Beamed ionizing radiation in radio galaxies

Abstract

The extended emission line regions (EELR) that are common around radio galaxies and quasars offer the possibility of detecting blazar beams when they are not pointing along the line of sight. In low redshift radio galaxies (z < 0.6) there are several indications, although as yet no firm proof, that the ionizing radiation field is anisotropic. These include the general tendency for the emission line structures to be aligned along the radio axis, and the fact that a power-law extrapolation of the nuclear continuum is not capable of ionizing some radio axis EELR. In the particular case of PKS 2152-69, the properties of a high ionization cloud 8 kpc from the nucleus are most consistent with a beaming/scattering model. Such a model may also be relevant to the high redshift (z > 0.6) radio galaxies which show even closer alignments between radio and emission line and optical/UV continuum structures. Potentially, observations of the EELR will allow us to place constraints on properties like the opening angle, power and spectrum of blazar beams.KeywordsEmission LineRadio GalaxyHigh RedshiftWollaston PrismLower Radio PowerThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.