Linear sizes and arm asymmetry of intrinsically symmetric doubles

Abstract

In an intrinsically symmetric model, the distribution px(x) of the fractional arm differences x of a sample of straight double radio sources reflects the distribution among the doubles of their orientations away from the line of sight. In a constant speed expansion model, the two distributions can be simply related, and the resultant distribution pl(l) of the projected linear sizes l can be derived, to be compared with the observed sitribution for the same sample. Such a calculation is illustrated using a sample of extended doubles. The model is perhaps more applicable to compact doubles. However, these are not yet numerous enough to construct usable samples.