The large-scale structure in the distribution of galaxies is thought to arise from the gravitational instability of small fluctuations in the initial density field of the Universe. A key test of this hypothesis is that forming superclusters of galaxies should generate a systematic infall of other galaxies. This would be evident in the pattern of recessional velocities, causing an anisotropy in the inferred spatial clustering of galaxies. Here we report a precise measurement of this clustering, using the redshifts of more than 141,000 galaxies from the two-degree-field (2dF) galaxy redshift survey. We determine the parameter beta = Omega0.6/b = 0.43 +/- 0.07, where Omega is the total mass-density parameter of the Universe and b is a measure of the 'bias' of the luminous galaxies in the survey. (Bias is the difference between the clustering of visible galaxies and of the total mass, most of which is dark.) Combined with the anisotropy of the cosmic microwave background, our results favour a low-density Universe with Omega approximately 0.3.

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We use more than 110 500 galaxies from the 2dF Galaxy Redshift Survey (2dFGRS) to estimate the bJ‐band galaxy luminosity function at redshift z= 0, taking account of evolution, the distribution of magnitude measurement errors and small corrections for incompleteness in the galaxy catalogue. Throughout the interval −16.5 > M italicb J− 5 log10h > −22, the luminosity function is accurately described by a Schechter function with M★ italicb J− 5 log10h=−19.66 ± 0.07, α=−1.21 ± 0.03 and Φ★= (1.61 ± 0.08) × 10−2h3 Mpc−3, giving an integrated luminosity density of ρL= (1.82 ± 0.17) × 108h L⊙ Mpc−3 (assuming an Ω0= 0.3, Λ0= 0.7 cosmology). The quoted errors have contributions from the accuracy of the photometric zero‐point, from large‐scale structure in the galaxy distribution and, importantly, from the uncertainty in the appropriate evolutionary corrections. Our luminosity function is in excellent agreement with, but has much smaller statistical errors than, an estimate from the Sloan Digital Sky Survey (SDSS) data when the SDSS data are accurately translated to the bJ band and the luminosity functions are normalized in the same way. We use the luminosity function, along with maps describing the redshift completeness of the current 2dFGRS catalogue, and its weak dependence on apparent magnitude, to define a complete description of the 2dFGRS selection function. Details and tests of the calibration of the 2dFGRS photometric parent catalogue are also presented.

We present a comprehensive set of mock 2dF and SDSS galaxy redshift surveys constructed from a set of large, high-resolution cosmological N-body simulations. The radial selection functions and geometrical limits of the catalogues mimic those of the genuine surveys. The catalogues span a wide range of cosmologies, including both open and flat universes. In all the models the galaxy distributions are biased so as to approximately reproduce the observed galaxy correlation function on scales of 1--10 Mpc/h In some cases models with a variety of different biasing prescriptions are included. All the mock catalogues are publically available at http://star-www.dur.ac.uk/~cole/mocks/main.html . We expect these catalogues to be a valuable aid in the development of the new algorithms and statistics that will be used to analyse the 2dF and SDSS surveys when they are completed in the next few years. Mock catalogues of the PSCZ survey of IRAS galaxies are also available at the same WWW location.Comment: Accepted by MNRAS after minor revisions. All the mock catalogues presented and related information and software are available at http://star-www.dur.ac.uk/~cole/mocks/main.html . This WWW site also contains versions of this paper with high resolution (and colour) figures and many other figures illustrating the 2dF and SDSS survey

In Galaxy And Mass Assembly Data Release 4 (GAMA DR4), we make available our full spectroscopic redshift sample. This includes 248 682 galaxy spectra, and, in combination with earlier surveys, results in 330 542 redshifts across five sky regions covering ∼250 deg2. The redshift density, is the highest available over such a sustained area, has exceptionally high completeness (95 per cent to rKiDS = 19.65 mag), and is well suited for the study of galaxy mergers, galaxy groups, and the low redshift (z < 0.25) galaxy population. DR4 includes 32 value-added tables or Data Management Units (DMUs) that provide a number of measured and derived data products including GALEX, ESO KiDS, ESO VIKING, WISE and Herschel Space Observatory imaging. Within this release, we provide visual morphologies for 15 330 galaxies to z < 0.08, photometric redshift estimates for all 18 million objects to rKiDS ∼ 25 mag, and stellar velocity dispersions for 111 830 galaxies. We conclude by deriving the total galaxy stellar mass function (GSMF) and its sub-division by morphological class (elliptical, compact-bulge and disc, diffuse-bulge and disc, and disc only). This extends our previous measurement of the total GSMF down to 106.75 M$_{\odot } \, h_{70}^{-2}$ and we find a total stellar mass density of ρ* = (2.97 ± 0.04) × 108 M⊙ h70 Mpc−3 or $\Omega _*=(2.17 \pm 0.03) \times 10^{-3} \, h_{70}^{-1}$. We conclude that at z < 0.1, the Universe has converted 4.9 ± 0.1 per cent of the baryonic mass implied by big bang Nucleosynthesis into stars that are gravitationally bound within the galaxy population.

The "Lambda Cold Dark Matter" (ΛCDM) model of cosmic structure formation is eminently falsifiable: once its parameters are fixed on large scales, it becomes testable in the nearby Universe. Observations within our Local Group of galaxies, including the satellite populations of the Milky Way and Andromeda, appear to contradict ΛCDM predictions: there are far fewer satellite galaxies than dark matter halos (the "missing satellites" problem (1, 2)), galaxies seem to avoid the largest substructures (the "too big to fail" problem (3, 4)), and the brightest satellites appear to orbit their host galaxies on a thin plane (the "planes of satellites" problem ( 5)). We present results from the first hydrodynamic simulations of the Local Group that match the observed abundance of galaxies. We find that when baryonic and dark matter are followed simultaneously in the context of a realistic galaxy formation model, all three "problems" are resolved within the ΛCDM paradigm.The ability of the cold dark matter model to predict observables on different scales and at different epochs lies at the root of its remarkable success. The anisotropy of the microwave background radiation and the large scale distribution of galaxies were predicted after the model was formulated, and have since been spectacularly validated by observations. However, observations on scales currently testable only within the Local Group (LG) have yielded results that no simulation to date has been able to reproduce. This has renewed interest in alternatives to ΛCDM, such as warm (6) or self-interacting (7) dark matter.

We present the status of the Dark Energy Spectroscopic Instrument (DESI) and its plans and opportunities for the coming decade. DESI construction and its initial five years of operations are an approved experiment of the U.S. Department of Energy and is summarized here as context for the Astro2020 panel. Beyond 2025, DESI will require new funding to continue operations. We expect that DESI will remain one of the world's best facilities for wide-field spectroscopy throughout the decade. More about the DESI instrument and survey can be found at https://www.desi.lbl.gov.

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