Polarization Alignment in JVAS/CLASS flat spectrum radio surveys
  We present a detailed statistical analysis of the alignment of polarizations
of radio sources at high redshift.
  We use the JVAS/CLASS 8.4-GHz surveys for our study. This study is motivated
by the puzzling signal of alignment of polarizations from distant quasars at
optical frequencies. We explore several different cuts on the polarization flux
for our analysis. We find that the entire data shows a very significant signal
of alignment on very large distance scales of order 500 Mpc. The alignment
starts to decay only at much larger distances of order Gpc. If we only consider
data with polarization flux greater than 1 mJy, we find alignment at distance
scales less than 150 Mpc. We also find that data with polarization flux less
than 0.5 mJy does not show significant alignment. Similar results are seen for
data with degree of polarization less than 0.01, although here a mild signal of
alignment is observed for a narrow range of angular separations. We argue that
the signal cannot be explained in terms of bias due to systematic errors in
removal of instrumental polarization. We also find that the degree of
polarization shows a strong negative correlation with the total flux. The data
appears to fall into two classes, one of which shows such a correlation. The
remaining set, which has total flux greater than 100 mJy and degree of
polarization lying between 0.01 and 0.1, shows a more random behaviour. The
latter set is also found to show no alignment whereas the first set shows a
very strong polarization alignment.
