A B S T R A C TThe 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure redshifts for approximately 250 000 galaxies. This paper describes the survey design, the spectroscopic observations, the redshift measurements and the survey data base. The 2dFGRS uses the 2dF multifibre spectrograph on the Anglo-Australian Telescope, which is capable of observing 400 objects simultaneously over a 28 diameter field. The source catalogue for the survey is a revised and extended version of the APM galaxy catalogue, and the targets are galaxies with extinction-corrected magnitudes brighter than b J ¼ 19:45. The main survey regions are two declination strips, one in the southern Galactic hemisphere spanning 808 Â 158 around the SGP, and the other in the northern Galactic hemisphere spanning 758 Â 108 along the celestial equator; in addition, there are 99 fields spread over the southern Galactic cap. The survey covers 2000 deg 2 and has a median depth of z ¼ 0:11. Adaptive tiling is used to give a highly uniform sampling rate of 93 per cent over the whole survey region. Redshifts are measured from spectra covering 3600-8000A at a two-pixel resolution of 9.0 Å and a median S/N of 13 pixel 21 . All redshift identifications are visually checked and assigned a quality parameter Q in the range 1-5; Q $ 3 redshifts are 98.4 per cent reliable and have an rms uncertainty of 85 km s 21 . The overall redshift completeness for Q $ 3 redshifts is 91.8 per cent, but this varies with magnitude from 99 per cent for the brightest galaxies to 90 per cent for objects at the survey limit. The 2dFGRS data base is available on the World Wide Web at http://www. mso.anu.edu.au/2dFGRS.

We present a power-spectrum analysis of the final 2dF Galaxy Redshift Survey (2dFGRS), employing a direct Fourier method. The sample used comprises 221 414 galaxies with measured redshifts. We investigate in detail the modelling of the sample selection, improving on previous treatments in a number of respects. A new angular mask is derived, based on revisions to the photometric calibration. The redshift selection function is determined by dividing the survey according to rest-frame colour, and deducing a self-consistent treatment of k-corrections and evolution for each population. The covariance matrix for the power-spectrum estimates is determined using two different approaches to the construction of mock surveys, which are used to demonstrate that the input cosmological model can be correctly recovered. We discuss in detail the possible differences between the galaxy and mass power spectra, and treat these using simulations, analytic models and a hybrid empirical approach. Based on these investigations, we are confident that the 2dFGRS power spectrum can be used to infer the matter content of the universe. On large scales, our estimated power spectrum shows evidence for the 'baryon oscillations' that are predicted in cold dark matter (CDM) models. Fitting to a CDM model, assuming a primordial n s = 1 spectrum, h = 0.72 and negligible neutrino mass, the preferred parameters are m h = 0.168 ± 0.016 and a baryon fraction b / m = 0.185 ± 0.046 (1σ errors). The value of m h is 1σ lower than the 0.20 ± 0.03 in our 2001 analysis of the partially E-mail: shaun.cole@durham.ac.uk C 2005 RAS 506 S. Cole et al.complete 2dFGRS. This shift is largely due to the signal from the newly sampled regions of space, rather than the refinements in the treatment of observational selection. This analysis therefore implies a density significantly below the standard m = 0.3: in combination with cosmic microwave background (CMB) data from the Wilkinson Microwave Anisotropy Probe (WMAP), we infer m = 0.231 ± 0.021.

We combine the Two Micron All Sky Survey (2MASS) Extended Source Catalogue and the 2dF Galaxy Redshift Survey to produce an infrared selected galaxy catalogue with 17 173 measured redshifts. We use this extensive data set to estimate the galaxy luminosity functions in the J‐ and KS‐bands. The luminosity functions are fairly well fitted by Schechter functions with parameters MJ*−5 log  h=−22.36±0.02, αJ=−0.93±0.04, ΦJ*=0.0104±0.0016 h3 Mpc−3 in the J‐band and MKS*−5 log  h=−23.44±0.03, αKS=−0.96±0.05, ΦKS*=0.0108±0.0016 h3 Mpc−3 in the KS‐band (2MASS Kron magnitudes). These parameters are derived assuming a cosmological model with Ω0=0.3 and Λ0=0.7. With data sets of this size, systematic rather than random errors are the dominant source of uncertainty in the determination of the luminosity function. We carry out a careful investigation of possible systematic effects in our data. The surface brightness distribution of the sample shows no evidence that significant numbers of low surface brightness or compact galaxies are missed by the survey. We estimate the present‐day distributions of bJ−KS and J−KS colours as a function of the absolute magnitude and use models of the galaxy stellar populations, constrained by the observed optical and infrared colours, to infer the galaxy stellar mass function. Integrated over all galaxy masses, this yields a total mass fraction in stars (in units of the critical mass density) of Ωstarsh =(1.6±0.24)×10−3 for a Kennicutt initial mass function (IMF) and Ωstarsh =(2.9±0.43)×10−3 for a Salpeter IMF. These values are consistent with those inferred from observational estimates of the total star formation history of the Universe provided that dust extinction corrections are modest.

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We have measured the equivalent width of the Hα emission line for 11 006 galaxies brighter than Mb=−19 (ΩΛ= 0.7, Ωm= 0.3, H0= 70 km s−1 Mpc−1) at 0.05 < z < 0.1 in the 2dF Galaxy Redshift Survey (2dFGRS), in the fields of 17 known galaxy clusters. The limited redshift range ensures that our results are insensitive to aperture bias, and to residuals from night sky emission lines. We use these measurements to trace μ*, the star formation rate normalized to L*, as a function of distance from the cluster centre, and local projected galaxy density. We find that the distribution of μ* steadily skews toward larger values with increasing distance from the cluster centre, converging to the field distribution at distances greater than ∼3 times the virial radius. A correlation between star formation rate and local projected density is also found, which is independent of cluster velocity dispersion and disappears at projected densities below ∼1 galaxy Mpc−2 (brighter than Mb=−19). This characteristic scale corresponds approximately to the mean density at the cluster virial radius. The same correlation holds for galaxies more than two virial radii from the cluster centre. We conclude that environmental influences on galaxy properties are not restricted to cluster cores, but are effective in all groups where the density exceeds this critical value. The present‐day abundance of such systems, and the strong evolution of this abundance, makes it likely that hierarchical growth of structure plays a significant role in decreasing the global average star formation rate. Finally, the low star formation rates well beyond the virialized cluster rule out severe physical processes, such as ram pressure stripping of disc gas, as being completely responsible for the variations in galaxy properties with environment.

zCOSMOS is a large redshift survey that is being undertaken in the COSMOS field using 600 hours of observation with the VIMOS spectrograph on the 8-m VLT. The survey is designed to characterise the environments of COSMOS galaxies from the 100 kpc scales of galaxy groups up to the 100 Mpc scale of the cosmic web and to produce diagnostic information on galaxies and active galactic nuclei. The zCOSMOS survey consists of two parts: (a) zCOSMOS-bright, a magnitude-limited I-band I AB < 22.5 sample of about 20,000 galaxies with 0.1 < z < 1.2 covering the whole 1.7 deg 2 COSMOS ACS field, for which the survey parameters at z ~ 0.7 are designed to be directly comparable to those of the 2dFGRS at z ~ 0.1; and (b) zCOSMOS-deep, a survey of approximately 10,000 galaxies selected through colourselection criteria to have 1.4 < z < 3.0, within the central 1 deg 2 . This paper describes the survey design and the construction of the target catalogues, and briefly outlines the observational program and the data pipeline. In the first observing season, spectra of 1303 zCOSMOS-bright targets and of 977 zCOSMOS-deep targets have been obtained. These are briefly analysed to demonstrate the characteristics that may be expected from zCOSMOS, and particularly zCOSMOS-bright, when it is finally completed between 2008-2009. The power of combining spectroscopic and photometric redshifts is demonstrated, especially in correctly identifying the emission line in single-line spectra and in determining which of the less reliable spectroscopic redshifts are correct and which are incorrect. These techniques bring the overall success rate in the zCOSMOS-bright so far to almost 90% and to above 97% in the 0.5 < z < 0.8 redshift range. Our zCOSMOS-deep spectra demonstrate the power of our selection techniques to isolate high redshift galaxies at 1.4 < z < 3.0 and of VIMOS to measure their redshifts using ultraviolet absorption lines.

Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.

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