Published online by Cambridge University Press: 14 August 2015
The distances of about 100 nearby groups, clouds and clusters of galaxies (δ < 52 Mpc) have been derived from the apparent magnitudes and diameters of the 3 to 5 major members. The linearity of the distance scale was verified for δ < 40 Mpc by comparison with luminosity classifications and diameters of ring structures. The velocity-distance relation of these groups is apparently non-linear for δ < 30 Mpc. The velocity/distance ratio increases from H ≃ 50 to 150 km s−1 Mpc−1 when δ increases from δ ≃ 5 to δ ≃ 25 Mpc. Such local departures from linearity are predicted in condensed regions of an inhomogeneous ‘big bang’ hierarchical model obeying the universal density-radius relation. The galactic apex varies with the apparent magnitude of galaxies used for reference in a manner generally consistent with a model of the Local Supercluster in differential rotation and expansion. The best-fit rotation-expansion constants are ω1R1 = 400 ± 50 km s−1, ε1R1 = 1250 ± 50 km s−1, ż = −250 ± 50 km s−1. The velocity-magnitude relation corrected for solar motion is linear with slope 0.2 in 9 < m < 14, confirming that apart from local departures reflecting the supercluster kinematics the underlying Hubble flow is linear and isotropic. If the distance modulus of the Virgo Cluster is (m - M)0 = 30.5 ± 0.2 the Hubble constant derived from the survey of groups is H0 = (100 ± 10) km s−1 Mpc−1.