Measurements of circular polarization in 13 radio sources at λ21 cm are presented, and are compared with similar measurements at λ49 cm. Quasars appear to have polarization if opaque by synchrotron self-absorption, but not if transparent. The degree of polarization does not vary with wavelength in the theoretically expected manner.
No takes yet. Share an insight, caveat, or question.
Conway et al. (1971) studied this question.