The Spitzer/IRAC view of black hole - bulge scaling relations
  We present a mid-IR investigation of the scaling relations between
supermassive black hole masses (MBH) and the structural parameters of the host
spheroids in local galaxies. The work is based on two-dimensional bulge-disk
decompositions of Spitzer/IRAC 3.6 um images of 57 galaxies with MBH estimates.
Our estimates of effective radii (Re) and surface brightnesses, combined with
velocity dispersions (sigma) from the literature, define a FP relation
consistent with previous determinations but doubling the observed range in Re.
None of our galaxies is an outlier of the FP, demonstrating the accuracy of our
bulge-disk decomposition which also allows us to independently identify
pseudobulges in our sample. We calibrate M/L at 3.6 um by using the tight
Mdyn-Lbul relation (~0.1 dex of rms) and find that no color corrections are
required to estimate the stellar mass. The 3.6 um luminosity is thus the best
tracer of Mstar yet studied. We then explore the connection between MBH and
bulge structural parameters (luminosity, mass, effective radius). We find tight
correlations of MBH with both 3.6 um bulge luminosity and dynamical mass
(MBH/Mdyn~1/1000), with rms of ~0.35 dex, similar to the MBH-sigma relation.
Our results are consistent with previous determinations at shorter wavelengths.
By using our calibrated M/L, we rescale MBH-Lbul to obtain the MBH-Mstar
relation, which can be used as the local reference for high-z studies which
probe the cosmic evolution of MBH-galaxy relations and where the stellar mass
is inferred directly from luminosity measurements. The analysis of pseudobulges
shows that 4 out of 9 lie on the scaling relations within the observed scatter,
while those with small MBH are significantly displaced. We explore the
different origins for such behavior, while considering the possibility of
nuclear morphological components not reproduced by our two-dimensional
decomposition.
