The 6dF Galaxy Survey: peculiar velocity field and cosmography

Abstract

Citation for published item:pringoD ghristopher wF nd wgoulsD ghristin nd gollessD wtthew nd wouldD teremy nd irdogduD irin nd tonesD hF reth nd vueyD tohn F nd gmpellD vhln nd plukeD ghristopher tF @PHIRA 9he Tdp qlxy urvey X peulir veloity (eld nd osmogrphyF9D wonthly noties of the oyl estronomil oietyFD RRS @QAF ppF PTUUEPTWUF Further information on publisher's website: Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTWe 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 χ 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.

Cosmicflows-3: Cold Spot Repeller?

“…The rough location is glon=168 • , glat=−71 • , velocity=23,000 km s −1 . It is in the general region of the negative velocity anomaly in Pisces-Cetus noted by Springob et al (2014). We particularly note that it is in the direction of a feature projected against the so-called CMB Cold Spot (Szapudi et al 2015).…”

Cosmological forecasts for combined and next-generation peculiar velocity surveys

“…In our study we choose a suitable value for the zero-point offset as follows. By fitting the 6dFGSv data within a "great circle" between −20 Springob et al (2014) find a statistical error on the zero-point offset of σm = 0.015 dex. This encompasses the effect of a dipole in the velocity field.…”

“…The velocity subsample consists of galaxies with z 0.05, with peculiar velocities derived using the Fundamental plane relation, calibrated in Magoulas et al (2012). The full Fundamental plane catalogue is presented in Campbell et al (2014) and subsequent measurements of the logarithmic distance ratios for the galaxies are given in Springob et al (2014).…”

Searching for modified gravity: scale and redshift dependent constraints from galaxy peculiar velocities

“…For further details on this calculation we refer the reader to Johnson et al (2014). We perform a full likelihood calculation using the 6dFGSv peculiar velocity sample (Springob et al 2014). To calculate the covariance matrix in Eq.…”