The 6dF Galaxy Survey: samples, observational techniques and the first data release

Abstract

The 6dF Galaxy Survey (6dFGS) aims to measure the redshifts of around 150 000 galaxies, and the peculiar velocities of a 15 000-member subsample, over almost the entire southern sky. When complete, it will be the largest redshift survey of the nearby Universe, reaching out to about z∼ 0.15, and more than an order of magnitude larger than any peculiar velocity survey to date. The targets are all galaxies brighter than Ktot= 12.75 in the 2MASS Extended Source Catalog (XSC), supplemented by 2MASS and SuperCOSMOS galaxies that complete the sample to limits of (H, J, rF, bJ) = (13.05, 13.75, 15.6, 16.75). Central to the survey is the Six-Degree Field (6dF) multifibre spectrograph, an instrument able to record 150 simultaneous spectra over the -field of the UK Schmidt Telescope. An adaptive tiling algorithm has been employed to ensure around 95 per cent fibring completeness over the 17 046 deg2 of the southern sky with | b | > 10°. Spectra are obtained in two observations using separate V and R gratings, that together give R∼ 1000 over at least 4000–7500 Å and signal-to-noise ratio ∼10 per pixel. Redshift measurements are obtained semi-automatically, and are assigned a quality value based on visual inspection. The 6dFGS data base is available at, with public data releases occurring after the completion of each third of the survey.