The cosmological evolution of flat-spectrum quasars

Astronomy and Astrophysics – Astronomy

Scientific paper

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Astronomical Spectroscopy, Cosmology, Quasars, Radio Astronomy, Galactic Evolution, Spectrum Analysis, Stellar Evolution

Scientific paper

The luminosity-volume (V/Vm) test is used to study the spatial distribution and determine the luminosity functions of a complete sample of quasars observed at 2.7 GHz in the declination zone between + and - 4 deg. The optical magnitudes of all sample members are remeasured to an accuracy of about 0.2 magnitude, and the distribution of apparent magnitudes for flat-spectrum objects is found to extend to lower magnitudes than that for steep-spectrum objects. A restricted sample of quasars with magnitudes of at least 19.5 after correction for galactic absorption is selected for further analysis to obtain V/Vm estimates, luminosity functions, and space distributions. Additional subsamples of flat- and steep-spectrum quasars are investigated for a correlation between V/Vm and spectral index as well as for indications of differences in the evolution of the two types. The results suggest that the cosmological evolution of both galaxies and quasars is restricted to powerful sources with extended radio structures.

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