Alignment of radio and optical orientations in high-redshift radio galaxies

Abstract

The results of a VLA (Very Large Array) radio and CCD (charge-coupled device) optical imaging survey of ultra-steep spectrum radio sources confirm their association with faint and presumably distant galaxies. These galaxies have an almost universal alignment between the major axis of the optical emission and the radio axis. The alignment is far more significant than the known opposite tendency for optically bright radio sources to be aligned with the minor axis of giant elliptical galaxies1–3. Such a strong relationship between the radio emission and the large-scale optical properties of the galaxies suggests that high-redshift radio galaxies are fundamentally different from their low-redshift counterparts. This has important consequences for current ideas on the nature of high-redshift radio galaxies and the cosmological work based upon them.