The extragalactic Cepheid bias: significant influence   on the cosmic distance scale

Paturel, G.; Teerikorpi, P.

doi:10.1051/0004-6361:20042144

Cited by 14 publications

(15 citation statements)

References 31 publications

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“…The optical depth of spiral galaxies is at particular interest in supernova surveys because of the need to correct supernova magnitudes (Hatano et al 1997(Hatano et al , 1998 and supernova rate determinations (Riello & Patat 2005;Botticella et al 2008) for the effects of extinction. Internal extinction is another important parameter related to selection bias in extragalactic Cepheid distance determinations (Paturel & Teerikorpi 2005).…”

Section: Introductionmentioning

confidence: 99%

Revisiting the optical depth of spiral galaxies using the Tully-Fisher B relation

Kankare¹,

Hanski²,

Theureau

et al. 2008

A&A

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Aims. We attempt to determine the optical depth of spiral galaxy disks by a statistical study of new Tully-Fisher data from the ongoing KLUN+ survey, and to clarify the difference between the true and apparent behavior of optical depth. Methods. By utilizing so-called normalized distances, a subsample of the data is identified to be as free from selection effects as possible. For these galaxies, a set of apparent quantities are calculated for face-on positions using the Tully-Fisher diameter and magnitude relations. These values are compared with direct observations to determine the mean value of the parameter C describing the optical depth.Results. The present study suggests that spiral galaxy disks are relatively optically thin τ B ≈ 0.1, at least in the outermost regions, while they appear in general to be optically thick τ B > 1 when the apparent magnitude and average surface brightness are studied statistically.

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Section: Introductionmentioning

confidence: 99%

Revisiting the optical depth of spiral galaxies using the Tully-Fisher B relation

Kankare¹,

Hanski²,

Theureau

et al. 2008

A&A

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“…When applied to the nearest distances 1-3 Mpc, the non-Friedmann cosmology (for a parabolic expansion) gives a typical velocity dispersion between v 1 = ( √ 3 − 1)R V /A = 60 km s −1 at r = R V and v(r = 2R V ) = 1 3 v 1 = 20 km s −1 at r = 2R V , which is near the observed figure 30-60 km s −1 (Karachentsev & Makarov 2001;Karachentsev et al 2002Karachentsev et al , 2003aEkholm et al 2001;Paturel & Teerikorpi 2005).…”

Section: The Vacuum Cooling Factormentioning

confidence: 51%

“…It is also here where the distances (TRGB, Cepheids) are expected to be less influenced by selection effects that cause systematic errors (Teerikorpi 1997;Paturel & Teerikorpi 2005). Indeed, recent data on the Local group vicinity (1-3 Mpc from the group barycenter) are given by Karachentsev et al (2002Karachentsev et al ( , 2004.…”

Section: Comparison With Observational Datamentioning

confidence: 92%

“…1 that a nonFriedmann counterpart of Friedmann's cosmological model is needed for the Local Universe where the matter distribution is highly non-uniform. In constructing a non-Friedmann theory, we focus first on the nearest and most important distances, 1−5 Mpc, where the observational data are fairly complete and distance determinations are accurate enough (Karachentsev & Makarov 2001;Karachentsev et al 2002Karachentsev et al , 2003aThim et al 2003;Karachentsev et al 2004;Paturel & Teerikorpi 2005;Rekola et al 2005). We start with a simple version of the theory in which the following physical conditions are assumed for the present epoch of cosmic evolution:…”

Section: Local Cosmology: Newtonian Theorymentioning

confidence: 99%

“…This value agrees with the value from the CMBR analysis and is a part of the concordance picture. However, one should not lose sight of the fact that H 0 has not yet been determined directly on large scales with a high accuracy and there are still possible sources of systematic error in the HST value for H 0 (Paturel & Teerikorpi 2005;Sandage et al 2006). …”

Section: The Stochastic Hubble Expansion Ratementioning

confidence: 99%

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Non-Friedmann cosmology for the Local Universe, significance of the universal Hubble constant, and short-distance indicators of dark energy

Chernin

Teerikorpi

Baryshev

2006

A&A

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Based on the increasing evidence of the cosmological relevance of the local Hubble flow, we consider a simple analytical cosmological model for the Local Universe. This is a non-Friedmann model with a non-uniform static space-time. The major dynamical factor controlling the local expansion is the antigravity produced by the omnipresent and permanent dark energy of the cosmic vacuum (or the cosmological constant). The antigravity dominates at larger distances than 1-2 Mpc from the center of the Local group. The model gives a natural explanation of the two key quantitative characteristics of the local expansion flow, which are the local Hubble constant and the velocity dispersion of the flow. The observed kinematical similarity of the local and global flows of expansion is clarified by the model. We analytically demonstrate the efficiency of the vacuum cooling mechanism that allows one to see the Hubble law this close to the Local group. The "universal Hubble constant" H V (≈60 km s −1 Mpc −1 ), depending only on the vacuum density, has special significance locally and globally. The model makes a number of verifiable predictions. It also unexpectedly shows that the dwarf galaxies of the local flow with the shortest distances and lowest redshifts may be the most sensitive indicators of dark energy in our neighborhood.

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Cosmic Distances and Selection Biases

Baryshev

Teerikorpi

2012

Fundamental Questions of Practical Cosmology

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Our ability to travel in space is badly limited. This is much felt in the process of extending distance measurements into deep space. Paul Hodge (1981) once began his review: "The determination of the extragalactic distance scale, like so many problems that occupy astronomers' attention, is essentially an impossible task". In fact, he was quite optimistic, and how else, the life is full of impossible things that nevertheless have been done.Various types of Gregory's standard candles are still the main method to measure extragalactic distances, and also used in cosmological tests. One should be aware of fundamental difficulties accompanying this method. Here we give an overview of problems appearing in distance determination, when the astronomer works, as usually, with samples gathered from the sky (magnitude-limited), instead of samples obtained unrestricted from space. Errors and BiasesAll determinations of a physical quantity, including a cosmic distance, contain some error. In fact, one may speak about (1) random errors, (2) systematic errors, and (3) crude errors. A supposed distance indicator may be simply erroneous, leading to crude errors, an example being Hubble's brightest stars in galaxies, which were actually HII regions. Evolution of standard candles or their classes may cause systematic errors. And even if there were no inherent differences in the objects in different places and epochs, a sample of the observed objects may be much deformed by selection effects, leading to systematic errors in the inferred average distances.Random peculiar velocities change the redshift from its ideal cosmological value, and generally these motions are not known for any individual galaxy. This adds always some error to the redshift distance.Sometimes the method is sensitive to a factor whose effect must be modelled. Thus when using the time delay in gravitational lenses to derive the Hubble constant, one has to use a model for the mass distribution of the lensing galaxy. It also happens that a distance indicator may be made better when one notes the influence of an extra factor. For instance, the peak luminosity of the supernovae SN Ia is correlated with the decay rate of their light curves. Before such effects are known, they may give rise to errors that are not simply random, but systematic and distance-dependent.Naturally, astronomer wants to see some measurable effect indicating the distance. Even if the observations are too inaccurate something is often seen and this is taken as a distance effect-usually leading to an underestimate.An early example is the derivation of the Sun's distance by . He knew that when the Moon appears exactly half full, then the Earth, the Moon and the Sun form a right-angled triangle with 90°at the Moon. He took the Moon-Sun angle to be 87 degrees and proved from the triangle that the ratio of the Sun's and the Moon's distances is between 18 and 20. In fact, the Moon-Sun angle in the half moon triangle is so close to 90 degrees (89.85°) that it was impossible to measure it and Aristarch...

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The extragalactic Cepheid bias: significant influence on the cosmic distance scale

Cited by 14 publications

References 31 publications

Revisiting the optical depth of spiral galaxies using the Tully-Fisher B relation

Revisiting the optical depth of spiral galaxies using the Tully-Fisher B relation

Non-Friedmann cosmology for the Local Universe, significance of the universal Hubble constant, and short-distance indicators of dark energy

Cosmic Distances and Selection Biases

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