TRUE2: unveiling the nature of true Seyfert 2 candidates through optical polarimetry

The so-called true Seyfert 2 candidates [1] are Seyferts galaxies whose optical spectra do not show broad lines. Yet, in the X-ray domain, they exhibit some characteristic behavior of Seyferts 1 such as lack of X-ray obscuration and/or short timescale variability. A true Seyfert 2 candidate will be confirmed as a true Seyfert 2 galaxy if the lack of the broad line region (BLR) emission is not only observational but physical. Since the BLR is hidden behind the circumnuclear, optically-thick, dusty torus, only polar-scattered light can probe the presence or absence of the BLR. Hence, scattering-induced polarization is the only way to probe the existence of hidden-BLRs (HBLR).