2016ApJ...821...72S

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 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}☉ \gtrsim 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.