# Hidden Broad-line Regions in Seyfert 2 Galaxies: from the spectropolarimetric perspective

## TL;DR

This study investigates the hidden broad-line regions in Seyfert 2 galaxies using spectropolarimetric data, revealing similarities in BLR geometry with type 1 AGNs and suggesting thick disk structures in hidden BLRs.

## Contribution

It provides the first compilation of polarized BELs and dynamical black hole mass measurements in Seyfert 2 galaxies, estimating virial factors to compare BLR properties with type 1 AGNs.

## Key findings

- BLR geometry and kinematics are similar in type 1 and type 2 AGNs with pseudobulges.
- Virial factors in Seyfert 2 galaxies are small, indicating thick disk BLRs.
- Results support the unified model of AGNs with similar BLR structures across types.

## Abstract

The hidden broad-line regions (BLRs) in Seyfert 2 galaxies, which display broad emission lines (BELs) in their polarized spectra, are a key piece of evidence in support of the unified model for active galactic nuclei (AGNs). However, the detailed kinematics and geometry of hidden BLRs are still not fully understood. The virial factor obtained from reverberation mapping of type 1 AGNs may be a useful diagnostic of the nature of hidden BLRs in type 2 objects. In order to understand the hidden BLRs, we compile six type 2 objects from the literature with polarized BELs and dynamical measurements of black hole masses. All of them contain pseudobulges. We estimate their virial factors, and find the average value is 0.60 and the standard deviation is 0.69, which agree well with the value of type 1 AGNs with pseudobulges. This study demonstrates that (1) the geometry and kinematics of BLR are similar in type 1 and type 2 AGNs of the same bulge type (pseudobulges), and (2) the small values of virial factors in Seyfert 2 galaxies suggest that, similar to type 1 AGNs, BLRs tend to be very thick disks in type 2 objects.