Comments on the HUBBLE Diagram, the Luminosity Function and the Space Density Evolution of Radio Quiet Quasars

Abstract

The consequences of a pure power law luminosity function on the distribution of objects in the HUBBLE diagram are described. As long as such a law acts, magnitudes do not contain any information on distances. A high value of the coefficient of the luminosity function of radio quiet quasars, b = 0.95 5 0.05 in the expression lg p(M) -6 . M , is shown to be plausible. This implies a high density evolution, e -(I + z)k, with k near g-10. Findings from modern samples, searched on low-dispersion spectral plates point to an even stronger evolution at z < z .5 ; the discrepancy may be removed if L,/Hb > 3 (about 30) for these radio-quiet QSOs.