The cosmic microwave background radiation and galaxy formation

1986 ◽  
Vol 64 (2) ◽  
pp. 147-151 ◽  
Author(s):  
Joseph Silk
Keyword(s):  
Galaxy Formation ◽  
Background Radiation ◽  
Gravitational Instability ◽  
Virgo Cluster ◽  
Inflationary Cosmology ◽  
Density Parameter ◽  
Microwave Background ◽  
Scale Invariant ◽  
Instability Theory ◽  
Microwave Background Radiation

Observational limits on the microwave-background-radiation anisotropy on various angular scales are reviewed. Comparison is made with the predictions of the gravitational-instability theory of galaxy formation from primordial fluctuations in the very early universe. There is no entirely satisfactory theory that presently reconciles inflationary cosmology predictions of the flatness of the universe and of the scale-invariant primordial fluctuation spectrum with the limits on the amplitude of the anisotropy (δT/T), with the Virgo-cluster motion inferred from the dipole anisotropy, and with astronomical determinations of the cosmological density parameter.

Statistics of Cosmic Microwave Background Radiation with the Cosmic String Model

1997 ◽  
Vol 06 (05) ◽  
pp. 535-544
Author(s):  
Petri Mähönen ◽  
Tetsuya Hara ◽  
Toivo Voll ◽  
Shigeru Miyoshi
Keyword(s):  
Cosmic Microwave Background ◽  
Cosmic String ◽  
Large Scale ◽  
Background Radiation ◽  
Unit Length ◽  
Angular Size ◽  
Cosmic Microwave Background Radiation ◽  
Density Parameter ◽  
Microwave Background ◽  
Microwave Background Radiation

We have studied the cosmic microwave background radiation by simulating the cosmic string network induced anisotropies on the sky. The large-angular size simulations are based on the Kaiser–Stebbins effect calculated from full cosmic-string network simulation. The small-angular size simulations are done by Monte-Carlo simulation of perturbations from a time-discretized toy model. We use these results to find the normalization of μ, the string mass per unit length, and compare this result with one needed for large-scale structure formation. We show that the cosmic string scenario is in good agreement with COBE, SK94, and MSAM94 microwave background radiation experiments with reasonable string network parameters. The predicted rms-temperature fluctuations for SK94 and MSAM94 experiments are Δ T/T=1.57×10-5 and Δ T/T=1.62×10-5, respectively, when the string mass density parameter is chosen to be Gμ=1.4×10-6. The possibility of detecting non-Gaussian signals using the present day experiments is also discussed.

scholarly journals Contributions to the Local Gravitational Field from beyond the Local Supercluster

1987 ◽  
Vol 117 ◽  
pp. 435-443
Author(s):  
A. Yahil
Keyword(s):  
Gravitational Field ◽  
Background Radiation ◽  
Nonlinear Effects ◽  
Linear Perturbation ◽  
Density Parameter ◽  
Microwave Background ◽  
Dipole Component ◽  
Local Supercluster ◽  
Microwave Background Radiation ◽  
Linear Perturbation Theory

IRAS 60μ sources are used to map the local (≲200h−1 Mpc, Ho =100h km s−1 Mpc−1) gravitational field, and to determine its dipole component, on the assumption that the infrared radiation traces the matter. The dipole moment is found to point in the direction of the anisotropy of the microwave background radiation. Comparison of the two anisotropies, using linear perturbation theory, yields an estimate of the cosmological density parameter, Ω =0.85±0.16, with nonlinear effects increasing Ωo by ∼15%. The quadrupolar tidal field within the Local Supercluster, due presumably to the same density inhomogeneities, is detected in a kinematical study of the velocity field.

scholarly journals Small Scale Fluctuations in the Microwave Background Radiation Associated with the Formation of Galaxies

1977 ◽  
Vol 74 ◽  
pp. 327-334
Author(s):  
R. A. Sunyaev
Keyword(s):  
Spatial Distribution ◽  
Background Radiation ◽  
Gravitational Instability ◽  
Thomson Scattering ◽  
Small Scale ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Microwave Background Radiation ◽  
Expansion Of The Universe ◽  
The Universe

According to current ideas, massive extragalactic systems such as galaxies and clusters of galaxies formed as a result of the growth of small fluctuations in density and velocity which were present in the early stages of expansion of the Universe under the influence of gravitational instability. According to the hot model of the Universe at the epoch corresponding to a redshift z ≈ 1500, recombination of primaeval hydrogen took place and as a result the optical depth of the Universe to Thomson scattering decreased abruptly from about 1000 to 1 - the Universe became transparent. Therefore the observed angular distribution of the microwave background radiation (MWBR) contains information about inhomogeneities in its spatial distribution at a redshift z ∼ 1000. Silk (1968) was the first to note that this “photograph” of the Universe at the epoch of recombination must be enscribed with fluctuations associated with perturbations in the space density and velocity of motion of matter which will later lead to the formation of galaxies and clusters of galaxies.

scholarly journals Cosmic Strings and Galaxy Formation

1988 ◽  
Vol 130 ◽  
pp. 281-288
Author(s):  
Neil Turok
Keyword(s):  
Early Universe ◽  
Galaxy Formation ◽  
Particle Physics ◽  
Background Radiation ◽  
Big Bang ◽  
High Symmetry ◽  
Particle Spectrum ◽  
Microwave Background ◽  
Hubble Expansion ◽  
Microwave Background Radiation

The hot big bang theory of the early universe is rather well established. Among its successful predictions are the Hubble expansion, the microwave background radiation and the abundances of the light elements. It also fits in rather nicely with ideas from particle physics. According to these ideas (which are firmly based on experiment) at high energies particle interactions become more symmetrical and the apparently complicated particle spectrum today becomes very simple. It is an appealing notion that such a state of high symmetry was actually realised in the very early universe at very high temperatures, and the symmetry was broken as the universe expanded and cooled.

Cosmic Density Fluctuations, Magnetic Fields and Gravitational Waves

1997 ◽  
Vol 12 (15) ◽  
pp. 1069-1076 ◽  
Author(s):  
M. D. Pollock
Keyword(s):  
Galaxy Formation ◽  
Background Radiation ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Superstring Theory ◽  
Higher Derivative ◽  
Microwave Background Radiation ◽  
Dynamo Mechanism ◽  
Gravitational Wave Background ◽  
The Universe

It has previously been shown, for the heterotic superstring theory including higher-derivative terms ℛ2, how metric fluctuations, sufficient for galaxy formation in the Universe, arise as a consequence of the Heisenberg indeterminacy principle, applied to the dynamical auxiliary coordinate [Formula: see text] and its canonically conjugate momentum πξ, defined from the Friedmann space-time [Formula: see text]. This indeterminacy is distributed amongst the scalar, vector and tensor modes of the metric. Therefore, in addition to the fluctuations δρ/ρ in the matter, and in the cosmic microwave background radiation, there is a magnetic field, whose magnitude is estimated to agree approximately with the phenomenological value B c ~ 10-10 G required for the present-day intergalactic field (in the absence of a dynamo mechanism acting on a primordial field B s ≲ 10-17 G), and also a stochastic gravitational wave background, whose energy density must be bounded by the limit Ω gw ≲ 2.6×10-14h-2≈ 10-13 obtained by Krauss and White from the Sachs–Wolfe effect.

Galaxy formation after z = 1000

1980 ◽  
Vol 296 (1419) ◽  
pp. 289-298 ◽  
Keyword(s):  
Hierarchical Clustering ◽  
Galaxy Formation ◽  
Radiation Spectrum ◽  
Background Radiation ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Microwave Background Radiation ◽  
Looking Back

The 'hierarchical clustering’ and ‘pancake’ theories for galaxy formation are reviewed. In spite of the considerable difference between these two schemes it is difficult to offer observational tests that might discriminate whether galaxies or clusters of galaxies formed first. Recent observations of the microwave background radiation spectrum suggest that we may be looking back to the time of galaxy formation, and future isotropy measurements below 1 mm may provide vital clues.

Interpretation of anisotropy in the cosmic background radiation

1982 ◽  
Vol 307 (1497) ◽  
pp. 97-110 ◽  
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Background Radiation ◽  
Cosmic Background Radiation ◽  
Microwave Background ◽  
Cosmic Background ◽  
Microwave Background Radiation

We review mechanisms for producing temperature and polarization anisotropies in the microwave background radiation, and summarize their relation to the large-scale distribution of matter and to theories of galaxy formation. We also review possible sources of ambiguity in interpreting data, in particular the unknown opacity of the pregalactic gas and the possible contribution of discrete sources of radiation. Strategies for removing these ambiguities are discussed.

ON THE ORIGIN OF DENSITY FLUCTUATIONS IN THE UNIVERSE

1993 ◽  
Vol 08 (14) ◽  
pp. 1285-1290 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Background Radiation ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Superstring Theory ◽  
Scale Invariant ◽  
Order Unity ◽  
Microwave Background Radiation ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
The Universe

It has been shown by Harrison that quantum fluctuations of the metric at the Planck era lead to a scale-invariant spectrum of density fluctuations ξ ≡ δρ/ρ at all subsequent times of the expansion of a Friedmann universe, irrespective of whether there is inflation. For the vacuum Einstein theory, ξ is of order unity, and thus is too large. But for the dimensionally reduced, heterotic superstring, ξ ≈ πfα/M P ≈ 6 × 10−4, where M P is the Planck mass and fa ≈ 2 × 10−4M P is the axion decay constant. This result is in approximate agreement with the observations of the temperature fluctuations in the cosmic microwave background radiation by COBE, δT/T ≈ 6 × 10−6, and thus constitutes evidence in favor of the superstring theory.

scholarly journals Galaxy Formation and Evolution: What to Expect from Hierarchical Clustering Models

1996 ◽  
Vol 171 ◽  
pp. 247-254 ◽  
Author(s):  
C.S. Frenk ◽  
C.M. Baugh ◽  
S. Cole
Keyword(s):  
Dark Matter ◽  
Hierarchical Clustering ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Background Radiation ◽  
Gravitational Instability ◽  
Density Fluctuations ◽  
Galaxy Formation And Evolution ◽  
Microwave Background Radiation

In hierarchical clustering theories of galaxy formation, galaxies form by gas cooling and condensing into dark matter halos which, in turn, form by a hierarchy of mergers (White & Rees 1978). The context in which this process takes place is specified by a cosmological model that determines the spectrum of primordial density fluctuations and the rate at which they grow by gravitational instability. The best known example of such a model is the cold dark matter (CDM) model (see Frenk 1991 for a review), but a number of alternatives (mostly variants of CDM), have recently become popular in response to new data on large-scale structure and the COBE detection of anisotropies in the microwave background radiation.

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