The Relation between Mid-infrared Emission and Black Hole Mass in Active Galactic Nuclei: a Direct Way to Probe Black Hole Growth?

We use a large, heterogeneous sample of local active galactic nuclei (AGNs) that includes Seyfert 1 galaxies, Seyfert 2 galaxies, and Palomar-Green quasars to investigate for the first time the relation between black hole mass ( ) and mid-infrared nuclear emission. We find a clear relation between and 10 mm nuclear luminosity M M BH BH for these local AGNs. There are no significant differences between type 1 and type 2 objects, implying that the reprocessing of the 10 mm nuclear emission is not severely affected by geometric and optical depth effects. We also confirm that is related to the 2–10 keV X-ray luminosity, but only for Compton-thin galaxies. We MBH present a theoretical basis for these empirical relations and discuss possible reasons for the observed scatter. Our results show that rest-frame 10 mm and hard X-ray luminosities (especially the former, which is applicable to all AGN types) can be powerful tools for conducting a census of BH masses at high redshift and for probing their cosmological evolution. Subject headings: black hole physics — galaxies: active — galaxies: nuclei — galaxies: Seyfert — quasars: general On-line material: color figures