Steps toward the Hubble constant. VI - The Hubble constant determined from redshifts and magnitudes of remote SC I galaxies: The value of Q sub 0

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view Abstract Citations (196) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steps toward the Hubble constant. VI. The Hubble constant determined from redshifts and magnitudes of remote Sc I galaxies: the value of q0. Sandage, A. ; Tammann, G. A. Abstract Newly measured redshifts are given for a sample of remote Sc I galaxies in the apparent magnitude range 13.5 < mpg < 15.8 that were found by inspecting 33 Palomar Sky Survey plates in both galactic polar caps. The redshifts range from 2700 to 21,000 km s '. These data, combined with redshifts and magnitudes for nearby Sc I galaxies, show a well-defined redshiftmagnitude relation that follows the slope dm0g0 '/d log cz = 5 required by the linear Rubble expansion. The distant and nearby samples define a common redshift-magnitude relation, which shows that the Rubble constant is the same for Sc I galaxies with V <% 2000 km s ' and V > 6000 km s '. There is no evidence for a perturbed velocity field, and, in particular, the Sc I spirals in the Virgo cluster lie within a/2 of the ridge line, confirming an earlier result from E cluster members that there is no measurable velocity anomaly of the Virgo cluster itself. A bias is identified, and the material is suitably restricted to change the sample from a magnitude-limited set to one that is distance-limited. The statistical properties of the unbiased sample, combined with the absolute magnitude calibration in Paper IV, give the Rubble constant to be H0 = 56.9 I 3.4km s ' Mpc-1. A test of the isotropy is made by comparing the remote value of H0 with that for the nearby galaxies to show that this value of H0 applies everywhere. The principal suspected systematic error rests with the Cepheid P-L-C relation, calibrated via the age-zero main sequence. An error of A(m - M) = 0.2 mag in the adopted van Bueren modulus for the Hyades (making the Ryades brighter) would reduce the Rubble constant by 10 percent to H0 50 + 5 km - 1 Mpc `Support for the larger Ryades modulus has recently been given by Upgren and by van Altena, following Wallerstein and Hodge. For H0 = 551 Skms-'Mpc-1, the Rubble time is H0-' = 17.7 (+1.8, -1.5) x 109yr, which is a factor of 10 increase from Rubble's 1936 value and removes the time-scale difficulty for the Friedmann singular models (A = 0). If H0 = 50 I 5 H0-' = 19.5 (+2.1, -1.8) x 109yr. The order-of-magnitude agreement of H0 ` with the age of globular clusters and of the chemical elements (for any value of the deceleration parameter in the range 0 q0 < 2, as given by other data) is taken as good evidence, second only to the presence of the 3 K radiation, for an evolving Universe of the Friedmann big bang type. Upper limits for the deceleration parameter are calculated by comparing H0 ` with the Friedmann time T0, found by adding 10 yr to the age of the halo globular clusters, with the result that q0(H0 = 55) = 0.10 [-0.08(a), +0.16(a)] and q0(H0 = 50) = 0.20 [-0.12(a), +0.26(a)]. If we assume instead that the Friedmann time T0 is 4 x 10 yr earlier than the Galactic globular clusters, based on the interpretation that the apparent redshift cutoff in quasar redshifts near z = 4 is real and is due to the matter-horizon of the formation of the first galaxies, then q0(H0 = 50) = 0.03 (-0.03, +0.07). These numbers are smaller than the crucial value of q0 = , in agreement with the results of Paper V from a different method, but the present result is vulnerable to uncertainties in the age of globular clusters and in T0. However, within the errors, the value of q0 determined this way agrees with that found by summing the light from visible galaxies (q0 0.03), suggesting that a large fraction of the mass of the Universe may be in the galaxies, and that the expansion will never stop. Subject headings: cosmology - galaxies, photometry of - redshifts Publication: The Astrophysical Journal Pub Date: April 1975 DOI: 10.1086/153510 Bibcode: 1975ApJ...197..265S Keywords: Cosmology; Galaxies; Hubble Diagram; Luminous Intensity; Red Shift; Astronomical Models; Astronomical Photometry; Galactic Clusters; Tables (Data); Velocity Distribution; Astrophysics full text sources ADS | data products NED (67) Related Materials (9) Part 1: 1974ApJ...190..525S Part 2: 1974ApJ...191..603S Part 3: 1974ApJ...194..223S Part 4: 1974ApJ...194..559S Part 5: 1975ApJ...196..313S Part 7: 1976ApJ...210....7S Part 8: 1982ApJ...256..339S Part 9: 1990ApJ...365....1S Part 10: 1995ApJ...446....1S