Investigating the Nuclear Obscuration in Two Types of Seyfert 2 Galaxies

We build a large sample of Seyfert 2 galaxies (Sy2s) with both opticalspectropolarimetric and X-ray data available, in which 29 Sy2s with thedetection of polarized broad emission line (PBL) and 25 without. We find thatfor luminous Sy2s with L_[OIII] > 10^41 erg/s, sources with PBL have smallerX-ray absorption column density comparing with those without PBL (at 92.3%confidence level): most of the Sy2s with N_H<10^23.8 cm^-2 show PBL (86%, 12out 14), while the fraction is much smaller for sources with heavierobscuration (54%, 15 out 28). The confidence level of the difference inabsorption bounces up to 99.1% while using the "T" ratio (F_2-10keV/F_[O III])as an indicator. We rule out observation or selection bias as the origin forthe difference. Our results, for the first time with high statisticalconfidence, show that, in additional to the nuclei activity, the nuclearobscuration also plays an important role in the visibility of PBL in Sy2s.These results can be interpreted in the framework of the unified model. We canreach these results in the unified model if: a) the absorption column densityis higher at large inclinations and b) the scattering region is obscured atlarge inclinations.Comment: 28 pages, including 7 figures and 3 tables, ApJ accepte