Study of LQGs with SDSS-DR7-QSO data

Optical quasar polarization appears to be preferentially either aligned or orthogonal to the host large-scale structure, specifically large quasar groups (LQGs). Using a sample of 71 LQGs at redshifts 1.0 <= z <= 1.8, we investigate whether LQGs themselves exhibit correlated orientation.

We find that LQG position angles (PAs) are unlikely to be drawn from a uniform distribution (p-values 0.008 <~ p <~ 0.07). The LQG PA distribution is bimodal, with median modes at {theta}^{bar}^ 45 +/- 2{deg}, 136 +/- 2^{deg}^, remarkably close to the mean angles of quasar radio polarization reported in two regions coincident with our LQG sample. We quantify the degree of alignment in the PA data, and find that LQGs are aligned and orthogonal across very large scales.