MORPHOLOGIES OF ∼190,000 GALAXIES AT z = 0–10 REVEALED WITH HST LEGACY DATA. II. EVOLUTION OF CLUMPY GALAXIES

Abstract

We investigate the evolution of clumpy galaxies with  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 we 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 the Madau–Lilly plot. A low average Sérsic 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 ⊙ ≳ 11 . All of these results are consistent with the picture that a majority of clumps form in the violent disk instability and migrate into the galactic centers.