The 6dF Galaxy Survey: peculiar velocity field and cosmography

Springob, Christopher M.; Magoulas, Christina; Colless, Matthew; Mould, Jeremy; Erdoğdu, Pirin; Jones, D. Heath; Lucey, John R.; Campbell, Lachlan; Fluke, Christopher J.

Abstract

We derive peculiar velocities for the 6dF Galaxy Survey (6dFGS) and describe the velocity field of the nearby (z < 0.055) Southern hemisphere. The survey comprises 8885 galaxies for which we have previously reported Fundamental Plane data. We obtain peculiar velocity probability distributions for the redshift-space positions of each of these galaxies using a Bayesian approach. Accounting for selection bias, we find that the logarithmic distance uncertainty is 0.11 dex, corresponding to 26 per cent in linear distance. We use adaptive kernel smoothing to map the observed 6dFGS velocity field out to cz ∼ 16 000 km s−1, and compare this to the predicted velocity fields from the PSCz Survey and the 2MASS Redshift Survey. We find a better fit to the PSCz prediction, although the reduced χ2 for the whole sample is approximately unity for both comparisons. This means that, within the observational uncertainties due to redshift-independent distance errors, observed galaxy velocities and those predicted by the linear approximation from the density field agree. However, we find peculiar velocities that are systematically more positive than model predictions in the direction of the Shapley and Vela superclusters, and systematically more negative than model predictions in the direction of the Pisces-Cetus Supercluster, suggesting contributions from volumes not covered by the models.

Citation

Springob, C. M., Magoulas, C., Colless, M., Mould, J., Erdoğdu, P., Jones, D. H., …Fluke, C. J. (2014). The 6dF Galaxy Survey: peculiar velocity field and cosmography. Monthly Notices of the Royal Astronomical Society, 445(3), 2677-2697. https://doi.org/10.1093/mnras/stu1743

• Journal Article Type: Article
• Acceptance Date: Aug 26, 2014
• Publication Date: Dec 11, 2014
• Deposit Date: Dec 22, 2015
• Publicly Available Date: Jan 25, 2016
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 445
• Issue: 3
• Pages: 2677-2697
• DOI: https://doi.org/10.1093/mnras/stu1743
• Keywords: Surveys, Galaxies: elliptical and lenticular, cD, Galaxies: fundamental parameters, Cosmology: distance scale, Cosmology: large-scale structure of Universe.
• Public URL: https://durham-repository.worktribe.com/output/1416332
• Related Public URLs: http://arxiv.org/abs/1409.6161