# Detection of faint broad emission lines in type 2 AGN: III. On the $M_{BH} - \sigma_\star$ relation of type 2 AGN

## TL;DR

This study investigates the black hole mass and stellar velocity dispersion relation in type 2 AGN, revealing they have systematically lower black hole masses than type 1 AGN at similar dispersions, challenging existing scaling relations.

## Contribution

It provides the first comprehensive analysis of the $M_{BH}-\sigma_
star$ relation for type 2 AGN, highlighting differences from type 1 AGN regardless of host galaxy morphology.

## Key findings

- Type 2 AGN have ~0.9 dex smaller BH masses than type 1 AGN at similar velocity dispersions.
- Type 2 AGN host galaxies exhibit ~0.2 dex higher stellar velocity dispersions at comparable BH masses.
- The results suggest potential differences in black hole growth or measurement biases between AGN types.

## Abstract

Type 2 active galactic nuclei (AGN) represent the majority of the AGN population. However, due to the difficulties in measuring their black hole (BH) masses, it is still unknown whether they follow the same BH mass-host galaxy scaling relations valid for quiescent galaxies and type 1 AGN. Here we present the locus of type 2 AGN having virial BH mass estimates in the $M_{BH}-\sigma_\star$ plane. Our analysis shows that the BH masses of type 2 AGN are $\sim0.9$ dex smaller than type 1 AGN at $\sigma_\star\sim 185$ km s$^{-1}$, regardless of the (early/late) AGN host galaxy morphology. Equivalently, type 2 AGN host galaxies have stellar velocity dispersions $\sim 0.2$ dex higher than type 1 AGN hosts at $M_{BH}\sim10^7$ M$_\odot$.