Defining the (Black Hole)–Spheroid Connection with the Discovery of Morphology-dependent Substructure in the M<sub>BH</sub>–n<sub>sph</sub> and M<sub>BH</sub>–R<sub>e,sph</sub> Diagrams: New Tests for Advanced Theories and Realistic Simulations
Nandini Sahu, Alister W. Graham, Benjamin L. Davis
Abstract
Abstract For 123 local galaxies with directly measured black hole masses ( M BH ), we provide the host spheroid’s Sérsic index ( n sph ), effective half-light radius ( R e,sph ), and effective surface brightness ( ), obtained from careful multicomponent decompositions, and we use these to derive the morphology-dependent M BH – n sph and M BH – R e,sph relations. We additionally present the morphology-dependent M *,sph – n sph and M *,sph – R e,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 M BH – n sph 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 M BH and the spheroid’s central concentration index, which varies monotonically with the Sérsic index. Furthermore, we observe a single, near-linear M *,sph – relation for ETGs and LTGs, which encompasses both classical and alleged pseudobulges. In contrast, ETGs and LTGs define two distinct M BH – R e,sph relations with (cf. ∼0.51 dex for the M BH – σ relation and ∼0.58 dex for the M BH – M *,sph relation), and the ETGs alone define two steeper M BH – R e,sph relations, offset by ∼1 dex in the direction, depending on whether they have a disk or not and explaining their similar offset in the M BH – 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.