An Examination of the Steady-state Model in the Light of Some Recent Observations of Radio Sources

Abstract

The results of some recent observations of radio sources have been used to investigate the “luminosity function” for the sources. Without making any assumptions about their nature, it can be shown from radio observations alone that most of the sources lying in any given range of flux density are extra-galactic with an emission at 178 Mc/s which exceeds 10 ²⁴ watts (c/s) ⁻¹ ster ⁻¹ . If it is assumed either that the physical dimensions or that the optical luminosities of the sources are comparable with those of the Galaxy, then the emission must lie in the range 3 × 10 ²⁵ –10 ²⁷ watts (c/s) ⁻¹ ster ⁻¹ . From these figures it is possible to derive the expected number-flux density relationship according to different cosmological models and special consideration has been given to the predictions of the steady-state model. With the new Cambridge interferometer it has become possible to observe sources considerably weaker than those reached in earlier surveys, and hence to make a more accurate determination of the actual number-flux density relationship; the new data has also allowed more detailed corrections for the effects of extended sources and source clustering to be made. A comparison of these observational results with those predicted by the steady-state model shows a marked discrepancy, the number of sources observed with a flux density in the range 0.5 to 2 × 10 ⁻²⁶ watts (c/s) ⁻¹ m ⁻² being at least 3 ± 0.5 times that predicted by the model. No attempt has been made to select an alternative model to account for the observations, but the results appear to provide conclusive evidence against the steady-state model.