Observations of OE323(4C34.13), MO758+120, and OS210(4C28.40) with the 5-km telescope

Abstract

FOUR extended radio sources identified with quasars of large redshift have been observed¹, they are important in defining the relationship between mean radio angular diameter and redshift and thus limiting the permissible range of q₀ and cosmological evolution of the radio source population. A difficulty with such analyses is that of allowing for the variation of the physical sizes of individual sources with time, particularly if there are different types of source present in the sample. The ideal would be to restrict the analysis to a single type with a comparatively small range of the relevant properties. We have, therefore, mapped three of the four sources—those accessible to the 5-km telescope—in order to study their structures with greater angular resolution and a better beam shape. We have also re-measured the optical positions of the associated quasars from the prints of the Palomar Sky Survey. Our results remove the positional discrepancy for MO758+120 (ref. 1) and confirm the association of an optical quasar with each of the radio sources. The suggestion that the optical and radio positions of MO758+120 (ref. 3) had been accidentally interchanged seems to be incorrect, since our optical position agrees with that given by Baldwin et al.³ to within 0.25 arc s.