Characterization of a sample of intermediate-type AGN. II. Host Bulge Properties and Black Hole Mass Estimates

TL;DR

This study investigates host bulge properties and black hole mass estimates in intermediate-type AGN, revealing a high prevalence of pseudobulges and examining the consistency of different black hole mass estimation methods.

Contribution

It provides the first detailed analysis of bulge types and black hole mass estimates in a sample of intermediate-type AGN, highlighting the frequent presence of pseudobulges and the agreement between mass estimation methods.

Findings

Most galaxies host pseudobulges or mixed bulge types.

Double-peaked emission lines are common in pseudobulge hosts.

Black hole mass estimates from different methods are generally consistent within a factor of 3.

Abstract

We present a study of the host bulge properties and their relations with the black hole mass on a sample of 10 intermediate-type active galactic nuclei (AGN). Our sample consists mainly of early type spirals, four of them hosting a bar. For 70$^{+10}_{-17}%$ of the galaxies we have been able to determine the type of the bulge, and find that these objects probably harbor a pseudobulge or a combination of classical bulge/ pseudobulge, suggesting that pseudobulges might be frequent in intermediate-type AGN. In our sample, 50\pm14% of the objects show double-peaked emission lines. Therefore, narrow double-peaked emission lines seem to be frequent in galaxies harboring a pseudobulge or a combination of classical bulge/ pseudobulge. Depending on the bulge type, we estimated the black hole mass using the corresponding $M_{BH} - {\sigma*}$ relation and found them with a range of: 5.69$\pm$0.21 $<$ $\log M_{BH}^{\sigma*}$ $<$ 8.09$\pm$0.24. Comparing these $M_{BH}^{\sigma*}$ values with masses derived from the FWHM of H$\beta$ and the continuum luminosity at 5100 \AA from their SDSS-DR7 spectra ($M_{BH}$) we find that eight out of ten (80$^{+7}_{-17}$%) galaxies have black hole masses that are compatible within a factor of 3. This result would support that $M_{BH}$ and $M_{BH}^{\sigma*}$ are the same for intermediate-type AGN as has been found for type 1 AGN. However, when the type of the bulge is taken into account only 3 out of the 7 (43$^{+18}_{-15}%$) objects of the sample have their $M_{BH}^{\sigma*}$ and $M_{BH}$ compatible within 3-$\sigma$ errors. We also find that estimations based on the $M_{BH}-\sigma*$ relation for pseudobulges are not compatible in 50$\pm20%$ of the objects.