Polarized extended Ly-alpha emission from a z=2.3 radio galaxy

TL;DR

This study reports the first detection of polarized Ly-alpha emission around a radio-loud galaxy at z=2.34, revealing scattering processes and potential dusty shell structures in the nebula's environment.

Contribution

It provides the first polarization measurements of Ly-alpha around a radio galaxy, demonstrating scattering effects and identifying possible dusty shell features.

Findings

Polarization increases to 16.4% in the nebula's eastern part.

First detection of polarized Ly-alpha emission around a radio-loud galaxy.

Possible dusty shell structure indicated by UV sources at nebula edges.

Abstract

We present spatially resolved spectropolarimetic measurements of the 100-kpc scale gaseous environment of the z=2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Ly-alpha 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 Ly-alpha photons by HI. Not only is this the first detection of polarized Ly-alpha around a radio-loud active galaxy, it is also the second detection to date for any kind of Ly-alpha nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Ly-alpha nebula, which we suggest may be the limb of a dusty shell, related to the large-scale HI absorbers often associated with high-z radio galaxies.