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Register a new userMorphologies of ~190,000 Galaxies at z=0-10 Revealed with HST Legacy Data I. Size Evolution
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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.
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We investigate evolution of clumpy galaxies with the Hubble Space Telescope (HST) samples of ~17,000 photo-z and Lyman break galaxies at z~0-8. We detect clumpy galaxies with off-center clumps in a self-consistent algorithm that is well tested with previous study results, and measure the number fraction of clumpy galaxies at the rest-frame UV, f_clumpy^UV. We identify an evolutionary trend of f_clumpy^UV over z~0-8 for the first time: f_clumpy^UV increases from z~8 to z~1-3 and subsequently decreases from z~1 to z~0, which follows the trend of Madau-Lilly plot. A low average Sersic index of n~1 is found in the underlining components of our clumpy galaxies at z~0-2, indicating that typical clumpy galaxies have disk-like surface brightness profiles. Our f_clumpy^UV values correlate with physical quantities related to star formation activities for star-forming galaxies at z~0-7. We find that clump colors tend to be red at a small galactocentric distance for massive galaxies with log(M_*/M_sun)>~11. All of these results are consistent with a picture that a majority of clumps form in the violent disk instability and migrate into the galactic centers.
We present the redshift evolution of the radial surface brightness (SB) profile of the rest-frame UV and optical stellar continua for 9119 Lya emitters (LAEs) at z~0-8 and 0-2, respectively. Using Hubble Space Telescope data and the LAE catalogs taken from the literature, we derive the structural quantities of the 9119 LAEs and ~180,000 comparison galaxies of photo-z star-forming galaxies (SFGs) and Lyman break galaxies (LBGs) by the well-tested profile fitting. From 936 well-fitted LAEs, we carefully define the homogeneous sample of LAEs falling in the same ranges of UV-continuum luminosity and Lya equivalent width over z~0-8, and evaluate the redshift evolution. We find that the effective radius r_e distribution is represented by a log-normal function, and that the median Sersic index is almost constant at n~1-1.5 for the LAEs over z~0-7, suggesting that typical LAEs have a stellar-disk morphology. The size-luminosity relation of the LAEs monotonically decreases towards high-z, following size-luminosity relations of SFGs and LBGs. The median r_e values of the LAEs significantly evolve as r_e~(1+z)^-1.37, similar to those of the SFGs and LBGs in the same luminosity range, in contrast with the claims of no evolution made by previous studies whose LAE samples are probably biased to faint sources at low-z. The r_e distribution, star-formation rate surface densities, and stellar-to-halo size ratios of the LAEs are comparable with those of the SFGs and LBGs, indicating that LAEs have stellar components similar to SFGs and LBGs with a Lya emissivity controlled by the non-stellar physics such as geometry, kinematics, and ionization states of the inter-stellar/circum-galactic medium.
The remarkable HST datasets from the CANDELS, HUDF09, HUDF12, ERS, and BoRG/HIPPIES programs have allowed us to map out the evolution of the UV LF from z~10 to z~4. We have identified 5859, 3001, 857, 481, 217, and 6 galaxy candidates at z~4, z~5, z~6, z~7, z~8, and z~10, respectively from the ~1000 arcmin**2 area probed. The selection of z~4-8 galaxies over the five CANDELS fields allows us to assess the cosmic variance; the largest variations are apparent at z>=7. Our new LF determinations at z~4 and z~5 span a 6-mag baseline (-22.5 to -16 AB mag). These determinations agree well with previous estimates, but the larger samples and volumes probed here result in a more reliable sampling of >L* galaxies and allow us to reassess the form of the UV LFs. Our new LF results strengthen our earlier findings to 3.4 sigma significance for a steeper faint-end slope to the UV LF at z>4, with alpha evolving from alpha=-1.64+/-0.04 at z~4 to alpha=-2.06+/-0.13 at z~7 (and alpha = -2.02+/-0.23 at z~8), consistent with that expected from the evolution of the halo mass function. With our improved constraints at the bright end, we find less evolution in the characteristic luminosity M* over the redshift range z~4 to z~7; the observed evolution in the LF is now largely represented by changes in phi*. No evidence for a non-Schechter-like form to the z~4-8 LFs is found. A simple conditional LF model based on halo growth and evolution in the M/L ratio of halos ((1+z)**-1.5) provides a good representation of the observed evolution.
Spectroscopic + photometric redshifts, stellar mass estimates, and rest-frame colors from the 3D-HST survey are combined with structural parameter measurements from CANDELS imaging to determine the galaxy size-mass distribution over the redshift range 0<z<3. Separating early- and late-type galaxies on the basis of star-formation activity, we confirm that early-type galaxies are on average smaller than late-type galaxies at all redshifts, and find a significantly different rate of average size evolution at fixed galaxy mass, with fast evolution for the early-type population, R_eff ~ (1+z)^-1.48, and moderate evolution for the late-type population, R_eff ~ (1+z)^-0.75. The large sample size and dynamic range in both galaxy mass and redshift, in combination with the high fidelity of our measurements due to the extensive use of spectroscopic data, not only fortify previous results, but also enable us to probe beyond simple average galaxy size measurements. At all redshifts the slope of the size-mass relation is shallow, R_eff ~ M_star^0.22, for late-type galaxies with stellar mass >3x10^9 M_sol, and steep, R_eff M_star^0.75, for early-type galaxies with stellar mass >2x10^10 M_sol. The intrinsic scatter is <~0.2 dex for all galaxy types and redshifts. For late-type galaxies, the logarithmic size distribution is not symmetric, but skewed toward small sizes: at all redshifts and masses a tail of small late-type galaxies exists that overlaps in size with the early-type galaxy population. The number density of massive (~10^11 M_sol), compact (R_eff < 2 kpc) early-type galaxies increases from z=3 to z=1.5-2 and then strongly decreases at later cosmic times.
We present clustering analysis results from 10,381 Lyman break galaxies (LBGs) at z~ 4-7, identified in the Hubble legacy deep imaging and new complimentary large-area Subaru/Hyper Suprime-Cam data. We measure the angular correlation functions (ACFs) of these LBGs at z~4, 5, 6, and 7, and fit these measurements using halo occupation distribution (HOD) models that provide an estimate of halo masses, M_h~(1-20)x10^11 Msun. Our M_h estimates agree with those obtained by previous clustering studies in a UV-magnitude vs. M_h plane, and allow us to calculate stellar-to-halo mass ratios (SHMRs) of LBGs. By comparison with the z~0 SHMR, we identify evolution of the SHMR from z~0 to z~4, and z~4 to z~7 at the >98% confidence levels. The SHMR decreases by a factor of ~2 from z~0 to 4, and increases by a factor of ~4 from z~4 to 7. We compare our SHMRs with results of a hydrodynamic simulation and a semi-analytic model, and find that these theoretical studies do not predict the SHMR increase from z~4 to 7. We obtain the baryon conversion efficiency (BCE) of LBGs at z~4, and find that the BCE increases with increasing dark matter halo mass. Finally, we compare our clustering+HOD estimates with results from abundance matching techniques, and conclude that the M_h estimates of the clustering+HOD analyses agree with those of the simple abundance matching within a factor of 3, and that the agreement improves when using more sophisticated abundance matching techniques that include subhalos, incompleteness, and/or evolution in the star formation and stellar mass functions.
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