The black hole–bulge relation in AGNs

We used the widths of Hβ and [OIII] emission lines to investigate the black hole–bulge relation in radio-loud AGNs, radio-quiet AGNs and NLS1s. The central black hole mass, Mbh, is estimated from the Hβ line width and the optical luminosity, and the bulge velocity dispersion, σ, is directly from the width of [OIII] line. We found that the radio-quiet AGNs follow the established Mbh − σ relationship in nearby inactive galaxies, while the radio-loud AGNs and NLS1s deviate from this relationship. There are two plausible interpretations for the deviation of radio-loud AGNs. One is that the size of broad line regions (BLRs) emitting Hβ line is overestimated because of the overestimation of optical luminosity, the other is that the dynamics of BLRs and/or narrow line regions (NLRs) in radio-loud AGNs is different from that in radio-quiet AGNs. The deviation of NLS1s may be due to the small inclination of BLRs to the line of sight or the reliability of [OIII] line width as the indicator of stellar velocity dispersion because of its complex multiple components.