DOUBLE SOURCE STRUCTURE

A comparison of the optical and radio maps of the same region of the sky shows that for many quasars, there are radio sources in their vicinity. Morphologically, these sources can be broadly divided in the following two classes (Miley) :

D - A double source consisting of two well-separated regions. There are two sub-classes,
- D1 - A double source with neither of its components coincident with the optical quasar (3C 47 is a well known example of this class)
- D2 - A double source for which one of its components coincides with the optical quasar.
C - A complex source consisting of three of more components.

A majority of quasars belong to the D class. The fact that such radio sources occur in close proximity to quasars on the two dimensional map of the sky is usually taken to imply that these sources are associated with quasars. According to the cosmological folklore, such double sources are supposed to occur only with quasars or radio - galaxies . In fig 7(a), we show 3C 47 (Ryle), the + denotes a quasar, and in Fig.7(b), we show 3C 435 (Mackay), the + denotes a galactic star (Wlerick and Veron). The similarity between the two cases is obvious. The evidence for the association of 3C 435 with the star in the middle is as good (or as bad) as that of 3C 47 with the quasar in the middle. There are at least two others stars, Sco X-1 and AD Leo, which are flanked by double radio sources.

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