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

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 $M_{BH} - {σ*}$ relation and found them with a range of: 5.69$\pm$0.21 $<$ $\log M_{BH}^{σ*}$ $<$ 8.09$\pm$0.24. Comparing these $M_{BH}^{σ*}$ values with masses derived from the FWHM of H$β$ and the continuum luminosity at 5100 Åfrom 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 $M_{BH}^{σ*}$ 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 $M_{BH}^{σ*}$ and $M_{BH}$ compatible within 3-$σ$ errors. We also find that estimations based on the $M_{BH}-σ*$ relation for pseudobulges are not compatible in 50$\pm20%$ of the objects.