Local group velocity versus gravity: Nonlinear effects

Pawel Cieciela̧g, Michał Chodorowski, Andrzej Kudlicki

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)103-115
Number of pages13
JournalActa Astronomica
Issue number2
StatePublished - 2001
Externally publishedYes


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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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