Defining the (Black Hole)–Spheroid Connection with the Discovery of Morphology-dependent Substructure in the MBH–nsph and MBH–Re,sph Diagrams: New Tests for Advanced Theories and Realistic Simulations

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.