3D-HST+CANDELS: THE EVOLUTION OF THE GALAXY SIZE-MASS DISTRIBUTION SINCEz= 3

Abstract

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 we 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 0.22 * , for late-type galaxies with stellar mass > 3 × 10 9 M , and steep, R eff ∝ M 0.75 * , for early-type galaxies with stellar mass > 2 × 10 10 M . 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 is 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 ), compact (R eff < 2kpc) early-type galaxies increases from z = 3 to z = 1.5 − 2 and then strongly decreases at later cosmic times.

The stellar metallicity gradients in galaxy discs in a cosmological scenario

“…The simulated r eff of the stellar discs as a function of stellar mass are consistent with observational estimations by van der Wel et al (2014) and by Sánchez-Blázquez et al (2014) within a standard deviation. Our simulated stellar discs are formed by conserving the specific angular momentum content with mean values in agreement with observations (Romanowsky & Fall 2012).…”

The rise and fall of stellar across the peak of cosmic star formation history: effects of mergers versus diffuse stellar mass acquisition

“…type galaxies) have β = 1.2 on average and disks (i.e. latetype galaxies) have β ≃ −0.5 for low values of δm and β ≃ 0.5 for large values of δm, which shows a similar discrepancy of the size-mass evolution between different galaxy morphologies to that observed in van der Wel et al (2014). This stresses the need to study the morphology of our galaxies in further detail, and we now turn to this issue.…”

Biases in Metallicity Measurements from Global Galaxy Spectra: The Effects of Flux Weighting and Diffuse Ionized Gas Contamination

“…If the trend between f DIG and Σ Hα holds out to high redshifts, we expect that DIG emission is negligible in typical high-redshift galaxies that are more highly star-forming (Whitaker et al 2014) and more compact (van der Wel et al 2014) than their z ∼ 0 counterparts at fixed M * . Inferring evolution in H ii region properties by comparing positions of high-redshift galaxies to those of global galaxy spectra in strong-line ratio diagrams will likely overestimate the magnitude of evolution in, e.g., metallicity and ionization parameter.…”