The M_BH-sigma* relation of AGN2 and the AGN unified model

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 MBH − σ⋆ plane. Our analysis shows that the BH masses of type 2 AGN are ∼ 0.9 dex smaller than type 1 AGN at σ⋆ ∼ 185 km s⁻¹, regardless of the (early/late) AGN host galaxy morphology. Equivalently, type 2 AGN host galaxies have stellar velocity dispersions ∼ 0.2 dex higher than type 1 AGN hosts at M_BH ∼ 10⁷ M⊙.

This result disagrees with standard AGN unification scenarios in which AGN1 and AGN2 are the same objects observed along different viewing angles with respect to a toroidal clumpy material.