Since the IAU XXIV meeting in 2000, the CMB anisotropy has matured from being one of a number of cosmological probes to forming the bedrock foundation for what is now the standard model of cosmology. The large advances over the past three years have come from making better and better maps of the cosmos. We review the state of measurements of the anisotropy and outline some of what we have learned since 2000. The recent advancements may be placed roughly into three categories: 1) What we learn from the CMB with minimal input from other cosmic measurements such as the Hubble constant; 2) What we learn from the CMB in combination with other probes of large scale structure; and 3) What we learn by using the CMB as a back light. Future directions are also discussed. It is clear: we have much more to learn from the CMB anisotropy.

The results of the first year WMAP sky survey are full sky microwave maps in five frequency bands from 23 to 94 GHz. Calibration errors are < 0.5% and the low systematic error level is well specified. The cosmic microwave background (CMB) is separated from the foregrounds using the multifrequency data. The 2 ≤ l ≤ 900 anisotropy power spectrum is cosmic variance limited for l < 354 with a signal-to-noise ratio >1 per mode to l = 658. The temperature-polarization cross-power spectrum reveals both acoustic features and a large angle correlation from reionization. The optical depth of reionization is τ = 0.17 ± 0.04. A best-fit cosmological model to the CMB and other measures of large scale structure works remarkably well with only a few parameters. The age of the best-fit universe is t0 = 13.7 ± 0.2 Gyr old. The matter density is Ωmh2 = 0.135+0.008--0.009, the baryon density is Ωbh2 = 0.0224 ± 0.0009, and the total mass-energy of the universe is Ωtot = 1.02±0.02. For WMAP data alone, ns = 0.99 ± 0.04. The lack of CMB fluctuation power on the largest angular scales reported by COBE and confirmed by WMAP is intriguing. WMAP continues to operate, so results will improve.

We reconstruct the shape of the primordial power spectrum from the latest cosmic microwave background data, including the new results from the Wilkinson Microwave Anisotropy Probe (WMAP), and large scale structure data from the two degree field galaxy redshift survey (2dFGRS). We discuss two parameterizations taking into account the uncertainties in four cosmological parameters. First we parameterize the initial spectrum by a tilt and a running spectral index, finding marginal evidence for a running spectral index only if the first three WMAP multipoles (ℓ = 2, 3, 4) are included in the analysis. Secondly, to investigate further the low CMB large scale power, we modify the conventional power-law spectrum by introducing a scale above which there is no power. We find a preferred position of the cut at kc ∼ 3 × 10--4 Mpc--1 although kc = 0 (no cut) is not ruled out.

In the 1998-99 flight, BOOMERanG has produced maps of ∼4% of the sky at high Galactic latitudes, at frequencies of 90, 150, 240 and 410 GHz, with resolution ≳ 10'. The faint structure of the Cosmic Microwave Background at horizon and sub-horizon scales is evident in these maps. These maps compare well to the maps recently obtained at lower frequencies by the WMAP experiment. Here we compare the amplitude and morphology of the structures observed in the two sets of maps. We also outline the polarization sensitive version of BOOMERanG, which was flown early this year to measure the linear polarization of the microwave sky at 150, 240 and 350 GHz.

The Arcminute Cosmology Bolometer Array Receiver (Acbar) is a multifrequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. Acbar was installed on the 2.1 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. The power spectrum of the CMB at 150 GHz over the range ℓ = 150 — 3000 measured by Acbar is presented along with estimates for the values of the cosmological parameters within the context of ΛCDM models. The inclusion of ΩΛ greatly improves the fit to the power spectrum. Three-frequency images of the SZ decrement/increment are also presented for the galaxy cluster 1E0657–67.

We discuss upcoming opportunities with cosmic microwave background (CMB) observations during the post-WMAP era. The curl-modes of CMB polarization probe inflationary gravitational waves (IGWs). While a significant source of confusion is expected from cosmic shear conversion of polarization related to density perturbations, higher resolution observations of CMB anisotropies can be used for a lensing reconstruction and to separate gravitational-wave polarization signature from that of lensing. Separations based on current lensing reconstruction techniques allow the possibility to probe inflationary energy scales below 1015 GeV in a range that includes grand unified theories. The observational detection of primordial curl-modes is aided by rescattering at late times during the reionized epoch with optical depth to electron scattering at the level of 0.1 and above. An improved measurement of this optical depth is useful to optimize experimental parameters of a post-WMAP mission attempting to target the IGW background.

The acceleration of the expansion of the universe has deep implications for structure formation, the composition of the universe, and its fate. Roughly 70% of the energy density is in a dark energy, whose nature remains unknown. Mapping the expansion history through supernovae, mapping the geometry of the universe and formation of structure through redshift surveys, and mapping the distance to recombination through the cosmic microwave background provide complementary, precise probes of the equation of state of the dark energy. Together these next generation maps of the cosmos can reveal not only the value today, but the redshift variation, of the equation of state, providing a critical clue to the underlying physics.

The Very Small Array (VSA) is a unique interferometric telescope operating at 33 GHz at Tenerife. It has the ability to measure fluctuations in the CMB over a large range of angular scales by means of three main array configurations: compact, extended and super-extended. These angular scales correspond to the multipole range ℓ = 150 —2500. Here we present new results from further observations of the extended array (February 2002 - June 2003). We cover ℓ-values up to ℓ ∼ 1600, thus doubling the ℓ-range of WMAP. The resulting power spectrum in the ℓ-range 800 – 1600 has very low noise coupled with good ℓ-resolution (Δℓ ∼ 80). Furthermore, the use of independently tracking aerials along with the dedicated source subtraction baseline allows unprecedented control of systematics. The latter is essential, since discrete sources are the dominant foreground at these angular scales. These measurements over larger ℓ-ranges are important in confirming the present cosmological paradigm and breaking degeneracies in the extraction of cosmological parameters.

The 2dF Galaxy Redshift Survey is now complete, and the full data are public. 2dFGRS was the first survey to observe more than 100,000 redshifts, making possible precise measurements of many aspects of galaxy clustering, which can be studied as a function of galaxy spectral type, and also of broad-band colour. Early-type galaxies are more strongly clustered than late types, with a relative bias of b = 1.25 ± 0.09 on large scales. For both types, luminosity dependence of clustering is detected at high significance, and is well described by a relative bias of b/b* = 0.85 + 0.15(L/L*). This is consistent with the observation that L* in rich clusters is brighter than the global value by 0.28 ± 0.08 mag. Redshift-space distortions from large-scale infall velocities measure the distortion parameter β = Ω0.6m/b = 0.49 ± 0.09. The power spectrum is measured to ≲ 10% accuracy for k > 0.02 h Mpc--1, and is well fitted by a CDM model with Ωmh = 0.18 ± 0.02 and a baryon fraction of 0.17 ± 0.06. The 2dFGRS plays an essential role in breaking model degeneracies inherent in CMB data; a joint analysis with WMAP results requires Ωm = 0.25 ± 15% and h = 0.73 ± 5%, assuming scalar fluctuations.

The 2dF QSO Redshift Survey (2QZ) is now complete and available to the astronomical community (see www.2dfquasar.org). In this paper we review some of the principle science results to come from the survey, in particular concentrating on tests for cosmological parameters. Measurements of large-scale structure using the correlation function and power spectrum, together with determinations of the geometric distortion of clustering in redshift-space have been used. These produce a consistent picture which is well matched to the now standard cosmological model with Ωm ≃ 0.3 and ΩΛ ≃ 0.7. In particular, geometric distortions provide evidence for non-zero ΩΛ independent of type Ia supernovae, the CMB, or the assumed type of dark matter (e.g. CDM). However, gravitational lensing results in the form of potential arcminute separation lensed pairs and a stronger than expected anti-correlation between QSOs and foreground galaxies in groups and clusters may prove to be inconsistent with the current standard model. These issues certainly require further investigation.

Simulations of large-scale structure in the universe have played a vital role in observational cosmology since the 1980's in particular. Their important role will definitely continue to be true in the 21st century; indeed the requirements for simulations in the precision cosmology era will become more progressively demanding as they are supposed to fill the missing link in an accurate and reliable manner between the “initial” condition at z=1000 revealed by WMAP and the galaxy/quasar distribution at z=0 − 6 surveyed by 2dF and SDSS. In this review, I will summarize what we have learned so far from the previous cosmological simulations, and discuss several remaining problems for the new millennium.

Maps of the cosmos, in particular maps of the cosmic microwave background and of the large scale distribution of galaxies have been crucial ingredients in the development of the standard model of structure formation, sometimes also labeled “concordance model”. This model has proven to be remarkably successful in explaining an impressive array of observations on scales of hundreds of kpc to thousands of Mpc. In this contribution I will attempt to extend those studies to smaller, (sub)galactic scales and will confront detailed gas-dynamical simulations of the formation of individual galaxies with observational data on these scales, reporting some successes and failures of this endeavor. Ongoing surveys that are mapping the distribution of stars in the Milky Way should be able to clearly identify the imprints of the hierarchical galaxy formation process providing an independent check of the validity of the structure formation paradigm.

We present estimates of cosmological parameters from the application of the Karhunen-Loève transform to the analysis of the 3D power spectrum of density fluctuations using Sloan Digital Sky Survey galaxy redshifts. We use Ωmh and fb = Ωb/Ωm to describe the shape of the power spectrum, σL8g for the (linearly extrapolated) normalization, and β to parametrize linear theory redshift space distortions. on scales k ≤ 0.16hMpc--1, our maximum likelihood values are Ωmh = 0.264 ± 0.043, fb = 0.286 ± 0.065, σL8g = 0.966 ± 0.048, and β = 0.45 ± 0.12. When we take a prior on Ωb from WMAP, we find Ωmh = 0.207 ± 0.030, which is in excellent agreement with WMAP and 2dF. This indicates that we have reasonably measured the gross shape of the power spectrum but we have difficulty breaking the degeneracy between and Ωmh and fb because the baryon oscillations are not resolved in the current spectroscopic survey window function.

Weak gravitational lensing of distant galaxies by foreground structures has proven to be a powerful tool to study the mass distribution in the universe. The advent of panoramic cameras on 4-m class telescopes has led to a first generation of surveys that already compete with large redshift surveys in terms of the accuracy with which cosmological parameters can be determined. The next surveys, which already have started taking data, will provide another major step forward. At the current level, systematics appear under control, and it is expected that weak lensing will develop into a key tool in the era of precision cosmology, provided we improve our knowledge of the non-linear matter power spectrum and the source redshift distribution. In this review we will briefly describe the principles of weak lensing and discuss the results of recent cosmic shear surveys. We show how the combination of weak lensing and cosmic microwave background measurements can provide tight constraints on cosmological parameters. We also demonstrate the usefulness of weak lensing in studies of the relation between the galaxy distribution and the underlying dark matter distribution (“galaxy biasing”), which can provide important constraints on models of galaxy formation. Finally, we discuss new and upcoming large cosmic shear surveys.

We have demonstrated that newly developed Suprime-Cam on the 8-m Subaru telescope is capable of blind searches of mass concentration via weak lensing. We then propose to extend the survey up to 33 square degrees where archival X-ray data is available (Suprime33 Survey). The survey status and the performance of Suprime-Cam in the weak lensing survey are shown.

“Early” maps of the cosmos included the 26th dynasty air god Shu supporting the sky goddess Nut above the earth god Geb, Descartes' Voronoi tesselation, William Herschel's star gauging, and Carl Charlier's 1922 plot of the nebulae in NGC, which he intended as observational support for the fractal nature of large scale cosmic structure (about which he was probably wrong, though right about there being more than one level of clustering). Because Shapley, van Maanen, and others were still denying the very existence of external galaxies at the same time that Lundmark and Opik were measuring their distances and masses and Charlier plotting hierarchies, the story of the discovery of very large scale structure (and streaming) in the universe cannot be told in perfectly linear fashion. There are, however, half a dozen or so discrete phases that can be recognized and three underlying themes, (1) expanding horizons, (2) additional levels of structure, and (3) increasing mediocrity of our vantage point.

The Two Micron All-Sky Survey was conceived over a decade ago for the express purpose of mapping the Milky Way and the Universe nearby. 2MASS is now complete and the final data products, including the extended source catalog (XSC), have been released. The XSC contains nearly a million galaxies to the stated completeness goal of K=13.5. While the catalog becomes incomplete at the faintest magnitudes and lowest galactic latitudes due to confusion, at the bright end the catalog is essentially complete down to very low latitudes (b less than 5 degrees), which makes it an excellent survey for the distribution of matter in the nearby Universe. Redshift information is now nearly complete for the 24,000 galaxies brighter than K=11.25 and above |b|=5°. We now have an amazing census of galaxy (baryonic mass) concentrations over the whole sky and inside z=0.04. Several new structures are elucidated and the characteristics of the structures are described. We also examine the match between the predicted gravitational velocity vector of the Local Group and the motions determined by other experiments including the CMB dipole.

The 6dF Galaxy Survey will provide 167 000 redshifts and about 15000 peculiar velocities for galaxies over most of the southern sky out to about cz = 30000 km s--1. The survey is currently almost half complete, with the final observations due in mid-2005. An initial data release was made public in December 2002; the first third of the dataset will be released at the end of 2003, with the remaining thirds being released at the end of 2004 and 2005. The status of the survey, the survey database and other relevant information can be obtained from the 6dFGS web site at http://www.mso.anu.edu.au/6dFGS.

In terms of constraining cosmological parameters, combining the 6dFGS redshift and peculiar velocity surveys will allow us to: (1) break the degeneracy between the redshift-space distortion parameter β = Ω0.6m/b and the galaxy-mass correlation parameter rg; (2) measure the four parameters Ag, Γ, β and rg with precisions of between 1% and 3%; (3) measure the variation of rg and b with scale to within a few percent over a wide range of scales.

A database of 30,000 galaxies within a cube ±8,000 km s--1 centered at our position is used to illustrate the properties of the nearby structure in the distribution of galaxies. The data cube can be manipulated in ways that enhance the visualization of the structure with special software. The dominant regions of high density are the Great Attractor, the Great Wall, and the Perseus-Pisces complexes. There are many voids.