부산대학교 도서관

The coevolution between supermassive black holes(SMBHs)and their host galaxies has been proposed for more than a decade,albeit with little direct evidence about black hole accretion activities regulating galaxy star formation at z＞1.In this paper,we study the lifetimes of X-ray active galactic nuclei(AGNs)in UV-selected red sequence(RS),blue cloud(BC)and green valley(GV)galaxies,finding that AGN accretion activities are most prominent in GV galaxies at z～1.5-2,compared with RS and BC galaxies.We also compare AGN accretion timescales with typical color transition timescales of UV-selected galaxies.We find that the lifetime of GV galaxies at z～1.5-2 is very close to the typical timescale when the AGNs residing in them stay in the high-accretion-rate mode at these redshifts;for BC galaxies,the consistency between the color transition timescale and the black hole strong accretion lifetime is more likely to happen at lower redshifts(z＜1).Our results support the scenario where AGN accretion activities govern UV color transitions of host galaxies,making galaxies and their central SMBHs coevolve with each other.