Where Have All the Old Radio Sources Gone?

Extragalactic radio sources are generally assumed to be produced by jets which transport energy and momentum from a nuclear source to the extended raido lobes. This model is well defined for Type II sources, and makes specific predictions for the evolution of the size and radio power of these sources. In this paper I test these predictions against the statistics of complete samples of Type II source. I find the size distribution can plausibly be explained by a Gaussian distribution of intrinsic jet power; but the luminosity distribution cannot be explained by any simple model of the relativistic electron population. In particular, many old sources should still be luminous, predicting a large, steep-sectrum population which does not exist in the sky. This is the ``old source problem''.

¹NMT

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