Showing papers on "Dipole anisotropy published in 1987"

Optical dipole anisotropy

Abstract: La distribution de la lumiere a grande echelle est illustree a l'aide de cartes de 15000 galaxies optiques environ, basees sur les catalogues UGC, ESO et MCG. L'anisotropie dipolaire de la distribution des galaxies pointe vers l=227°±23°, b=42°±8°

Observations and Nonstandard FRW Models

Abstract: The observational predictions of various nonstandard cosmological models which have an FRW metric as their space-time geometry are investigated. The general numerical predictions of the models are found to be in accord with actual observations; in particular, they predict a current relative velocity of the Galaxy with respect to the CMB consistent with measurements of the dipole anisotropy of the CMB temperature distribution, and also predict a quadrupole anisotropy, the magnitude of which is well below the upper limits obtained from observations. The distance versus redshift relationship is calculated in a typical model and is found to be the same as in the corresponding standard FRW model. The critical density problem is addressed, and the behavior of the expansion in the models is investigated. The thermodynamics of the models is considered, and the predicted helium abundance in the models is calculated and found to be in accord with current estimates. In particular, in a class of two-fluid models the predicted helium abundance is virtually the same as that in the corresponding standard FRW model. 31 references.

Measurement of the microwave background radiation

Abstract: Absolute flux measurements of the 2.7 K background radiation show a blackbody spectrum with good accuracy ( ca . + 5 %) over two orders of magnitude of wavelength (12 cm to 1 mm). This is in agreement with the thermal history of matter and radiation envisaged by the hot Big Bang model. In particular, experimental limits on spectral distortion constrain processes that release energy into the early Universe. The extreme isotropy of the 2.7 K radiation on small angular scales (10" to 1°) sets interesting limits on models for the formation of mass structure. Some types of perturbations can be ruled out because the accompanying spatial fluctuations in radiation temperature are not seen (Δ T / T -4 ). Large-scale (1-90°) anisotropy of the radiation is plausible because at the time of decoupling (z « 1000), regions separated by more than a few degrees in the sky were not in causal contact. Explanation of the observed isotropy is a major feature of inflationary models. Finally, the observed dipole anisotropy is mostly due to the peculiar velocity of the Galaxy with respect to the radiation frame. An interesting question is: how much of this velocity is primordial and how much can be accounted for by local mass attractors?

A Distance Scale From The IR Magnitude/HI Velocity Width Relation

Abstract: A summary is given of recent work using the IR/H I method, arguably the best global distance indicator presently available Reflex motion toward the microwave dipole anisotropy has been seen relative to a sample of nearby galaxy clusters; this result is contrasted with the somewhat divergent conclusions obtained by Burstein et al from a similar study of elliptical galaxies A best guess calibration of the IR/H I zero point continues to lead to a high value for the expansion rate This finding cannot be explained by appealing to Malmquist bias, as demonstrated by a straightforward linearity test of the velocity-distance relation However, all current estimates of the Hubble constant are plagued by the large uncertainties to the distances of nearby calibrating galaxies, a problem whose full solution probably must await the launch of the Hubble Space Telescope

Measurement of the Dipole Moment of the Cosmic Background Radiation at mm and Sub-mm Wavelengths

Abstract: Sensitive measurements of a dipole anisotropy of the Cosmic Background Radiation at wavelengths of 1.7 and 0.8 mm are presented. Under the assumption that the dipole moment is caused by a doppler shift, these measurements are of sufficient precision to constrain spectral distortions of the CBR at short wavelengths. Measurements of the brightness and shape of diffuse galactic emission are also presented.

The dipole anisotropy in the decaying-particle universe models with nonzero cosmological constant

Abstract: 4) using the IRAS galaxies catalogue, and by Lahav 5 ) using the optical catalogues. The directions of the dipole anisotropy are approximately the same as that of the motion of the Local Group with the velocity VLG to the cosmic blackbody radiation_ This motion consists of the large-scale stream motion and the local motion within the Local Supercluster, and the dipole anisotropy is produced by the two corresponding density perturbations_