Fundamental planes and the barless MBH-σ relation for supermassive black holes

The residuals about the standard M-bh-sigma relation correlate with the effective radius, absolute magnitude, and Sersic index of the host bulge, giving rise to an apparent black hole "fundamental plane.'' However, we show that the elliptical galaxies do not define such a plane. Instead, it is a handful of barred galaxies, which are shown to systematically deviate from the M-bh-sigma relation by delta log M-bh approximate to -0.5 to -1.0 dex (their sigma-values are too large) and generate much of the aforementioned three-parameter correlations. Removal of the seven barred galaxies from the Tremaine et al. set of 31 galaxies gives a "barless'' M-bh-sigma relation with an intrinsic scatter of 0.17 dex (vs. 0.27 dex for the 31 galaxies) and a total scatter of 0.25 dex (vs. 0.34 dex for the 31 galaxies). Furthermore, removal of the barred galaxies, or all the disk galaxies, from an expanded and updated set of 40 galaxies with direct black hole mass measurements gives a consistent result, such that log (M-bh/M-circle dot) (8.25 +/- 0.05) + (3.68 +/- 0.25) log (sigma/200 km s(-1)). In addition, the barless sigma-L relation for galaxies with direct black hole mass measurements is found to be consistent with that from the SDSS sample of early-type galaxies, and the barless M-bh-sigma relation, the M-bh-n relation, and the K-band M-bh-L relation are all shown to yield SMBH masses less than 2-4 x 10(9) M-circle dot.