Authors: Nandini Sahu, Alister W. Graham, Benjamin L. Davis
For 123 local galaxies with directly measured black hole masses (MBH), we provide the host spheroid's Sérsic index (nsph), effective half-light radius (Re,sph), and effective surface brightness (μe), obtained from careful multicomponent decompositions, and we use these to derive the morphology-dependent MBH–nsph and MBH–Re,sph relations. We additionally present the morphology-dependent M*,sph–nsph and M*,sph–Re,sph relations. We explored differences due to early-type galaxies (ETGs) versus late-type galaxies (LTGs), Sérsic versus core-Sérsic galaxies, barred versus non-barred galaxies, and galaxies with and without a stellar disk. We detect two different MBH–nsph relations due to ETGs and LTGs with power-law slopes 3.95±0.34 and 2.85±0.31. We additionally quantified the correlation between MBH and the spheroid's central concentration index, which varies monotonically with the Sérsic index. Furthermore, we observe a single, near-linear M*,sph–Re,sph1.08±0.04 relation for ETGs and LTGs, which encompasses both classical and alleged pseudobulges. In contrast, ETGs and LTGs define two distinct MBH–Re,sph relations with Δrms|BH ≈0.60 dex (cf. 0.51 dex for the MBH—σ relation and ≈0.58 dex for the MBH–M*,sph relation, and the ETGs alone define two steeper MBH—Re,sph relations, offset by ≈1 dex in the log(MBH) direction, depending on whether they have a disk or not and explaining their similar offset in the MBH—M*,sph diagram. This trend holds using 10%, 50%, or 90% radii. These relations offer pivotal checks for simulations trying to reproduce realistic galaxies, and for theoretical studies investigating the dependence of black hole mass on basic spheroid properties.