Bivariate correlation of the linear polarization Q/I (first row) and U/I (second row) with the ﹩{J}_{2}^{2}﹩ radiation field tensor. The third (fourth) row shows a 2D plane fit to the panels of the first (second) row. From left to right, we show the bivariate correlation for the simulation (left column, constructed from panels (f)–(h) of Figure 1), the observation (center column, constructed from panels (a)–(c) of Figure 1), and for an artificial observation (right column; see Section 3.1.1 for further details).