Re-examination of the Source Counts for the 3C Revised Catalogue

Abstract

ON the basis of optical identifications by Veron¹ and Wyndham², the 254 extragalactic sources of the 3C Revised Catalogue³ have been divided into the following classes: radio galaxies (RG), quasi-stellar sources (QSS) empty fields (E) and unidentified (?). Log N–log S curves for all the 254 extragalactic sources, for the RG + RG ? (certain and possible), for the QSS + QSS ? and for the QSS + QSS ? + E + E ? + ?, have been derived^1,4, with exponents of −1.85 ± 0.05, −1.55 ± 0.05, −2.2 ± 0.1 and −2.2 (no quoted error), respectively. The conclusion was then drawn that the −2.2 ± 0.1 exponent for the quasars indicated an evolutionary effect which was not shown by the radio galaxies with an exponent of −1.55 ± 0.05. Furthermore, that the quasars plus the empty fields and the unidentified fields showed the same exponent as the quasars alone was taken as an indication that the empty fields and unidentified fields were quasars.