Composite Hubble diagram

The composite Hubble diagram for 663 normal galaxies, 235 radio galaxies, and 265 quasi-stellar objects is given. The least squares solution to the Hubble diagram slope for each of the three classes of objects is compatible, within the errors, with that expected for a homogeneous, isotropic, expanding universe. If the Hubble constant H0=50 km s-1 Mpc-1, then =-21.150, =1043.96 ergs s-1, and sigma/subM/=0.887 for normal galaxies; =-23.061, =1044.72 ergs s-1, and sigma/subM/=0.684 for radio galaxies; and =-25.784, =1045.81 ergs s-1 and sigma/subM/=1.451 for the quasi-stellar objects. Here denotes the mean absolute visual magnitude, denotes the mean absolute optical luminosity, and sigma/subM/ denotes the dispersion in magnitude. It is shown that the uncertainty in the slope of the Hubble diagram for QSOs is comparable to that obtained for normal galaxies over a similar range in magnitude. This means that the scatter in the QSO Hubble diagram should not be used in arguments which question their cosmological nature. It is shown that the absolute optical luminosity of extragalactic objects increases with increasing redshift, and that any given object class occurs infrequently in the magnitude and redshift range of the others. These facts suggest an evolutionary sequence in which bright young QSOs evolve into older, less luminous radio galaxies, which in turn evolve into the weaker, still older normal galaxies