The redshift-distance relation. VIII - Magnitudes and redshifts of southern galaxies in groups: A further mapping of the local velocity field and an estimate of the deceleration parameter

Abstract

New redshifts and magnitudes have been obtained at the Mount Stromlo and Siding Spring Observatories for many galaxies in the Shapley-Ames catalog south of deltaapprox. =-30degree. A subset of the material: multiplets, groups, and clusters of E and S0 galaxies: is used to test again the isotropy of the Hubble expansion. Redshifts of 138 galaxies in 22 southern multiplets, groups, and clusters, and photoelectric UBVR magnitudes for 74 of the first few brightest galaxies in each aggregate give the following results. The color excess as a function of galactic latitude for southern galaxies increases less steeply toward the galactic plane than expected from galaxy counts, confirming an earlier result from northern data. The absolute magnitude for first-ranked E galaxies is a very shallow function of richness for N/subc/$sup 48$approximately-greater-than20, but steepens for N/subc/$sup 48$<20. This requires the luminosity function to be nearly vertical at the bright end. Deviations from the redshift-magnitude (Hubble) diagram are uncorrelated with either supergalactic longitude, with Rubin- Ford-Rubin (RFR) regions, or with the apex of the Rubin-Ford proposed motion of the Local Group.A crude estimate of q$sub 0$, found from the upper limit of deltaH/H$sub 0$<0.08(sigma) for any possible velocity perturbation for the E groups inmore » the presence of an density contrast of deltarho/rho =3.4+-0.2(sigma), is theta$sub 0$< or =0.02+-0.02, from the idealized model of Silk. These low values of q$sub 0$ agree with similar low values from five other methods summarized in the paper. (AIP)« less