Supermassive Black Holes and Their Host Galaxies - II. The correlation with near-infrared luminosity revisited

We present an investigation of the scaling relations between Supermassive Black Hole (SMBH) masses (Mbh), and their host galaxies' K-band bulge (Lbul) and total (Ltot) luminosities. The wide-field WIRCam imager at the Canada-France-Hawaii-Telescope (CFHT) was used to obtain the deepest and highest resolution near infrared images available for a sample of 35 galaxies with securely measured Mbh, selected irrespective of Hubble type. For each galaxy, we derive bulge and total magnitudes using a two-dimensional image decomposition code that allows us to account, if necessary, for large- and small-scale disks, cores, bars, nuclei, rings, envelopes and spiral arms. We find that the present-day Mbh-Lbul and Mbh-Ltot relations have consistent intrinsic scatter, suggesting that Mbh correlates equally well with bulge and total luminosity of the host. Our analysis provides only mild evidence of a decreased scatter if the fit is restricted to elliptical galaxies. The log-slopes of the Mbh-Lbul and Mbh-Ltot relations are 0.75+/-0.10 and 0.92+/-0.14, respectively. However, while the slope of the Mbh-Lbul relation depends on the detail of the image decomposition, the characterization of Mbh-Ltot does not. Given the difficulties and ambiguities of decomposing galaxy images into separate components, our results indicate that Ltot is more suitable as a tracer of SMBH mass than Lbul, and that the Mbh-Ltot relation should be used when studying the co-evolution of SMBHs and galaxies.