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Recent measurements of the spectrum and anisotropy of the cosmic microwave may be showing deviations from a perfectly homogeneous blackbody flux. Improved spectral measurements at wavelengths of 3 cm and 1.2 cm disagree weakly; and new results from a rocket show large excess flux at wavelengths of 0.71 and 0.48 mm. The same instrument measured a radiation temperature at λ = 1.16 mm of 2.795 ± 0.018 K in good agreement with results at longer wavelengths. The observed excess flux at short wavelengths may be due to: local contaminants; dust emission from active galaxies at high redshift; or inverse Compton scattering of microwave photons from hot electrons at large redshift (Sunyaev-Zel'dovich effect). Anisotropy of ΔT/T = 3.7 × 10−5 has been reported on an angular scale of 8° at a wavelength of 3 cm. Measurements on a similar angular scale at λ = 6 cm (reported at this meeting) do not show the anisotropy at the flux level expected if Galactic emission were the source of the anisotropy at λ = 3 cm. The standard model has not yet predicted anisotropy this large at 8°, but without doubt it soon will. Long integrations with the Very Large Array at λ = 6 cm are showing resolved structures on angular scales of 15 to 30 arcseconds. Observations at another wavelength are needed to see if these are radio sources at high redshift or perturbations in the 2.77 K radiatoin.
We analyze the anisotropies in the extragalactic infrared background and in the source counts in standard cosmology perturbed by large-scale, small-amplitude density fluctuations. The dipole anisotropy of the diffuse background is connected to the dipole of the cosmic background radiation and of the source counts, and a full consistency with a large (≃ 7%) anisotropy in the IRAS source counts is found to imply a low density (Ω0 ≃ 0.2) universe, contrary to a previous claim. We analyze also higher order harmonics. Using the IRAS Low-Resolution All-Sky Maps we obtain an upper limit of 0.17MJy/sr on the dipole of the 100 μm background and show that it is consistent with a source-count anisotropy of 7% only for a low intensity, I ≤ 1.2 M Jy/sr, of the background itself.
The Jodrell-IAC anisotropy experiment operating with twin 8° beams at 10.45 GHz over a two-year period, produced the reported limit of δ T/T≤3.7×10−5 (Davies et al., 1987: Nature 326, 462). Given the ability of this angular scale to strongly constrain cosmological models, it was decided to continue and expand the experiment by extending the horns to reduce the beam-size to 5°, while retaining the 8° separation. This improves the sensitivity to fluctuations by extending the angular range and decreasing beam-smearing.
We carried out the first satellite experiment for searching the anisotropies of the microwave background. The main goal of the experiment was to obtain a radio brightness map of the sky at 8 mm. We obtained the direction and amplitude of the dipole component at 90% confidence level
The variance analysis gives the most stringent constraints on fluctuations of the relic background. For the model with the Zeldovich spectrum of primordial fluctuations we found an upper limit on the quadrupole as 1.6×10−5 at 95% level. We are first to obtain model-independent estimates of the first 15 multipole components. We obtained upper limits on correlation function of angular fluctuations 〈ΔT1ΔT2〉 = 0.005 mK2 for the angular range from 20° to 160°. Intense galactic emission was observed over longitude interval from 90° to 270° and latitudes ±5°. The total flux from this longitude interval is approximately 56,000 Jy. The experiment studies confirmed that a space experiment gives a possibility to reach sensitivities high enough to estimate an anisotropy that is less than the values predicted by modern cosmological models.
Complete review of all (about 80) measurments made in US, USSR, GB, GFR, Australia, may be found in Parijskij and Korolkov (1986). Here we present very short summary of the astrophysical motivations and main results obtained in USSR during the last 20 years through ground based observations of 3 K anisotrory.
For the last four years we have been engaged on a program to look for intrinsic variations in the Microwave Background Radiation (MBR) at the Owens Valley Radio Observatory (OVRO). We summarize here the results of this continuing search.
Fluctuations in the microwave background will have been imprinted at z ≃ 1000, when the photons and the plasma decoupled. On angular scales greater than a few degrees these fluctuations provide a clear view of any primordial density perturbations, and therefore a clean test of theories which invoke such fluctuations from which to form the structure we see in the universe. On smaller angular scales the predictions are less certain: reionization of the gas may modify the spectrum of the primordial fluctuations, and secondary fluctuations may be generated.
Here I shall review some recent theoretical developments. A brief survey is made of the currently popular theories for the primordial perturbations, with emphasis on the predictions for large scale anisotropy. One major uncetainty in the predictions arises from the normalisation of the fluctuations to e.g. galaxy clustering, and much attention is given to the question of ‘biased’ galaxy formation. The effect of reionization on the primordial fluctuations is discussed, as is the anisotropy generated from scattering off hot gas in clusters, groups and galaxies.
Before the development of the inflationary universe scenario many cosmological problems of the standard hot universe theory remained unsolved. In particular, the origin of primordial density perturbations remained obscure.
The basic idea of inflation in cosmology is very simple: It is the assumption that the expansion factor R(t) of a Friedmann-Lemaltre cosmological model grows exponentially during a brief time interval in the very early universe. The phase of exponential growth is followed by a thermalizatlon stage and a subsequent “normal” evolution R(t)∼vt. This “Inflationary expansion“ can help to solve cosmological puzzles inherent in the standard model - such as the large-scale flatness, the horizon structure, the numerical value of the entropy in a comoving volume [for a review see Brandenberger 1985]. To turn this romantic idea of inflation into a quantitative model requires still a lot of work: The simple change in the thermal history of the universe must be derived from a fundamental particle theory. The models proposed so far do not inspire much confidence. In the following a few difficulties of the Higgs field idea, especially the Coleman-Weinberg formalism will be pointed out (section 1). In section 2 some problems connected with the investigation of initially strongly anisotropic or Inhomogeneous cosmological models will be mentioned.
Recent investigations on the evolution of the inhomogeneities in the inflationary universe are reviewed. 1) Strict cosmological no hair theorem does not hold, but the class of inhomogeneous universe which evolve to homogeneous de Sitter universe is finite, i.e, “weak cosmic no hair theorem” holds. 2) High density regions in the inhomogeneous universe evolve to wormholes provided that i) the size of the regions is greater than the horizon length, but smaller than a critical length which is the function of the density contrast, and ii) the density is three times higher than that of surrounding region. 3) If wormholes are formed copiously in the period of inflation, they evolve to causally disconnected “child- universes”. In this scenario, the universe we are now observing is one of the locally flat regions.
The increasing precision of experiments designed to detect angular anisotropies and spectral distortions of the microwave background has now brought us near to or below the levels predicted by most theories of the formation of structure in the universe. Here I review the quantitative theoretical results for anisotropies and distortions for a wide variety of models. Many of these were presented in the Monday afternoon discussion session on the microwave background held at IAU Symposium 130. Primary and secondary anisotropies (and the associated distortions) are considered for universes with structure arising from initially Gaussian perturbations, especially the scale-invariant ones predicted by inflation, from accretion onto cosmic strings, and from shells generated by explosive energy injection, including that from superconducting strings as well as from supernovae.
The first CfA Survey is now over 90% spectroscopically complete. Over 60% of all galaxies exhibit detectable emission lines. We have also completed five slices of the Center for Astrophysics (CfA) redshift survey extension. The geometry of the structures in the first slice persists; galaxies are distributed on thin surfaces of “bubble-like” structures. Empty regions or “voids” are common, come in a variety of sizes ranging up to 5,000 km s−1, and are underdense by factors of up to 5 w.r.t. the mean. These voids fill ∼ 80% of the volume of the local universe. Clusters of galaxies lie at the interstices of bubbles; some of the poor Abell clusters do not exist as “fingers” in redshift space. The surfaces are very thin with an average FWHM less than 500 km s−1 in redshift space (σ ∼ 200 to 250 km s−1).
We report on the current status of the HI redshift survey in the Pisces-Perseus supercluster and present results based on a sample of approximately 4700 redshifts known in the 6h by 45° region of the sky dominated by the supercluster. In particular we derive density contrasts between voids and high density regions and discuss the existence of a luminosity bias between galaxies that reside in regions of different local density. Such a bias is not the consequence of the well-known pattern of morphological type segregation, but results from a difference in the shape of the luminosity function of galaxies in high and low density regions. Bright galaxies tend to be relatively less abundant, and faint ones relatively more so, in low density environments.