Morphologies of ∼190,000 Galaxies at z = 0-10 Revealed with HST Legacy Data. I. Size Evolution

Abstract

We present the redshift evolution of the galaxy effective radius r_e 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 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 toward high z, regardless of statistics choices (e.g., {r}_{{e}}\propto {(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 Sérsic index (n∼ 1.5). Moreover, the r_e distribution is well represented by log-normal functions whose standard deviation {σ }_{ln{r}_{{e}}} does not show significant evolution within the range of {σ }_{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 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∼ 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∼ 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 major stellar components of galaxies, and the detailed study of clumpy subcomponents is presented in the paper II.