MORPHOLOGIES OF ∼190,000 GALAXIES AT <i>z</i> = 0–10 REVEALED WITH <i>HST</i> LEGACY DATA. I. SIZE EVOLUTION

Abstract

We present the redshift evolution of the galaxy effective radius re obtained from the Hubble Space Telescope (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 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 re 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., for median). For star-forming galaxies, there is no evolution of the power-law slope of the size–luminosity relation and the median Sérsic index (). Moreover, the re distribution is well represented by log-normal functions whose standard deviation does not show significant evolution within the range of . 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 at z = 0–8. The combination of the re-distribution shape+standard deviation, the constant , and 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 . If high-z star-forming galaxies are truly dominated by disks, the value and the disk-formation model indicate that the specific angular momentum of the disk normalized by the host halo is . These are statistical results for major stellar components of galaxies, and the detailed study of clumpy subcomponents is presented in the paper II.