Cosmological Evolution of the Duty Cycle of Quasars

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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

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Outline

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

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Background

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

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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)

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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
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Duty cycle episodic activity
Definition
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Duty cycle

• The mass-averaged duty cycle
• Soltan Argument (1982)

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Sample

• Sample SDSS DR3 (Richards et al. 2006)
• Total 10, 979
• Redshift zlt2.1
• Estimation of BH mass
• (Mclure Dunlop, 2004, MNRAS, 352, 1390)

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• Main results
• d ? (10-3 , 1)
• strong evolution
• consistent with history of SFR density

• Open questions
• how to explain the relation
• between d and SFR density?
• feedback?
• duty cycle beyond z2.1?
• how does duty cycle
• depend on BH mass?

(Pablo G. Perez-Gonzalez et al., 2005, ApJ, 630,
82)
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• Thank You !