Cosmology with peculiar velocities: observational effects

Andersen, P., Davis, T. M. and Howlett, C. (2016) Cosmology with peculiar velocities: observational effects. Monthly Notices of the Royal Astronomical Society, 463 4: 4083-4092. doi:10.1093/mnras/stw2252

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Author Andersen, P.
Davis, T. M.
Howlett, C.
Title Cosmology with peculiar velocities: observational effects
Journal name Monthly Notices of the Royal Astronomical Society   Check publisher's open access policy
ISSN 0035-8711
Publication date 2016-12-01
Sub-type Article (original research)
DOI 10.1093/mnras/stw2252
Open Access Status File (Publisher version)
Volume 463
Issue 4
Start page 4083
End page 4092
Total pages 10
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Language eng
Formatted abstract
In this paper we investigate how observational effects could possibly bias cosmological inferences from peculiar velocity measurements. Specifically, we look at how bulk flow measurements are compared with theoretical predictions. Usually bulk flow calculations try to approximate the flow that would occur in a sphere around the observer. Using the Horizon Run 2 simulation we show that the traditional methods for bulk flow estimation can overestimate the magnitude of the bulk flow for two reasons: when the survey geometry is not spherical (the data do not cover the whole sky), and when the observations undersample the velocity distributions. Our results may explain why several bulk flow measurements found bulk flow velocities that seem larger than those expected in standard Λ cold dark matter cosmologies. We recommend a different approach when comparing bulk flows to cosmological models, in which the theoretical prediction for each bulk flow measurement is calculated specifically for the geometry and sampling rate of that survey. This means that bulk flow values will not be comparable between surveys, but instead they are comparable with cosmological models, which is the more important measure.
Keyword Cosmology: observations
Cosmology: theory
Dark energy
Large-scale structure of Universe
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
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