scholarly journals Astronomical Signatures of Dark Matter

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Paul Gorenstein ◽  
Wallace Tucker
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Background Radiation ◽  
Electromagnetic Spectrum ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Solar Mass ◽  
Rotation Rates ◽  
Microwave Background Radiation ◽  
Unambiguous Detection

Several independent astronomical observations in different wavelength bands reveal the existence of much larger quantities of matter than what we would deduce from assuming a solar mass to light ratio. They are very high velocities of individual galaxies within clusters of galaxies, higher than expected rotation rates of stars in the outer regions of galaxies, 21 cm line studies indicative of increasing mass to light ratios with radius in the halos of spiral galaxies, hot gaseous X-ray emitting halos around many elliptical galaxies, and clusters of galaxies requiring a much larger component of unseen mass for the hot gas to be bound. The level of gravitational attraction needed for the spatial distribution of galaxies to evolve from the small perturbations implied by the very slightly anisotropic cosmic microwave background radiation to its current web-like configuration requires much more mass than is observed across the entire electromagnetic spectrum. Distorted shapes of galaxies and other features created by gravitational lensing in the images of many astronomical objects require an amount of dark matter consistent with other estimates. The unambiguous detection of dark matter and more recently evidence for dark energy has positioned astronomy at the frontier of fundamental physics as it was in the 17th century.

scholarly journals Dragging Force on Galaxies Due to Streaming Dark Matter

1990 ◽  
Vol 124 ◽  
pp. 645-649
Author(s):  
Tetsuya Hara ◽  
Shigeru Miyoshi
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Rest Frame ◽  
Background Radiation ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
The Galaxy ◽  
Microwave Background Radiation ◽  
The Universe

It has been reported that galaxies in large regions (~102Mpc), including some clusters of galaxies, may be streaming coherently with velocities up to 600km/sec or more with respect to the rest frame determined by the microwave background radiation.) On the other hand, it is suggested that the dominant mass component of the universe is dark matter. Because we can only speculate the motion of dark matter from the galaxy motions, much attention should be paid to the correlation of velocities between the observed galaxies and cold dark matter. So we investigate whether such coherent large-scale streaming velocities are due to dark matter or only to baryonic objects which may be formed by piling up of gases due to some explosive events.

scholarly journals The Microwave Background from Cambridge

1986 ◽  
Vol 7 ◽  
pp. 325-331
Author(s):  
Richard Saunders
Keyword(s):  
Background Radiation ◽  
Black Body ◽  
Private Communication ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Simple Theories ◽  
Microwave Background Radiation ◽  
Hard Evidence ◽  
Unambiguous Detection

Microwave background astronomy has arrived. Largely because of improvements in receivers, the last three years have seen the emergence of agreement concerning important measurements of the microwave background radiation (MBR):– hard evidence that the MBR has a black-body spectrum (see Smoot in these proceedings);– the unambiguous detection of the Sunyaev-Zeldovich decrement in clusters of galaxies (Birkinshaw et al 1984), and indeed profiles of the decrement across clusters (Birkinshaw in these proceedings);– the lack of anisotropy in the MBR temperature T on scales of a few arcmin down to ΔT/T˜5×10-5 (Uson & Wilkinson 1984; Readhead, private communication) and the consequent elimination of simple theories of adiabatic primordial fluctuations.

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 Measurements of the Scattering of the Microwave Background Radiation in Clusters of Galaxies

1980 ◽  
Vol 92 ◽  
pp. 313-319
Author(s):  
M. Birkinshaw
Keyword(s):  
Background Radiation ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Microwave Background Radiation

Results for the decrements in the microwave background radiation towards the centres of 13 clusters of galaxies are presented. It is shown that these data imply central gas densities of about 2 × 10−24 kg m−3 and cluster masses of about 5 × 1045 kg.

scholarly journals Hot Electrons and Cold Photons: Galaxy Clusters and the Sunyaev-Zel'dovich Effect

1998 ◽  
Vol 188 ◽  
pp. 189-192
Author(s):  
J.P. Hughes
Keyword(s):  
Background Radiation ◽  
Hubble Constant ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Hot Gas ◽  
Wide Range ◽  
Inverse Compton ◽  
Microwave Background Radiation ◽  
Sunyaev Zel'dovich Effect ◽  
Bremsstrahlung Emission

The hot gas in clusters of galaxies emits thermal bremsstrahlung emission that can be probed directly through measurements in the X-ray band. Another probe of this gas comes from its effect on the cosmic microwave background radiation (CMBR): the hot cluster electrons inverse Compton scatter the CMBR photons and thereby distort the background radiation from its blackbody spectral form. Although this, the Sunyaev-Zel'dovich (SZ) effect, is quite small, heroic efforts during the 1980's resulted in its detection in three moderately distant clusters of galaxies: A665, A2218, and CL 0016+16. It is well known that one of the purposes of conducting such measurements is to determine the Hubble constant. The technique has generated considerable interest because it is independent of all other rungs of the cosmic distance ladder and is effective over a wide range of redshifts: ~0.02 to ~1.

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