift evolution of galaxy effective radius r_e obtained from
the HST samples of ~190,000 galaxies at z=0-10. Our HST samples consist of
176,152 photo-z galaxies at z=0-6 from the 3D-HST+CANDELS catalogue and 10,454
LBGs at z=4-10 identified in CANDELS, HUDF09/12, and HFF parallel fields,
providing the largest data set to date for galaxy size evolution studies. We
derive r_e with the same technique over the wide-redshift range of z=0-10,
evaluating the optical-to-UV morphological K-correction and the selection bias
of photo-z galaxies+LBGs as well as the cosmological surface brightness dimming
effect. We find that r_e values at a given luminosity significantly decrease
towards high-z, regardless of statistics choices. For star-forming galaxies,
there is no evolution of the power-law slope of the size-luminosity relation
and the median Sersic index (n~1.5). Moreover, the r_e-distribution is well
represented by log-normal functions whose standard deviation \sigma_{\ln{r_e}}
does not show significant evolution within the range of
\sigma_{\ln{r_e}}~0.45-0.75. We calculate the stellar-to-halo size ratio from
our r_e measurements and the dark-matter halo masses estimated from the
abundance matching study, and obtain a nearly constant value of
r_e/r_vir=1.0-3.5% at z=0-8. The combination of the r_e-distribution
shape+standard deviation, the constant r_e/r_vir, and n~1.5 suggests a picture
that typical high-z star-forming galaxies have disk-like stellar components in
a sense of dynamics and morphology over cosmic time of z~0-6. If high-z
star-forming galaxies are truly dominated by disks, the r_e/r_vir value and the
disk formation model indicate that the specific angular momentum of the disk
normalized by the host halo is j_d/m_d=0.5-1. These are statistical results for
galaxies' major stellar components, and the detailed study of clumpy
sub-components is presented in the paper II.
