Small-scale angular fluctuations in the microwave background radiation and the existence of isolated large-scale structures in the universe

1985 ◽  
Vol 293 ◽  
pp. 17 ◽  
Author(s):  
L. J. Goicoechea ◽  
J. L. Sanz
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Small Scale ◽  
Microwave Background ◽  
Large Scale Structures ◽  
Microwave Background Radiation ◽  
Scale Structures ◽  
The Universe

Observational and astrophysical cosmology: 1940–1980

2019 ◽  
pp. 205-244
Author(s):  
Malcolm S. Longair
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Second World War ◽  
Field Equations ◽  
Microwave Background ◽  
Cosmological Time ◽  
Large Scale Structures ◽  
Microwave Background Radiation ◽  
Second World ◽  
The Universe

Following the pioneering studies of galaxies and the universe during the pre-Second World War years, the period 1940-1980 saw the consolidation of the observational and theoretical basis of geometrical and astrophysical cosmology. By the early 1950s, the cosmological time-scale problem had been resolved by Baade’s recalibration of the Cepheid distance scale, but new disputes arose about the best estimate of Hubble’s constant, the value of the deceleration parameter and the presence or otherwise of the cosmological constant in the cosmological field equations. The evolution of the contents of the universe was established by radio astronomical observations of active galaxies and, most spectacularly, by the discovery of the cosmic microwave background radiation. The latter enabled the problems of the origin of galaxies and large scale structures in the universe to be placed on a secure physical basis, but many issues remained unresolved, including the dark matter problem.

scholarly journals Constraints on the mean density of the Universe which follow from the theories of adiabatic and whirl perturbations

1978 ◽  
Vol 79 ◽  
pp. 404-405
Author(s):  
A. A. Kurskov ◽  
L. M. Ozernoy
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Small Scale ◽  
Microwave Background ◽  
Scale Temperature ◽  
Microwave Background Radiation ◽  
Initial Spectrum ◽  
Density Perturbations ◽  
The Mean ◽  
The Universe

The aim of this communication is to investigate what constraints to the cosmological parameter Ω = 2qO can be obtained if one assumes that primaeval whirl motions or adiabatic density perturbations with an appropriate initial spectrum were responsible for the formation of large scale structure in the Universe. These constraints are readily obtained from the two conditions: (i) an upper limit to small scale temperature fluctuations of the microwave background radiation, and (ii) the requirement that the primaeval perturbations should be large enough in order to produce observed structures.

scholarly journals Fluctuations of the Microwave Background Radiation

1978 ◽  
Vol 79 ◽  
pp. 393-404
Author(s):  
R. A. Sunyaev
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Small Scale ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
X Ray ◽  
M 10 ◽  
Microwave Background Radiation ◽  
Density Perturbations ◽  
The Universe

Investigations of small scale angular fluctuations and the spectrum of the microwave background radiation is one of the main methods of studying the large scale structure of the Universe. Figure 1 shows the principal stages of the evolution of the Universe. Today we can directly observe galaxies, clusters of galaxies and quasars in the redshift range z ≤ 3.5 by optical, radio and X-ray astronomy. These observations show that significant density perturbations δρ/ρ > 1 are present on mass scales M < 1016 M⊙. the Universe is essentially uniform δρ/ρ < 1 on large scales M ≫ 1016 M⊙.

The TopHat Cosmic Microwave Background Anisotropy Experiment

2005 ◽  
Vol 201 ◽  
pp. 65-70
Author(s):  
Robert F. Silverberg ◽  
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Background Radiation ◽  
High Sensitivity ◽  
Microwave Background ◽  
Long Duration ◽  
Cosmic Microwave Background Anisotropy ◽  
Microwave Background Radiation ◽  
The Universe ◽  
Large Scale Structure Formation

We have developed a balloon-borne experiment to measure the Cosmic Microwave Background Radiation anisotropy on angular scales from ˜50° down to ˜20′. The instrument observes at frequencies between 150 and 690 GHz and will be flown on an Antarctic circumpolar long duration flight. To greatly improve the experiment performance, the front-end of the experiment is mounted on the top of the balloon. With high sensitivity, broad sky coverage, and well-characterized systematic errors, the results of this experiment can be used to strongly constrain cosmological models and probe the early stages of large-scale structure formation in the Universe.

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 Large Scale Anisotropy of the Cosmic Microwave Background

1974 ◽  
Vol 63 ◽  
pp. 157-162 ◽  
Author(s):  
R. B. Partridge
Keyword(s):  
Angular Distribution ◽  
Large Scale ◽  
Background Radiation ◽  
Big Bang ◽  
Microwave Background ◽  
Initial State ◽  
Microwave Background Radiation ◽  
Cosmological Data ◽  
The Big Bang ◽  
The Universe

It is now generally accepted that the microwave background radiation, discovered in 1965 (Penzias and Wilson, 1965; Dicke et al., 1965), is cosmological in origin. Measurements of the spectrum of the radiation, discussed earlier in this volume by Blair, are consistent with the idea that the radiation is in fact a relic of a hot, dense, initial state of the Universe – the Big Bang. If the radiation is cosmological, measurements of both its spectrum and its angular distribution are capable of providing important – and remarkably precise – cosmological data.

scholarly journals Large-Scale Anisotropy of the Cosmic Relic Radiation in Spatially Open Cosmological Models

1983 ◽  
Vol 104 ◽  
pp. 149-152
Author(s):  
V. N. Lukash
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Microwave Background ◽  
Spatial Homogeneity ◽  
Sensitive Tool ◽  
Microwave Background Radiation ◽  
Universal Expansion ◽  
Celestial Sphere ◽  
The Universe ◽  
Small Anisotropy

The observed microwave background radiation is a sensitive tool for studying the fundamental features of the universe. A puzzling constancy on the celestial sphere of the temperature, T, of the equilibrium relic radiation coming to us from causally nonrelated regions of space-time points to the global spatial homogeneity and isotropy of the cosmological expansion. On the other hand, a small anisotropy of the relic background can tell a lot about the physics of the beginning of the universal expansion, where primordial cosmological perturbations, which later affect the relic isotropy, formed (see, e.g., [1,2] and other reviews on the early universe). We would like to emphasize another factor that forms mainly the large-scale structure of relic anisotropy: the spatial curvature of the background Friedmann Universe. In the light of the discovery of the large-scale anisotropy of the cosmic radiation [3–5], this problem becomes very important.

scholarly journals Deep learning for Sunyaev–Zel’dovich detection in Planck

2020 ◽  
Vol 634 ◽  
pp. A81
Author(s):  
V. Bonjean
Keyword(s):  
Deep Learning ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Galaxy Cluster ◽  
Proof Of Concept ◽  
Microwave Background ◽  
Large Scale Structures ◽  
Hot Gas ◽  
Scale Structures ◽  
The Universe

The Planck collaboration has extensively used the six Planck HFI frequency maps to detect the Sunyaev–Zel’dovich (SZ) effect with dedicated methods, for example by applying (i) component separation to construct a full-sky map of the y parameter or (ii) matched multi-filters to detect galaxy clusters via their hot gas. Although powerful, these methods may still introduce biases in the detection of the sources or in the reconstruction of the SZ signal due to prior knowledge (e.g. the use of the generalised Navarro, Frenk, and White profile model as a proxy for the shape of galaxy clusters, which is accurate on average but not for individual clusters). In this study, we use deep learning algorithms, more specifically, a U-net architecture network, to detect the SZ signal from the Planck HFI frequency maps. The U-net shows very good performance, recovering the Planck clusters in a test area. In the full sky, Planck clusters are also recovered, together with more than 18 000 other potential SZ sources for which we have statistical indications of galaxy cluster signatures, by stacking at their positions several full-sky maps at different wavelengths (i.e. the cosmic microwave background lensing map from Planck, maps of galaxy over-densities, and the ROSAT X-ray map). The diffuse SZ emission is also recovered around known large-scale structures such as Shapley, A399–A401, Coma, and Leo. Results shown in this proof-of-concept study are promising for potential future detection of galaxy clusters with low SZ pressure with this kind of approach, and more generally, for potential identification and characterisation of large-scale structures of the Universe via their hot gas.

DYNAMICS OF FERROMAGNETIC WALLS: GRAVITATIONAL PROPERTIES

2005 ◽  
Vol 14 (03n04) ◽  
pp. 521-541 ◽  
Author(s):  
L. CAMPANELLI ◽  
P. CEA ◽  
G. L. FOGLI ◽  
L. TEDESCO
Keyword(s):  
Domain Wall ◽  
Large Scale ◽  
Domain Walls ◽  
Background Radiation ◽  
Ideal Gas ◽  
Microwave Background ◽  
Electroweak Phase Transition ◽  
Microwave Background Radiation ◽  
The Universe ◽  
Negligible Contribution

We discuss a new mechanism which allows domain walls produced during the primordial electroweak phase transition. We show that the effective surface tension of these domain walls can be made vanishingly small due to a peculiar magnetic condensation induced by fermion zero modes localized on the wall. We find that in the perfect gas approximation the domain wall network behaves like a radiation gas. We consider the recent high-red shift supernova data and we find that the corresponding Hubble diagram is compatible with the presence in the Universe of an ideal gas of ferromagnetic domain walls. We show that our domain wall gas induces a completely negligible contribution to the large-scale anisotropy of the microwave background radiation.

scholarly journals DIVISION VIII: GALAXIES AND THE UNIVERSE

2008 ◽  
Vol 4 (T27A) ◽  
pp. 283-285
Author(s):  
Sadanori Okamura ◽  
Elaine Sadler ◽  
Francesco Bertola ◽  
Mark Birkinshaw ◽  
Françoise Combes ◽  
...  
Keyword(s):  
Computer Simulations ◽  
Large Scale ◽  
Background Radiation ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Wide Range ◽  
Microwave Background Radiation ◽  
The Universe

Division VIII provides a focus for astronomers studying a wide range of problems related to galaxies and cosmology. Objects of the study include individual galaxies, groups and clusters of galaxies, large scale structure, comic microwave background radiation and the universe itself. Approaches are diverse from observational one to theoretical one including computer simulations.

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