Gravitational mechanics of systems of galaxies. I. Corrections for errors in redshifts

Modern 21 cm hydrogen-line redshifts (published and unpublished), accurate to approx.8 km s-1, are used as standards to derive zero point corrections, rms uncertainties (sigma/sub V/), and the percentage of discordant (i.e., differing by more than 3 sigma/sub V/ from the zero point redshift) optical and 21 cm redshifts from earlier catalogs. Optical redshifts have a typical uncertainty of approx.100 km s-1 (independent of the epoch of the source of redshift), but the variation in sigma/sub V/ from source to source is considerable. Optical redshifts by Kelton (sigma/sub V/ = 43 km s-1), the Center for Astrophysics (Davis et al.) (sigma/sub V/ = 37 km s-1), and Rubin, Ford, and Thonnard (sigma/sub V/ = 8 km s-1) are especially noteworthy. The rms correction factor appropriate to optical redshifts listed in the First Reference Catalog (de Vaucouleurs and de Vaucouleurs) is 1.33 and that for the Second Reference Catalog (de Vaucouleurs, de Vaucouleurs, and Corwin) is 1.42. A new catalog of galaxy redshifts (CGR) containing known redshifts for approx.4000 galaxies and reliable estimates of rms uncertainties was compiled and is available for circulation