To test dual supermassive black hole model for broad line AGN with double-peaked narrow [OIII] lines

TL;DR

This study tests the dual supermassive black hole model for AGN with double-peaked narrow [OIII] lines by comparing virial mass estimates from broad Balmer lines, finding results inconsistent with the model.

Contribution

The paper introduces a method to evaluate the dual black hole model using broad Balmer line properties and applies it to a sample of double-peaked narrow emitters.

Findings

Virial black hole masses are larger in double-peaked emitters than in normal AGN.

Results do not support the dual black hole model for these emitters.

Further observational efforts are needed to identify dual supermassive black holes.

Abstract

In this manuscript, we proposed an interesting method to test the dual supermassive black hole model for AGN with double-peaked narrow \oiii lines (double-peaked narrow emitters), through their broad optical Balmer line properties. Under the dual supermassive black hole model for double-peaked narrow emitters, we could expect statistically smaller virial black hole masses estimated by observed broad Balmer line properties than true black hole masses (total masses of central two black holes). Then, we compare the virial black hole masses between a sample of 37 double-peaked narrow emitters with broad Balmer lines and samples of SDSS selected normal broad line AGN with single-peaked \oiii lines. However, we can find clearly statistically larger calculated virial black hole masses for the 37 broad line AGN with double-peaked \oiii lines than for samples of normal broad line AGN. Therefore, we give our conclusion that the dual supermassive black hole model is probably not statistically preferred to the double-peaked narrow emitters, and more efforts should be necessary to carefully find candidates for dual supermassive black holes by observed double-peaked narrow emission lines.