Morphological Evolution of Radio Galaxies

Abstract

Powerful radio galaxies are unique at the present time in that they have optically resolvable structures that can observed over a range of look-back times comparable to the Hubble time. This allows us to examine how their morphologies evolve with cosmic time in their stellar continuum, thermal line-emitting gas, and non-thermal synchrotron emitting plasmas. The continuum shapes of high redshift radio galaxies become more elongated at high redshift and are closely aligned with their radio source axes. The extended emission line regions were larger and more luminous in the past and they too are well aligned with their radio source axes. Finally, the radio sources themselves were more asymmetric in the past both in terms of their structures and in the flux densities, spectral indices and polarization of the diffuse lobes.