Seyfert 2 galaxies with spectropolarimetric observations

We present a compilation of radio, infrared, optical, and hard X-ray (2-10 keV) data for a sample of 90 Seyfert 2 galaxies (Sy2s) with spectropolarimetric observations ( 41 Sy2s with detection of polarized broad lines [PBLs] and 49 without PBLs). Compared to Sy2s without PBLs, Sy2s with PBLs tend to be earlier type spirals and show warmer midinfrared color and significant excess of emissions ( including the hard X-ray [2-10 keV], [O III] lambda5007, infrared [25 mum], and radio). Our analyses indicate that the majority of Sy2s without PBLs are those sources having less powerful active galactic nucleus (AGN) activities, most likely caused by a low accretion rate. It implies that the detectability of the polarized broad emission lines in Sy2s may depend on their central AGN activities in most cases. Based on the available data, we find no compelling evidence for the presence of two types of Sy2s; one of which has been proposed to be intrinsically different from Sy2s claimed in the unification model.