Figure 19

Figure 19

Images of the Stokes I(a), Q(b), and U(c) V-band fluxes from the high redshift radio galaxy (HZRG) 3C 256 (z=1.8). For all images North is up, East is to the left. The field of view of each displayed image is 15.5" by 18.13". Jannuzi et al (1995) obtained these images of the total and polarized emission during two nights of observation with the KPNO 4-m Mayall telescope. Spatially extended linearly polarized (rest frame) emission is clearly detected. The degree of polarization of the observed radiation ranges between 11 and 16% with uncertainties of order 2%. The fact that polarized emission appears only in the U Stokes image indicates that the position angle of the polarized emission is orthogonal to the major axis of the galaxy, which is itself aligned with the extended radio emission from this object. While it had been suggested that the UV continuum of 3C256 might be due to star formation or a protogalaxy based on its extremely blue spectral energy distribution and similar morphology at UV and visible wavelengths, the observed high degree of polarization and spatial extent of the polarized radiation are not consistent with such models. These data lend support to the suggestion first made by di Serego Alighieri and collaborators that the "alignment effect", the tendency for the extended UV continuum radiation and line emission from HZRGs to be aligned with the major axis of the extended radio emission is in large part due to scattering of anisotropic nuclear emission.