Supermassive Black Holes and Their Host Spheroids. II. The Red and Blue Sequence in the MBH-M*,sph Diagram

Abstract

In our first paper, we performed a detailed (I.e., bulge, disks, bars, spiral arms, rings, halo, nucleus, etc.) decomposition of 66 galaxies, with directly measured black hole masses, M<SUB>BH</SUB>, imaged at 3.6 μ {{m}} with Spitzer. Our sample is the largest to date and, for the first time, the decompositions were checked for consistency with the galaxy kinematics. We present correlations between M<SUB>BH</SUB> and the host spheroid (and galaxy) luminosity, L<SUB>sph</SUB> (and L<SUB>gal</SUB>), and also stellar mass, {M}<SUB>*,{sph</SUB>}. While most previous studies have used galaxy samples that were overwhelmingly dominated by high-mass, early-type galaxies, our sample includes 17 spiral galaxies, half of which have {M}<SUB>{BH</SUB>}\lt {10}<SUP>7</SUP> {M}<SUB>☉ </SUB>, and allows us to better investigate the poorly studied low-mass end of the {M}<SUB>{BH</SUB>}{--}{M}<SUB>*,{sph</SUB>} correlation. The bulges of early-type galaxies follow {M}<SUB>{BH</SUB>} \propto \{M}<SUB>*,{sph</SUB>}<SUP>1.04+/- 0.10</SUP> and define a tight red sequence with intrinsic scatter {∊ }<SUB>({M</SUB><SUB>{BH</SUB>}| {M}<SUB>*,{sph</SUB>})}\quad =\quad 0.43\quad +/- \quad 0.06 {dex} and a median {M}<SUB>{BH</SUB>}/{M}<SUB>*,{sph</SUB>} ratio of 0.68 ± 0.04%, I.e., a +/- 2σ range of 0.1%-5%. At the low-mass end, the bulges of late-type galaxies define a much steeper blue sequence, with {M}<SUB>{BH</SUB>} \propto {M}<SUB>*,{sph</SUB>}<SUP>2-3</SUP> and {M}<SUB>{BH</SUB>}/{M}<SUB>*,{sph</SUB>} equal to 0.02% at {M}<SUB>{BH</SUB>} ≈ {10}<SUP>6</SUP> {M}<SUB>☉ </SUB>. We additionally report that (1) our Sérsic galaxy sample follows {M}<SUB>{BH</SUB>} \propto \{M}<SUB>*,{sph</SUB>}<SUP>1.48+/- 0.20</SUP>, a less steep sequence than previously reported; (2) bulges with Sérsic index {n}<SUB>{sph</SUB>}\lt 2, argued by some to be pseudo-bulges, are not offset to lower M<SUB>BH</SUB> from the correlation defined by the current bulge sample with {n}<SUB>{sph</SUB>}\gt 2; and (3) L<SUB>sph</SUB> and L<SUB>gal</SUB> correlate equally well with M<SUB>BH</SUB>, in terms of intrinsic scatter, only for early-type galaxies—once reasonable numbers of spiral galaxies are included, the correlation with L<SUB>sph</SUB> is better than that with Lgal.