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-sigma 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 f(vir). Direct modelling of the broad-line region suggests that f(vir) similar to 3.5. However, this results in an 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 M-bh-sigma relation. Matching the high-mass end of the M-bh-M-star and M-bh-sigma relations observed in quiescent samples requires f(vir) greater than or similar to 15 and f(vir) greater than or similar to 7, respectively. On the other hand, f(vir) similar to 3.5 yields M-bh-sigma 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 sigma, thus providing additional key constraints to black hole-galaxy co-evolution models.