Abstract
The frequent occurrence of extranuclear emission line regions in radio galaxies and quasars is well known1,2, but the origin and excitation of gas at temperatures of (l–2) × 104 K, extending to distances beyond 100 kpc from the nucleus, are not understood in detail. In some cases there is evidence that highly excited gas is associated with the transport of energy from the active nucleus of the galaxy out to the extended radio structures, and in one such case, the radio galaxy PKS2152–69, Tadhunter et al.3 reported a blue continuum source coincident with the highest ionization region of a gas cloud, at a projected distance of 8 kpc from the nucleus and lying approximately along the radio axis. Here we report optical observations of the continuum showing that its spectrum rises into the near ultraviolet with fv∝v3±1 and that its degree of polarization is about 10% with the electric vector perpendicular to the radius vector from the nucleus. In the absence of a workable intrinsic emission mechanism, we propose that a beamed nuclear source could excite the highly ionized extranuclear cloud and scatter off associated dust to produce the observed continuum.
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di Serego Alighieri, S., Binette, L., Courvoisier, TL. et al. A blue, polarized continuum source near radio galaxy PKS2152–69. Nature 334, 591–593 (1988). https://doi.org/10.1038/334591a0
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DOI: https://doi.org/10.1038/334591a0
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