The Linearity of the Cosmic Expansion Field and the Value of the Hubble Constant

Tammann, G.

doi:10.1017/s0074180900132061

Cited by 2 publications

(2 citation statements)

References 60 publications

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“…At low redshifts its asymptotic slope is very close to 0.2 and fits at higher redshifts the slope corresponding to Ω M = 0.3, Ω Λ = 0.7. Yet the authors, reviving similar suggestions by Tammann (1998) and Zehavi et al (1998), propose a break of the Hubble line of SNe Ia at ∼ 7400 km s −1 , implying a decrease of H 0 at larger distances by ∼ 6.5%, but the effect is not seen in the aforementioned studies.…”

Section: The Hubble Diagram Of Sne Iamentioning

confidence: 72%

The expansion field: the value of H 0

Tammann¹,

Sandage

Reindl³

2008

Astron Astrophys Rev

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Any calibration of the present value of the Hubble constant (H 0 ) requires recession velocities and distances of galaxies. While the conversion of observed velocities into true recession velocities has only a small effect on the result, the derivation of unbiased distances which rest on a solid zero point and cover a useful range of about 4 to 30 Mpc is crucial. A list of 279 such galaxy distances within v < 2000 km s −1 is given which are derived from the tip of the red-giant branch (TRGB), from Cepheids, and/or from supernovae of type Ia (SNe Ia). Their random errors are not more than 0.15 mag as shown by intercomparison. They trace a linear expansion field within narrow margins, supported also by external evidence, from v = 250 to at least 2000 km s −1 . Additional 62 distant SNe Ia confirm the linearity to at least 20, 000 km s −1 . The dispersion about the Hubble line is dominated by random peculiar velocities, amounting locally to < 100 km s −1 but increasing outwards. Due to the linearity of the expansion field the Hubble constant H 0 can be found at any distance > 4.5 Mpc. RR Lyr star-calibrated TRGB distances of 78 galaxies above this limit give H 0 = 63.0 ± 1.6 at an effective distance of 6 Mpc. They compensate the effect of peculiar motions by their large number. Support for this result comes from 28 independently calibrated Cepheids that give H 0 = 63.4 ± 1.7 at 15 Mpc. This agrees also with the large-scale value of H 0 = 61.2 ± 0.5 from the distant, Cepheid-calibrated SNe Ia. A mean value of H 0 = 62.3 ± 1.3 is adopted. Because the value depends on two independent zero points of the distance scale its systematic error is estimated to be 6%. -Other determinations of H 0 are discussed. They either conform with the quoted value (e.g. line width data of spirals or the D n − σ method of E galaxies) or are judged to be inconclusive. Typical errors of H 0 come from the use of a universal, yet unjustified P-L relation of Cepheids, the neglect of selection bias in magnitude-limited samples, or they are inherent to the adopted models.

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Section: The Hubble Diagram Of Sne Iamentioning

confidence: 72%

The expansion field: the value of H 0

Tammann¹,

Sandage

Reindl³

2008

Astron Astrophys Rev

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“…The possibility that selection effects may bias the inference of distances from TF relations in clusters of galaxies has repeatedly been raised by Sandage and Tammann (1997), Teerikoorpi (1997) and Tammann (1998). Essential points in this assertion are:…”

Section: Cluster Population Incompleteness Biasmentioning

confidence: 99%

The calibration of the extragalactic distance scale: methods and problems

2000

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Measuring distances in the expanding universe by the classical method of 'standard candles' creates a calibration problem: what is the power of the standard candles, and how standard are they? Hubble's law has recession velocity proportional to distance from the observer, v = H 0 d; but what is the value of H 0 , the Hubble constant? Ten years after the launch of the Hubble Space Telescope (HST), which has made a major impact on this problem, we review progress. The HST Key Project on the extragalactic distance scale has provided a number of calibration points, galaxies at characteristic distances of 10 Mpc. HST has resolved the primary standard candles, Cepheid variable stars, beyond the reach of ground based telescopes.These galaxy 'survey markers' in turn calibrate a number of more penetrating distance indicators which reach out an order of magnitude further, sufficiently far that noise in the Hubble flow δv v in a frame at rest with respect to the microwave background radiation. Supernovae, galaxy scaling relations, and the properties of their stellar populations are among these secondary distance indicators. The Key Project finds that the mean over four different measurement techniques is H 0 = 68 ± 7 km s −1 Mpc −1 . The use of different measurement techniques identifies the degree of systematic error in the calibration, although some uncertainties, for example the distance of the Large Magellanic Cloud, affect all these techniques systematically.More accurate measurements are possible, by this methodology and by stand-alone experiments, through interferometry, extended and improved HST instruments, and through observations at a variety of regions in the electromagnetic spectrum.

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The Linearity of the Cosmic Expansion Field and the Value of the Hubble Constant

Cited by 2 publications

References 60 publications

The expansion field: the value of H 0

The expansion field: the value of H 0

The calibration of the extragalactic distance scale: methods and problems

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