Revealing Hidden Substructures in the M BH –σ Diagram, and Refining the Bend in the L–σ Relation

Abstract

Using 145 early- and late-type galaxies (ETGs and LTGs) with directly measured supermassive black hole masses, M BH , we build upon our previous discoveries that: (i) LTGs, most of which have been alleged to contain a pseudobulge, follow the relation M BH ∝ M * , sph 2.16 ± 0.32 ; and (ii) the ETG relation M BH ∝ M * , sph 1.27 ± 0.07 is an artifact of ETGs with/without disks following parallel M BH ∝ M * , sph 1.9 ± 0.2 relations that are offset by an order of magnitude in the M BH direction. Here, we searched for substructure in the diagram of M BH versus central velocity dispersion σ , using our recently published multi-component galaxy decompositions, by investigating divisions based on the presence of a depleted stellar core (major dry merger), a disk (minor wet/dry merger, gas accretion), or a bar (evolved unstable disk). The Sérsic and core-Sérsic galaxies define two distinct relations: M BH ∝ σ 5.75 ± 0.34 and M BH ∝ σ 8.64 ± 1.10 , with Δ rms ∣ BH = 0.55 and 0.46 dex, respectively. We also report on the consistency with the slopes and bends in the galaxy luminosity ( L )– σ relation due to Sérsic and core-Sérsic ETGs, and LTGs that all have Sérsic light profiles. Two distinct relations (superficially) reappear in the M BH – σ diagram upon separating galaxies with/without a disk (primarily for the ETG sample), while we find no significant offset between barred and non-barred galaxies, nor between galaxies with/without active galactic nuclei. We also address selection biases purported to affect the scaling relations for dynamically measured M BH samples. Our new M BH – σ relations, dependent on morphological type, more precisely estimate M BH in other galaxies, and hold implications for galaxy/black hole coevolution theories, simulations, feedback, the pursuit of a black-hole fundamental plane, and calibration of virial f -factors for reverberation mapping.