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The 6dF Galaxy Survey: Final Redshift Release (DR3) and Southern Large-Scale Structures

D. Heath Jones, Mike A. Read, Will Saunders, Matthew Colless, Tom Jarrett, Quentin Parker, Anthony Fairall, Thomas Mauch, Elaine Sadler, Fred Watson, Donna Burton, Lachlan Campbell, Paul Cass, Scott Croom, John Dawe, Kristin Fiegert, Leela Frankcombe, Malcolm Hartley, John Huchra, Dionne James, Emma Kirby, Ofer Lahav, John Lucey, Gary Mamon, Lesa Moore, Bruce Peterson, Sayuri Prior, Dominique Proust, Ken Russell, Vicky Safouris, Ken-ichi Wakamatsu, Eduard Westra, Mary Williams

TL;DR

This paper presents the final redshift release of the 6dF Galaxy Survey (DR3) and its implications for mapping the southern local universe. It characterizes a comprehensive, near-infrared–selected redshift and peculiar velocity dataset over most of the southern sky, with 125,071 extragalactic redshifts and 136,304 spectra, of which 110,256 are new measurements, hosted in a richly cross-referenced online database. The study delivers detailed redshift distributions, robust quality and uncertainty analyses, and extensive maps of large-scale structure out to z ≈ 0.1, including major features such as Shapley and Hydra-Centaurus, while rigorously addressing data revisions, cross-talk, and other systematic considerations. The results provide a lasting southern-hemisphere benchmark for deriving luminosity and stellar-mass functions, calibrating peculiar velocity work for the brightest galaxies, and enabling future multi-wavelength studies and cosmological analyses with minimized systematics. The DR3 release thus establishes a high-fidelity, publicly accessible legacy dataset for the local universe spanning unprecedented southern coverage and depth.

Abstract

We report the final redshift release of the 6dF Galaxy Survey, a combined redshift and peculiar velocity survey over the southern sky (|b|>10 deg). Its 136,304 spectra have yielded 110,256 new extragalactic redshifts and a new catalogue of 125,071 galaxies making near-complete samples with (K, H, J, r_F, b_J) <= (12.65, 12.95, 13.75, 15.60, 16.75). The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online database. We describe changes to the information in the database since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10% of the sample. Here we provide redshift maps of the southern local universe with z<=0.1, showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS database is http://www-wfau.roe.ac.uk/6dFGS

The 6dF Galaxy Survey: Final Redshift Release (DR3) and Southern Large-Scale Structures

TL;DR

This paper presents the final redshift release of the 6dF Galaxy Survey (DR3) and its implications for mapping the southern local universe. It characterizes a comprehensive, near-infrared–selected redshift and peculiar velocity dataset over most of the southern sky, with 125,071 extragalactic redshifts and 136,304 spectra, of which 110,256 are new measurements, hosted in a richly cross-referenced online database. The study delivers detailed redshift distributions, robust quality and uncertainty analyses, and extensive maps of large-scale structure out to z ≈ 0.1, including major features such as Shapley and Hydra-Centaurus, while rigorously addressing data revisions, cross-talk, and other systematic considerations. The results provide a lasting southern-hemisphere benchmark for deriving luminosity and stellar-mass functions, calibrating peculiar velocity work for the brightest galaxies, and enabling future multi-wavelength studies and cosmological analyses with minimized systematics. The DR3 release thus establishes a high-fidelity, publicly accessible legacy dataset for the local universe spanning unprecedented southern coverage and depth.

Abstract

We report the final redshift release of the 6dF Galaxy Survey, a combined redshift and peculiar velocity survey over the southern sky (|b|>10 deg). Its 136,304 spectra have yielded 110,256 new extragalactic redshifts and a new catalogue of 125,071 galaxies making near-complete samples with (K, H, J, r_F, b_J) <= (12.65, 12.95, 13.75, 15.60, 16.75). The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online database. We describe changes to the information in the database since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10% of the sample. Here we provide redshift maps of the southern local universe with z<=0.1, showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS database is http://www-wfau.roe.ac.uk/6dFGS

Paper Structure

This paper contains 13 sections, 2 equations, 9 figures, 6 tables.

Table of Contents

  1. Introduction
  2. Survey Overview
  3. Background
  4. Redshift Distribution
  5. Sample Composition
  6. Redshift uncertainties and blunder rates
  7. New Data Release
  8. Online database
  9. Changes made for the final redshift release
  10. Southern Large-Scale Structures
  11. Sky projections
  12. Declination slice projections
  13. Conclusion

Figures (9)

  • Figure 1: (a) Density of 6dFGS target sources (per square degree) on the sky; key supercluster over-densities are labelled. (b) Full 6dFGS field coverage (filled discs) and unobserved target fields (open circles). (c) Redshift completeness for $\hbox{$K$} \leq 12.65$. All panels show equal-area Aitoff projections.
  • Figure 2: Distribution of all 6dFGS redshifts in terms of (a) right ascension and (b) number. Panel (c) shows the same as (b) but limited to the primary $K$-selected sample. The dashed blue line is the redshift distribution calculated from the $K$-band luminosity function of the same sample (Jones et al., in prep). The solid red line is an empirical fit to the blue curve.
  • Figure 3: (Top panel:) Repeat 6dF redshift measurements for a sample of 6dFGS galaxies obtained with the VPH gratings over the period 2002.5 to 2006 (4570 galaxies). Redshift blunders (circled) are those for which $|\,\Delta cz\,| > 330$km s$^{-1}$. (Inset panel:) Distribution of the $|\,\Delta cz\,|$ diffferences for the individual redshift quality $Q=3$ (dotted line) and $Q=4$ (solid line) samples, normalised to the total sample size in each case. (Bottom panel:) Distribution of redshift difference as a function of redshift, with a running $\pm2\sigma$ boundary (solid lines).
  • Figure 4: Redshift comparison of 6dFGS (VPH grating) with SDSS Data Release 7 abazajian09.
  • Figure 5: Example spectroscopic and photometric frames from the 6dFGS online database for (a) a nearby bright galaxy at $z=0.057$ ($Q=4$)from the $K$-selected sample ( PROGID = 1), and (b) a candidate double QSO at $z=2.524$ ($Q=2$) from the Hamburg-ESO QSO sample ( PROGID = 129). 2MASS and UKST frames are only available for sources selected as part of the original 6dFGS primary samples, where available in one or more of $KHJr_{\rm F}b_{\rm J}$.
  • ...and 4 more figures