The Galaxy as Fundamental Calibrator of the Extragalactic Distance Scale - Part Two - Comparisons of Metric and Photometric Scale Lengths and Three Further Tests of the Long and Short Distance Scales

The traditional approach to the extragalactic distance scale rests on a pyramid of primary, secondary and tertiary indicators of increasing range and decreasing accuracy. This multi-step procedure, fraught with the danger of cumulative errors, has led in recent years to two main, widely diverging scales: the ‘long’ scale (Sandage and Tammann 1974, 1975, 1976) implying a Hubble constant and the ‘short’ scale (de Vaucouleurs 1978, 1979; de Vaucouleurs and Bollinger 1979; de Vaucouleurs and Peters 1981; de Vaucouleurs et al. 1981) leading to H0 ≃ 100. Several authors have already shown that the long scale rests on very precarious foundations (Capaccioli and Fasano 1980, de Vaucouleurs 1981, Hanes 1980); counter arguments have been offered in its defence and to criticize the short scale (Tammann, Sandage and Yahil 1979, Sandage and Tammann 1982). For want of a conclusive test a consensus was still lacking.

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Masers and the Cosmic Distance Scale

Symposium - International Astronomical Union ◽

10.1017/s0074180900134412 ◽

1988 ◽

Vol 129 ◽

pp. 169-174 ◽

Cited By ~ 1

Author(s):

Mark J. Reid ◽

James M. Moran ◽

Carl R. Gwinn

Keyword(s):

Sufficient Accuracy ◽

Distance Scale ◽

Proper Motions ◽

Fundamental Parameters ◽

The Galaxy ◽

Nearby Galaxies ◽

Extragalactic Distance Scale ◽

Maser Sources ◽

Better Than

Studies of H2O masers have demonstrated the power of VLBI techniques to measure relative positions with sufficient accuracy (∼ 10 μas) to determine proper motions and to estimate distances to maser sources throughout the Galaxy. The distance to four H2O masers have been determined, and the distance to the center of the Galaxy has been determined to be 7.1 ± 1.5 kpc from observations of the H2O masers in Sgr-B2. Proper motion distances for other H2O masers, and possibly for OH masers, may allow the determination of the fundamental parameters describing the size (Ro) and rotation rate (Θo) of the Galaxy with accuracies of better than 10%. Finally, the measurement of the proper motions of H2O masers in nearby galaxies (< 10 Mpc) is feasible and offers the possibility of direct calibration of the extragalactic distance scale.

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Five Crucial Tests of the Extragalactic Distance Scale Using the Galaxy as Fundamental Calibrator

Highlights of Astronomy ◽

10.1017/s153929960000530x ◽

1983 ◽

Vol 6 ◽

pp. 315-317

Author(s):

G. de Vaucouleurs

Keyword(s):

Local Group ◽

Traditional Approach ◽

Virgo Cluster ◽

Distance Scale ◽

Short Scale ◽

The Galaxy ◽

Extragalactic Distance Scale

The traditional approach to the extragalactic distance scale has been through several levels of primary, secondary and tertiary indicators of increasing range and decreasing precision. This piecemeal approach, fraught with the danger of cumulative errors, has led in recent years to two widely divergent scales, the “long” scale of Sandage and Tammann (1974–1982), leading to ≃ 50 km s-1 Mpc-1, and the “short” scale of the author (1978–79), leading to Ho ≃ 100 (de Vaucouleurs and Bollinger 1979; de Vaucouleurs and Peters 1981; de Vaucouleurs et al. 1981). The divergence, increasing from ~ 0.4 mag in the Local Group to ~ 1.2 mag at the distance of the Virgo Cluster, indicates that at least one of the scales is not linear (de Vaucouleurs 1981).

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The Extragalactic Distance Scale Key Project. XVIII. The Discovery of Cepheids and a New Distance to NGC 4535 Using theHubble Space Telescope

The Astrophysical Journal ◽

10.1086/307541 ◽

1999 ◽

Vol 521 (1) ◽

pp. 155-178 ◽

Cited By ~ 53

Author(s):

L. M. Macri ◽

J. P. Huchra ◽

P. B. Stetson ◽

N. A. Silbermann ◽

W. L. Freedman ◽

...

Keyword(s):

Distance Scale ◽

Space Telescope ◽

Extragalactic Distance Scale

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Recent improvements to the Cepheid distance scale

International Astronomical Union Colloquium ◽

10.1017/s0252921100116914 ◽

1993 ◽

Vol 139 ◽

pp. 61-71

Author(s):

Wendy L. Freedman ◽

Barry F. Madore

Keyword(s):

Near Infrared ◽

Hubble Space Telescope ◽

Systematic Difference ◽

Distance Scale ◽

Nearby Galaxy ◽

Rr Lyrae ◽

Cepheid Variables ◽

Level Of Significance ◽

Extragalactic Distance Scale ◽

Better Than

AbstractIn the course of the last decade significant advances have been made in the observations of Cepheid variables and in their successful application to the extragalactic distance scale. Much of this progress has come about as a result of new CCD and near-infrared photometry. These recent improvements are discussed, and a comparison is given of Population I Cepheids and Population II distances. The correspondence is good, with the zero points agreeing at a level of better than 15% in distance. At this same level of significance, a systematic difference between these distances scales may exist, in the sense that the RR Lyrae distances appear to be smaller than the Cepheid distances (if it is assumed, as has generally been done for extragalactic studies of RR Lyraes, that Mv(RR) = 0.77 mag, independent of [Fe/H]). However, several recently-published calibrations of Mv(RR) significantly reduce this discrepancy. Finally, new Cepheid data for the nearby galaxy M81 are presented based on recent Hubble Space Telescope observations.

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Nonlinear Convective Pulsation Models of Second Overtone SMC Cepheids

International Astronomical Union Colloquium ◽

10.1017/s0252921100016699 ◽

2002 ◽

Vol 185 ◽

pp. 420-423

Author(s):

M. Marconi ◽

G. Bono ◽

F. Caputo

Keyword(s):

Short Distance ◽

Selection Criteria ◽

Distance Scale ◽

Model Predictions ◽

Distance Indicators

AbstractNonlinear convective pulsation models representative of SMC Cepheids pulsating in the second overtone mode are presented. Model predictions are compared with observations and implications are derived for second overtone selection criteria. The role of overtone Cepheids as distance indicators is finally investigated and the derived distance scale is at odds with the so called short distance scale.

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