Determination Of H0 Research Articles

A physical distance indicator for spiral galaxies and the determination of H0

We consider the effect of dark matter on the Tully-Fisher relation for spiral galaxies. We show that a significant fraction of the scatter in this relation could stem from a systematic dependence of the ratio of dark to luminous mass on luminosity. The dynamical effect of the dark matter can be accounted for once a mass decomposition procedure, based on photometry and rotation curve data, has been carried out. We show that the contribution to the circular velocity from the luminous disc alone correlates better with luminosity than does the total velocity, which contains an additional contribution from the dark halo. This correlation is closer to a linear law, has less scatter, and is subject to fewer biases than the conventional Tully-Fisher relation

Supernova Distance Measurements Suggest an Older, Larger Universe

The Hubble constant, the conversion factor that translates the recessional velocities of remote galaxies into distances, is the only fundamental parameter of cosmology that astronomers think they know to within a factor of two. In the 1970s H0 was thought to be somewhere around 50 km/sec per megaparsec. (A megaparsec is 3.3 million light years.) Then in the next decade, measurements of H0 seemed to be converging on 80 or 90 km/sec-Mpc. But in just the last few months, three novel determinations of H0 based on the observation of supernovae have placed the Hubble constant back down in the regime 50–60 km/sec-Mpc.

Distances to the Virgo and Ursa Major clusters and a determination of H0

view Abstract Citations (332) References (72) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Distances to the Virgo and Ursa Major Clusters and a Determination of H 0 Pierce, Michael J. ; Tully, R. Brent Abstract Multicolor CCD photometry of spiral galaxies within the Ursa Major and Virgo Clusters is presented and combined with accurate 21 cm H I line-width measurements in order to investigate the luminosity-line-width relations (Tully-Fisher [hereafter TF] relations) as a distance indicator. There is evidence for a slight morphological-type dependence of the TF relations, although the effect is present only at the 1-2 σ level. No difference in the slope of the TF relations is found between the two clusters, despite the considerable difference in densities and crossing times. A significant reduction in the dispersion of the TF relations is made possible from both accurate total magnitudes and accurate inclinations derived from ellipse fitting to galaxy isophotes. As a result, galaxies with inclinations as low as 30^deg^ can now be included in the sample. In the Ursa Major Cluster, the intrinsic dispersion in the TF relations is found to be only ~0.25 mag. We show that the use of aperture magnitudes (e.g., H band data) results in an artificially large slope to the TF relations. The use of total magnitudes yields a slope of ~8 at near-infrared wavelengths, as a result L is proportional to V^3.2^_max_. An absolute calibration of the TF relations was obtained by fitting to three nearby galaxies with reasonably accurate distances: M31, M33, and NGC 2403. These systems establish the distance to the Ursa Major Cluster to be 15.5 +/- 1.2 Mpc and the mean distance to the Virgo Cluster to be 15.6 +/- 1.5 Mpc, with slightly greater uncertainty due to the possible presence of superposed galaxies. A determination of the value of the Hubble Constant was made by assuming a Virgocentric flow of 300 km s^-1^ at the Local Group, yielding a derived value of H_0_ = 85 +/- 10 km s^-1^ Mpc^-1^. Publication: The Astrophysical Journal Pub Date: July 1988 DOI: 10.1086/166495 Bibcode: 1988ApJ...330..579P Keywords: Astrometry; Galactic Clusters; Hubble Constant; Virgo Galactic Cluster; Astronomical Photometry; Calibrating; Centimeter Waves; Distance; Luminosity; Magnitude; Radio Astronomy; Spectral Line Width; Spiral Galaxies; Astrophysics; COSMOLOGY; GALAXIES: CLUSTERING; GALAXIES: DISTANCES; GALAXIES: PHOTOMETRY; RADIO SOURCES: 21 CM RADIATION full text sources ADS | data products SIMBAD (64) NED (63)

The local value of the Hubble constant from luminosity classification of SB galaxies

view Abstract Citations (13) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The local value of the Hubble constant from luminosity classification of SB galaxies Stenning, M. ; Hartwick, F. D. A. Abstract Luminosity classification on the DDO system for 670 Sb galaxies is presented. Combining these new classifications with data on velocities, magnitudes, and diameters available in the literature, we have determined a local value for the Hubble constant (H0). We attempted to form complete samples limited by magnitude, diameter, and velocity using the V/Vmax test and find possible evidence for a local density enhancement (from galaxies with V0 ≤ 750 km/sec). Using the Sandage and Tammann (ST) values for the distance and reddening of M31 to set the zero point, we obtained values of H0 (after correction for observational selection effects) in excellent agreement with the ST value from nearby small samples. However on isolating a more distant, more uniformly distributed, velocity limited sample of Sb I, Sb I-II, and Sb II galaxies with V0 < 3000 km/sec we found a value for H0 about 40% larger. On performing solutions for H0 allowing for the existence of a peculiar motion of the Galaxy we found (1) a Galactic peculiar motion in very good agreement with recent observations of the anisotropy in the cosmic back- ground radiation and (2) improved agreement between determinations of H0 among the three nearby samples and the more distant one. Our best value for H0 is 75±15 km/sec/Mpc based on the ST data for M3l. Publication: The Astronomical Journal Pub Date: February 1980 DOI: 10.1086/112646 Bibcode: 1980AJ.....85..101S Keywords: Cosmology; Galactic Structure; Hubble Constant; Luminosity; Spiral Galaxies; Classifications; Hubble Diagram; Milky Way Galaxy; Red Shift; Tables (Data); Astrophysics full text sources ADS | data products NED (670)