Galaxy Zoo: Observing Secular Evolution Through Bars by Cheung, E, Athanassoula, E, Masters, K, Nichol, R, Bosma, A, Bell, E, Faber, S, Koo, D, Lintott, C, Melvin, T, Schawinski, K, Skibba, R, Willett, K

“…These results represent empirical evidence for secular evolution driven by bars in disk galaxies. …”

Galaxy Zoo: Bulgeless Galaxies With Growing Black Holes by Simmons, B, Lintott, C, Schawinski, K, Moran, E, Han, A, Kaviraj, S, Masters, K, Urry, C, Willett, K, Bamford, S, Nichol, R

“…The growth of supermassive black holes appears to be driven by galaxy mergers, violent merger-free processes and/or `secular' processes. In order to quantify the effects of secular evolution on black hole growth, we study a sample of active galactic nuclei (AGN) in galaxies with a calm formation history free of significant mergers, a population that heretofore has been difficult to locate. …”

Galaxy Zoo: Bars in Disk Galaxies by Masters, K, Nichol, R, Hoyle, B, Lintott, C, Bamford, S, Edmondson, E, Fortson, L, Keel, W, Schawinski, K, Smith, A, Thomas, D

“…We discuss these results in the context of internal (secular) galaxy evolution scenarios and the possible links to the formation of bars and bulges in disk galaxies.…”

Galaxy Zoo and ALFALFA: Atomic Gas and the Regulation of Star Formation in Barred Disc Galaxies by Masters, K, Nichol, R, Haynes, M, Keel, W, Lintott, C, Simmons, B, Skibba, R, Bamford, S, Giovanelli, R, Schawinski, K

“…In addition our observations suggest bars may reduce or halt star formation in the outer parts of discs by holding back the infall of external gas beyond bar co-rotation, reddening the global colours of barred disc galaxies. This suggests that secular evolution driven by the exchange of angular momentum between stars in the bar, and gas in the disc, acts as a feedback mechanism to regulate star formation in intermediate mass disc galaxies.…”

The Green Valley is a Red Herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxies by Schawinski, K, Urry, C, Simmons, B, Fortson, L, Kaviraj, S, Keel, W, Lintott, C, Masters, K, Nichol, R, Sarzi, M, Ramin, Skibba, Treister, E, Willett, K, Wong, O, Yi, S

“…We conclude that late-type galaxies are consistent with a scenario where the cosmic supply of gas is shut off, perhaps at a critical halo mass, followed by a slow exhaustion of the remaining gas over several Gyr, driven by secular and/or environmental processes. In contrast, early-type galaxies require a scenario where the gas supply and gas reservoir are destroyed virtually instantaneously, with rapid quenching accompanied by a morphological transformation from disk to spheroid. …”

Galaxy Zoo: An independent look at the evolution of the bar fraction over the last eight billion years from HST-COSMOS by Melvin, T, Masters, K, Lintott, C, Nichol, R, Simmons, B, Bamford, S, Casteels, K, Cheung, E, Edmondson, E, Fortson, L, Schawinski, K, Skibba, R, Smith, A, Willett, K

“…Our results are consistent with a picture in which the evolution of massive disc galaxies begins to be affected by slow (secular) internal process at z~1. We discuss possible connections of the decrease in bar fraction to the redshift, including the growth of stable disc galaxies, mass evolution of the gas content in disc galaxies, as well as the mass dependent effects of tidal interactions.…”