The Background Radiation in a Milne Universe.
Abstract
The flux density from all unresolved galaxies in the universe is considered. Calculation of this quantity depends on the luminosity function and the spectrum function of the sources and also on the general motion of recession. It is shown that the spectrum function and the model of the universe must be given a priori if the calculation is to be possible. The particular spectrum functions discussed here imply uniformity of radiating sources; Milne's model of the universe is selected so as to include recessional, and omit gravitational, effects. For radio sources the spectrum is assumed to be proportional to an inverse power of the frequency. The total flux density is computed for a Milne universe and compared with that from a partly filled static Newtonian universe. Comparison with observation leads to the radio power per unit volume emitted by sources in a Milne universe. For optical sources a black-body spectrum is assumed. Very distant galaxies whose optical radiation is red-shifted to radio frequencies contribute a negligible amount to the radio flux density. The possibility and problems of observing the background flux density from the universe at optical frequencies are also discussed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1959
- DOI:
- 10.1086/146688
- Bibcode:
- 1959ApJ...130....1M