We present the results of a radio polarimetric study of the high-redshift radio galaxy PKS B0529 - 549 ( z = 2.575 ) , based on high-resolution 12 mm and 3 cm images obtained with the Australia Telescope Compact Array ( ATCA ) .
The source is found to have a rest-frame Faraday rotation measure of - 9600 rad m ^ { -2 } , the largest seen thus far in the environment of a z > 2 radio galaxy .
In addition , the rest-frame Faraday dispersion in the screen responsible for the rotation is calculated to be 5800 rad m ^ { -2 } , implying rotation measures as large as - 15 400 rad m ^ { -2 } .
Using supporting near-IR imaging from the Very Large Telescope ( VLT ) , we suggest that the rotation measure originates in the Ly \alpha halo surrounding the host galaxy , and estimate the magnetic field strength to be \sim 10 \mu G. We also present a new optical spectrum of PKS B0529 - 549 obtained with the New Technology Telescope ( NTT ) , and propose that the emission-line ratios are best described by a photoionization model .
Furthermore , the host galaxy is found to exhibit both hot dust emission at 8.0 \mu m and significant internal visual extinction ( \sim 1.6 mag ) , as inferred from Spitzer Space Telescope near/mid-IR imaging .