### Abstract

We use numerical simulations to study the relation between the velocity of the Local Group (LG) and its gravitational acceleration. This relation serves as a test for the kinematic origin of the CMB dipole and as a method for estimating ß= Ω^{0.6}/b. We calculate the misalignment angle between the two vectors and compare it to the observed value for the PSCz survey. The latter value is beyond the upper limit of the 90% confidence interval for the angle; therefore, the nonlinear effects are unlikely to be responsible for the whole observed misalignment. We also study the relation between the amplitudes of the LG velocity and gravity vectors. In an Ω = 1 Universe, the smoothed gravity of the LG turns out to be a biased low estimator of the LG (unsmoothed) velocity. In an Ω = 0.3 Universe, the estimator is biased high. The discussed biases are, however, only a few per cent, thus the linear theory works to good accuracy. The gravity-based estimator of the LG velocity has also a scatter that limits the precision of the estimate of β in the LG velocity-gravity comparisons. The random error of β due to nonlinear effects amounts to several per cent.

Original language | English (US) |
---|---|

Pages (from-to) | 103-115 |

Number of pages | 13 |

Journal | Acta Astronomica |

Volume | 51 |

Issue number | 2 |

State | Published - 2001 |

Externally published | Yes |

### Fingerprint

### Keywords

- Cosmology: theory
- Dark matter
- Large scale
- Methods: numerical
- Structure of Universe

### ASJC Scopus subject areas

- Space and Planetary Science
- Astronomy and Astrophysics

### Cite this

*Acta Astronomica*,

*51*(2), 103-115.

**Local group velocity versus gravity : Nonlinear effects.** / Cieciela̧g, Pawel; Chodorowski, Michał; Kudlicki, Andrzej.

Research output: Contribution to journal › Article

*Acta Astronomica*, vol. 51, no. 2, pp. 103-115.

}

TY - JOUR

T1 - Local group velocity versus gravity

T2 - Nonlinear effects

AU - Cieciela̧g, Pawel

AU - Chodorowski, Michał

AU - Kudlicki, Andrzej

PY - 2001

Y1 - 2001

N2 - We use numerical simulations to study the relation between the velocity of the Local Group (LG) and its gravitational acceleration. This relation serves as a test for the kinematic origin of the CMB dipole and as a method for estimating ß= Ω0.6/b. We calculate the misalignment angle between the two vectors and compare it to the observed value for the PSCz survey. The latter value is beyond the upper limit of the 90% confidence interval for the angle; therefore, the nonlinear effects are unlikely to be responsible for the whole observed misalignment. We also study the relation between the amplitudes of the LG velocity and gravity vectors. In an Ω = 1 Universe, the smoothed gravity of the LG turns out to be a biased low estimator of the LG (unsmoothed) velocity. In an Ω = 0.3 Universe, the estimator is biased high. The discussed biases are, however, only a few per cent, thus the linear theory works to good accuracy. The gravity-based estimator of the LG velocity has also a scatter that limits the precision of the estimate of β in the LG velocity-gravity comparisons. The random error of β due to nonlinear effects amounts to several per cent.

AB - We use numerical simulations to study the relation between the velocity of the Local Group (LG) and its gravitational acceleration. This relation serves as a test for the kinematic origin of the CMB dipole and as a method for estimating ß= Ω0.6/b. We calculate the misalignment angle between the two vectors and compare it to the observed value for the PSCz survey. The latter value is beyond the upper limit of the 90% confidence interval for the angle; therefore, the nonlinear effects are unlikely to be responsible for the whole observed misalignment. We also study the relation between the amplitudes of the LG velocity and gravity vectors. In an Ω = 1 Universe, the smoothed gravity of the LG turns out to be a biased low estimator of the LG (unsmoothed) velocity. In an Ω = 0.3 Universe, the estimator is biased high. The discussed biases are, however, only a few per cent, thus the linear theory works to good accuracy. The gravity-based estimator of the LG velocity has also a scatter that limits the precision of the estimate of β in the LG velocity-gravity comparisons. The random error of β due to nonlinear effects amounts to several per cent.

KW - Cosmology: theory

KW - Dark matter

KW - Large scale

KW - Methods: numerical

KW - Structure of Universe

UR - http://www.scopus.com/inward/record.url?scp=0346673794&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0346673794&partnerID=8YFLogxK

M3 - Article

VL - 51

SP - 103

EP - 115

JO - Acta Astronomica

JF - Acta Astronomica

SN - 0001-5237

IS - 2

ER -