MORPHOLOGIES OF ∼190,000 GALAXIES AT z=0-10 REVEALED WITH HST LEGACY DATA. I. SIZE EVOLUTION

We present the redshift evolution of the galaxy effective radius r(e) obtained from the Hubble Space Telescope (HST) samples of similar to 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 catalog and 10,454 Lyman break galaxies (LBGs) at z = 4-10 identified in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), HUDF 09/12, 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 re values at a given luminosity significantly decrease toward high z, regardless of statistics choices (e.g., r(e) proportional to (1 + z)(-1.10 +/- 0.06) for median). For star-forming galaxies, there is no evolution of the power-law slope of the size-luminosity relation and the median Sersic index (n similar to 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) similar to 0.45-0.75. We calculate the stellar-to-halo size ratio from our re measurements and the dark-matter halo masses estimated from the abundance-matching study, and we 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 similar to 1.5 suggests a picture in which typical high-z star-forming galaxies have disk-like stellar components in a sense of dynamics and morphology over cosmic time of z similar to 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) similar or equal to 0.5-1. These are statistical results for major stellar components of galaxies, and the detailed study of clumpy subcomponents is presented in the paper II.