On the vorticity of flow in redshift space

Chodorowski, Michal; Nusser, Adi

doi:10.1046/j.1365-8711.1999.03084.x

Cited by 6 publications

(5 citation statements)

References 26 publications

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“… s = cz / H 0 ) and v ( s ). To the first order, the peculiar velocity is irrotational in redshift space (Chodorowski & Nusser 1999) and can be expressed as v g ( s ) =−∇ϕ( s ) where ϕ( s ) is a potential function. As an estimate of the fluctuations in the fractional density field δ 0 ( s ) traced by the discrete distribution of galaxies in redshift space we consider where and w weighs each galaxy according to its estimated luminosity, L 0 i .…”

Section: Reconstruction Of Peculiar Velocitiesmentioning

confidence: 99%

See 1 more Smart Citation

Local gravity versus local velocity: solutions for β and non-linear bias

Davis¹,

Nusser²,

Masters³

et al. 2011

Monthly Notices of the Royal Astronomical Society

162

143

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We perform a reconstruction of the cosmological large‐scale flows in the nearby Universe using two complementary observational sets. The first, the SFI++ sample of Tully–Fisher (TF) measurements of galaxies, provides a direct probe of the flows. The second, the whole sky distribution of galaxies in the 2MASS (Two Micron All Sky Survey) redshift survey (2MRS), yields a prediction of the flows given the cosmological density parameter, Ω, and a biasing relation between mass and galaxies. We aim at an unbiased comparison between the peculiar velocity fields extracted from the two data sets and its implication on the cosmological parameters and the biasing relation. We expand the fields in a set of orthonormal basis functions, each representing a plausible realization of a cosmological velocity field smoothed in such a way as to give a nearly constant error on the derived SFI++ velocities. The statistical analysis is done on the coefficients of the modal expansion of the fields by means of the basis functions. Our analysis completely avoids the strong error covariance in the smoothed TF velocities by the use of orthonormal basis functions and employs elaborate mock data sets to extensively calibrate the errors in 2MRS predicted velocities. We relate the 2MRS galaxy distribution to the mass density field by a linear bias factor, b, and include a luminosity‐dependent, ∝Lα, galaxy weighting. We assess the agreement between the fields as a function of α and β=f(Ω)/b, where f is the growth factor of linear perturbations. The agreement is excellent with a reasonable χ2 per degree of freedom. For α= 0, we derive 0.28 < β < 0.37 and 0.24 < β < 0.43, respectively, at the 68.3 per cent and 95.4 per cent confidence levels (CLs). For β= 0.33, we get α < 0.25 and α < 0.5, respectively, at the 68.3 per cent and 95.4 per cent CLs. We set a constraint on the fluctuation normalization, finding σ8= 0.66 ± 0.10, which is only 1.5σ deviant from Wilkinson Microwave Anisotropy Probe (WMAP) results. It is remarkable that σ8 determined from this local cosmological test is close to the value derived from the cosmic microwave background, an indication of the precision of the standard model.

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Section: Reconstruction Of Peculiar Velocitiesmentioning

confidence: 99%

“…s = cz/H0) and v v v(s s s). To first order, the peculiar velocity is irrotational in redshift space (Chodorowski & Nusser 1999) and can be expressed as…”

Section: Peculiar Velocities From the Distribution Of Galaxies In Red...mentioning

confidence: 99%

Local gravity versus local velocity: solutions for β and non-linear bias

Davis¹,

Nusser²,

Masters³

et al. 2011

Monthly Notices of the Royal Astronomical Society

162

143

View full text Add to dashboard Cite

show abstract

“…s = cz/H 0 ) and v v v(s s s). To first order, the peculiar velocity is irrotational in redshift space (Chodorowski & Nusser 1999) and can be expressed…”

Section: Methodsmentioning

confidence: 99%

“…s = cz/H 0 ) and v v v(s s s). To first order, the peculiar velocity is irrotational in redshift space (Chodorowski & Nusser 1999) and can be expressed as v v v g (s s s) = −∇ ∇ ∇Φ(s s s) where Φ(s s s) is a potential function. As an estimate of the fluctuations in the fractional density field δ 0 (s s s) traced by the discrete distribution of galaxies in redshift space we consider,…”

Section: Methodsmentioning

confidence: 99%

Re-examination of Large Scale Structure & Cosmic Flows

Davis¹,

Nusser²

2014

Proc. IAU

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Comparison of galaxy flows with those predicted from the local galaxy distribution ended as an active field after two analyses came to vastly different conclusions 25 years ago, but that was due to faulty data. All the old results are therefore suspect. With new data collected in the last several years, the problem deserves another look. For this we analyze the gravity field inferred from the enormous data set derived from the 2MASS collection of galaxies (Huchra et al. 2005), and compare it to the velocity field derived from the well calibrated SFI++ Tully-Fisher catalog (Springob et al. 2007). Using the "Inverse Method" to minimize Malmquist biases, within 10,000 km/s the gravity field is seen to predict the velocity field (Davis et al. 2011) to remarkable consistency. This is a beautiful demonstration of linear perturbation theory and is fully consistent with standard values of the cosmological variables.

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“…To linear order, velocity fields expressed in real and redshift spaces are equivalent. In the quasilinear regime, dynamical relations can be derived for the velocity field in redshift space (Nusser & Davis 1994), thanks to the interesting property that an irrotational (or potential) flow in real space remain irrotational also in redshift space (Chodorowski & Nusser 1999).…”

Section: Methodsmentioning

confidence: 99%

GAIA: A WINDOW TO LARGE-SCALE MOTIONS

Nusser¹,

Branchini

Davis

2012

ApJ

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Using redshifts as a proxy for galaxy distances, estimates of the 2D transverse peculiar velocities of distant galaxies could be obtained from future measurements of proper motions. We provide the mathematical framework for analyzing 2D transverse motions and show that they offer several advantages over traditional probes of large scale motions. They are completely independent of any intrinsic relations between galaxy properties, hence they are essentially free of selection biases. They are free from homogeneous and inhomogeneous Malmquist biases that typically plague distance indicator catalogs. They provide additional information to traditional probes which yield line-of-sight peculiar velocities only. Further, because of their 2D nature, fundamental questions regarding vorticity of large scale flows can be addressed. Gaia for example is expected to provide proper motions of at least bright galaxies with high central surface brightness, making proper motions a likely contender traditional probes based on current and future distance indicator measurements.Subject headings: Cosmology: large scale structure of the Universe, dark matter

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On the vorticity of flow in redshift space

Cited by 6 publications

References 26 publications

Local gravity versus local velocity: solutions for β and non-linear bias

Local gravity versus local velocity: solutions for β and non-linear bias

Re-examination of Large Scale Structure & Cosmic Flows

GAIA: A WINDOW TO LARGE-SCALE MOTIONS

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