Cosmology, Black-Body Radiation, and the Diffuse X-Ray Background

1967 ◽  
Vol 150 ◽  
pp. L61 ◽  
Author(s):  
K. Brecher ◽  
P. Morrison
Keyword(s):  
Black Body ◽  
Black Body Radiation ◽  
X Ray ◽  
X Ray Background

scholarly journals The X-Ray Background in Isotropic World Models

1969 ◽  
Vol 22 (4) ◽  
pp. 521 ◽  
Author(s):  
AD Payne
Keyword(s):  
Characteristic Time ◽  
Cosmic Ray ◽  
Black Body ◽  
Black Body Radiation ◽  
Fast Electrons ◽  
X Ray ◽  
Intergalactic Space ◽  
Source Spectra ◽  
X Ray Background ◽  
The Universe

This paper is an attempt to describe the diffuse X-ray background in terms of Compton radiation from cosmic ray electrons in intergalactic space. Similarities between the X-ray and radio source spectra suggest that fast electrons escape more or less freely from radio galaxies. It is assumed that the time scale of electron injection is small compared with the characteristic time of evolution of the universe. The electrons are considered to lose energy through Compton scattering (due to the presence of the universal black-body radiation at 3�K) and by expansion of the coordinate system.

scholarly journals Origin of the cosmic X-ray background: (Invited discourse)

1970 ◽  
Vol 37 ◽  
pp. 352-371
Author(s):  
G. Setti ◽  
M. J. Rees
Keyword(s):  
Energy Band ◽  
Black Body ◽  
Relativistic Electrons ◽  
Intergalactic Gas ◽  
Satisfactory Explanation ◽  
X Ray ◽  
The Galaxy ◽  
Simple Extrapolation ◽  
X Ray Background ◽  
Natural Way

In this paper we review the theories which have been proposed to account for the extra-galactic X-ray background. Although there is still no detailed theory, one may devise reasonable models which account in a natural way both for the intensity and the spectral shape over the whole energy band, provided that cosmological evolutionary effects are included. A model based on Compton scattering of cosmic black body photons by relativistic electrons in radio sources at large redshifts (z ≳ 4) seems to give the most satisfactory explanation. However, the data are not yet good enough to discriminate against alternative models.A discussion of the recent observations in the soft X-ray region (< 1 keV), and their relevance to the physics of interstellar and intergalactic gas, is given. The available data are somewhat confusing, but it seems that this part of the spectrum may still be consistent with a simple extrapolation of the non-thermal spectrum at higher energies, though various workers have claimed the detection of a new component probably due to hot intergalactic gas. If this interpretation is correct one may deduce interesting conclusions about the state of ionization and composition of the intergalactic gas, because of the importance of the absorption effects in this energy band.Also it appears that the Galaxy is more transparent than one would deduce from 21-cm observations. However, due to the lack of observational data, no firm conclusions can be reached.

scholarly journals Cosmic X-Rays and Interstellar Dust

1973 ◽  
Vol 52 ◽  
pp. 283-296
Author(s):  
Satio Hayakawa
Keyword(s):  
Interstellar Dust ◽  
Black Body ◽  
Ionization Rate ◽  
Black Body Radiation ◽  
Relativistic Energy ◽  
X Rays ◽  
Dust Grains ◽  
X Ray ◽  
Interstellar Dust Grains ◽  
Celestial Sphere

Observational results of cosmic diffuse X-rays are reviewed with particular emphasis on soft X-rays. The intensity distribution of soft X-rays over the celestial sphere indicates that the diffuse component of soft X-rays consists of an extra-galactic and a galactic component. The absorption of the soft X-rays in the interstellar medium results in heating and ionization of interstellar matter. The ionization rate by X-rays is estimated as about 10–16 s–1 per H atom.The scattering of X-rays by interstellar dust grains produces a halo of an X-ray source and smears out the pulsation of X-ray emission. The scattering coefficient and the halo size are given for some typical grain models.The possibility that the dust grains gain relativistic energy is suggested. It is speculated that the relativistic dust grains in metagalactic space may be responsible for cosmic rays of ultrahigh energies and also for the diffuse X-rays by the interactions with cosmic black-body radiation.

Interpretation of the cosmic X-ray background

1969 ◽  
Vol 313 (1514) ◽  
pp. 349-355 ◽  
Keyword(s):  
Emission Measure ◽  
Black Body ◽  
High Energy ◽  
Relativistic Electrons ◽  
Intergalactic Gas ◽  
X Ray ◽  
Carbon And Nitrogen ◽  
The Galaxy ◽  
The Status ◽  
X Ray Background

Recent work on the X-ray background is reviewed. The most attractive explanation of the high energy background (> 1 keV) is Compton collisions between cosmic black body photons and relativistic electrons in radio sources of large red shift (~ 5). The recently discovered low energy background (~ 0.25 keV) may have the same origin, or be due to emission from either a dense (about 10 atoms m -3 ) hot (about 0.5 MK) intergalactic gas or to a more local hot gas with an emission measure ~ 1 cm -6 pc. Absorption effects are important at 0.25 keV, and one may be able to draw significant conclusions about hydrogen, helium, carbon and nitrogen in the intergalactic gas. The status of absorption in the Galaxy is confused.

Ariel 5 hard X-ray measurements of galactic and extragalactic X-ray sources

1976 ◽  
Vol 350 (1663) ◽  
pp. 521-545 ◽  
Keyword(s):  
Crab Nebula ◽  
Black Body ◽  
Black Body Radiation ◽  
Photon Flux ◽  
Galactic Centre ◽  
Coma Cluster ◽  
X Ray ◽  
Inverse Compton ◽  
Photon Acceleration ◽  
Data Yield

The paper surveys the hard X-ray measurements obtained from the Ariel-5 CsI crystal scintillator detector, 8 cm 2 area, 4 cm thick, f. w. h. m. 8 0 and energy range 26 keV to 1.2 MeV. Implications arising from the pre-launch laboratory calibration of the instrument in connection with radioactivity corrections to previous satellite results are briefly mentioned. Various post-launch results are then discussed. Upper limits to the Coma cluster flux are given out to 800 keV and, together with radio data, yield a halo field <̃ 10 -12 T (10 -8 G). The hard flux from near the galactic centre is probably 60 % from GCX and 40 % from GX3 + 1. Crab Nebula data is consistent with an E -2.1 differential power law for photon flux. Combined proportional counter and scintillator data on the transient A1118-61 near Cen X-3 and measurements on the very intense transient A0535 + 26 in Taurus are consistent with multi-layer sources with layer temperatures varying from 3 to 13 keV while Her X-1 during its ‘on’ state appears to shine by modified black-body radiation at 13 keV. The Cyg X-1 transition on 9 May, 1975 is examined in detail and although most variation in intensity occurred at <̃ 25 keV, some harder X-ray change in anti-phase with the soft photons appeared to occur. These changes are discussed in terms of an inverse-Compton photon acceleration model. The spectral shape of A0620-00 is considered in relation to the possibility that it is a black hole.

The Physical World

2017 ◽  
Author(s):  
Nicholas Manton ◽  
Nicholas Mee
Keyword(s):  
Quantum Mechanics ◽  
Particle Physics ◽  
Variational Principles ◽  
Black Body ◽  
Black Body Radiation ◽  
Physical World ◽  
Atomic Scale ◽  
Solid State Physics ◽  
Least Action ◽  
Dimensional Spacetime

The book is an inspirational survey of fundamental physics, emphasizing the use of variational principles. Chapter 1 presents introductory ideas, including the principle of least action, vectors and partial differentiation. Chapter 2 covers Newtonian dynamics and the motion of mutually gravitating bodies. Chapter 3 is about electromagnetic fields as described by Maxwell’s equations. Chapter 4 is about special relativity, which unifies space and time into 4-dimensional spacetime. Chapter 5 introduces the mathematics of curved space, leading to Chapter 6 covering general relativity and its remarkable consequences, such as the existence of black holes. Chapters 7 and 8 present quantum mechanics, essential for understanding atomic-scale phenomena. Chapter 9 uses quantum mechanics to explain the fundamental principles of chemistry and solid state physics. Chapter 10 is about thermodynamics, which is built around the concepts of temperature and entropy. Various applications are discussed, including the analysis of black body radiation that led to the quantum revolution. Chapter 11 surveys the atomic nucleus, its properties and applications. Chapter 12 explores particle physics, the Standard Model and the Higgs mechanism, with a short introduction to quantum field theory. Chapter 13 is about the structure and evolution of stars and brings together material from many of the earlier chapters. Chapter 14 on cosmology describes the structure and evolution of the universe as a whole. Finally, Chapter 15 discusses remaining problems at the frontiers of physics, such as the interpretation of quantum mechanics, and the ultimate nature of particles. Some speculative ideas are explored, such as supersymmetry, solitons and string theory.

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