The extragalactic distance scale. VII. The velocitydistance relations in different directions and the Hubble ratio within and without the local supercluster.
Abstract
The velocitydistance relations in different directions are derived from a sample of 322 spirals whose distance moduli 0 were obtained in Paper VI from tertiary distance indicators. The range of distance moduli is 26.5 < oW < 33.2 (2 < A < 42 Mpc) and of corrected velocities 90< V0 < 5760 km 1 Solutions of the form y  = a1(x  x ) and x  = a21(y  y ), where y = 5 log V0, x = 0 , are presented for 11 sky areas (seven in supergalactic equatorial belt, four in the polar caps). Neither the mean slope a nor the mean Hubble ratio H is constant but varies with supergalactic longitude L and latitude B. Both tend to be lower than average in the supergalactic center sector (L < 1800) and higher in the anticenter sector (L > 1800), with intermediate values in the polar caps (IBI > 300). In particular H varies from a minimum 70 near L 750 to a maximum H 110 near L 3300, and significant systematic departures from a linear isotropic expansion are in evidence. In particular the anisotropy of the velocity field in the supergalactic equatorial belt is illustrated for seven distance intervals (7 < A < 29 Mpc). If the equatorial belt sector dominated by the Local Supercluster (0 < L < 1800) is excluded, a close approximation of the asymptotic (lowdensity) Hubble expansion rate is obtained, H0 = 100 + 10 km 1 Mpc1, where the mean error includes the zeropoint error of the tertiary indicators. This value is in good agreement with a number of recent, independent estimates corrected for zero point. Possible sources of systematic errors and selection effects are investigated by dividing the data according to distance modulus, apparent magnitude, luminosity index, and corrected velocity. Minimum bias intervals are identified. Regression and sizeofsample effects in the (log H, log V0)diagram are discussed. Subject headings: cosmology  galaxies: redshifts
 Publication:

The Astrophysical Journal
 Pub Date:
 October 1979
 DOI:
 10.1086/157405
 Bibcode:
 1979ApJ...233..433D
 Keywords:

 Astrometry;
 Cosmology;
 Galactic Clusters;
 Hubble Diagram;
 Radial Velocity;
 Red Shift;
 Distance;
 Error Analysis;
 Position Errors;
 Statistical Distributions;
 Velocity Errors;
 Velocity Measurement;
 Astrophysics;
 Distance Scale:Universe;
 Galaxies:Statistics;
 Hubble Constant;
 Local Supercluster:Velocity Dispersion