J/MNRAS/445/2677 Peculiar velocities in 6dFGS (Springob+, 2014) ================================================================================ The 6dF Galaxy Survey: peculiar velocity field and cosmography. Springob C.M., Magoulas C., Colless M., Mould J., Erdogdu P., Jones D.H., Lucey J.R., Campbell L., Fluke C.J. =2014MNRAS.445.2677S ================================================================================ ADC_Keywords: Surveys ; Galaxies, nearby ; Redshifts Keywords: surveys - galaxies: elliptical and lenticular, cD - galaxies: fundamental parameters - cosmology: distance scale - cosmology: large-scale structure of Universe 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~16000km/s, 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 {chi}^2^ 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. Description: The details of the sample selection and data reduction are presented in Magoulas et al. (2012MNRAS.427..245M) and Campbell et al. (2014MNRAS.443.1231C, Cat. J/MNRAS/443/1231). In brief, the 6dFGSv includes all 6dFGS early-type galaxies with spectral signal-to-noise ratios greater than 5, heliocentric redshift z_helio_<0.055, velocity dispersion greater than 112km/s, and J-band total magnitude brighter than m_J_=13.65. The galaxies were identified as 'early-type' by matching the observed spectrum, via cross-correlation, to template galaxy spectra. They include both ellipticals and spiral bulges (in cases where the bulge fills the 6dF fibre). Each galaxy image was subsequently examined by eye, and galaxies were removed from the sample in cases where the morphology was peculiar, the galaxy had an obvious dust lane, or the fibre aperture was contaminated by the galaxy's disc (if present), or by a star or another galaxy. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 74 8885 6dFGSv logarithmic distance ratios, and associated parameters -------------------------------------------------------------------------------- See also: J/MNRAS/443/1231 : 6dF Galaxy Survey: Fundamental Plane data (Campbell+, 2014) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 15 A15 --- 6dFGS Source name in 6dFGS catalog (gHHMMSSs+DDMMSS) 17- 25 F9.5 deg RAdeg Right ascension (J2000) 27- 34 F8.4 deg DEdeg Declination (J2000) 36- 40 I5 km/s czgal [762/16689] CMB frame galaxy redshift 42- 46 I5 km/s czgr [1523/16082]?=-1 CMB frame group redshift (1) 48- 51 I4 --- grID [11/1672]?=-1 Group ID (1) 53- 59 F7.4 [-] log(Dz/DH) [-0.6/0.4] logarithmic distance ratio log(D_z_/D_H_) (2) 61- 66 F6.4 [-] e_log(Dz/DH) [0.09/0.22] Error on log(Dz/DH) 68- 74 F7.4 --- alpha [-0.07/0.11] Skew {alpha} in the log(Dz/DH) probability distribution -------------------------------------------------------------------------------- Note (1): Galaxies not in groups are signified by "-1". Note (2): logarithm of the ratio of the comoving distance associated with galaxy's redshift to the true comoving distance of the galaxy. -------------------------------------------------------------------------------- History: * 20-May-2015: from electronic version of the journal * 28-Oct-2015: removed the duplicated last row of the table (thanks H.A. Andernach) ================================================================================ (End) Patricia Vannier [CDS] 20-May-2015