Intergalactic Matter and Radiation

Abstract

Abstract. This paper presents a critical discussion of our present knowledge of intergalactic matter and radiation as it relates to cosmology. While there have been some observational successes and much theoretical speculation, studies of intergalactic matter and radiation have still not allowed us to draw certain conclusions about the origin and evolution of the universe.One of the most important quantities which we need to detect and understand from the point of observational cosmology is the total amount of matter and radiation in the universe. We are able to detect comparatively easily the discrete sources which emit electromagnetic radiation, but it would be very rash to assume that these are all that are present in the universe.Other components which may be present are: Knowledge of the relative importance of these different components can certainly be expected to increase our understanding (or, more appropriately, decrease our ignorance by a small amount) concerning the formation and evolution of galaxies and other condensed objects. If we could make a direct estimate of the total massenergy density of all of these components, Q C9 this could be directly used to restrict the possible cosmological models, the point being that, in the Friedman models and in the steady-state models, Q C is directly related to the other cosmological parameters H 0 , A, q 0 by the relations

How dark matter came to matter

“…These had been produced by considering familiar luminous matter and typically yielded a mass density of the universe of the order of ∼ 10 −31 g/cm −3 . 79,80,85,89,90 This value was two orders of magnitude lower than the critical density necessary to close the universe. So, the visible mass density (ρ) of galaxies could be only a small fraction of the density needed to close the universe: Ω = ρ/ρ c ∼ 0.01.…”

“…The amount of matter in the universe was "[o]ne of the most important quantities" to detect and understand, Geoffrey Burbidge stated in 1970. 85 Similarly, Dennis Sciama emphasized the "key role" of knowing the overall mean density of the universe in his 1971 textbook. 69 Yet, not only direct observations drove subsequent developments.…”

Closing in on the Cosmos: Cosmology's Rebirth and the Rise of the Dark Matter Problem

“…Such mass would ultimately vindicate Mach's principle 35 See e.g. Oort (1958); Peebles (1971); Shapiro (1971); Noonan (1971); Weinberg (1972), p. 478;Burbidge (1972), p. 493. The critical density is ρ c = 3H 2 8πG ∼ 10 −29 gr.…”