The 6dF Galaxy Survey: peculiar velocity field and cosmography
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 redshiftspace 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 χ^{2} for the whole sample is approximately unity for both comparisons. This means that, within the observational uncertainties due to redshiftindependent 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 PiscesCetus Supercluster, suggesting contributions from volumes not covered by the models.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 December 2014
 DOI:
 10.1093/mnras/stu1743
 arXiv:
 arXiv:1409.6161
 Bibcode:
 2014MNRAS.445.2677S
 Keywords:

 surveys;
 galaxies: elliptical and lenticular;
 cD;
 galaxies: fundamental parameters;
 cosmology: distance scale;
 cosmology: largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 22 pages, 14 figures, accepted for publication in MNRAS. Table 1 is available in its entirety as an ancillary file. Fully interactive 3D versions of Figures 11 and 12 are also available as ancillary files. A version of this paper with the 3D versions of Figs. 11 and 12 embedded within the pdf can also be accessed from http://www.6dfgs.net/vfield/veldata.pdf