The Angular Size-Redshift Test for Compact Radio Sources in the Caltech-Jodrell Bank Surveys

Wilkinson, P. N.; Browne, I. W. A.; Alcock, D.; Myles, S.D.; Henstock, D. R.; Readhead, A. C. S.; Pearson, T. J.; Xu, W.; Taylor, G. B.; Polatidis, A. G.; Vermeulen, R. C.

doi:10.1007/978-94-011-5238-9_38

“…Miley 1971;Kapahi 1975;and recently several authors Kellermann 1993;Wilkinson et al 1998, have reported a redshift dependence of radio source angular sizes at 0.5 < z < 3, which is not easily reconciled with other recent measurements of the cosmological parameters (but see Daly & Djorgovski 2004, for results more consistent with the concordance model. )…”

Section: The Standard Rodmentioning

confidence: 88%

Geometrical tests of cosmological models

Marinoni¹,

Saintonge

²

,

Giovanelli

³

et al. 2007

A&A

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We suggest to use the observationally measured and theoretically justified correlation between size and rotational velocity of galactic discs as a viable method to select a set of high redshift standard rods which may be used to explore the dark energy content of the universe via the classical angular-diameter test. Here we explore a new strategy for an optimal implementation of this test. We propose to use the rotation speed of high redshift galaxies as a standard size indicator and show how high resolution multi-object spectroscopy and ACS/HST high quality spatial images, may be combined to measure the amplitude of the dark energy density parameter Ω Q , or to constrain the cosmic equation of state parameter for a smooth dark energy component (w = p/ρ, −1 ≤ w < −1/3). Nearly 1300 standard rods with high velocity rotation in the bin V = 200 ± 20 km s −1 are expected in a field of 1 sq. degree and over the redshift baseline 0 < z < 1.4. This sample is sufficient to constrain the cosmic equation of state parameter w at a level of 20% (without priors in the [Ω m , Ω Q ] plane) even when the [OII]λ3727 Å linewidth-diameter relationship is calibrated with a scatter of ∼40%. We evaluate how systematics may affect the proposed tests, and find that a linear standard rod evolution, causing galaxy dimensions to be up to 30% smaller at z = 1.5, can be uniquely diagnosed, and will minimally bias the confidence level contours in the [Ω Q , w] plane. Finally, we show how to derive, without a priori knowing the specific functional form of disc evolution, a cosmologyevolution diagram with which it is possible to establish a mapping between different cosmological models and the amount of galaxy disc/luminosity evolution expected at a given redshift.

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“…In recent years many studies have been published on θ − z relation of milliarcsecond structures in AGN cores (Kellermann 1993;Gurvits 1994;Stelmach 1994;Stepanas & Saha 1995;Wilkinson et al 1997;Gurvits et al 1999). While the angular size of the compact radio sources seemed to show the expected turnover, there has been criticism of possible biases in these samples.…”

Section: Traditional Methodsmentioning

confidence: 99%

“…In these studies the standard rod has been defined as the jet length from peak flux down to 2% (Kellermann 1993) or 1% (Wilkinson et al 1997) contour or as a size estimate from a single component modelfit to uv-data (Gurvits 1994). The fact that the jet length, observed using these methods, can change rapidly due to moving shocks in the jet does not necessarily cause a bias, only random errors if it is assumed that on average all sources produce similar moving shocks.…”

Section: Traditional Methodsmentioning

confidence: 99%

The geometry of the universe from high resolution VLBI data of AGN shocks

Wiik

¹

,

Valtaoja

²

2001

A&A

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Abstract. We propose to use the linear diameters of the shocks in AGN jets as standard rods for estimating the geometry of the Universe. The unique feature of shocks is that we can directly estimate their linear diameters from total flux density monitoring data and light travel time arguments. We demonstrate this method by using a small sample of 14 22 GHz VLBI observations. The accuracy of the derived values (q0 0, Ωm 0) compares favorably with traditional methods using much larger samples.

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Testing Cosmological Models Using the Kinematics of High Redshift Galaxies

Marinoni¹,

Fèvre²

2004

3K, SN’s, Clusters: Hunting the Cosmological Parameters With Precision Cosmology

0

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We suggest to use the observationally measured and theoretically justified correlation between size and rotational velocity of galactic discs as a viable method to select a set of high redshift standard rods which may be used to explore the dark energy content of the universe via the classical angular-diameter test. Here we explore a new strategy for an optimal implementation of this test. We propose to use the rotation speed of high redshift galaxies as a standard size indicator and show how high resolution multi-object spectroscopy and ACS/HST high quality spatial images, may be combined to measure the amplitude of the dark energy density parameter Ω Q , or to constrain the cosmic equation of state parameter for a smooth dark energy componentNearly 1300 standard rods with high velocity rotation in the bin V = 200 ± 20km/s are expected in a field of 1 sq. degree and over the redshift baseline 0 < z < 1.4. This sample is sufficient to constrain the cosmic equation of state parameter w at a level of 20% (without priors in the [Ω m , Ω Q ] plane) even when the [OII]λ3727Å linewidth-diameter relationship is calibrated with a scatter of ∼ 40%. We evaluate how systematics may affect the proposed tests, and find that a linear standard rod evolution, causing galaxy dimensions to be up to 30% smaller at z = 1.5, can be uniquely diagnosed, and will minimally bias the confidence level contours in the [Ω Q , w] plane. Finally, we show how to derive, without a priori knowing the specific functional form of disc evolution, a cosmology-evolution diagram with which it is possible to establish a mapping between different cosmological models and the amount of galaxy disc/luminosity evolution expected at a given redshift. affiliated to FRUMAM (FR 2291). dark energy (Ω Λ = 0.761 +0.017 −0.018 ), with large negative pressure (w = −0.941 +0.017 −0.018 ), and with a very low baryon content (Ω b = 0.0416 +0.0019 −0.0018 ). Mounting and compelling evidence for accelerated expansion of the universe, driven by a dark energy component, presently relies on our comprehension of the mechanisms with which Supernovae Ia (SNIa) emit radiation (see Perlmutter et al. (1999); Riess et al. (2001)) and of the physical processes that produced temperature fluctuations in the primeval plasma (see Lee et al. (2001);de Bernardis et al. (2002); Halverson et al. (2002);Spergel et al. (2006).) Even if the ambitious task of determining geometry and evolution of the universe as a whole, which commenced in the 1930s, now-day shows that the relativistic Friedman-Lemaître model passes impressively demanding checks, we are faced with the challenge of developing and adding new lines of evidence supporting (or falsifying) the concordance model. Moreover, even if we parameterize our ignorance about dark

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The Angular Size-Redshift Test for Compact Radio Sources in the Caltech-Jodrell Bank Surveys

Cited by 6 publications

References 11 publications

Geometrical tests of cosmological models

Geometrical tests of cosmological models

The geometry of the universe from high resolution VLBI data of AGN shocks

Testing Cosmological Models Using the Kinematics of High Redshift Galaxies

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