The Black Hole Mass - Spheroid Luminosity relation

The differing Mbh-L relations presented in McLure & Dunlop, Marconi & Hunt and Erwin et al. have been investigated. A number of issues have been identified and addressed in each of these studies, including but not limited to: the removal of a dependency on the Hubble constant; a correction for dust attenuation in the bulges of disc galaxies; the identification of lenticular galaxies previously treated as elliptical galaxies; and application of the same (Y |X) regression analysis. These adjustments result in relations which now predict similar black hole masses. The optimal K-band relation is log(Mbh/M⊙) = −0.37(±0.04)[MK + 24] + 8.29(±0.08), with a total (not intrinsic) scatter in logMbh equal to 0.33 dex. This level of scatter is similar to the value of 0.34 dex from the Mbh-σ relation of Tremaine et al. and compares favourably with the value of 0.31 dex from the Mbh-n relation of Graham & Driver. Using different photometric data, consistent relations in the Band R-band are also provided, although we do note that the small (N = 13) R-band sample used by Erwin et al. is found here to have a slope of −0.30 ± 0.06 and a total scatter of 0.31 dex. Performing a symmetrical regression on the larger K-band sample gives a slope of ∼ −0.40, implying Mbh ∝ L . Implications for galaxy-black hole coevolution, in terms of dry mergers, are briefly discussed, as are the predictions for intermediate mass black holes. Finally, as previously noted by Tundo et al., a potential bias in the galaxy sample used to define the Mbh-L relations is shown and a corrective formula provided.