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Cosmological Evolution of the Duty Cycle of Quasars

Cosmological Evolution of the Duty Cycle of Quasars. Yan-Mei Chen Collaborator: Jian-Min Wang, Fan Zhang Institute of High Energy Physics, CAS, China 21 Oct 2006. Outline. Motivation The definition of duty cycle Black hole mass function Results. Background. Continuity equation:

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Cosmological Evolution of the Duty Cycle of Quasars

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  1. Cosmological Evolution of the Duty Cycle of Quasars Yan-Mei Chen Collaborator: Jian-Min Wang, Fan Zhang Institute of High Energy Physics, CAS, China 21 Oct 2006

  2. Outline • Motivation • The definition of duty cycle • Black hole mass function • Results

  3. Background • Continuity equation: • Luminosity function • Quasars’ duty cycle Ref: Marconi et al., 2004, MNRAS, 351, 169 Small & Blandford, 1992, MNRAS, 259, 725

  4. Motivation • During entire evolution, how many times and how many black holes are triggered ? • What is the trigger mechanism and why do quasars switch off ? • Constant Eddington ratio ? (Vestergaard, 2004, ApJ, 601, 676)

  5. BH birth active active active dormant dormant a single episodic phase Duty cycle: episodic activity (Kharb et al., 2006) today (1)For a single BH, ; (2)In statistic, duty cycle can be defined as the fraction of active BHs to their total number

  6. where Duty cycle: episodic activity Definition:

  7. Duty cycle The mass-averaged duty cycle: Soltan Argument (1982):

  8. Sample • Sample: SDSS DR3 (Richards et al. 2006) Total: 10, 979 Redshift: z<2.1 • Estimation of BH mass (Mclure & Dunlop, 2004, MNRAS, 352, 1390)

  9. Mass distribution Total: triple power law Mass function in each redshift z-bin

  10. Main results: • δ∈ (10-3 , 1) • strong evolution • consistent with history of SFR density • Open questions: • how to explain the relation • between δand SFR density? • feedback? • duty cycle beyond z=2.1? • how does duty cycle • depend on BH mass? (Pablo G. Perez-Gonzalez et al., 2005, ApJ, 630, 82)

  11. Thank You !

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