Constraining the Lifetime of Quasars from their Spatial Clustering

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  • 9 February 2000
Abstract
If quasars are short lived, their intrinsic duty cycle is small: to account for their observed number density, they likely reside in abundant, low-mass dark matter halos. Conversely, if quasars live longer, they should be hosted by rarer, more massive and therefore more strongly clustered halos. Reasonable values of L/M (quasar light to halo mass) allow the lifetime of the luminous phase of quasars to be between 10^6 and 10^8 years. We model the quasar luminosity function in detail in the optical and X-ray bands using the Press-Schechter formalism, and show that the expected clustering of quasars is a strong function of their assumed lifetime within this range. Existing measurements of the correlation length of quasars are consistent with any lifetime in the range 10^6-10^8 years. Future measurements of the power spectrum of quasars out to redshift z=3, from the 2dF or Sloan Digital Sky Survey, can significantly improve this constraint, and in principle allow a precise determination of the lifetime. We estimate the systematic errors introduced by uncertainties in the modeling of the quasar-halo relationship, as well as by the possible existence of obscured quasars.

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