Yet another sample of RFGC galaxies

Parnovsky, S. L.; Parnowski, A. S.

doi:10.1007/s10509-012-1267-3

Cited by 7 publications

(8 citation statements)

References 38 publications

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“…It is the reason for the appearance of non-Hubble flows of galaxies. When processing real data, we take these collective non-Hubble motions into account either by using their multipole expansion [15], or by directly simulating the influence of attractors and voids. In Section 7.3, I consider the influence of a collective motion in the bulk motion approximation.…”

Section: The Simplest Model Of Motion Of Galaxies and Errors In Distance And Velocities Measurementsmentioning

confidence: 99%

“…I used the values 𝑎 = 0.2 and 𝛿𝑉 = 1000 km • s −1 as a main choice. For details on how these parameters were obtained, see [15]. The values of the coefficient 𝑘 and its root-mean-square error Δ𝑘 are determined using the LSM formulae for each of these mock samples.…”

Section: Demonstration Of the Effect With The Use Of Monte Carlo Simulations Data And Routinementioning

confidence: 99%

“…The radial component of the velocity depends both on the distance to the galaxy and on the direction toward it. The form of this dependence can be quite complex and includes many terms, whose values and statistical significances are determined when processing the observational data as it is done in papers [15,16]. By the way, the influence of errors in determining the distance by the parameters of the velocity field of collective motion was investigated in [14].…”

Section: An Impact Of the Large-scale Collective Motion Of Galaxiesmentioning

confidence: 99%

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Bias of the Hubble Constant Value Caused by Errors in Galactic Distance Indicators

Parnovsky

2021

Ukr. J. Phys.

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The bias in the determination of the Hubble parameter and the Hubble constant in the modern Universe is discussed. It could appear due to the statistical processing of data on the redshifts of galaxies and the estimated distances based on some statistical relations with limited accuracy. This causes a number of effects leading to either underestimation or overestimation of the Hubble parameter when using any methods of statistical processing, primarily the least squares method (LSM). The value of the Hubble constant is underestimated when processing a whole sample; when the sample is constrained by distance, especially when constrained from above. Moreover, it is significantly overestimated due to the data selection. The bias significantly exceeds the values of the erro ofr the Hubble constant calculated by the LSM formulae. These effects are demonstrated both analytically and using Monte Carlo simulations, which introduce deviations in the velocities and estimated distances to the original dataset described by the Hubble law. The characteristics of the deviations are similar to real observations. Errors in the estimated distances are up to 20%. They lead to the fact that, when processing the same mock sample using LSM, it is possible to obtain an estimate of the Hubble constant from 96% of the true value when processing the entire sample to 110% when processing the subsample with distances limited from above. The impact of these effects can lead to a bias in the Hubble constant obtained from real data and an overestimation of the accuracy of determining this value. This may call into question the accuracy of determining the Hubble constant and can significantly reduce the tension between the values obtained from the observations in the early and modern Universes, which were actively discussed during the last year.

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Section: The Simplest Model Of Motion Of Galaxies and Errors In Distance And Velocities Measurementsmentioning

confidence: 99%

Section: Demonstration Of the Effect With The Use Of Monte Carlo Simulations Data And Routinementioning

confidence: 99%

Section: An Impact Of the Large-scale Collective Motion Of Galaxiesmentioning

confidence: 99%

See 1 more Smart Citation

Bias of the Hubble Constant Value Caused by Errors in Galactic Distance Indicators

Parnovsky

2021

Ukr. J. Phys.

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show abstract

“…It is the reason for the appearance of non-Hubble flows of galaxies. When processing real data, we take into account these collective non-Hubble motions either by using their multipole expansion [15], or by directly simulating the influence of attractors and voids. In Section 7 7.3 I consider the influence of collective motion in the bulk motion approximation.…”

Section: The Simplest Model Of Motion Of Galaxies and Errors In Dista...mentioning

confidence: 99%

“…I used the values a = 0.2 and δV = 1000 km s −1 as a main choise. For details on how these parameters were obtained, see [15]. The values of the coefficient k and its root-mean-square error ∆k are determined using the LSM formulae for each of these mock samples.…”

Section: Demonstration Of the Effect Using Monte Carlo Simulations Da...mentioning

confidence: 99%

Bias of the Hubble constant value caused by errors in galactic distance indicators

Parnovsky¹

2021

Preprint

Self Cite

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The bias in the determination of the Hubble parameter and the Hubble constant in the modern Universe is discussed. It could appear due to statistical processing of data on galaxies redshifts and estimated distances based on some statistical relations with limited accuracy. This causes a number of effects leading to either underestimation or overestimation of the Hubble parameter when using any methods of statistical processing, primarily the least squares method (LSM). The value of the Hubble constant is underestimated when processing a whole sample; when the sample is constrained by distance, especially when constrained from above, it is significantly overestimated due to data selection. The bias significantly exceeds the values of the error the Hubble constant calculated by the LSM formulae. These effects are demonstrated both analytically and using Monte Carlo simulations, which introduce deviations in both velocities and estimated distances to the original dataset described by the Hubble law. The characteristics of the deviations are similar to real observations. Errors in estimated distances are up to 20%. They lead to the fact that when processing the same mock sample using LSM, it is possible to obtain an estimate of the Hubble constant from 96% of the true value when processing the entire sample to 110% when processing the subsample with distances limited from above. The impact of these effects can lead to a bias in the Hubble constant obtained from real data and an overestimation of the accuracy of determining this value. This may call into question the accuracy of determining the Hubble constant and significantly reduce the tension between the values obtained from the observations in the early and modern Universe, which were actively discussed during the last year.

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The quadrupole in the local Hubble parameter: first constraints using Type Ia supernova data and forecasts for future surveys

Dhawan

Borderies

MacPherson

et al. 2022

Monthly Notices of the Royal Astronomical Society

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The cosmological principle asserts that the Universe looks spatially homogeneous and isotropic on sufficiently large scales. Given its fundamental implications, it is important to empirically test its validity. In this paper, we use the Type Ia supernova (SN Ia) magnitude-redshift relation, from both the Pantheon and JLA compilations, to constrain theoretically motivated anisotropies in the Hubble flow. In particular, we constrain the quadrupole in the effective Hubble parameter and the dipole in the effective deceleration parameter. We find no significant quadrupole term regardless of the redshift frame used. Our results are consistent with the theoretical expectation of a quadrupole moment of a few percent at scales of ∼100 h−1 Mpc. We place an upper limit of a $\sim 10{{\%}}$ quadrupole amplitude relative to the monopole, H0, at these scales. We find that we can detect a $\sim 7{{\%}}$ quadrupole at the 5σ level, for a forecast low-z sample of 1055 SNe Ia. We find the signficance of an exponentially decaying dipole of the deceleration parameter depends on the redshift frame used. In the heliocentric frame, as expected, it is detected at ∼3σ significance. In the cosmic microwave background (CMB) rest-frame, we find a marginal ∼2σ dipole, however, after applying peculiar velocity corrections, the dipole is insignificant. Finally, we find the best-fit frame of rest relative to the supernovae to differ from that of the CMB at ∼2σ for both compilations, which reduces to <1σ when including peculiar velocity covariance.

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Yet another sample of RFGC galaxies

Cited by 7 publications

References 38 publications

Bias of the Hubble Constant Value Caused by Errors in Galactic Distance Indicators

Bias of the Hubble Constant Value Caused by Errors in Galactic Distance Indicators

Bias of the Hubble constant value caused by errors in galactic distance indicators

The quadrupole in the local Hubble parameter: first constraints using Type Ia supernova data and forecasts for future surveys

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