Black hole scaling relations of active and quiescent galaxies: addressing selection effects and constraining virial factors

Local samples of quiescent galaxies with dynamically measured black hole masses (M_bh) may suffer from an angular resolution-related selection effect, which could bias the observed scaling relations between M_bh and host galaxy properties away from the intrinsic relations. In particular, previous work has shown that the observed M_bh-M_star relation is more strongly biased than the M_bh-σ relation. Local samples of active galactic nuclei (AGN) do not suffer from this selection effect, as in these samples M_bh is estimated from megamasers and/or reverberation mapping-based techniques. With the exception of megamasers, M_bh-estimates in these AGN samples are proportional to a virial coefficient ƒ_vir. Direct modelling of the broad line region suggests that ƒ_vir~3.5. However, this results in a M_bh-M_star relation for AGN which lies below and is steeper than the one observed for quiescent black hole samples. A similar though milder trend is seen for the Mbh-sigma relation. Matching the high-mass end of the M_bh-M_star and M_bh-sigma relations observed in quiescent samples requires ƒ_vir≳15 and ƒ_vir≳7, respectively. On the other hand, ƒ_vir~3.5 yields M_bh-σ and M_bh-M_star relations for AGN which are remarkably consistent with the expected 'intrinsic' correlations for quiescent samples (i.e., once account has been made of the angular resolution-related selection effect), providing additional evidence that the sample of local quiescent black holes is biased. We also show that, as is the case for quiescent black holes, the M_bh-M_star scaling relation of AGN is driven by σ, thus providing additional key constraints to black hole-galaxy co-evolution models.