Cosmological Evolution of the Duty Cycle of Quasars

Abstract

Quasars are powered by accretion onto supermassive black holes, but the problem of the duty cycle related to the episodic activity of the black holes remains open as one of the major questions of cosmological evolution of quasars. In this Letter, we obtain quasar duty cycles based on analyses of a large sample composed of 10,979 quasars with redshifts $z\le2.1$ from the Sloan Digital Sky Survey (SDSS) Data Release Three. We estimate masses of quasar black holes and obtain their mass function (MF) of the present sample. We then get the duty cycle $\bar{\delta}(z)=10^{-3}\sim 1$ based on the So{\l}tan's argument, implying that black holes are undergoing multiple episodic activity. We find that the duty cycle has a strong evolution. By comparison, we show that evolution of the duty cycle follows the history of cosmic star formation rate (SFR) density in the Universe, providing intriguing evidence for a natural connection between star formation and triggering of black hole activity. Feedback on star formation from black hole activity is briefly discussed.Comment: Accepted by ApJL, 4 pages and 2 Figure

Suppressed Star Formation in Circumnuclear Regions in Seyfert Galaxies

“…It has been found that black hole duty cycles follow the history of the star formation rate density (Wang et al 2006). The above scenario then implies that both the black hole activities and the starbursts are episodic (Davies et al 2006).…”

UNSHIFTED METASTABLE He I* MINI-BROAD ABSORPTION LINE SYSTEM IN THE NARROW-LINE TYPE 1 QUASAR SDSS J080248.18+551328.9

“…Supernova explosions observed today are related to their past star formation history, in that a progenitor with mass M * will explode t(M * ) years later after its formation, with t(M * ) = 13(M * /M ) −2.5 . If a constant star formation rate of 10 M yr −1 such as in SDSS J0802+5513 holds for the past 100 Myr, i.e., the typical AGN life cycle (Wang et al 2006), all star with mass larger than 7 M will explode today. Assuming a Salpeter initial mass function, a large fraction f c = 0.38 of star formation mass will be recycled into the ISM ).…”

Spatially Resolved Patchy Lyα Emission within the Central Kiloparsec of a Strongly Lensed Quasar Host Galaxy at z = 2.8

“…Galaxies with AGNs that outshine their host galaxies ("quasars") are ubiquitous at  z 1 (e.g., Pâris et al 2017), i.e., during the epoch in which the universe formed most of its stars (Madau & Dickinson 2014). However, quasars are transient phenomena with duty cycles that are difficult to measure (Martini & Schneider 2003;Wang et al 2006;Shen et al 2007;Shankar et al 2010;Schmidt et al 2017). AGNs also acts as a source of feedback, injecting energy both radiatively and mechanically back into their immediate environments.…”