## Abstract

We constrain the intrinsic Eddington ratio (λ _{Edd}) distribution function for local active galactic nuclei (AGN) in bins of low and high obscuration [ log ( N H / cm − 2 ) ≤ 22 and 22 < log ( N H / cm − 2 ) < 25 ], using the Swift Burst Alert Telescope 70 month/BASS DR2 survey. We interpret the fraction of obscured AGN in terms of circumnuclear geometry and temporal evolution. Specifically, at low Eddington ratios ( log λ Edd < −2), obscured AGN outnumber unobscured ones by a factor of ∼4, reflecting the covering factor of the circumnuclear material (0.8, or a torus opening angle of ∼34°). At high Eddington ratios ( log λ Edd > −1), the trend is reversed, with <30% of AGN having log ( N H / cm − 2 ) > 22 , which we suggest is mainly due to the small fraction of time spent in a highly obscured state. Considering the Eddington ratio distribution function of narrow-line and broad-line AGN from our prior work, we see a qualitatively similar picture. To disentangle temporal and geometric effects at high λ _{Edd}, we explore plausible clearing scenarios such that the time-weighted covering factors agree with the observed population ratio. We find that the low fraction of obscured AGN at high λ _{Edd} is primarily due to the fact that the covering factor drops very rapidly, with more than half the time spent with <10% covering factor. We also find that nearly all obscured AGN at high-λ _{Edd} exhibit some broad lines. We suggest that this is because the height of the depleted torus falls below the height of the broad-line region, making the latter visible from all lines of sight.

Original language | English |
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Article number | L13 |

Journal | Astrophysical Journal Letters |

Volume | 939 |

Issue number | 1 |

DOIs | |

State | Published - 1 Nov 2022 |

### Funding

Funders | Funder number |
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YCAA | |

National Science Foundation | AST-1715512, 1554584, 80NSSC18K0418 |

National Science Foundation | |

National Aeronautics and Space Administration | 80NSSC19K0580, NNH22ZDA001N |

National Aeronautics and Space Administration | |

John Templeton Foundation | |

Gordon and Betty Moore Foundation | |

Harvard University | |

Horizon 2020 Framework Programme | 950533, NNH16CT03C |

Horizon 2020 Framework Programme | |

European Commission | |

Fondo Nacional de Desarrollo Científico y Tecnológico | 1190818, 1200495, PHY-1607611, 11190831 |

Fondo Nacional de Desarrollo Científico y Tecnológico | |

Korea Astronomy and Space Science Institute | 2022-1-830-06 |

Korea Astronomy and Space Science Institute | |

National Research Foundation of Korea | ICN12\_009, FB210003, NRF-2020R1C1C1005462, NCN19\_058, CATA-BASAL - ACE210002 |

National Research Foundation of Korea | |

Israel Science Foundation | 1849/19 |

Israel Science Foundation |