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.
<Mon. Not. R. Astron. Soc., 445, 2677-2697 (2014)>
=2014MNRAS.445.2677S 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 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.
Description:
The details of the sample selection and data reduction are presented
in Magoulas et al. (2012MNRAS.427..245M 2012MNRAS.427..245M) and Campbell et al.
(2014MNRAS.443.1231C 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
zhelio<0.055, velocity dispersion greater than 112km/s, and
J-band total magnitude brighter than mJ=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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 74 8885 6dFGSv logarithmic distance ratios, and associated
parameters
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See also:
J/MNRAS/443/1231 : 6dF Galaxy Survey: Fundamental Plane data (Campbell+, 2014)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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(Dz/DH) (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 α in the log(Dz/DH)
probability distribution
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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.
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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