Vol 22, No 1

AGN Lifetimes in UV-selected Galaxies: A Clue to Supermassive Black Holegalaxy Coevolution

Xiaozhi Lin, Yongquan Xue, Guanwen Fang, Lulu Fan, Huynh Anh N. Le, Ashraf Ayubinia


Abstract 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.


Keywords : galaxies: active – galaxies: formation – galaxies: evolution – galaxies: high-redshift – galaxies: nuclei – (galaxies:) quasars: supermassive black holes – galaxies: star formatio n – galaxies: statistics

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