Observations of Faint Quasars: Shape and Evolution of the Luminosity Function

  • David C. Koo
Part of the Astrophysics and Space Science Library book series (ASSL, volume 121)


We highlight results from a study of faint quasars in SA 57 using 4-m photographic multicolor photometry, astrometry, variability, and CCD spectroscopy. Quasar candidates with B < 22.6 were chosen as stellar-like objects with colors unlike normal stars. Together, these techniques allow additional corrections for white dwarfs, hot subdwarfs, and narrow-emission-line galaxies in the sample and yield a quasar density of about 150/deg2 to B = 22.6. A major surprise was that no quasars were found with redshifts above 2.54 among the 8 bonafide quasars fainter than B = 21.5, a result strongly supported by the relative paucity of non-ultraviolet excess candidates. We discuss the importance of our faint counts and redshifts in defining the shape and evolution of the luminosity function (LF) of quasars. In general, the simplest fit to our faint data is made by assuming mainly luminosity evolution of the local LF of Seyfert 1 galaxies, with luminosity increasing by (1 + z)4.0 (low qo, spectral index α=1) up to redshifts about 2 to 3, beyond which we find a decline in the volume density.


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Copyright information

© Springer Science+Business Media Dordrecht 1986

Authors and Affiliations

  • David C. Koo
    • 1
  1. 1.Space Telescope Science InstituteBaltimoreUSA

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