Polarized Extended Lyalpha Emission from a z = 2.3 Radio Galaxy

We present spatially resolved spectropolarimetric measurements of the 100 kpc scale gaseous environment of the z = 2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Lyalpha emission is low centrally (P < 5%), but rises to P = 16.4% ± 4.6% in the eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Lyalpha photons by H I. Not only is this the first detection of polarized Lyalpha around a radio-loud active galaxy, it is also the second detection to date for any kind of Lyalpha nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Lyalpha nebula, which we suggest may be the limb of a dusty shell, related to the large-scale H I absorbers often associated with high-z radio galaxies.